THE SKELETAL SYSTEM

 

     How could the human skeletal system possibly have evolved?  Isn’t too complex?

      A bony skeleton is nor necessary for animals—well over 95% of animal species (the invertebrates) lack such a skeleton.  After the first animals evolved,  upwards towards a hundred million years passed without any advances towards the vertebrate skeletal system (other than the manufacture of the protein collagen).  Once skeletal systems began to evolve, they clearly could have done so in a stepwise manner.  Cartilage supported head structures long before there was bone in the head.  The first traces of vertebrae were mere supplements to the longitudinal support provided by the notochord and over a few hundred million years the vertebral column gradually became more prominent until it essentially  replaced the notochord.  The first amphibian pelvises were not attached to the vertebral column and could not support the body’s weight.  Many mammalian skeletal specializations (erect posture, loss of lumbar and cervical ribs, a secondary palate, etc.) evolved gradually in a progression of “mammal-like” reptiles: pelycosaurs, therapsids, and cynodonts.  Modern bones such as the occipital, temporal, and sphenoid are indeed large and complex but they formed gradually over time as a number of smaller, simpler bones fused together. 

     The following cladogram depicts the major branches in the evolution of the earliest cells into modern animals, including humans.  Each number represents a branch-point or node. 


 

 



 


CUMULATIVE VIEW OF THE SKELETAL SYSTEM CLADOGRAM

(the numbers correspond to the branch points on the cladogram given on the previous page)

     Although there are many changes which had to occur to transform the first animal skeletons into the human skeleton, they did not all happen at once.  Instead, they occurred gradually over more than 600 million years.  In the following pages, the skeletal features of organisms at each of our cladogram’s nodes are presented.  (These traits are known either through the study of fossils, the study of modern descendants of these organisms, or both.)  YOU DO NOT HAVE TO UNDERSTAND THE ANATOMICAL TERMS USED IN THE FOLLOWING PAGES.  YOU DO NOT EVEN HAVE TO READ THEM IF YOU CHOOSE NOT TO.  THE ONLY IMPORTANT FEATURE IS THE AMOUNT OF NEW CHARACTERISTICS HIGHLIGHTED IN YELLOW.

     When you look at the list of skeletal features listed at number 11—the Vertebrate Ancestor , you will notice that only one of the characterisitics is highlighted in yellow.  In other words, all of the major features of this animal’s skeletal system were essentially the same as that of its ancestors, with the exception of the one new trait in yellow which was developed.  What is the purpose of skimming the following pages?  I hope you will appreciate that the human skeleton did not have to appear all at once, fully formed.  The evidence from fossils and living organisms indicates that the skeletal modifications which converted ancestral skeletal systems to modern ones occurred gradually, a few changes at a time.

 

NODES FROM CLADOGRAM

1.       LUCA—Last common ancestor of all modern life on earth

2.       Ancestor of Protists, Plants, Fungi, and Animals

3.       Ancestor of Animals (primitive animals are known from the Precambrian Ediacaran fauna)

                --collagen

4.        Metazoan Ancestor (metazoan animals are known from the Precambrian Ediacaran fauna)

5.        Bilateran Ancestor (traces of worms are known from the Precambrian Ediacaran fauna)

6.        Higher Bilateran Ancestor (traces of advanced worms are known from the Precambrian Ediacaran fauna)

7.        Ancestor of Coelomates (a number of animals thought to be coelomates are known from the Precambrian Ediacaran fauna)

8.        Ancestor of Deuterostomes (a number hemichordates and primitive deuterostomes exist today; Yunnanozoan is known from the Early Cambrian)

9.        Chordate Ancestor (lancets are modern chordates; Haikouella is known from the Early Cambrian)

--a gelatinous matrix in lancets may be a precursor to collagen and thus lancets may approach the ancestral form of the splanchnocranium and ribs

10.     Craniate Ancestor  (Hagfish are modern craniates; Myllokumingia is known from the Early Cambrian)

       --collagen

       --calcified internal skeleton derived from embryonic mesoderm tissue

       --cartilage

       --cartilage in cranium (chondrocranium)

       --splanchnochranium supports the roof of the pharynx

 

11.  Vertebrate Ancestor (Lampreys are modern vertebrates; Haikouichtyhys is known from the early Cambrian)

       --collagen

       --calcified internal skeleton derived from embryonic mesoderm tissue

       --cartilage

       --cartilage in cranium (chondrocranium)

       --splanchnochranium supports the roof of the pharynx

       --Vertebrae

                       --paired neural arches over notochord

 

12A.  Gnathostome (jawed vertebrate) Ancestor: Placoderms (placoderms are an extinct group of primitive fish, the only class of vertebrates which is completely extinct)

       --collagen

       --calcified internal skeleton derived from embryonic mesoderm tissue

       --cartilage

--teeth composed of dentin and enamel

       --bone

       --bone forms first in head region; rest of skeleton cartilaginous

       Skull

                --cartilage in cranium (chondrocranium)

                       --splanchnochranium supports the roof of the pharynx

                                       --palatoquadrate (forms quadrate/incus and epipterygoid/alisphenoid)

                                       --Meckel’s cartilage (forms articular/malleus)

--hyomandibula (forms stapes and 2 bones lost in mammals, interhyal and extracolumella)

                       --dermatocranium of dermal bone

                       --jaws

--paired pectoral and pelvic fins

       --Vertebrae

                       --paired neural arches over notochord

                       --hemal spines

       --Appendicular Skeleton

                       --scapulocoracoid

 

12B.  Gnatostome Ancestor: last common ancestor between cartilaginous fish and bony fish

1)       Skeletal System

       --collagen

       --calcified internal skeleton derived from embryonic mesoderm tissue

       --cartilage

--teeth composed of dentin and enamel

                --tooth replacement

       --bone

       --bone forms first in head region; rest of skeleton cartilaginous

       Skull

                --cartilage in cranium (chondrocranium)

                                --mesethmoid

                                --presphenoid

                                --orbitosphenoid

                                --basisphenoid

                                --supraoccipital

                                --basioccipital

                                --exoccipital

                                --opisthotic

                                --prootic

                       --splanchnochranium supports the roof of the pharynx

                                       --palatoquadrate (forms quadrate/incus and epipterygoid/alisphenoid)

                                       --Meckel’s cartilage (forms articular/malleus)

--hyomandibula (forms stapes and 2 bones lost in mammals, interhyal and extracolumella)

                                       --ceratohyal (contributes to hyoid)

                                       --basihyal (contributes to hyoid)

                                       --epibranchial (contributes to hyoid)

                                       --ceratobranchial (contributes to hyoid)

                                       --hypobranchial (contributes to hyoid)

                                       --branchial arches IV and V(contribute to larynx)

                       --dermatocranium of dermal bone

                       --jaws

                       --paired pectoral and pelvic fins

       --Vertebrae

                       --paired neural arches over notochord

                       --hemal spines     

--Appendicular Skeleton

                       --scapulocoracoid

                       --lateral halves of girdles fuse

 

13A. Bony Fish Ancestor: Acanthodians  (Acanthodians are an extinct group of bony fish known as early as the Early Siluran which share some characteristics with sharks)

 

       Organization

--collagen

                       --calcified internal skeleton derived from embryonic mesoderm tissue

                       --cartilage

                       --teeth composed of dentin and enamel

                       --tooth replacement

                       --bone

                       --bone forms first in head region; rest of skeleton cartilaginous

       Axial Skeleton      

--Skull

                --cartilage in cranium (chondrocranium)

                                --mesethmoid

                                --presphenoid

                                --orbitosphenoid

                                --basisphenoid

                                --supraoccipital

                                --basioccipital

                                --exoccipital

                                --opisthotic

                                --prootic

                       --splanchnochranium supports the roof of the pharynx

                                       --palatoquadrate (forms quadrate/incus and epipterygoid/alisphenoid)

                                       --Meckel’s cartilage (forms articular/malleus)

--hyomandibula (forms stapes and 2 bones lost in mammals, interhyal and extracolumella)

                                       --ceratohyal (contributes to hyoid)

                                       --basihyal (contributes to hyoid)

                                       --epibranchial (contributes to hyoid)

                                       --ceratobranchial (contributes to hyoid)

                                       --hypobranchial (contributes to hyoid)

                                       --branchial arches IV and V(contribute to larynx)

                       --dermatocranium of dermal bone composed of small elements rather than large plates

                       --jaws

                       --hyoid

            --Vertebrae

                       --paired neural arches over notochord

                       --hemal spines

       Appendicular Skeleton

                       --scapulocoracoid

                       --paired pectoral and pelvic fins

                       --lateral halves of girdles fuse

                       --ball and socket joints between each girdle and first endoskeletal element of fin/limb

 

12B.  Bony Fish Ancestor  (Psarolepis is known from the Upper Siluran; it is not yet clear whether it is close to the base of all bony fish or of the sarcopterygians only)

1)       Skeletal System

       Organization

--collagen

                       --calcified internal skeleton derived from embryonic mesoderm tissue

                       --cartilage

                       --teeth composed of dentin and enamel

                                       --tooth replacement

                       --bone

                       --bone forms first in head region; rest of skeleton cartilaginous

       Axial Skeleton      

                       --palate covered in dermal bone

                       --braincase more completely ossified

                                --teeth from Meckel’s cartilage and palatoquadrate lost

--Skull

                --cartilage in cranium (chondrocranium)

                       --splanchnochranium supports the roof of the pharynx

                       --jaws

                       --hyoid

--Braincase

                --Frontal (2)

                --Parietal (2)

                --(Occipital)

                                --Supraoccipital

                                --Exoccipital

                                --Basioccipital 

                                --Postparietal

                                --Tabular

                --(Temporal)

                                --Prootic  (forms petrosal with Opisthotic)

                                --Epiotic (becomes Opisthotic in amphibians)

                                --Angular

                                --Pterygoid

                --(Sphenoid)

                                --Sphenethmoid

                                --Orbitosphenoid

                                --Basisphenoid

                                --Epipterygoid (becomes alisphenoid in mammals)

                                --Parasphenoid ?

                --(Ethmoid)

                                --Mesethmoid

                                --Turbinals

--Face

                --Vomers

                --Palantine

                --Jugal (Zygomatic)

                --Nasal

                --Maxillary

                --Premaxillary (fuses to maxillary in humans)

--Auditory Ossicles

                                --Stapes (Hyomandibula in bony fish)

--Articular (Meckel’s cartilage in sharks; becomes malleus in mammals)

--Quadrate (incus in mammals)

--[Hyoid]

                --Basihyal

                --Ceratohyal

                --Epibranchial

                --Ceratobranchial

                --Hypobranchial

--Bones Which were Lost in Human Lineage

                --Extrascapular

                --Opercular

                --Preopercular

                --Subopercular

                --Submandibular

                --Interhyal [lost in amphibians]

                --Pharyngobranchial [lost in amphibians]

                --Hypohyal [lost in reptiles]

                --Prefrontal

                --Postfrontal

                --Postorbital

                --Intertemporal

                --Supratemporal

                --Quadratojugal

                --Septomaxilla

                --Sphenotic

                --Pleurosphenoid [lost in mammals]

                --Extracolumella (Symplectic) [lost in mammals]

                --Coronoids [lost in mammals]

                --Prearticular [lost in mammals]

                --Surangular [lost in mammals]

                --Splenials [lost in mammals]

            --Vertebrae

                       --paired neural arches over notochord

                       --hemal spines

            --Thorax

                       --ribs

       Appendicular Skeleton

                       --paired pectoral and pelvic fins

                       --lateral halves of girdles fuse

                       --ball and socket joints between each girdle and first endoskeletal element of fin/limb

            --Pectoral Girdle and Fin

                       --scapulocoracoid

                       --cleithrum

                       --supracleithrum

                       --clavicle

            --Pelvic Girdle and Fin

 

 

 

 

 


13.  Sarcopterygian Fish Ancestor (most sarcopterygians are extinct; lungfish and coelocanths have survived to modern times)

1)       Skeletal System

       Organization

--collagen

                       --calcified internal skeleton derived from embryonic mesoderm tissue

                       --cartilage

                       --teeth composed of dentin and enamel

                                       --tooth replacement

                                       --teeth with a central pulp cavity

                       --bone

                       --bone forms first in head region; rest of skeleton cartilaginous

       Axial Skeleton      

                       --palate covered in dermal bone

                       --braincase more completely ossified

                                --teeth from Meckel’s cartilage and palatoquadrate lost

--Skull

                --cartilage in cranium (chondrocranium)

                       --splanchnochranium supports the roof of the pharynx

                       --jaws

                                       --upper jaw fuses to braincase

                       --hyoid

--Braincase

                --Frontal (2)

                --Parietal (2)

                --(Occipital)

                                --Supraoccipital

                                --Exoccipital

                                --Basioccipital 

                                --Postparietal

                                --Tabular

                --(Temporal)

                                --Prootic  (forms petrosal with Opisthotic)

                                --Epiotic (becomes Opisthotic in amphibians)

                                --Angular

                                --Pterygoid

                                --Squamosal

                --(Sphenoid)

                                --Sphenethmoid

                                --Orbitosphenoid

                                --Basisphenoid

                                --Epipterygoid (becomes alisphenoid in mammals)

                                --Parasphenoid ?

                --(Ethmoid)

                                --Mesethmoid

                                --Turbinals

--Face

                --Vomers

                --Palantine

                --Jugal (Zygomatic)

                --Nasal

                --Maxillary

                --Premaxillary (fuses to maxillary in humans)

--Auditory Ossicles

                                --Stapes (Hyomandibula in bony fish)

--Articular (Meckel’s cartilage in sharks; becomes malleus in mammals)

--Quadrate (incus in mammals)

--[Hyoid]

                --Basihyal

                --Ceratohyal

                --Epibranchial

                --Ceratobranchial

                --Hypobranchial

--Bones Which were Lost in Human Lineage

                --Extrascapular

                --Opercular

                --Preopercular

                --Subopercular

                --Submandibular

                --Interhyal [lost in amphibians]

                --Pharyngobranchial [lost in amphibians]

                --Hypohyal [lost in reptiles]

                --Prefrontal

                --Postfrontal

                --Postorbital

                --Intertemporal

                --Supratemporal

                --Quadratojugal

                --Septomaxilla

                --Sphenotic

                --Pleurosphenoid [lost in mammals]

                --Extracolumella (Symplectic) [lost in mammals]

                --Coronoids [lost in mammals]

                --Prearticular [lost in mammals]

                --Surangular [lost in mammals]

                --Splenials [lost in mammals]

                --Dermohyal

            --Vertebrae

                       --paired neural arches over notochord

                       --pleurocentra

--intercentra

                       --hemal spines

            --Thorax

                       --ribs

       Appendicular Skeleton

                       --paired pectoral and pelvic fins

                       --lateral halves of girdles fuse

                       --ball and socket joints between each girdle and first endoskeletal element of fin/limb

            --Pectoral Girdle and Fin

                       --scapulocoracoid

                       --cleithrum

                       --supracleithrum

                       --anocleithrum

                       --clavicle

                       --interclavicle

                       --humerus

                       --radius

                       --ulna

                       --carpal bones (2)

            --Pelvic Girdle and Fin

                       --pelvis

                       --femur

                       --tibia

                       --fibula

 

14A.  Amphibian Ancestor: Acanthostega

 

       Organization

--collagen

                       --calcified internal skeleton derived from embryonic mesoderm tissue

                       --cartilage

                       --teeth composed of dentin and enamel

                                       --tooth replacement

                                       --teeth with a central pulp cavity

                       --bone

                       --bone forms first in head region; rest of skeleton cartilaginous

       Axial Skeleton      

                       --palate covered in dermal bone

                       --braincase more completely ossified

                                --teeth from Meckel’s cartilage and palatoquadrate lost

--Skull

                         --reduction in the number of skull bones

                --cartilage in cranium (chondrocranium)

                                --tighter junctions between elements, less mobility of snout

                       --splanchnocranium supports the roof of the pharynx

                       --dermatocranium

--elements joined together more solidly; joined to braincase

                                       --solid attachment of skull to cheek

                       --jaws

                                       --upper jaw fuses to braincase

                       --hyoid

--Braincase

                --Frontal (2)

                --Parietal (2)

                --(Occipital)

                                --Supraoccipital

                                --Exoccipital

                                --Basioccipital 

                                --Postparietal

                                --Tabular

                --(Temporal)

                                --Prootic  (forms petrosal with Opisthotic)

                                --Epiotic (becomes Opisthotic in amphibians)

                                --Angular

                                --Pterygoid

                                --Squamosal

                --(Sphenoid)

                                --Sphenethmoid

                                --Orbitosphenoid

                                --Basisphenoid

                                --Epipterygoid (becomes alisphenoid in mammals)

                                --Parasphenoid ?

                --(Ethmoid)

                                --Mesethmoid

                                --Turbinals

--Face

                --Vomers

                --Palantine

                --Jugal (Zygomatic)

                --Nasal

                --Maxillary

                --Premaxillary (fuses to maxillary in humans)

--Auditory Ossicles

                                --Stapes (Hyomandibula in bony fish)

                                                --Hyomandibular no longer a jaw support

--Articular (Meckel’s cartilage in sharks; becomes malleus in mammals)

--Quadrate (incus in mammals)

--[Hyoid]

                --Basihyal

                --Ceratohyal

                --Epibranchial

                --Ceratobranchial

                --Hypobranchial

--Bones Which were Lost in Human Lineage

                --Extrascapular lost (medial and lateral)

                --Opercular lost

                --Preopercular lost

                --Subopercular lost

                --Submandibular

                --Interhyal [lost in amphibians]

                --Pharyngobranchial [lost in amphibians]

                --Hypohyal [lost in reptiles]

                --Prefrontal

                --Postfrontal

                --Postorbital

                --Intertemporal

                --Supratemporal

                --Quadratojugal

                --Septomaxilla

                --Sphenotic

                --Pleurosphenoid [lost in mammals]

                --Extracolumella (Symplectic) [lost in mammals]

                --Coronoids [lost in mammals]

                --Prearticular [lost in mammals]

                --Surangular [lost in mammals]

                --Splenials [lost in mammals]

                --Dermohyal

            --Vertebrae

                       --paired neural arches over notochord

                       --pleurocentra

                       --intercentra

                       --hemal spine

                       --shoulder girdle separated from skull creating a neck

 

                       --sacrum

            --Thorax

                       --ribs

       Appendicular Skeleton

                       --paired pectoral and pelvic fins

                       --lateral halves of girdles fuse

                       --ball and socket joints between each girdle and first endoskeletal element of fin/limb

            --Pectoral Girdle and Fin

                       --scapulocoracoid

                       --cleithrum

                       --supracleithrum

                       --anocleithrum

                       --clavicle

                       --interclavicle

                       --humerus

                       --radius

                       --ulna

                       --carpal bones

                       --bony jointed digits

            --Pelvic Girdle and Fin

                       --pelvis

                       --femur

                       --tibia

                       --fibula

                       --bony jointed digits

 

 

 

 

 

 

 

 

 

 


14B.  Amphibian Ancestor: Ichthyostega

 

       Organization

--collagen

                       --calcified internal skeleton derived from embryonic mesoderm tissue

                       --cartilage

                       --teeth composed of dentin and enamel

                                       --tooth replacement

                                       --teeth with a central pulp cavity

                       --bone

                       --bone forms first in head region; rest of skeleton cartilaginous

       Axial Skeleton      

                       --palate covered in dermal bone

                       --braincase more completely ossified

                                --teeth from Meckel’s cartilage and palatoquadrate lost

--Skull

                         --reduction in the number of skull bones

                --cartilage in cranium (chondrocranium)

                                --tighter junctions between elements, less mobility of snout

                       --splanchnocranium supports the roof of the pharynx

                       --dermatocranium

--elements joined together more solidly; joined to braincase

                                       --solid attachment of skull to cheek

                       --jaws

                                       --upper jaw fuses to braincase

                       --hyoid

--Braincase

                --Frontal (2)

                --Parietal (2)

                --(Occipital)

                                --Supraoccipital

                                --Exoccipital

                                --Basioccipital 

                                --Postparietal

                                --Tabular

                --(Temporal)

                                --Prootic  (forms petrosal with Opisthotic)

                                --Epiotic (becomes Opisthotic in amphibians)

                                --Angular

                                --Pterygoid

                                --Squamosal

                --(Sphenoid)

                                --Sphenethmoid

                                --Orbitosphenoid

                                --Basisphenoid

                                --Epipterygoid (becomes alisphenoid in mammals)

                                --Parasphenoid ?

                --(Ethmoid)

                                --Mesethmoid

                                --Turbinals

--Face

                --Vomers

                --Palantine

                --Jugal (Zygomatic)

                --Nasal

                --Maxillary

                --Premaxillary (fuses to maxillary in humans)

--Auditory Ossicles

                                --Stapes (Hyomandibula in bony fish)

                                                --Hyomandibular no longer a jaw support

--Articular (Meckel’s cartilage in sharks; becomes malleus in mammals)

--Quadrate (incus in mammals)

--[Hyoid]

                --Basihyal

                --Ceratohyal

                --Epibranchial

                --Ceratobranchial

                --Hypobranchial

--Bones Which were Lost in Human Lineage

                --Extrascapular lost (medial and lateral)

                --Opercular lost

                --Preopercular lost

                --Subopercular lost

                --Submandibular

                --Interhyal [lost in amphibians]

                --Pharyngobranchial [lost in amphibians]

                --Hypohyal [lost in reptiles]

                --Prefrontal

                --Postfrontal

                --Postorbital

                --Intertemporal

                --Supratemporal

                --Quadratojugal

                --Septomaxilla

                --Sphenotic

                --Pleurosphenoid [lost in mammals]

                --Extracolumella (Symplectic) [lost in mammals]

                --Coronoids [lost in mammals]

                --Prearticular [lost in mammals]

                --Surangular [lost in mammals]

                --Splenials [lost in mammals]

                --Dermohyal

            --Vertebrae

                       --paired neural arches over notochord

                                       --well developed zygapophyses linking neural arches

                       --pleurocentra

                       --intercentra

                       --hemal spine

                       --sacrum

                                       --loss of sacral ribs

                                       --sacrum attached to pelvis

            --Thorax

                       --ribs

                                       --ribs stronger and directed ventrally

                                       --shoulder girdle separated from skull creating a neck

       Appendicular Skeleton

                       --paired pectoral and pelvic fins

                       --lateral halves of girdles fuse

                       --weight bearing girdles

                       --ball and socket joints between each girdle and first endoskeletal element of fin/limb

            --Pectoral Girdle and Fin

                       --scapulocoracoid

                       --cleithrum

                       --supracleithrum lost

                       --anocleithrum lost

                       --clavicle

                       --interclavicle

                       --humerus

                       --radius

                       --ulna

                       --carpal bones

                       --bony jointed digits

            --Pelvic Girdle and Fin

                       --pelvis

                                       --composed of three bones: ilium, ischium, pubis

                       --femur

                       --tibia

                       --fibula

                       --bony jointed digits


14C.  Ampbian Ancestor: Last common ancestor of modern amphibians and amniotes

 

       Organization

--collagen

                       --calcified internal skeleton derived from embryonic mesoderm tissue

                       --cartilage

                       --teeth composed of dentin and enamel

                                       --tooth replacement

                                       --teeth with a central pulp cavity

                       --bone

                       --bone forms first in head region; rest of skeleton cartilaginous

       Axial Skeleton      

                       --palate covered in dermal bone

                       --braincase more completely ossified

                                --teeth from Meckel’s cartilage and palatoquadrate lost

--Skull

                         --reduction in the number of skull bones

                --cartilage in cranium (chondrocranium)

                                --tighter junctions between elements, less mobility of snout

                       --splanchnocranium supports the roof of the pharynx

                       --dermatocranium

--elements joined together more solidly; joined to braincase

                                       --solid attachment of skull to cheek

                       --jaws

                                       --upper jaw fuses to braincase

                       --hyoid

--Braincase

                --Frontal (2)

                --Parietal (2)

                --(Occipital)

                                --Supraoccipital

                                --Exoccipital

                                --Basioccipital 

                                --Postparietal

                                --Tabular

                --(Temporal)

                                --Prootic  (forms petrosal with Opisthotic)

                                --Epiotic (becomes Opisthotic in amphibians)

                                --Angular

                                --Pterygoid

                                --Squamosal

                --(Sphenoid)

                                --Sphenethmoid

                                --Orbitosphenoid

                                --Basisphenoid

                                --Epipterygoid (becomes alisphenoid in mammals)

                                --Parasphenoid ?

                --(Ethmoid)

                                --Mesethmoid

                                --Turbinals

--Face

                --Vomers

                --Palantine

                --Jugal (Zygomatic)

                --Nasal

                --Maxillary

                --Premaxillary (fuses to maxillary in humans)

--Auditory Ossicles

                                --Stapes (Hyomandibula in bony fish)

                                                --Hyomandibular no longer a jaw support

--Articular (Meckel’s cartilage in sharks; becomes malleus in mammals)

--Quadrate (incus in mammals)

--[Hyoid]

                --Basihyal

                --Ceratohyal

                --Epibranchial

                --Ceratobranchial

                --Hypobranchial

--Bones Which were Lost in Human Lineage

                --Extrascapular lost (medial and lateral)

                --Opercular lost

                --Preopercular lost

                --Subopercular lost

                --Submandibular

                --Interhyal [lost in amphibians]

                --Pharyngobranchial [lost in amphibians]

                --Hypohyal [lost in reptiles]

                --Prefrontal

                --Postfrontal

                --Postorbital

                --Intertemporal

                --Supratemporal

                --Quadratojugal

                --Septomaxilla

                --Sphenotic

                --Pleurosphenoid [lost in mammals]

                --Extracolumella (Symplectic) [lost in mammals]

                --Coronoids [lost in mammals]

                --Prearticular [lost in mammals]

                --Surangular [lost in mammals]

                --Splenials [lost in mammals]

                --Dermohyal

            --Vertebrae

                       --parts of vertebrae fuse

                       --paired neural arches over notochord

                                       --well developed zygapophyses linking neural arches

                       --pleurocentra

                       --intercentra

                       --hemal spine

                       --sacrum

                                       --loss of sacral ribs

                                       --sacrum attached to pelvis

            --Thorax

                       --ribs

                                       --ribs stronger and directed ventrally

                                       --shoulder girdle separated from skull creating a neck

       Appendicular Skeleton

                       --paired pectoral and pelvic fins

                       --lateral halves of girdles fuse

                       --weight bearing girdles

                       --ball and socket joints between each girdle and first endoskeletal element of fin/limb

            --Pectoral Girdle and Fin

                       --scapulocoracoid

                       --cleithrum

                       --supracleithrum lost

                       --anocleithrum lost

                       --clavicle

                       --interclavicle

                       --humerus

                       --radius

                       --ulna

                       --carpal bones

                       --wrist joint

                       --bony jointed digits

            --Pelvic Girdle and Fin

                       --pelvis

                                       --composed of three bones: ilium, ischium, pubis

                       --femur

                       --tibia

                       --fibula

                       --ankle joint

                       --bony jointed digits

 

15A.  Amniote ancestor: anthracosaur amphibians

       Organization

--collagen

                       --calcified internal skeleton derived from embryonic mesoderm tissue

                       --cartilage

                       --teeth composed of dentin and enamel

                                       --tooth replacement

                                       --teeth with a central pulp cavity

                                       --teeth located in grooves in skull bones

                       --bone

                       --bone forms first in head region; rest of skeleton cartilaginous

       Axial Skeleton      

                       --palate covered in dermal bone

                       --braincase more completely ossified

                                --teeth from Meckel’s cartilage and palatoquadrate lost

--Skull

                         --reduction in the number of skull bones

                --cartilage in cranium (chondrocranium)

                                --tighter junctions between elements, less mobility of snout

                       --splanchnocranium supports the roof of the pharynx

                       --dermatocranium

--elements joined together more solidly; joined to braincase

                                       --solid attachment of skull to cheek

                       --jaws

                                       --upper jaw fuses to braincase

                       --hyoid

--Braincase

                --Frontal (2)

                --Parietal (2)

                --(Occipital)

                                --Supraoccipital

                                --Exoccipital

                                --Basioccipital 

                                --Postparietal

                                --Tabular

                --(Temporal)

                                --Prootic  (forms petrosal with Opisthotic)

                                --Epiotic (becomes Opisthotic in amphibians)

                                --Angular

                                --Pterygoid

                                                --transverse phlange of pterygoid

                                --Squamosal

                --(Sphenoid)

                                --Sphenethmoid

                                --Orbitosphenoid

                                --Basisphenoid

                                --Epipterygoid (becomes alisphenoid in mammals)

                                --Parasphenoid ?

                --(Ethmoid)

                                --Mesethmoid

                                --Turbinals

--Face

                --Vomers

                --Palantine

                --Jugal (Zygomatic)

                --Nasal

                --Maxillary

                --Premaxillary (fuses to maxillary in humans)

--Auditory Ossicles

                                --Stapes (Hyomandibula in bony fish)

                                                --Hyomandibular no longer a jaw support

--Articular (Meckel’s cartilage in sharks; becomes malleus in mammals)

--Quadrate (incus in mammals)

--[Hyoid]

                --Basihyal

                --Ceratohyal

                --Epibranchial

                --Ceratobranchial

                --Hypobranchial

--Bones Which were Lost in Human Lineage

                --Extrascapular lost (medial and lateral)

                --Opercular lost

                --Preopercular lost

                --Subopercular lost

                --Submandibular

                --Interhyal [lost in amphibians]

                --Pharyngobranchial [lost in amphibians]

                --Hypohyal [lost in reptiles]

                --Prefrontal

                --Postfrontal

                --Postorbital

                --Intertemporal

                --Supratemporal

                --Quadratojugal

                --Septomaxilla

                --Sphenotic

                --Pleurosphenoid [lost in mammals]

                --Extracolumella (Symplectic) [lost in mammals]

                --Coronoids [lost in mammals]

                --Prearticular [lost in mammals]

                --Surangular [lost in mammals]

                --Splenials [lost in mammals]

                --Dermohyal

            --Vertebrae

                       --parts of vertebrae fuse

                       --paired neural arches over notochord

                                       --well developed zygapophyses linking neural arches

                       --pleurocentra

                                       --pleurocentra predominate in vertebral centrum

                       --intercentra

                                       --reduced

                       --hemal spine

                       --sacrum

                                       --loss of sacral ribs

                                       --sacrum attached to pelvis

            --Thorax

                       --ribs

                                       --ribs stronger and directed ventrally

                                       --shoulder girdle separated from skull creating a neck

       Appendicular Skeleton

                       --paired pectoral and pelvic fins

                       --lateral halves of girdles fuse

                       --weight bearing girdles

                       --ball and socket joints between each girdle and first endoskeletal element of fin/limb

            --Pectoral Girdle and Fin

                       --scapulocoracoid

                       --cleithrum

                       --supracleithrum lost

                       --anocleithrum lost

                       --clavicle

                       --interclavicle

                       --humerus

                       --radius

                       --ulna

                       --carpal bones

                       --wrist joint

                       --bony jointed digits

            --Pelvic Girdle and Fin

                       --pelvis

                                       --composed of three bones: ilium, ischium, pubis

                       --femur

                       --tibia

                       --fibula

                       --ankle joint

                       --bony jointed digits

15B.  Amniote Ancestor: anapsid reptiles

       Organization

--collagen

                       --calcified internal skeleton derived from embryonic mesoderm tissue

                       --cartilage

                       --teeth composed of dentin and enamel

                                       --tooth replacement

                                       --teeth with a central pulp cavity

                                       --teeth located in grooves in skull bones

                       --bone

                       --bone forms first in head region; rest of skeleton cartilaginous

       Axial Skeleton      

                       --palate covered in dermal bone

                       --braincase more completely ossified

                                --teeth from Meckel’s cartilage and palatoquadrate lost

--Skull

                         --reduction in the number of skull bones

                --cartilage in cranium (chondrocranium)

                                --tighter junctions between elements, less mobility of snout

                       --splanchnocranium supports the roof of the pharynx

                       --dermatocranium

--elements joined together more solidly; joined to braincase

                                       --solid attachment of skull to cheek

                       --jaws

                                       --upper jaw fuses to braincase

                                       --stronger, greater pressure possible

                       --hyoid

--Braincase

                --Frontal (2)

                --Parietal (2)

                --(Occipital)

                                --Supraoccipital

                                --Exoccipital

                                --Basioccipital 

                                --Postparietal reduced

                                --Tabular reduced

                --(Temporal)

                                --Prootic  (forms petrosal with Opisthotic)

                                --Epiotic (becomes Opisthotic in amphibians)

                                --Angular

                                --Pterygoid

                                                --transverse phlange of pterygoid

                                --Squamosal

                --(Sphenoid)

                                --Sphenethmoid

                                --Orbitosphenoid

                                --Basisphenoid

                                --Epipterygoid (becomes alisphenoid in mammals)

--epipterygoid and quadrate only portions of palatoquadrate retained

                                --Parasphenoid ?

                --(Ethmoid)

                                --Mesethmoid

                                --Turbinals

--Face

                --Vomers

                --Palantine

                --Jugal (Zygomatic)

                --Nasal

                --Maxillary

                --Premaxillary (fuses to maxillary in humans)

--Auditory Ossicles

                                --Stapes (Hyomandibula in bony fish)

                                                --Hyomandibular no longer a jaw support

--Articular (Meckel’s cartilage in sharks; becomes malleus in mammals)

--Quadrate (incus in mammals)

--[Hyoid]

                --Basihyal

                --Ceratohyal

                --Epibranchial

                --Ceratobranchial

                --Hypobranchial

--Bones Which were Lost in Human Lineage

                --Extrascapular lost (medial and lateral)

                --Opercular lost

                --Preopercular lost

                --Subopercular lost

                --Submandibular

                --Interhyal [lost in amphibians]

                --Pharyngobranchial [lost in amphibians]

                --Hypohyal [lost in reptiles]

                --Prefrontal

                --Postfrontal

                --Postorbital

                --Intertemporal

                --Supratemporal reduced

                --Quadratojugal

                --Septomaxilla

                --Sphenotic

                --Pleurosphenoid [lost in mammals]

                --Extracolumella (Symplectic) [lost in mammals]

                --Coronoids [lost in mammals]

                --Prearticular [lost in mammals]

                --Surangular [lost in mammals]

                --Splenials [lost in mammals]

                --Dermohyal

            --Vertebrae

                       --parts of vertebrae fuse

                       --paired neural arches over notochord

                                       --well developed zygapophyses linking neural arches

                       --pleurocentra

                                       --pleurocentra predominate in vertebral centrum

                       --intercentra

                                       --reduced

                       --hemal spine

                       --sacrum

                                       --loss of sacral ribs

                                       --sacrum attached to pelvis

                                       --becomes stronger

                       --atlas and axis

            --Thorax

                       --ribs

                                       --ribs stronger and directed ventrally

                                       --shoulder girdle separated from skull creating a neck

                                       --true ribs contact sternum

       Appendicular Skeleton

                       --paired pectoral and pelvic fins

                       --lateral halves of girdles fuse

                       --weight bearing girdles

                       --ball and socket joints between each girdle and first endoskeletal element of fin/limb

            --Pectoral Girdle and Fin

                       --scapulocoracoid

                       --cleithrum

                                       --reduced

                       --supracleithrum lost

                       --anocleithrum lost

                       --clavicle

                                       --reduced

                       --interclavicle

                       --humerus

                                       --becomes a narrow shaft

                                       --supinator process—on humerus?

                       --radius

                       --ulna

                       --carpal bones

                       --wrist joint

                       --bony jointed digits

            --Pelvic Girdle and Fin

                       --pelvis

                                       --composed of three bones: ilium, ischium, pubis

                       --femur

                       --tibia

                       --fibula

                       --ankle joint

                                       --fibulare enlarges; becomes calcaneum

                                       --tibiale, intermedium, and proximal centrale fuse to form astragalus

                       --bony jointed digits

 

 

16A.  Mammal Ancestor: Primitive pelycosaurs--Archaeothyris

1)       Skeletal System

       Organization

--collagen

                       --calcified internal skeleton derived from embryonic mesoderm tissue

                       --cartilage

                       --teeth composed of dentin and enamel

                                       --tooth replacement

                                       --teeth with a central pulp cavity

                                       --teeth located in grooves in skull bones

                                       --different kinds of teeth

                                                       --canine enlarges

                       --bone

                       --bone forms first in head region; rest of skeleton cartilaginous

       Axial Skeleton      

                       --palate covered in dermal bone

                       --braincase more completely ossified

                                --teeth from Meckel’s cartilage and palatoquadrate lost

--Skull

                         --reduction in the number of skull bones

                --cartilage in cranium (chondrocranium)

                                --tighter junctions between elements, less mobility of snout

                       --splanchnocranium supports the roof of the pharynx

                       --dermatocranium

--elements joined together more solidly; joined to braincase

                                       --solid attachment of skull to cheek

                       --jaws

                                       --upper jaw fuses to braincase

                                       --stronger, greater pressure possible

                       --hyoid

                       --the synapsid temporal opening

--Braincase

                --Frontal (2)

                --Parietal (2)

                --(Occipital)

                                --occipital region solidifies

                                --Supraoccipital

                                --Exoccipital

                                --Basioccipital 

                                --Postparietal reduced

                                --Tabular reduced

                --(Temporal)

                                --Prootic  (forms petrosal with Opisthotic)

                                --Epiotic (becomes Opisthotic in amphibians)

                                --Angular

                                --Pterygoid

                                                --transverse phlange of pterygoid

                                --Squamosal

                --(Sphenoid)

                                --Sphenethmoid

                                --Orbitosphenoid

                                --Basisphenoid

                                --Epipterygoid (becomes alisphenoid in mammals)

--epipterygoid and quadrate only portions of palatoquadrate retained

                                --Parasphenoid ?

                --(Ethmoid)

                                --Mesethmoid

                                --Turbinals

--Face

                --Vomers

                --Palantine

                --Jugal (Zygomatic)

                --Nasal

                --Maxillary

                --Premaxillary (fuses to maxillary in humans)

--Auditory Ossicles

                                --Stapes (Hyomandibula in bony fish)

                                                --Hyomandibular no longer a jaw support

--Articular (Meckel’s cartilage in sharks; becomes malleus in mammals)

--Quadrate (incus in mammals)

--[Hyoid]

                --Basihyal

                --Ceratohyal

                --Epibranchial

                --Ceratobranchial

                --Hypobranchial

--Bones Which were Lost in Human Lineage

                --Extrascapular lost (medial and lateral)

                --Opercular lost

                --Preopercular lost

                --Subopercular lost

                --Submandibular

                --Interhyal [lost in amphibians]

                --Pharyngobranchial [lost in amphibians]

                --Hypohyal [lost in reptiles]

                --Prefrontal

                --Postfrontal

                --Postorbital

                --Intertemporal

                --Supratemporal reduced

                --Quadratojugal

                --Septomaxilla

                --Sphenotic

                --Pleurosphenoid [lost in mammals]

                --Extracolumella (Symplectic) [lost in mammals]

                --Coronoids [lost in mammals]

                --Prearticular [lost in mammals]

                --Surangular [lost in mammals]

                --Splenials [lost in mammals]

                --Dermohyal

            --Vertebrae

                       --parts of vertebrae fuse

                       --paired neural arches over notochord

                                       --well developed zygapophyses linking neural arches

                       --pleurocentra

                                       --pleurocentra predominate in vertebral centrum

                       --intercentra

                                       --reduced

                       --hemal spine

                       --sacrum

                                       --loss of sacral ribs

                                       --sacrum attached to pelvis

                                       --becomes stronger

                       --atlas and axis

                       --enlarged neural spines and transverse processes for muscle attachment

            --Thorax

                       --ribs

                                       --ribs stronger and directed ventrally

                                       --shoulder girdle separated from skull creating a neck

                                       --true ribs contact sternum

       Appendicular Skeleton

                       --paired pectoral and pelvic fins

                       --lateral halves of girdles fuse

                       --weight bearing girdles

                       --ball and socket joints between each girdle and first endoskeletal element of fin/limb

            --Pectoral Girdle and Fin

                       --scapulocoracoid

                       --cleithrum

                                       --reduced to a very thin bone

                       --supracleithrum lost

                       --anocleithrum lost

                       --clavicle

                                       --reduced

                       --interclavicle

                       --humerus

                                       --becomes a narrow shaft

                                       --supinator process—on humerus?

                       --radius

                       --ulna

                       --carpal bones

                       --wrist joint

                       --bony jointed digits

            --Pelvic Girdle and Fin

                       --pelvis

                                       --composed of three bones: ilium, ischium, pubis

                       --femur

                       --tibia

                       --fibula

                       --ankle joint

                                       --fibulare enlarges; becomes calcaneum

                                       --tibiale, intermedium, and proximal centrale fuse to form astragalus

                       --bony jointed digits

 

 

 

 

 

 

 

 

 

 

 

 

 


16B.  Mammal Ancestor: Sphenacodont Pelycosaur

       Organization

--collagen

                       --calcified internal skeleton derived from embryonic mesoderm tissue

                       --cartilage

                       --teeth composed of dentin and enamel

                                       --tooth replacement

                                       --teeth with a central pulp cavity

                                       --teeth located in grooves in skull bones

                                       --different kinds of teeth

                                                       --canine enlarges

                       --bone

                       --bone forms first in head region; rest of skeleton cartilaginous

       Axial Skeleton      

                       --palate covered in dermal bone

                       --braincase more completely ossified

                                --teeth from Meckel’s cartilage and palatoquadrate lost

--Skull

                         --reduction in the number of skull bones

                         --skull deeper

                --cartilage in cranium (chondrocranium)

                                --tighter junctions between elements, less mobility of snout

                       --splanchnocranium supports the roof of the pharynx

                       --dermatocranium

--elements joined together more solidly; joined to braincase

                                       --solid attachment of skull to cheek

                       --jaws

                                       --upper jaw fuses to braincase

                                       --stronger, greater pressure possible

                       --hyoid

                       --the synapsid temporal opening

--Braincase

                --Frontal (2)

                                --forms part of orbit

                --Parietal (2)

                --(Occipital)

                                --occipital region solidifies

                                --Supraoccipital

                                --Exoccipital

                                --Basioccipital 

                                --Postparietal reduced

                                --Tabular reduced

                --(Temporal)

                                --Prootic  (forms petrosal with Opisthotic)

                                --Epiotic (becomes Opisthotic in amphibians)

                                --Angular

                                --Pterygoid

                                                --transverse phlange of pterygoid

                                --Squamosal

                --(Sphenoid)

                                --Sphenethmoid

                                --Orbitosphenoid

                                --Basisphenoid

                                --Epipterygoid (becomes alisphenoid in mammals)

--epipterygoid and quadrate only portions of palatoquadrate retained

                                --Parasphenoid ?

                --(Ethmoid)

                                --Mesethmoid

                                --Turbinals

--Face

                --Vomers

                --Palantine

                --Jugal (Zygomatic)

                --Nasal

                --Maxillary

                --Premaxillary (fuses to maxillary in humans)

                --Lower Jaw

                                --angular reflected

--Auditory Ossicles

                                --Stapes (Hyomandibula in bony fish)

                                                --Hyomandibular no longer a jaw support

--Articular (Meckel’s cartilage in sharks; becomes malleus in mammals)

--Quadrate (incus in mammals)

--[Hyoid]

                --Basihyal

                --Ceratohyal

                --Epibranchial

                --Ceratobranchial

                --Hypobranchial

--Bones Which were Lost in Human Lineage

                --Extrascapular lost (medial and lateral)

                --Opercular lost

                --Preopercular lost

                --Subopercular lost

                --Submandibular

                --Interhyal [lost in amphibians]

                --Pharyngobranchial [lost in amphibians]

                --Hypohyal [lost in reptiles]

                --Prefrontal

                --Postfrontal

                --Postorbital

                --Intertemporal

                --Supratemporal reduced

                --Quadratojugal

                --Septomaxilla

                --Sphenotic

                --Pleurosphenoid [lost in mammals]

                --Extracolumella (Symplectic) [lost in mammals]

                --Coronoids [lost in mammals]

                --Prearticular [lost in mammals]

                --Surangular [lost in mammals]

                --Splenials [lost in mammals]

                --Dermohyal

            --Vertebrae

                       --parts of vertebrae fuse

                       --paired neural arches over notochord

                                       --well developed zygapophyses linking neural arches

                       --pleurocentra

                                       --pleurocentra predominate in vertebral centrum

                       --intercentra

                                       --reduced

                       --hemal spine

                       --sacrum

                                       --loss of sacral ribs

                                       --sacrum attached to pelvis

                                       --becomes stronger

                       --atlas and axis

                       --enlarged neural spines and transverse processes for muscle attachment

            --Thorax

                       --ribs

                                       --ribs stronger and directed ventrally

                                       --shoulder girdle separated from skull creating a neck

                                       --true ribs contact sternum

                                       --shorter ribs on anterior caudal vertebrae

       Appendicular Skeleton

                       --paired pectoral and pelvic fins

                       --lateral halves of girdles fuse

                       --weight bearing girdles

                       --ball and socket joints between each girdle and first endoskeletal element of fin/limb

                       --limbs longer

            --Pectoral Girdle and Fin

                       --scapulocoracoid

                       --cleithrum

                                       --reduced to a very thin bone

                       --supracleithrum lost

                       --anocleithrum lost

                       --clavicle

                                       --reduced

                       --interclavicle

                       --humerus

                                       --becomes a narrow shaft

                                       --supinator process—on humerus?

                       --radius

                       --ulna

                       --carpal bones

                       --wrist joint

                       --bony jointed digits

            --Pelvic Girdle and Fin

                       --pelvis

                                       --composed of three bones: ilium, ischium, pubis

                                       --ilium expanded

                       --femur

                       --tibia

                       --fibula

                       --ankle joint

                                       --fibulare enlarges; becomes calcaneum

                                       --tibiale, intermedium, and proximal centrale fuse to form astragalus

                       --bony jointed digits


16C.  Mammal Ancestor. Therapsids

       Organization

--collagen

                       --calcified internal skeleton derived from embryonic mesoderm tissue

                       --cartilage

                       --teeth composed of dentin and enamel

                                       --tooth replacement

                                       --teeth with a central pulp cavity

                                       --teeth located in grooves in skull bones

                                       --different kinds of teeth

                                                       --canine enlarges

                                       --reduction in number of postcanine teeth

--reduction in number of incisors (6 in first known cynodont, Dvinia; 4 in Procynoschus)

--increased complexity of postcanine teeth

                       --bone

                       --bone forms first in head region; rest of skeleton cartilaginous

       Axial Skeleton      

                       --palate covered in dermal bone

                       --braincase more completely ossified

                                --teeth from Meckel’s cartilage and palatoquadrate lost

--Skull

                         --reduction in the number of skull bones

                         --skull deeper

                         --larger posterior portion of skull

                --cartilage in cranium (chondrocranium)

                                --tighter junctions between elements, less mobility of snout

                       --splanchnocranium supports the roof of the pharynx

                       --dermatocranium

--elements joined together more solidly; joined to braincase

                                       --solid attachment of skull to cheek

                       --jaws

                                       --upper jaw fuses to braincase

                                       --stronger, greater pressure possible

                       --hyoid

                       --the synapsid temporal opening

                                       --temporal opening widens

--Braincase

                --Frontal (2)

                                --forms part of orbit

                --Parietal (2)

                --(Occipital)

                                --occipital region solidifies

                                --Supraoccipital

--supraoccipital and paraoccipital processes support squamosal

                                --Exoccipital

                                --Basioccipital 

                                --Postparietal reduced

                                --Tabular reduced

                --(Temporal)

                                --Prootic  (forms petrosal with Opisthotic)

                                --Epiotic (becomes Opisthotic in amphibians)

                                --Angular

                                --Pterygoid

                                                --transverse phlange of pterygoid

                                --Squamosal

                --(Sphenoid)

                                --Sphenethmoid

                                --Orbitosphenoid

                                --Basisphenoid

                                                --joint between basisphenoid and pterygoid solidifies

                                --Epipterygoid (becomes alisphenoid in mammals)

--epipterygoid and quadrate only portions of palatoquadrate retained

                                --Parasphenoid ?

                --(Ethmoid)

                                --Mesethmoid

                                --Turbinals

--Face

                --Vomers

                                --2 vomers fuse (still unfused in Dvinia, the earliest cynodont)

                --Palantine

                --Jugal (Zygomatic)

                --Nasal

                --Maxillary

                --Premaxillary (fuses to maxillary in humans)

                --Lower Jaw

                                --angular reflected

                                --jaw joint moves anteriorly

--Auditory Ossicles

                                --Stapes (Hyomandibula in bony fish)

                                                --Hyomandibular no longer a jaw support

                                                --smaller; rests on quadrate

--Articular (Meckel’s cartilage in sharks; becomes malleus in mammals)

--Quadrate (incus in mammals)

--[Hyoid]

                --Basihyal

                --Ceratohyal

                --Epibranchial

                --Ceratobranchial

                --Hypobranchial

--Bones Which were Lost in Human Lineage

                --Extrascapular lost (medial and lateral)

                --Opercular lost

                --Preopercular lost

                --Subopercular lost

                --Submandibular

                --Interhyal [lost in amphibians]

                --Pharyngobranchial [lost in amphibians]

                --Hypohyal [lost in reptiles]

                --Prefrontal

                --Postfrontal

                --Postorbital

                --Intertemporal

                --Supratemporal lost

                --Quadratojugal

                --Septomaxilla

                --Sphenotic

                --Pleurosphenoid [lost in mammals]

                --Extracolumella (Symplectic) [lost in mammals]

                --Coronoids [lost in mammals]

                --Prearticular [lost in mammals]

                --Surangular [lost in mammals]

                --Splenials [lost in mammals]

                --Dermohyal

            --Vertebrae

                       --parts of vertebrae fuse

                       --paired neural arches over notochord

                                       --well developed zygapophyses linking neural arches

                       --pleurocentra

                                       --pleurocentra predominate in vertebral centrum

                       --intercentra

                                       --reduced

                                       --lost in trunk

                       --hemal spine

                       --sacrum

                                       --loss of sacral ribs

                                       --sacrum attached to pelvis

                                       --becomes stronger

                       --atlas and axis

                       --enlarged neural spines and transverse processes for muscle attachment

                       --tail shorter

                       --vertebral column no longer capable of undulating laterally as in reptiles

            --Thorax

                       --ribs

                                       --ribs stronger and directed ventrally

                                       --shoulder girdle separated from skull creating a neck

                                       --true ribs contact sternum

                                       --shorter ribs on anterior caudal vertebrae

       Appendicular Skeleton

                       --paired pectoral and pelvic fins

                       --lateral halves of girdles fuse

                       --weight bearing girdles

                       --ball and socket joints between each girdle and first endoskeletal element of fin/limb

                       --limbs longer

                       --length of phalanges reduced

                       --gait more erect but can still sprawl; ankle accommodates both

            --Pectoral Girdle and Fin

                       --scapulocoracoid

                       --cleithrum

                                       --reduced to a very thin bone

                       --supracleithrum lost

                       --anocleithrum lost

                       --clavicle

                                       --reduced

                       --interclavicle

                       --humerus

                                       --becomes a narrow shaft

                                       --supinator process—on humerus?

                       --radius

                       --ulna

                       --carpal bones

                       --wrist joint

                       --bony jointed digits

            --Pelvic Girdle and Fin

                       --pelvis

                                       --composed of three bones: ilium, ischium, pubis

                                       --ilium expanded

                                       --obturator foramen

                       --femur

                                       --head more medial

                                       --2 trochanters

                       --tibia

                       --fibula

                       --ankle joint

                                       --fibulare enlarges; becomes calcaneum

                                       --tibiale, intermedium, and proximal centrale fuse to form astragalus

                       --bony jointed digits


16D.  Mammal Ancestor: Early Cynodont (Procynosuchus-like)

 

1)       Skeletal System

       Organization

--collagen

                       --calcified internal skeleton derived from embryonic mesoderm tissue

                       --cartilage

                       --teeth composed of dentin and enamel

                                       --tooth replacement

                                       --teeth with a central pulp cavity

                                       --teeth located in grooves in skull bones

                                       --different kinds of teeth

                                                       --canine enlarges

                                       --reduction in number of postcanine teeth

                       --bone

                       --bone forms first in head region; rest of skeleton cartilaginous

       Axial Skeleton      

                       --palate covered in dermal bone

                       --braincase more completely ossified

                                --teeth from Meckel’s cartilage and palatoquadrate lost

--Skull

                         --reduction in the number of skull bones

                         --skull deeper

                         --larger posterior portion of skull

                --cartilage in cranium (chondrocranium)

                                --tighter junctions between elements, less mobility of snout

                       --splanchnocranium supports the roof of the pharynx

                       --dermatocranium

--elements joined together more solidly; joined to braincase

                                       --solid attachment of skull to cheek

                       --jaws

                                       --upper jaw fuses to braincase

                                       --stronger, greater pressure possible

                       --hyoid

                       --the synapsid temporal opening

                                       --temporal opening widens

--Braincase

                --Frontal (2)

                                --forms part of orbit

                --Parietal (2)

                --(Occipital)

                                --occipital region solidifies

                                --Supraoccipital

--supraoccipital and paraoccipital processes support squamosal

                                --Exoccipital

                                --Basioccipital 

                                --Postparietal reduced

                                --Tabular reduced

                --(Temporal)

                                --Prootic  (forms petrosal with Opisthotic)

                                --Epiotic (becomes Opisthotic in amphibians)

                                --Angular

                                --Pterygoid

                                                --transverse phlange of pterygoid

                                --Squamosal

                --(Sphenoid)

                                --Sphenethmoid

                                --Orbitosphenoid

                                --Basisphenoid

                                                --joint between basisphenoid and pterygoid solidifies

                                --Epipterygoid (becomes alisphenoid in mammals)

--epipterygoid and quadrate only portions of palatoquadrate retained

                                --Parasphenoid ?

                --(Ethmoid)

                                --Mesethmoid

                                --Turbinals

--Face

                --Vomers

                --Palantine

                                --fuse at midline, creating secondary palate

                --Jugal (Zygomatic)

                --Nasal

                --Maxillary

                --Premaxillary (fuses to maxillary in humans)

                --Lower Jaw

                                --angular reflected

                                --jaw joint moves anteriorly

--Auditory Ossicles

                                --Stapes (Hyomandibula in bony fish)

                                                --Hyomandibular no longer a jaw support

                                                --smaller; rests on quadrate

--Articular (Meckel’s cartilage in sharks; becomes malleus in mammals)

--Quadrate (incus in mammals)

--[Hyoid]

                --Basihyal

                --Ceratohyal

                --Epibranchial

                --Ceratobranchial

                --Hypobranchial

--Bones Which were Lost in Human Lineage

                --Extrascapular lost (medial and lateral)

                --Opercular lost

                --Preopercular lost

                --Subopercular lost

                --Submandibular

                --Interhyal [lost in amphibians]

                --Pharyngobranchial [lost in amphibians]

                --Hypohyal [lost in reptiles]

                --Prefrontal

                --Postfrontal

                --Postorbital

                --Intertemporal

                --Supratemporal lost

                --Quadratojugal

                --Septomaxilla

                --Sphenotic

                --Pleurosphenoid [lost in mammals]

                --Extracolumella (Symplectic) [lost in mammals]

                --Coronoids [lost in mammals]

                --Prearticular [lost in mammals]

                --Surangular [lost in mammals]

                --Splenials [lost in mammals]

                --Dermohyal

            --Vertebrae

                       --parts of vertebrae fuse

                       --paired neural arches over notochord

                                       --well developed zygapophyses linking neural arches

                       --pleurocentra

                                       --pleurocentra predominate in vertebral centrum

                       --intercentra

                                       --reduced

                                       --lost in trunk

                       --hemal spine

                       --sacrum

                                       --loss of sacral ribs

                                       --sacrum attached to pelvis

                                       --becomes stronger

                       --atlas and axis

                       --enlarged neural spines and transverse processes for muscle attachment

                       --tail shorter

                       --vertebral column no longer capable of undulating laterally as in reptiles

            --Thorax

                       --ribs

                                       --ribs stronger and directed ventrally

                                       --shoulder girdle separated from skull creating a neck

                                       --true ribs contact sternum

                                       --shorter ribs on anterior caudal vertebrae

--lumbar ribs reduced and attached to vertebrae; no movement between rib and vertebrae

--two heads of thoracic ribs fuse to form head and capitulum

       Appendicular Skeleton

                       --paired pectoral and pelvic fins

                       --lateral halves of girdles fuse

                       --weight bearing girdles

                       --ball and socket joints between each girdle and first endoskeletal element of fin/limb

                       --limbs longer

                       --length of phalanges reduced

                       --gait more erect but can still sprawl; ankle accommodates both

            --Pectoral Girdle and Fin

                       --scapulocoracoid

                       --cleithrum

                                       --reduced to a very thin bone

                       --supracleithrum lost

                       --anocleithrum lost

                       --clavicle

                                       --reduced

                       --interclavicle

                       --humerus

                                       --becomes a narrow shaft

                                       --supinator process—on humerus?

                       --radius

                       --ulna

                       --carpal bones

                       --wrist joint

                       --bony jointed digits

            --Pelvic Girdle and Fin

                       --pelvis

                                       --composed of three bones: ilium, ischium, pubis

                                       --ilium expanded

                                       --obturator foramen

                       --femur

                                       --head more medial

                                       --2 trochanters

                       --tibia

                       --fibula

                       --ankle joint

                                       --fibulare enlarges; becomes calcaneum

                                       --tibiale, intermedium, and proximal centrale fuse to form astragalus

                                --bony jointed digits

 

16E.  Mammal Ancestor: Cynodont (Thrinaxodon-like)

1)       Skeletal System

       Organization

--collagen

                       --calcified internal skeleton derived from embryonic mesoderm tissue

                       --cartilage

                       --teeth composed of dentin and enamel

                                       --tooth replacement

                                       --teeth with a central pulp cavity

                                       --teeth located in grooves in skull bones

                                       --different kinds of teeth

                                                       --canine enlarges

                                       --reduction in number of postcanine teeth

--mammalian tooth formula with 4 upper and 3 lower incisors; canines, and 7-9 compressed cheek teeth with cusps

                       --bone

                       --bone forms first in head region; rest of skeleton cartilaginous

       Axial Skeleton      

                       --palate covered in dermal bone

                       --braincase more completely ossified

                                --teeth from Meckel’s cartilage and palatoquadrate lost

--Skull

                         --reduction in the number of skull bones

                         --skull deeper

                         --larger posterior portion of skull

                --cartilage in cranium (chondrocranium)

                                --tighter junctions between elements, less mobility of snout

                       --splanchnocranium supports the roof of the pharynx

                       --dermatocranium

--elements joined together more solidly; joined to braincase

                                       --solid attachment of skull to cheek

                       --jaws

                                       --upper jaw fuses to braincase

                                       --stronger, greater pressure possible

                       --hyoid

                       --the synapsid temporal opening

                                       --temporal opening widens

--Braincase

                --Frontal (2)

                                --forms part of orbit

                --Parietal (2)

                --(Occipital)

                                --occipital region solidifies

                                --2 occipital condyles (as opposed to 1 in reptiles)

                                --Supraoccipital

--supraoccipital and paraoccipital processes support squamosal

                                --Exoccipital

                                --Basioccipital 

                                --Postparietal reduced

                                --Tabular reduced

                --(Temporal)

                                --Prootic  (forms petrosal with Opisthotic)

                                --Epiotic (becomes Opisthotic in amphibians)

                                --Angular

                                --Pterygoid

                                                --transverse phlange of pterygoid

                                --Squamosal

                --(Sphenoid)

                                --Sphenethmoid

                                --Orbitosphenoid

                                --Basisphenoid

                                                --joint between basisphenoid and pterygoid solidifies

                                --Epipterygoid (becomes alisphenoid in mammals)

--epipterygoid and quadrate only portions of palatoquadrate retained

                                --Parasphenoid ?

                --(Ethmoid)

                                --Mesethmoid

                                --Turbinals

--Face

                --Vomers

                                --fused

                --Palantine

                                --fuse at midline, creating secondary palate

                --Jugal (Zygomatic)

                --Nasal

                --Maxillary

                --Premaxillary (fuses to maxillary in humans)

                --Lower Jaw

                                --angular reflected

                                --jaw joint moves anteriorly

                                --dentary becomes predominant bone

--Auditory Ossicles

                                --Stapes (Hyomandibula in bony fish)

                                                --Hyomandibular no longer a jaw support

                                                --smaller; rests on quadrate

--Articular (Meckel’s cartilage in sharks; becomes malleus in mammals)

--Quadrate (incus in mammals)

--[Hyoid]

                --Basihyal

                --Ceratohyal

                --Epibranchial

                --Ceratobranchial

                --Hypobranchial

--Bones Which were Lost in Human Lineage

                --Extrascapular lost (medial and lateral)

                --Opercular lost

                --Preopercular lost

                --Subopercular lost

                --Submandibular

                --Interhyal [lost in amphibians]

                --Pharyngobranchial [lost in amphibians]

                --Hypohyal [lost in reptiles]

                --Prefrontal

                --Postfrontal

                --Postorbital

                --Intertemporal

                --Supratemporal lost

                --Quadratojugal

                --Septomaxilla

                --Sphenotic

                --Pleurosphenoid [lost in mammals]

                --Extracolumella (Symplectic) [lost in mammals]

                --Coronoids [lost in mammals]

                --Prearticular [lost in mammals]

                --Surangular [lost in mammals]

                --Splenials [lost in mammals]

                --Dermohyal

            --Vertebrae

                       --parts of vertebrae fuse

                       --paired neural arches over notochord

                                       --well developed zygapophyses linking neural arches

                       --pleurocentra

                                       --pleurocentra predominate in vertebral centrum

                       --intercentra

                                       --reduced

                                       --lost in trunk

                       --hemal spine

                       --sacrum

                                       --loss of sacral ribs

                                       --sacrum attached to pelvis

                                       --becomes stronger

                       --atlas and axis

                                       --pleurocentrum of atlas attached to axis (but still a suture)

                       --enlarged neural spines and transverse processes for muscle attachment

                       --tail shorter

                       --vertebral column no longer capable of undulating laterally as in reptiles

                       --distinct thoracic and lumbar regions

                       --7 cervical vertebrae (as in most mammals)

                       --tail shorter

            --Thorax

                       --ribs

                                       --ribs stronger and directed ventrally

                                       --shoulder girdle separated from skull creating a neck

                                       --true ribs contact sternum

                                       --shorter ribs on anterior caudal vertebrae

--lumbar ribs reduced and attached to vertebrae; no movement between rib and vertebrae

--two heads of thoracic ribs fuse to form head and capitulum

       Appendicular Skeleton

                       --paired pectoral and pelvic fins

                       --lateral halves of girdles fuse

                       --weight bearing girdles

                       --ball and socket joints between each girdle and first endoskeletal element of fin/limb

                       --limbs longer

                       --length of phalanges reduced

                       --gait more erect

            --Pectoral Girdle and Fin

                       --scapulocoracoid

                       --cleithrum

                                       --reduced to a very thin bone

                       --supracleithrum lost

                       --anocleithrum lost

                       --clavicle

                                       --reduced

                       --interclavicle

                       --humerus

                                       --becomes a narrow shaft

                                       --supinator process—on humerus?

                       --radius

                       --ulna

                       --carpal bones

                       --wrist joint

                       --bony jointed digits

            --Pelvic Girdle and Fin

                       --pelvis

                                       --composed of three bones: ilium, ischium, pubis

                                       --ilium expanded

                                       --pubis reduced

                                       --obturator foramen

                       --femur

                                       --head more medial

                                       --2 trochanters

                       --tibia

                       --fibula

                       --ankle joint

                                       --fibulare enlarges; becomes calcaneum

                                       --tibiale, intermedium, and proximal centrale fuse to form astragalus

                       --bony jointed digits


16F: Mammal Ancestor: Advanced Cynodont

1)       Skeletal System

       Organization

--collagen

                       --calcified internal skeleton derived from embryonic mesoderm tissue

                       --cartilage

                       --teeth composed of dentin and enamel

                                       --tooth replacement

                                       --teeth with a central pulp cavity

                                       --teeth located in grooves in skull bones

                                       --different kinds of teeth

                                                       --canine enlarges

                                       --reduction in number of postcanine teeth

--mammalian tooth formula with 4 upper and 3 lower incisors; canines, and 7-9 compressed cheek teeth with cusps

--tooth occlusion (upper and lower teeth contact each other and have matching surfaces)

                       --bone

                       --bone forms first in head region; rest of skeleton cartilaginous

       Axial Skeleton      

                       --palate covered in dermal bone

                       --braincase more completely ossified

                                --teeth from Meckel’s cartilage and palatoquadrate lost

--Skull

                         --reduction in the number of skull bones

                         --skull deeper

                         --larger posterior portion of skull

                --cartilage in cranium (chondrocranium)

                                --tighter junctions between elements, less mobility of snout

                       --splanchnocranium supports the roof of the pharynx

                       --dermatocranium

--elements joined together more solidly; joined to braincase

                                       --solid attachment of skull to cheek

                       --jaws

                                       --upper jaw fuses to braincase

                                       --stronger, greater pressure possible

                       --hyoid

                       --the synapsid temporal opening

                                       --temporal opening widens

--Braincase

                --Frontal (2)

                                --forms part of orbit

--expanded ventrally and contacts palantine (in most advanced cynodonts)

                --Parietal (2)

                --(Occipital)

                                --occipital region solidifies

                                --2 occipital condyles (as opposed to 1 in reptiles)

                                --Supraoccipital

--supraoccipital and paraoccipital processes support squamosal

                                --Exoccipital

                                --Basioccipital 

                                --Postparietal reduced

                                --Tabular reduced

                --(Temporal)

                                --Prootic  (forms petrosal with Opisthotic)

                                                --prootic becomes periotic

                                                --fenestra ovalis located within periotic

                                --Epiotic (becomes Opisthotic in amphibians)

                                --Angular

                                --Pterygoid

                                                --transverse phlange of pterygoid

                                                --reduced laterally

                                --Squamosal

                                                --the mammalian jaw joint between squamosal and dentary

                --(Sphenoid)

                                --Sphenethmoid

                                --Orbitosphenoid

                                --Basisphenoid

                                                --joint between basisphenoid and pterygoid solidifies

                                --Epipterygoid becomes alisphenoid

--epipterygoid and quadrate only portions of palatoquadrate retained

                                --Parasphenoid ?

                --(Ethmoid)

                                --Mesethmoid

                                --Turbinals

--Face

                --Vomers

                                --fused

                --Palantine

                                --fuse at midline, creating secondary palate

                                --secondary palate extends to same point as in mammals

                --Jugal (Zygomatic)

                --Nasal

                --Maxillary

                --Premaxillary (fuses to maxillary in humans)

                --Lower Jaw

                                --angular reflected

                                                --supports tympanum

                                --jaw joint moves anteriorly

                                --dentary becomes predominant bone

                                                --high coronoid process

                                                --deep fossa for masseter muscle

--Auditory Ossicles

                                --Stapes (Hyomandibula in bony fish)

                                                --Hyomandibular no longer a jaw support

                                                --smaller; rests on quadrate

--Articular (Meckel’s cartilage in sharks; becomes malleus in mammals)

--Quadrate (incus in mammals)

--[Hyoid]

                --Basihyal

                --Ceratohyal

                --Epibranchial

                --Ceratobranchial

                --Hypobranchial

--Bones Which were Lost in Human Lineage

                --Extrascapular lost (medial and lateral)

                --Opercular lost

                --Preopercular lost

                --Subopercular lost

                --Submandibular

                --Interhyal [lost in amphibians]

                --Pharyngobranchial [lost in amphibians]

                --Hypohyal [lost in reptiles]

                --Prefrontal lost

                --Postfrontal

                --Postorbital lost

                                --lose postorbital bar

                --Intertemporal

                --Supratemporal lost

                --Quadratojugal

                --Septomaxilla

                --Sphenotic

                --Pleurosphenoid [lost in mammals]

                --Extracolumella (Symplectic) [lost in mammals]

                --Coronoids [lost in mammals]

                --Prearticular [lost in mammals]

                --Surangular [lost in mammals]

                --Splenials [lost in mammals]

                --Dermohyal

            --Vertebrae

                       --parts of vertebrae fuse

                       --paired neural arches over notochord

                                       --well developed zygapophyses linking neural arches

                       --pleurocentra

                                       --pleurocentra predominate in vertebral centrum

                       --intercentra

                                       --reduced

                                       --lost in trunk

                       --hemal spine

                       --sacrum

                                       --loss of sacral ribs

                                       --sacrum attached to pelvis

                                       --becomes stronger

                       --atlas and axis

                                       --pleurocentrum of atlas attached to axis (but still a suture)

                       --enlarged neural spines and transverse processes for muscle attachment

                       --tail shorter

                       --vertebral column no longer capable of undulating laterally as in reptiles

                       --distinct thoracic and lumbar regions

                       --7 cervical vertebrae (as in most mammals)

                       --tail shorter

            --Thorax

                       --ribs

                                       --ribs stronger and directed ventrally

                                       --shoulder girdle separated from skull creating a neck

                                       --true ribs contact sternum

                                       --shorter ribs on anterior caudal vertebrae

--lumbar ribs reduced and attached to vertebrae; no movement between rib and vertebrae

--two heads of thoracic ribs fuse to form head and capitulum

       Appendicular Skeleton

                       --paired pectoral and pelvic fins

                       --lateral halves of girdles fuse

                       --weight bearing girdles

                       --ball and socket joints between each girdle and first endoskeletal element of fin/limb

                       --limbs longer

                       --length of phalanges reduced

                       --gait more erect

            --Pectoral Girdle and Fin

                       --scapulocoracoid

                       --cleithrum

                                       --reduced to a very thin bone

                       --supracleithrum lost

                       --anocleithrum lost

                       --coracoid bones reduced

                       --clavicle

                                       --reduced

                       --interclavicle

                       --humerus

                                       --becomes a narrow shaft

                                       --supinator process—on humerus?

                       --radius

                       --ulna

                       --carpal bones

                       --wrist joint

                       --bony jointed digits

            --Pelvic Girdle and Fin

                       --pelvis

                                       --composed of three bones: ilium, ischium, pubis

                                       --ilium expanded

                                       --pubis reduced

                                       --obturator foramen

                                       --takes on mammalian form (although three bones unfused)

                       --femur

                                       --head more medial

                                       --2 trochanters

                       --tibia

                       --fibula

                       --ankle joint

                                       --fibulare enlarges; becomes calcaneum

                                       --tibiale, intermedium, and proximal centrale fuse to form astragalus

                       --bony jointed digits


 

 

19) ANCESTRAL PLACENTAL MAMMAL (included here are traits which insectivores and dermopterans share with primates)

 

       Organization

--collagen

                       --calcified internal skeleton derived from embryonic mesoderm tissue

                       --cartilage

                       --teeth composed of dentin and enamel

                                       --tooth replacement

                                       --teeth with a central pulp cavity

                                       --teeth located in grooves in skull bones

                                       --different kinds of teeth

                                                       --canine enlarges

                                       --reduction in number of postcanine teeth

--mammalian tooth formula with 4 upper and 3 lower incisors; canines, and 7-9 compressed cheek teeth with cusps

--tooth occlusion (upper and lower teeth contact each other and have matching surfaces)

                       --bone

                       --bone forms first in head region; rest of skeleton cartilaginous

       Axial Skeleton      

                       --palate covered in dermal bone

                       --braincase more completely ossified

                                --teeth from Meckel’s cartilage and palatoquadrate lost

--Skull

                         --reduction in the number of skull bones

                         --skull deeper

                         --larger posterior portion of skull

                         --orbits encircled by bone

                --cartilage in cranium (chondrocranium)

                                --tighter junctions between elements, less mobility of snout

                       --splanchnocranium supports the roof of the pharynx

                       --dermatocranium

--elements joined together more solidly; joined to braincase

                                       --solid attachment of skull to cheek

                       --jaws

                                       --upper jaw fuses to braincase

                                       --stronger, greater pressure possible

                       --hyoid

                       --the synapsid temporal opening

                                       --temporal opening widens

                       --bone growth stops when adult size is reached

--Braincase

                --Frontal (2)

                                --forms part of orbit

--expanded ventrally and contacts palantine (in most advanced cynodonts)

                --Parietal (2)

                --(Occipital)

                                --occipital region solidifies

                                --occipital bone forms

                                --2 occipital condyles (as opposed to 1 in reptiles)

                                --Supraoccipital

--supraoccipital and paraoccipital processes support squamosal

                                --Exoccipital

                                --Basioccipital 

                                --Postparietal reduced

                                --Tabular reduced

                --(Temporal)

                                --Prootic  (forms petrosal with Opisthotic)

                                                --prootic becomes periotic

                                                --fenestra ovalis located within periotic

                                --Epiotic (becomes Opisthotic in amphibians)

                                --Angular

                                --Pterygoid

                                                --transverse phlange of pterygoid

                                                --reduced laterally

                                --Squamosal

                                                --the mammalian jaw joint between squamosal and dentary

                                --Petrosal Bulla

                --(Sphenoid)

                                --sphenoid forms

                                --Sphenethmoid

                                --Orbitosphenoid

                                --Basisphenoid

                                                --joint between basisphenoid and pterygoid solidifies

                                --Epipterygoid becomes alisphenoid

--epipterygoid and quadrate only portions of palatoquadrate retained

                                --Parasphenoid ?

                --(Ethmoid)

                                --Mesethmoid

                                --Turbinals

--Face

                --Vomers

                                --fused

                --Palantine

                                --fuse at midline, creating secondary palate

                                --secondary palate extends to same point as in mammals

                --Jugal (Zygomatic)

                --Nasal

                --Maxillary

                --Premaxillary (fuses to maxillary in humans)

                --Lower Jaw

                                --angular reflected

                                                --supports tympanum

                                --jaw joint moves anteriorly

                                --dentary becomes predominant bone

                                                --high coronoid process

                                                --deep fossa for masseter muscle

--Auditory Ossicles

                                --Stapes (Hyomandibula in bony fish)

                                                --Hyomandibular no longer a jaw support

                                                --smaller; rests on quadrate

--Articular (Meckel’s cartilage in sharks; becomes malleus in mammals)

--Quadrate (incus in mammals)

--[Hyoid]

                --Basihyal

                --Ceratohyal

                --Epibranchial

                --Ceratobranchial

                --Hypobranchial

--Bones Which were Lost in Human Lineage

                --Extrascapular lost (medial and lateral)

                --Opercular lost

                --Preopercular lost

                --Subopercular lost

                --Submandibular

                --Interhyal [lost in amphibians]

                --Pharyngobranchial [lost in amphibians]

                --Hypohyal [lost in reptiles]

                --Prefrontal lost

                --Postfrontal

                --Postorbital lost

                                --lose postorbital bar

                --Intertemporal

                --Supratemporal lost

                --Quadratojugal

                --Septomaxilla

                --Sphenotic

                --Pleurosphenoid [lost in mammals]

                --Extracolumella (Symplectic) [lost in mammals]

                --Coronoids [lost in mammals]

                --Prearticular [lost in mammals]

                --Surangular [lost in mammals]

                --Splenials [lost in mammals]

                --Dermohyal

            --Vertebrae

                       --parts of vertebrae fuse

                       --paired neural arches over notochord

                                       --well developed zygapophyses linking neural arches

                       --pleurocentra

                                       --pleurocentra predominate in vertebral centrum

                       --intercentra

                                       --reduced

                                       --lost except for atlas; perhaps contribute to capitulum of ribs

                       --hemal spine

                       --sacrum

                                       --loss of sacral ribs

                                       --sacrum attached to pelvis

                                       --becomes stronger

                       --atlas and axis

                                       --pleurocentrum of atlas attached to axis (but still a suture)

                       --enlarged neural spines and transverse processes for muscle attachment

                       --tail shorter

                       --vertebral column no longer capable of undulating laterally as in reptiles

                       --distinct thoracic and lumbar regions

                       --7 cervical vertebrae (as in most mammals)

                       --tail shorter

            --Thorax

                       --ribs

                                       --ribs stronger and directed ventrally

                                       --shoulder girdle separated from skull creating a neck

                                       --true ribs contact sternum

                                       --shorter ribs on anterior caudal vertebrae

--lumbar ribs reduced and attached to vertebrae; no movement between rib and vertebrae

--two heads of thoracic ribs fuse to form head and capitulum

                                --sternum (arose independently in other amniotes)

       Appendicular Skeleton

                       --paired pectoral and pelvic fins

                       --lateral halves of girdles fuse

                       --weight bearing girdles

                       --ball and socket joints between each girdle and first endoskeletal element of fin/limb

                       --limbs longer

                       --length of phalanges reduced

                       --gait more erect

            --Pectoral Girdle and Fin

                       --scapulocoracoid

                       --cleithrum

                                       --reduced to a very thin bone

                       --supracleithrum lost

                       --anocleithrum lost

                       --coracoid bones reduced

                                       --anterior coracoid lost

                                       --posterior coracoid fuses to scapula

                       --clavicle

                                       --reduced

                       --interclavicle

                                       --lost

                       --humerus

                                       --becomes a narrow shaft

                                       --supinator process—on humerus?

                       --radius

                       --ulna

                       --carpal bones

                       --wrist joint

                       --bony jointed digits

            --Pelvic Girdle and Fin

                       --pelvis

                                       --composed of three bones: ilium, ischium, pubis

                                       --ilium expanded

                                       --pubis reduced

                                       --obturator foramen

                                       --takes on mammalian form (although three bones unfused)

                                       --fuses completely

                       --femur

                                       --head more medial

                                       --2 trochanters

                       --tibia

                       --fibula

                       --ankle joint

                                       --fibulare enlarges; becomes calcaneum

                                       --tibiale, intermedium, and proximal centrale fuse to form astragalus

                       --bony jointed digits

 

20) Primate Ancestor

1)       Skeletal System

       Organization

--collagen

                       --calcified internal skeleton derived from embryonic mesoderm tissue

                       --cartilage

                       --teeth composed of dentin and enamel

                                       --tooth replacement

                                       --teeth with a central pulp cavity

                                       --teeth located in grooves in skull bones

                                       --different kinds of teeth

                                                       --canine enlarges

                                       --reduction in number of postcanine teeth

--mammalian tooth formula with 4 upper and 3 lower incisors; canines, and 7-9 compressed cheek teeth with cusps

--tooth occlusion (upper and lower teeth contact each other and have matching surfaces)

--loss of third pair of incisors

--cheek teeth simple and low crowned

                       --bone

                       --bone forms first in head region; rest of skeleton cartilaginous

       Axial Skeleton      

                       --palate covered in dermal bone

                       --braincase more completely ossified

                                --teeth from Meckel’s cartilage and palatoquadrate lost

--Skull

                         --reduction in the number of skull bones

                         --skull deeper

                         --larger posterior portion of skull

                         --orbits encircled by bone

                --cartilage in cranium (chondrocranium)

                                --tighter junctions between elements, less mobility of snout

                       --splanchnocranium supports the roof of the pharynx

                       --dermatocranium

--elements joined together more solidly; joined to braincase

                                       --solid attachment of skull to cheek

                       --jaws

                                       --upper jaw fuses to braincase

                                       --stronger, greater pressure possible

                       --hyoid

                       --the synapsid temporal opening

                                       --temporal opening widens

                       --bone growth stops when adult size is reached

--Braincase

                --Frontal (2)

                                --forms part of orbit

--expanded ventrally and contacts palantine (in most advanced cynodonts)

                --Parietal (2)

                --(Occipital)

                                --occipital region solidifies

                                --occipital bone forms

                                --2 occipital condyles (as opposed to 1 in reptiles)

                                --Supraoccipital

--supraoccipital and paraoccipital processes support squamosal

                                --Exoccipital

                                --Basioccipital 

                                --Postparietal reduced

                                --Tabular reduced

                --(Temporal)

                                --Prootic  (forms petrosal with Opisthotic)

                                                --prootic becomes periotic

                                                --fenestra ovalis located within periotic

                                --Epiotic (becomes Opisthotic in amphibians)

                                --Angular

                                --Pterygoid

                                                --transverse phlange of pterygoid

                                                --reduced laterally

                                --Squamosal

                                                --the mammalian jaw joint between squamosal and dentary

                                --Petrosal Bulla

                --(Sphenoid)

                                --sphenoid forms

                                --Sphenethmoid

                                --Orbitosphenoid

                                --Basisphenoid

                                                --joint between basisphenoid and pterygoid solidifies

                                --Epipterygoid becomes alisphenoid

--epipterygoid and quadrate only portions of palatoquadrate retained

                                --Parasphenoid ?

                --(Ethmoid)

                                --Mesethmoid

                                --Turbinals

--Face

                --Vomers

                                --fused

                --Palantine

                                --fuse at midline, creating secondary palate

                                --secondary palate extends to same point as in mammals

                --Jugal (Zygomatic)

                --Nasal

                --Maxillary

                --Premaxillary (fuses to maxillary in humans)

                --Lower Jaw

                                --angular reflected

                                                --supports tympanum

                                --jaw joint moves anteriorly

                                --dentary becomes predominant bone

                                                --high coronoid process

                                                --deep fossa for masseter muscle

--Auditory Ossicles

                                --Stapes (Hyomandibula in bony fish)

                                                --Hyomandibular no longer a jaw support

                                                --smaller; rests on quadrate

--Articular (Meckel’s cartilage in sharks; becomes malleus in mammals)

--Quadrate (incus in mammals)

--[Hyoid]

                --Basihyal

                --Ceratohyal

                --Epibranchial

                --Ceratobranchial

                --Hypobranchial

--Bones Which were Lost in Human Lineage

                --Extrascapular lost (medial and lateral)

                --Opercular lost

                --Preopercular lost

                --Subopercular lost

                --Submandibular

                --Interhyal [lost in amphibians]

                --Pharyngobranchial [lost in amphibians]

                --Hypohyal [lost in reptiles]

                --Prefrontal lost

                --Postfrontal

                --Postorbital lost

                                --lose postorbital bar

                --Intertemporal

                --Supratemporal lost

                --Quadratojugal

                --Septomaxilla

                --Sphenotic

                --Pleurosphenoid [lost in mammals]

                --Extracolumella (Symplectic) [lost in mammals]

                --Coronoids [lost in mammals]

                --Prearticular [lost in mammals]

                --Surangular [lost in mammals]

                --Splenials [lost in mammals]

                --Dermohyal

            --Vertebrae

                       --parts of vertebrae fuse

                       --paired neural arches over notochord

                                       --well developed zygapophyses linking neural arches

                       --pleurocentra

                                       --pleurocentra predominate in vertebral centrum

                       --intercentra

                                       --reduced

                                       --lost except for atlas; perhaps contribute to capitulum of ribs

                       --hemal spine

                       --sacrum

                                       --loss of sacral ribs

                                       --sacrum attached to pelvis

                                       --becomes stronger

                       --atlas and axis

                                       --pleurocentrum of atlas attached to axis (but still a suture)

                       --enlarged neural spines and transverse processes for muscle attachment

                       --tail shorter

                       --vertebral column no longer capable of undulating laterally as in reptiles

                       --distinct thoracic and lumbar regions

                       --7 cervical vertebrae (as in most mammals)

                       --tail shorter

            --Thorax

                       --ribs

                                       --ribs stronger and directed ventrally

                                       --shoulder girdle separated from skull creating a neck

                                       --true ribs contact sternum

                                       --shorter ribs on anterior caudal vertebrae

--lumbar ribs reduced and attached to vertebrae; no movement between rib and vertebrae

--two heads of thoracic ribs fuse to form head and capitulum

                                --sternum (arose independently in other amniotes)

       Appendicular Skeleton

                       --paired pectoral and pelvic fins

                       --lateral halves of girdles fuse

                       --weight bearing girdles

                       --ball and socket joints between each girdle and first endoskeletal element of fin/limb

                       --limbs longer

                       --length of phalanges reduced

                       --gait more erect

                       --grasping hands and feet

            --Pectoral Girdle and Fin

                       --scapulocoracoid

                       --cleithrum

                                       --reduced to a very thin bone

                       --supracleithrum lost

                       --anocleithrum lost

                       --coracoid bones reduced

                                       --anterior coracoid lost

                                       --posterior coracoid fuses to scapula

                       --clavicle

                                       --reduced

                       --interclavicle

                                       --lost

                       --humerus

                                       --becomes a narrow shaft

                                       --supinator process—on humerus?

                       --radius

                       --ulna

                       --carpal bones

                       --wrist joint

                       --bony jointed digits

            --Pelvic Girdle and Fin

                       --pelvis

                                       --composed of three bones: ilium, ischium, pubis

                                       --ilium expanded

                                       --pubis reduced

                                       --obturator foramen

                                       --takes on mammalian form (although three bones unfused)

                                       --fuses completely

                       --femur

                                       --head more medial

                                       --2 trochanters

                       --tibia

                       --fibula

                       --ankle joint

                                       --fibulare enlarges; becomes calcaneum

                                       --tibiale, intermedium, and proximal centrale fuse to form astragalus

                       --bony jointed digits

 

 

21) Anthropoid Primate Ancestor (Monkeys and Apes)

1)       Skeletal System

       Organization

--collagen

                       --calcified internal skeleton derived from embryonic mesoderm tissue

                       --cartilage

                       --teeth composed of dentin and enamel

                                       --tooth replacement

                                       --teeth with a central pulp cavity

                                       --teeth located in grooves in skull bones

                                       --different kinds of teeth

                                                       --canine enlarges

                                       --reduction in number of postcanine teeth

--mammalian tooth formula with 4 upper and 3 lower incisors; canines, and 7-9 compressed cheek teeth with cusps

--tooth occlusion (upper and lower teeth contact each other and have matching surfaces)

--loss of third pair of incisors

--cheek teeth simple and low crowned

--loss of paraconid on lower molars

--incisors near each other; no rhinarium

                       --bone

                       --bone forms first in head region; rest of skeleton cartilaginous

       Axial Skeleton      

                       --palate covered in dermal bone

                       --braincase more completely ossified

                                --teeth from Meckel’s cartilage and palatoquadrate lost

--Skull

                         --reduction in the number of skull bones

                         --skull deeper

                         --larger posterior portion of skull

                         --orbits encircled by bone

                         --orbits closed posteriorly and posterolataterally

                --cartilage in cranium (chondrocranium)

                                --tighter junctions between elements, less mobility of snout

                       --splanchnocranium supports the roof of the pharynx

                       --dermatocranium

--elements joined together more solidly; joined to braincase

                                       --solid attachment of skull to cheek

                       --jaws

                                       --upper jaw fuses to braincase

                                       --stronger, greater pressure possible

                       --hyoid

                       --the synapsid temporal opening

                                       --temporal opening widens

                       --bone growth stops when adult size is reached

--Braincase

                --inner region of skull base rounder

                --postsellar region of skull base angled

                --Frontal (2)

                                --forms part of orbit

--expanded ventrally and contacts palantine (in most advanced cynodonts)

--2 frontal bones fuse

                --Parietal (2)

                --(Occipital)

                                --occipital region solidifies

                                --occipital bone forms

                                --2 occipital condyles (as opposed to 1 in reptiles)

                                --Supraoccipital

--supraoccipital and paraoccipital processes support squamosal

                                --Exoccipital

                                --Basioccipital 

                                --Postparietal reduced

                                --Tabular reduced

                --(Temporal)

                                --Prootic  (forms petrosal with Opisthotic)

                                                --prootic becomes periotic

                                                --fenestra ovalis located within periotic

                                --Epiotic (becomes Opisthotic in amphibians)

                                --Angular

                                --Pterygoid

                                                --transverse phlange of pterygoid

                                                --reduced laterally

                                --Squamosal

                                                --the mammalian jaw joint between squamosal and dentary

                                --Petrosal Bulla

                                --carotid foramen closer to ear and wider

                --(Sphenoid)

                                --sphenoid forms

                                --Sphenethmoid

                                --Orbitosphenoid

                                --Basisphenoid

                                                --joint between basisphenoid and pterygoid solidifies

                                --Epipterygoid becomes alisphenoid

--epipterygoid and quadrate only portions of palatoquadrate retained

                                --Parasphenoid ?

                --(Ethmoid)

                                --Mesethmoid

                                --Turbinals

                                --forms part of orbit

                                --2 pairs of ethmoid turbinals

--Face

                --Vomers

                                --fused

                --Palantine

                                --fuse at midline, creating secondary palate

                                --secondary palate extends to same point as in mammals

                                --forms part of orbit

                --Jugal (Zygomatic)

                --Nasal

                --Lacrimal

-- bones almost always confined to orbit, as is lacrimal canal

                --Maxillary

                --Premaxillary (fuses to maxillary in humans)

                --Lower Jaw

                                --angular reflected

                                                --supports tympanum

                                --jaw joint moves anteriorly

                                --dentary becomes predominant bone

                                                --high coronoid process

                                                --deep fossa for masseter muscle

                                --two halves of mandible fuse

                                --manidble U shaped (as opposed to V shaped)

--Auditory Ossicles

                                --Stapes (Hyomandibula in bony fish)

                                                --Hyomandibular no longer a jaw support

                                                --smaller; rests on quadrate

--Articular (Meckel’s cartilage in sharks; becomes malleus in mammals)

--Quadrate (incus in mammals)

--[Hyoid]

                --Basihyal

                --Ceratohyal

                --Epibranchial

                --Ceratobranchial

                --Hypobranchial

--Bones Which were Lost in Human Lineage

                --Extrascapular lost (medial and lateral)

                --Opercular lost

                --Preopercular lost

                --Subopercular lost

                --Submandibular

                --Interhyal [lost in amphibians]

                --Pharyngobranchial [lost in amphibians]

                --Hypohyal [lost in reptiles]

                --Prefrontal lost

                --Postfrontal

                --Postorbital lost

                                --lose postorbital bar

                --Intertemporal

                --Supratemporal lost

                --Quadratojugal

                --Septomaxilla

                --Sphenotic

                --Pleurosphenoid [lost in mammals]

                --Extracolumella (Symplectic) [lost in mammals]

                --Coronoids [lost in mammals]

                --Prearticular [lost in mammals]

                --Surangular [lost in mammals]

                --Splenials [lost in mammals]

                --Dermohyal

            --Vertebrae

                       --parts of vertebrae fuse

                       --paired neural arches over notochord

                                       --well developed zygapophyses linking neural arches

                       --pleurocentra

                                       --pleurocentra predominate in vertebral centrum

                       --intercentra

                                       --reduced

                                       --lost except for atlas; perhaps contribute to capitulum of ribs

                       --hemal spine

                       --sacrum

                                       --loss of sacral ribs

                                       --sacrum attached to pelvis

                                       --becomes stronger

                       --atlas and axis

                                       --pleurocentrum of atlas attached to axis (but still a suture)

                       --enlarged neural spines and transverse processes for muscle attachment

                       --tail shorter

                       --vertebral column no longer capable of undulating laterally as in reptiles

                       --distinct thoracic and lumbar regions

                       --7 cervical vertebrae (as in most mammals)

                       --tail shorter

            --Thorax

                       --ribs

                                       --ribs stronger and directed ventrally

                                       --shoulder girdle separated from skull creating a neck

                                       --true ribs contact sternum

                                       --shorter ribs on anterior caudal vertebrae

--lumbar ribs reduced and attached to vertebrae; no movement between rib and vertebrae

--two heads of thoracic ribs fuse to form head and capitulum

                                --sternum (arose independently in other amniotes)

       Appendicular Skeleton

                       --paired pectoral and pelvic fins

                       --lateral halves of girdles fuse

                       --weight bearing girdles

                       --ball and socket joints between each girdle and first endoskeletal element of fin/limb

                       --limbs longer

                       --length of phalanges reduced

                       --gait more erect

                       --grasping hands and feet

            --Pectoral Girdle and Fin

                       --scapulocoracoid

                       --cleithrum

                                       --reduced to a very thin bone

                       --supracleithrum lost

                       --anocleithrum lost

                       --coracoid bones reduced

                                       --anterior coracoid lost

                                       --posterior coracoid fuses to scapula

                       --clavicle

                                       --reduced

                       --interclavicle

                                       --lost

                       --humerus

                                       --becomes a narrow shaft

                                       --supinator process—on humerus?

                       --radius

                       --ulna

                       --carpal bones

                       --wrist joint

                       --bony jointed digits

            --Pelvic Girdle and Fin

                       --pelvis

                                       --composed of three bones: ilium, ischium, pubis

                                       --ilium expanded

                                       --pubis reduced

                                       --obturator foramen

                                       --takes on mammalian form (although three bones unfused)

                                       --fuses completely

                       --femur

                                       --head more medial

                                       --2 trochanters

                       --tibia

                       --fibula

                       --ankle joint

                                       --fibulare enlarges; becomes calcaneum

                                       --tibiale, intermedium, and proximal centrale fuse to form astragalus

                       --bony jointed digits

 

 

 


22. Catarrhine Primate Ancestor: Old World Monkeys and Apes

 

1)       Skeletal System

       Organization

--collagen

                       --calcified internal skeleton derived from embryonic mesoderm tissue

                       --cartilage

                       --teeth composed of dentin and enamel

                                       --tooth replacement

                                       --teeth with a central pulp cavity

                                       --teeth located in grooves in skull bones

                                       --different kinds of teeth

                                                       --canine enlarges

                                       --reduction in number of postcanine teeth

--mammalian tooth formula with 4 upper and 3 lower incisors; canines, and 7-9 compressed cheek teeth with cusps

--tooth occlusion (upper and lower teeth contact each other and have matching surfaces)

--loss of third pair of incisors

--cheek teeth simple and low crowned

--loss of paraconid on lower molars

--incisors near each other; no rhinarium

--4 cusps in all first and secondary molars  (also in one family of New World monkeys

--2 premolars

                       --bone

                       --bone forms first in head region; rest of skeleton cartilaginous

       Axial Skeleton      

                       --palate covered in dermal bone

                       --braincase more completely ossified

                                --teeth from Meckel’s cartilage and palatoquadrate lost

--Skull

                         --reduction in the number of skull bones

                         --skull deeper

                         --larger posterior portion of skull

                         --orbits encircled by bone

                         --orbits closed posteriorly and posterolataterally

                         --larger face

                --cartilage in cranium (chondrocranium)

                                --tighter junctions between elements, less mobility of snout

                       --splanchnocranium supports the roof of the pharynx

                       --dermatocranium

--elements joined together more solidly; joined to braincase

                                       --solid attachment of skull to cheek

                       --jaws

                                       --upper jaw fuses to braincase

                                       --stronger, greater pressure possible

                       --hyoid

                       --the synapsid temporal opening

                                       --temporal opening widens

                       --bone growth stops when adult size is reached

--Braincase

                --inner region of skull base rounder

                --postsellar region of skull base angled

                --Frontal (2)

                                --forms part of orbit

--expanded ventrally and contacts palantine (in most advanced cynodonts)

--2 frontal bones fuse

                --Parietal (2)

                --(Occipital)

                                --occipital region solidifies

                                --occipital bone forms

                                --2 occipital condyles (as opposed to 1 in reptiles)

                                --Supraoccipital

--supraoccipital and paraoccipital processes support squamosal

                                --Exoccipital

                                --Basioccipital 

                                --Postparietal reduced

                                --Tabular reduced

                --(Temporal)

                                --Prootic  (forms petrosal with Opisthotic)

                                                --prootic becomes periotic

                                                --fenestra ovalis located within periotic

                                --Epiotic (becomes Opisthotic in amphibians)

                                --Angular

                                --Pterygoid

                                                --transverse phlange of pterygoid

                                                --reduced laterally

                                --Squamosal

                                                --the mammalian jaw joint between squamosal and dentary

                                --Petrosal Bulla

                                --carotid foramen closer to ear and wider

                                --smaller petrosal

                                --external auditory meatus bony and elongate

                                --tympanic ring inside auditory meatus

                --(Sphenoid)

                                --sphenoid forms

                                --Sphenethmoid

                                --Orbitosphenoid

                                --Basisphenoid

                                                --joint between basisphenoid and pterygoid solidifies

                                --Epipterygoid becomes alisphenoid

--epipterygoid and quadrate only portions of palatoquadrate retained

                                --Parasphenoid ?

                --(Ethmoid)

                                --Mesethmoid

                                --Turbinals

                                --forms part of orbit

                                --2 pairs of ethmoid turbinals

--Face

                --Vomers

                                --fused

                                --septum narrow

                --Palantine

                                --fuse at midline, creating secondary palate

                                --secondary palate extends to same point as in mammals

                                --forms part of orbit

                --Jugal (Zygomatic)

                --Nasal

                                --nose bridge raised

                                --cartilaginous nasal wings closer together

--nostrils face frontwards; they open downwards and are closer                together

                --Lacrimal

-- bones almost always confined to orbit, as is lacrimal canal

                --Maxillary

                --Premaxillary (fuses to maxillary in humans)

                --Lower Jaw

                                --angular reflected

                                                --supports tympanum

                                --jaw joint moves anteriorly

                                --dentary becomes predominant bone

                                                --high coronoid process

                                                --deep fossa for masseter muscle

                                --two halves of mandible fuse

                                --manidble U shaped (as opposed to V shaped)

--Auditory Ossicles

                                --Stapes (Hyomandibula in bony fish)

                                                --Hyomandibular no longer a jaw support

                                                --smaller; rests on quadrate

--Articular (Meckel’s cartilage in sharks; becomes malleus in mammals)

--Quadrate (incus in mammals)

--[Hyoid]

                --Basihyal

                --Ceratohyal

                --Epibranchial

                --Ceratobranchial

                --Hypobranchial

--Bones Which were Lost in Human Lineage

                --Extrascapular lost (medial and lateral)

                --Opercular lost

                --Preopercular lost

                --Subopercular lost

                --Submandibular

                --Interhyal [lost in amphibians]

                --Pharyngobranchial [lost in amphibians]

                --Hypohyal [lost in reptiles]

                --Prefrontal lost

                --Postfrontal

                --Postorbital lost

                                --lose postorbital bar

                --Intertemporal

                --Supratemporal lost

                --Quadratojugal

                --Septomaxilla

                --Sphenotic

                --Pleurosphenoid [lost in mammals]

                --Extracolumella (Symplectic) [lost in mammals]

                --Coronoids [lost in mammals]

                --Prearticular [lost in mammals]

                --Surangular [lost in mammals]

                --Splenials [lost in mammals]

                --Dermohyal

            --Vertebrae

                       --parts of vertebrae fuse

                       --paired neural arches over notochord

                                       --well developed zygapophyses linking neural arches

                       --pleurocentra

                                       --pleurocentra predominate in vertebral centrum

                       --intercentra

                                       --reduced

                                       --lost except for atlas; perhaps contribute to capitulum of ribs

                       --hemal spine

                       --sacrum

                                       --loss of sacral ribs

                                       --sacrum attached to pelvis

                                       --becomes stronger

                       --atlas and axis

                                       --pleurocentrum of atlas attached to axis (but still a suture)

                       --enlarged neural spines and transverse processes for muscle attachment

                       --tail shorter

                       --vertebral column no longer capable of undulating laterally as in reptiles

                       --distinct thoracic and lumbar regions

                       --7 cervical vertebrae (as in most mammals)

                       --tail shorter

                       --12 thoracic vertebrae

                       --reduction in the number of caudal vertebrae (17 instead of 27-31)

            --Thorax

                       --ribs

                                       --ribs stronger and directed ventrally

                                       --shoulder girdle separated from skull creating a neck

                                       --true ribs contact sternum

                                       --shorter ribs on anterior caudal vertebrae

--lumbar ribs reduced and attached to vertebrae; no movement between rib and vertebrae

--two heads of thoracic ribs fuse to form head and capitulum

                                --sternum (arose independently in other amniotes)

       Appendicular Skeleton

                       --paired pectoral and pelvic fins

                       --lateral halves of girdles fuse

                       --weight bearing girdles

                       --ball and socket joints between each girdle and first endoskeletal element of fin/limb

                       --limbs longer

                       --length of phalanges reduced

                       --gait more erect

                       --grasping hands and feet

                       --opposable thumb

            --Pectoral Girdle and Fin

                       --scapulocoracoid

                       --cleithrum

                                       --reduced to a very thin bone

                       --supracleithrum lost

                       --anocleithrum lost

                       --coracoid bones reduced

                                       --anterior coracoid lost

                                       --posterior coracoid fuses to scapula

                       --clavicle

                                       --reduced

                       --interclavicle

                                       --lost

                       --humerus

                                       --becomes a narrow shaft

                                       --supinator process—on humerus?

                       --radius

                       --ulna

                       --carpal bones

                       --wrist joint

                       --bony jointed digits

            --Pelvic Girdle and Fin

                       --pelvis

                                       --composed of three bones: ilium, ischium, pubis

                                       --ilium expanded

                                       --pubis reduced

                                       --obturator foramen

                                       --takes on mammalian form (although three bones unfused)

                                       --fuses completely

                       --femur

                                       --head more medial

                                       --2 trochanters

                       --tibia

                       --fibula

                       --ankle joint

                                       --fibulare enlarges; becomes calcaneum

                                       --tibiale, intermedium, and proximal centrale fuse to form astragalus

                       --bony jointed digits


23. Ape Ancestor (traits of higher ape ancestors are highlighted in blue)

 

1)       Skeletal System

       Organization

--collagen

                       --calcified internal skeleton derived from embryonic mesoderm tissue

                       --cartilage

                       --teeth composed of dentin and enamel

                                       --tooth replacement

                                       --teeth with a central pulp cavity

                                       --teeth located in grooves in skull bones

                                       --different kinds of teeth

                                                       --canine enlarges

                                       --reduction in number of postcanine teeth

--mammalian tooth formula with 4 upper and 3 lower incisors; canines, and 7-9 compressed cheek teeth with cusps

--tooth occlusion (upper and lower teeth contact each other and have matching surfaces)

--loss of third pair of incisors

--cheek teeth simple and low crowned

--loss of paraconid on lower molars

--incisors near each other; no rhinarium

--4 cusps in all first and secondary molars  (also in one family of New World monkeys

--2 premolars

--oblique crest on tricuspid upper molar

--cusps of upper molars alterante rather than opposite

                       --bone

                       --bone forms first in head region; rest of skeleton cartilaginous

       Axial Skeleton      

                       --palate covered in dermal bone

                       --braincase more completely ossified

                                --teeth from Meckel’s cartilage and palatoquadrate lost

--Skull

                         --reduction in the number of skull bones

                         --skull deeper

                         --larger posterior portion of skull

                         --orbits encircled by bone

                         --orbits closed posteriorly and posterolataterally

                         --larger orbit

                         --larger face

                --cartilage in cranium (chondrocranium)

                                --tighter junctions between elements, less mobility of snout

                       --splanchnocranium supports the roof of the pharynx

                       --dermatocranium

--elements joined together more solidly; joined to braincase

                                       --solid attachment of skull to cheek

                       --jaws

                                       --upper jaw fuses to braincase

                                       --stronger, greater pressure possible

                       --hyoid

                       --the synapsid temporal opening

                                       --temporal opening widens

                       --bone growth stops when adult size is reached

--Braincase

                --inner region of skull base rounder

                --postsellar region of skull base angled

                --Frontal (2)

                                --forms part of orbit

--expanded ventrally and contacts palantine (in most advanced cynodonts)

--2 frontal bones fuse

--frontal sinuses (higher apes)

--brow ridges (higher apes)

                --Parietal (2)

                --(Occipital)

                                --occipital region solidifies

                                --occipital bone forms

                                --2 occipital condyles (as opposed to 1 in reptiles)

                                --Supraoccipital

--supraoccipital and paraoccipital processes support squamosal

                                --Exoccipital

                                --Basioccipital 

                                --Postparietal reduced

                                --Tabular reduced

                --(Temporal)

                                --Prootic  (forms petrosal with Opisthotic)

                                                --prootic becomes periotic

                                                --fenestra ovalis located within periotic

                                --Epiotic (becomes Opisthotic in amphibians)

                                --Angular

                                --Pterygoid

                                                --transverse phlange of pterygoid

                                                --reduced laterally

                                --Squamosal

                                                --the mammalian jaw joint between squamosal and dentary

                                --Petrosal Bulla

                                --carotid foramen closer to ear and wider

                                --smaller petrosal

                                --external auditory meatus bony and elongate

                                --tympanic ring inside auditory meatus

                --(Sphenoid)

                                --sphenoid forms

                                --Sphenethmoid

                                --Orbitosphenoid

                                --Basisphenoid

                                                --joint between basisphenoid and pterygoid solidifies

                                --Epipterygoid becomes alisphenoid

--epipterygoid and quadrate only portions of palatoquadrate retained

                                --Parasphenoid ?

                                --central sphenoidal sinuses

                --(Ethmoid)

                                --Mesethmoid

                                --Turbinals

                                --forms part of orbit

                                --2 pairs of ethmoid turbinals

--Face

                --Vomers

                                --fused

                                --septum narrow

                --Palantine

                                --fuse at midline, creating secondary palate

                                --secondary palate extends to same point as in mammals

                                --forms part of orbit

                --Jugal (Zygomatic)

                --Nasal

                                --nose bridge raised

                                --cartilaginous nasal wings closer together

--nostrils face frontwards; they open downwards and are closer                together

                --Lacrimal

-- bones almost always confined to orbit, as is lacrimal canal

                --Maxillary

                --Premaxillary (fuses to maxillary in humans)

                --Lower Jaw

                                --angular reflected

                                                --supports tympanum

                                --jaw joint moves anteriorly

                                --dentary becomes predominant bone

                                                --high coronoid process

                                                --deep fossa for masseter muscle

                                --two halves of mandible fuse

                                --manidble U shaped (as opposed to V shaped)

--Auditory Ossicles

                                --Stapes (Hyomandibula in bony fish)

                                                --Hyomandibular no longer a jaw support

                                                --smaller; rests on quadrate

--Articular (Meckel’s cartilage in sharks; becomes malleus in mammals)

--Quadrate (incus in mammals)

--[Hyoid]

                --Basihyal

                --Ceratohyal

                --Epibranchial

                --Ceratobranchial

                --Hypobranchial

--Bones Which were Lost in Human Lineage

                --Extrascapular lost (medial and lateral)

                --Opercular lost

                --Preopercular lost

                --Subopercular lost

                --Submandibular

                --Interhyal [lost in amphibians]

                --Pharyngobranchial [lost in amphibians]

                --Hypohyal [lost in reptiles]

                --Prefrontal lost

                --Postfrontal

                --Postorbital lost

                                --lose postorbital bar

                --Intertemporal

                --Supratemporal lost

                --Quadratojugal

                --Septomaxilla

                --Sphenotic

                --Pleurosphenoid [lost in mammals]

                --Extracolumella (Symplectic) [lost in mammals]

                --Coronoids [lost in mammals]

                --Prearticular [lost in mammals]

                --Surangular [lost in mammals]

                --Splenials [lost in mammals]

                --Dermohyal

            --Vertebrae

                       --parts of vertebrae fuse

                       --paired neural arches over notochord

                                       --well developed zygapophyses linking neural arches

                       --pleurocentra

                                       --pleurocentra predominate in vertebral centrum

                       --intercentra

                                       --reduced

                                       --lost except for atlas; perhaps contribute to capitulum of ribs

                       --hemal spine

                       --sacrum

                                       --loss of sacral ribs

                                       --sacrum attached to pelvis

                                       --becomes stronger

                       --atlas and axis

                                       --pleurocentrum of atlas attached to axis (but still a suture)

                       --enlarged neural spines and transverse processes for muscle attachment

                       --tail shorter

                       --vertebral column no longer capable of undulating laterally as in reptiles

                       --distinct thoracic and lumbar regions

                       --7 cervical vertebrae (as in most mammals)

                       --tail shorter

                       --12 thoracic vertebrae

                       --reduction in the number of caudal vertebrae (17 instead of 27-31)

                       --reduction in number of lumbar vertebrae (to 4-5 as opposed to 7-8 in monkeys)

                       --increase in the number of sacral vertebrae (to 5-6 as opposed to 3 in monkeys)

--reduction in the number of caudal vertebrae (to 3-4 as opposed to 17 in old world monkeys)

--caudal vertebrae form coccyx

--vertebral bodies wider

--large dorsal processes on cervical vertebrae associated with well-developed neck musculature

            --Thorax

                       --ribs

                                       --ribs stronger and directed ventrally

                                       --shoulder girdle separated from skull creating a neck

                                       --true ribs contact sternum

                                       --shorter ribs on anterior caudal vertebrae

--lumbar ribs reduced and attached to vertebrae; no movement between rib and vertebrae

--two heads of thoracic ribs fuse to form head and capitulum

--thorax much deeper

--ribs more heavily bent where they join thoracic vertebrae

                                --sternum (arose independently in other amniotes)

                                                --3 bones of sternum fuse

       Appendicular Skeleton

                       --paired pectoral and pelvic fins

                       --lateral halves of girdles fuse

                       --weight bearing girdles

                       --ball and socket joints between each girdle and first endoskeletal element of fin/limb

                       --limbs longer

                       --length of phalanges reduced

                       --gait more erect

                       --grasping hands and feet

                       --opposable thumb

            --Pectoral Girdle and Fin

                       --scapulocoracoid

                       --cleithrum

                                       --reduced to a very thin bone

                       --supracleithrum lost

                       --anocleithrum lost

                       --coracoid bones reduced

                                       --anterior coracoid lost

                                       --posterior coracoid fuses to scapula

                       --clavicle

                                       --reduced

                       --interclavicle

                                       --lost

                       --humerus

                                       --becomes a narrow shaft

                                       --supinator process—on humerus?

                       --radius

                       --ulna

                                       --distal end doesn’t articulate with carpal bones

                       --carpal bones

                                       --reduction of carpal bones to 8 (from 9) in chimps, gorillas, and humans

                       --wrist joint

                       --bony jointed digits

            --Pelvic Girdle and Fin

                       --increased use of bipedal stance?  (Bonobo chimps use often)

                       --pelvis

                                       --composed of three bones: ilium, ischium, pubis

                                       --ilium expanded

                                       --pubis reduced

                                       --obturator foramen

                                       --takes on mammalian form (although three bones unfused)

                                       --fuses completely

                       --femur

                                       --head more medial

                                       --2 trochanters

                       --tibia

                       --fibula

                       --ankle joint

                                       --fibulare enlarges; becomes calcaneum

                                       --tibiale, intermedium, and proximal centrale fuse to form astragalus

                       --bony jointed digits

 


25) Human Ancestors

 

1)       Skeletal System

       Organization

--collagen

                       --calcified internal skeleton derived from embryonic mesoderm tissue

                       --cartilage

                       --teeth composed of dentin and enamel

                                       --tooth replacement

                                       --teeth with a central pulp cavity

                                       --teeth located in grooves in skull bones

                                       --different kinds of teeth

                                                       --canine enlarges

                                       --reduction in number of postcanine teeth

--mammalian tooth formula with 4 upper and 3 lower incisors; canines, and 7-9 compressed cheek teeth with cusps

--tooth occlusion (upper and lower teeth contact each other and have matching surfaces)

--loss of third pair of incisors

--cheek teeth simple and low crowned

--loss of paraconid on lower molars

--incisors near each other; no rhinarium

--4 cusps in all first and secondary molars  (also in one family of New World monkeys

--2 premolars

--oblique crest on tricuspid upper molar

--cusps of upper molars alterante rather than opposite

--thicker enamel on teeth

                       --bone

                       --bone forms first in head region; rest of skeleton cartilaginous

       Axial Skeleton      

                       --palate covered in dermal bone

                       --braincase more completely ossified

                                --teeth from Meckel’s cartilage and palatoquadrate lost

--Skull

                         --reduction in the number of skull bones

                         --skull deeper

                         --larger posterior portion of skull

                         --orbits encircled by bone

                         --orbits closed posteriorly and posterolataterally

                         --larger orbit

                         --larger face

                         --greatly expanded cranium

                --cartilage in cranium (chondrocranium)

                                --tighter junctions between elements, less mobility of snout

                       --splanchnocranium supports the roof of the pharynx

                       --dermatocranium

--elements joined together more solidly; joined to braincase

                                       --solid attachment of skull to cheek

                       --jaws

                                       --upper jaw fuses to braincase

                                       --stronger, greater pressure possible

                       --hyoid

                       --the synapsid temporal opening

                                       --temporal opening widens

                       --bone growth stops when adult size is reached

--Braincase

                --inner region of skull base rounder

                --postsellar region of skull base angled

                --Frontal (2)

                                --forms part of orbit

--expanded ventrally and contacts palantine (in most advanced cynodonts)

--2 frontal bones fuse

--frontal sinuses (higher apes)

--brow ridges (higher apes)

                --Parietal (2)

                --(Occipital)

                                --occipital region solidifies

                                --occipital bone forms

                                --2 occipital condyles (as opposed to 1 in reptiles)

                                --Supraoccipital

--supraoccipital and paraoccipital processes support squamosal

                                --Exoccipital

                                --Basioccipital 

                                --Postparietal reduced

                                --Tabular reduced

                --(Temporal)

                                --Prootic  (forms petrosal with Opisthotic)

                                                --prootic becomes periotic

                                                --fenestra ovalis located within periotic

                                --Epiotic (becomes Opisthotic in amphibians)

                                --Angular

                                --Pterygoid

                                                --transverse phlange of pterygoid

                                                --reduced laterally

                                --Squamosal

                                                --the mammalian jaw joint between squamosal and dentary

                                --Petrosal Bulla

                                --carotid foramen closer to ear and wider

                                --smaller petrosal

                                --external auditory meatus bony and elongate

                                --tympanic ring inside auditory meatus

                --(Sphenoid)

                                --sphenoid forms

                                --Sphenethmoid

                                --Orbitosphenoid

                                --Basisphenoid

                                                --joint between basisphenoid and pterygoid solidifies

                                --Epipterygoid becomes alisphenoid

--epipterygoid and quadrate only portions of palatoquadrate retained

                                --Parasphenoid ?

                                --central sphenoidal sinuses

                --(Ethmoid)

                                --Mesethmoid

                                --Turbinals

                                --forms part of orbit

                                --2 pairs of ethmoid turbinals

--Face

                --Vomers

                                --fused

                                --septum narrow

                --Palantine

                                --fuse at midline, creating secondary palate

                                --secondary palate extends to same point as in mammals

                                --forms part of orbit

                --Jugal (Zygomatic)

                --Nasal

                                --nose bridge raised

                                --cartilaginous nasal wings closer together

--nostrils face frontwards; they open downwards and are closer                together

                --Lacrimal

-- bones almost always confined to orbit, as is lacrimal canal

                --Maxillary

                --Premaxillary (fuses to maxillary in humans)

                --Lower Jaw

                                --angular reflected

                                                --supports tympanum

                                --jaw joint moves anteriorly

                                --dentary becomes predominant bone

                                                --high coronoid process

                                                --deep fossa for masseter muscle

                                --two halves of mandible fuse

                                --manidble U shaped (as opposed to V shaped)

--Auditory Ossicles

                                --Stapes (Hyomandibula in bony fish)

                                                --Hyomandibular no longer a jaw support

                                                --smaller; rests on quadrate

--Articular (Meckel’s cartilage in sharks; becomes malleus in mammals)

--Quadrate (incus in mammals)

--[Hyoid]

                --Basihyal

                --Ceratohyal

                --Epibranchial

                --Ceratobranchial

                --Hypobranchial

--Bones Which were Lost in Human Lineage

                --Extrascapular lost (medial and lateral)

                --Opercular lost

                --Preopercular lost

                --Subopercular lost

                --Submandibular

                --Interhyal [lost in amphibians]

                --Pharyngobranchial [lost in amphibians]

                --Hypohyal [lost in reptiles]

                --Prefrontal lost

                --Postfrontal

                --Postorbital lost

                                --lose postorbital bar

                --Intertemporal

                --Supratemporal lost

                --Quadratojugal

                --Septomaxilla

                --Sphenotic

                --Pleurosphenoid [lost in mammals]

                --Extracolumella (Symplectic) [lost in mammals]

                --Coronoids [lost in mammals]

                --Prearticular [lost in mammals]

                --Surangular [lost in mammals]

                --Splenials [lost in mammals]

                --Dermohyal

            --Vertebrae

                       --parts of vertebrae fuse

                       --paired neural arches over notochord

                                       --well developed zygapophyses linking neural arches

                       --pleurocentra

                                       --pleurocentra predominate in vertebral centrum

                       --intercentra

                                       --reduced

                                       --lost except for atlas; perhaps contribute to capitulum of ribs

                       --hemal spine

                       --sacrum

                                       --loss of sacral ribs

                                       --sacrum attached to pelvis

                                       --becomes stronger

                       --atlas and axis

                                       --pleurocentrum of atlas attached to axis (but still a suture)

                       --enlarged neural spines and transverse processes for muscle attachment

                       --tail shorter

                       --vertebral column no longer capable of undulating laterally as in reptiles

                       --distinct thoracic and lumbar regions

                       --7 cervical vertebrae (as in most mammals)

                       --tail shorter

                       --12 thoracic vertebrae

                       --reduction in the number of caudal vertebrae (17 instead of 27-31)

                       --reduction in number of lumbar vertebrae (to 4-5 as opposed to 7-8 in monkeys)

                       --increase in the number of sacral vertebrae (to 5-6 as opposed to 3 in monkeys)

--reduction in the number of caudal vertebrae (to 3-4 as opposed to 17 in old world monkeys)

--caudal vertebrae form coccyx

--vertebral bodies wider

--large dorsal processes on cervical vertebrae associated with well-developed neck musculature

            --Thorax

                       --ribs

                                       --ribs stronger and directed ventrally

                                       --shoulder girdle separated from skull creating a neck

                                       --true ribs contact sternum

                                       --shorter ribs on anterior caudal vertebrae

--lumbar ribs reduced and attached to vertebrae; no movement between rib and vertebrae

--two heads of thoracic ribs fuse to form head and capitulum

--thorax much deeper

--ribs more heavily bent where they join thoracic vertebrae

                                --sternum (arose independently in other amniotes)

                                                --3 bones of sternum fuse

       Appendicular Skeleton

                       --paired pectoral and pelvic fins

                       --lateral halves of girdles fuse

                       --weight bearing girdles

                       --ball and socket joints between each girdle and first endoskeletal element of fin/limb

                       --limbs longer

                       --length of phalanges reduced

                       --gait more erect

                       --grasping hands and feet

                       --opposable thumb

            --Pectoral Girdle and Fin

                       --scapulocoracoid

                       --cleithrum

                                       --reduced to a very thin bone

                       --supracleithrum lost

                       --anocleithrum lost

                       --coracoid bones reduced

                                       --anterior coracoid lost

                                       --posterior coracoid fuses to scapula

                       --clavicle

                                       --reduced

                       --interclavicle

                                       --lost

                       --humerus

                                       --becomes a narrow shaft

                                       --supinator process—on humerus?

                       --radius

                       --ulna

                                       --distal end doesn’t articulate with carpal bones

                       --carpal bones

                                       --reduction of carpal bones to 8 (from 9) in chimps, gorillas, and humans

                       --wrist joint

                       --bony jointed digits

            --Pelvic Girdle and Fin

                       --increased use of bipedal stance?  (Bonobo chimps use often)

                       --pelvis

                                       --composed of three bones: ilium, ischium, pubis

                                       --ilium expanded

                                       --pubis reduced

                                       --obturator foramen

                                       --takes on mammalian form (although three bones unfused)

                                       --fuses completely

                                       --hips parallel to spine

                       --femur

                                       --head more medial

                                       --2 trochanters

                       --tibia

                       --fibula

                       --ankle joint

                                       --fibulare enlarges; becomes calcaneum

                                       --tibiale, intermedium, and proximal centrale fuse to form astragalus

                       --bony jointed digits