The following cladogram depicts an evolutionary lineage proceeding from the most primitive cells to modern humans.  Did it really happen?  Does anatomical evidence support this evolutionary tree?


     How can anatomical evidence test this evolutionary tree?  First of all, if the various systems of the body were “irreducibly complex”, all of the parts would have to be present from the beginning.  The following pages will clearly show that a wide range of anatomical possibilities exist in modern organisms, many of which contain some, but not all, of the anatomical features possessed by humans.  The systems found in the human body are not “irreducibly complex” in that the ancestors of humans could have lived quite well without all of the modern anatomical features.

     Secondly, the evolutionary model predicts similarities between organisms which a non-evolutionary model (e.g. creationism) does not.  If organisms appeared fully formed without any relationship to other organisms, there is absolutely nothing that they have to have in common.  Not only does an evolutionary model predict similarities while the creationist model does not, the evolutionary model predicts a pattern of similarities while the creationist model does not.  In an evolutionary model, all primates should share certain characteristics that their last common ancestor possessed after the other mammalian lineages had separated.  Placental mammals should share certain characteristics and so on through the mammals, amniotes, tetrapods, gnathostomes, vertebrates, chordates, etc.  If life is a family tree, then comparative anatomy should reveal a hierarchy of degrees of relatedness. 

     In a creationist model, there do not have to be any similarities at all between the anatomical systems of different organisms.  If there are similarities, these similarities do not have to form a nested hierarchy—a certain trait could be distributed amongst animals not according to their ancestry but according to their size, or habitat, or color, or whatever.   A nested hierarchy is only predicted in the evolutionary model.

     The following pages depict just such a nested hierarchy of anatomical features of the various systems of the animal body.  All vertebrates posses the traits given at the node for the vertebrate ancestor (node 11).  All tetrapods possess the traits given at the node for the tetrapod ancestor (node 15).   All placental mammals possess the traits given at the node for the placental mammal ancestor (node 19).

     Nested Hierarchies Coincide!

     You can make a hypothetical family tree based on traits of the circulatory system.  If evolution has not occurred, it is not only unexpected that you could devise such a tree, it is certainly unexpected that such a tree coincides with family trees designed based on the traits of the nervous system.  Or the skeletal system.  Or the muscular system.  Or embryological development.  Or the fossil record.  Or molecular evidence.  But they do coincide.  Life on earth does not give the impression of having appeared from nowhere without common ancestors—the groups of living things are a series of branches from a great, ancient family tree.

     Apes consistently appear as a real, biological group—not a group of completely unrelated organisms which happen to share traits for no apparent reason.  Placental mammals are a real group.  Amniotes are a real group.  Deuterostomes are a real group, etc.  Biological groups are real—or at least there is an overwhelming amount of evidence that suggests that they are. 

      What should you do as you skim through the following pages?  You should see if the numbers referring to the nodes of the cladogram on the previous page correspond to new anatomical traits which exist in the animal groups above the node.  If there are traits given for the various nodes, then this forms a nested hierarchy of anatomical traits.  After looking at all of the cladograms for the body’s diverse systems, do you think that all of this anatomical evidence would support the gradual branching of an evolutionary lineage if no such lineage ever existed?






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

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

3.        Ancestor of Animals

--wandering phagocytes to for defense against microbes

4.        Metazoan Ancestor

5.        Bilateran Ancestor

6.        Higher Bilateran Ancestor

--blood vessels (Hickman)

--contractile muscle surrounding blood vessels (which primitively pumped blood in the absence of a heart) (Hickman)

--minor blood vessels branching from major ones (Hickman)

--corpuscles and amebocytes in blood (Hickman)

--pigments in blood?—some nemertines have hemoglobin but others can have no pigment or one of several other pigments (Hickman)

--endothelial lining in blood vessels (Dutta, 365) 

--fenstrated basilar layer of endothelial lining (Dutta, 366)

7.        Ancestor of Coelomates

--directional blood flow; in nemertines blood can flow both directions through blood vessels (Hickman)

8.        Ancestor of Deuterostomes

--ventral blood vessel more muscular

--heart? Pericardium? --since lancets lack a heart, it is not clear whether the heart of hemichordates is the ancestral condition of craniate hearts (meaning that lancets have lost this ancestral feature in their more recent evolution) or whether a heart evolved in hemichordates after the lineage of cephalochordates separated) (Harris)

--blood vessels to pharyngeal slits for gas exchange  (Harris)

9.        Chordate Ancestor

--(urochordates, 9A) blood vessels to pharyngeal slits more extensive  (Harris)

--(cephalochordates, 9B) branchial artery homologous to vertebrate truncus arteriosus (Willey, 47)

--(cephalochordates, 9B) aortic arches (Willey, 49)

--(cephalochordates, 9B) aortic arches carry oxygenated blood to the dorsal aorta (Willey, 49)

--(cephalochordates, 9B) subintestal vein carries blood from gastrointestinal tract to liver where portal system is formed (from the embryonic subintestinal vein in craniates the hepatic portal vein forms) (Willey, 54)

--(cephalochordates, 9B) Amphioxus has capillaries, valves in veins and arteries; vessels have the same structure as vertebrates (Dutta, 367)

--(cephalochordates, 9B) Endostylar artery in Amphioxus is homologue of abdominal aorta (Dutta 367)


10.     Craniate Ancestor

--reduction in the number of aortic arches (Romer)

--closed circulatory system

--In lampreys and hagfish, the circulatory system is almost a closed one, but a system of venous sinuses and plexuses are reminiscent of the open circulatory system of many invertebrates (Hardisty, p. 242).

--primitive lymphatic vessels?

--thin walled vessels of vascular plexuses in both lampreys and hagfish may be primitive lymphatic vessels; most agree that there are no true lymphatic vessels in lampreys.   (Hardisty, 249)

--increase in blood vessels to skeletal muscle over condition in Amphioxus (Willey)

--cells homologous to thymus (Romer 448)

--external and internal carotid arteries; internal carotids servicing brain (2)

--celiac, anterior mesenteric, posterior mesenteric, renal, and gonadal arteries (2)

--first blood cells form in yolk sac and are nucleated (even in mammals) (2)



11.     Vertebrate Ancestor

--cartilage surrounding the pericardial cavity Hardisty (242) 

--skeletal and cardiac muscle (including desmosomes and intercalated disks in cardiac muscle) is similar to that of higher vertebrates (Hardisty 242).

--artery walls in lampreys contain smooth muscle and collagen; the walls of the aorta also contain elastic fibers.  (The walls of veins are thinner with less smooth muscle, Hardisty, 248). 

Hematopoeisis occurs in pronephros and in primitive bone marrow of cartilaginous provertebral arches (Hardisty 251).

--unpaired arteries from the dorsal aorta to the gastrointestinal tract, including the celiac (Hardisty 250)

--thymus (Romer 448)

--a heart with 3 chambers: sinus venosus, atrium, and ventricle (Kardong)

--heart valves are present (Kardong)

 --pericardium present although in hagfish, it is a continuation of the peritoneum that lines the abdominal cavity (Guenther, 151).

--the heart forms from the anterior part of the subintestinal vein during embryonic development, and the subintestinal vein forms originally from a fused pair of vitelline veins.  (Hardisty 242-5)

--atrioventricular and semilunar valves (Kardong, p. 463).

--the heart is composed of four chambers: a sinus venosus, atrium, ventricle, and bulbus arteriosus (Kardong)

--The sinus venosus collects blood from the cardinal veins, jugular vein, and the hepatic vein (Kardong)




12.     Gnathostome Ancestor (vertebrates with jaws)

--coronary blood vessels (in lampreys, blood can pass between cardiac muscle fibers) (Kardong 460; Hardisty 242)

--vagus nerve and neurotransmitter ACh inhibit the heart (in lampreys, both stimulate the heart) (Hardisty 251)

--reduction in the number of aortic arches (to 6) (Romer)

--hematopoeisis in embryonic kidney (through to reptiles and birds) and adult kidney (through reptiles) (Romer 448-9)

--spleen (Romer 452)

--renal portal veins (through birds) (Romer 474-5)

--posterior portion of posterior cardinal veins interrupted Romer 474

--lateral abdominal veins (which mammals retain only as umbilical veins) Romer 477

--external and internal carotid arteries (Kardong)

--hepatic portal vein no longer contractile (Guenter 154)

--increase in blood vessels to skeletal muscle over condition in lamprey (Hardisty)

--subclavian and iliac vessels to fins

--loss of accessory hearts—contractile portions of blood vessels other than the branchial heart in Amphioxus and hagfish (Kardong)

--innervation of heart (no nerves innervate heart in hagfish) Kardong

13.     Bony Fish Ancestor

--lymphatic vessels, lined by endothelium (Dutta, 371)

--hematopoesis in liver (through to amphibians and turtles) (Romer 450)

14.     Sarcopterygian Fish Ancestor

--partial interatrial septa (although a partial interventricular septum may be present, it may not be homologous with that of amniotes) (Kardong 465)

--sinus venosus empties into right atrium, pulmonary vein into left (Kardong p. 465).

--pulomary vein from lungs to left atrium

--posterior vena cava (Romer 475)

--the pulmonary artery develops as a branch of aortic arch VI which also services gills before emptying into the dorsal aorta through the ductus arteriosus (amphibians have the same) (Kardong)


15.     Amphibian Ancestor

--completely separate right and left atria

--subclavian veins empty into anterior vena cavae (Romer 478)

--the aortic arches are reorganized and the common carotid forms from the ventral aorta which formerly connected aortic arches III and IV;  the internal carotid, together with aortic arch III and part of the dorsal aorta, joins it and the carotid body forms at the terminus of the common carotid (Kardong, Romer)

--further development of limb vessels: axillary, brachial, radial, ulnar, femoral, saphenous, popliteal, tibial blood vessels

-- lymph “hearts” with skeletal muscle and valves (Romer 479)

--first two aortic arches disappear early in development (5)

16.     Amniote Ancestor

--a completely separate pulmonary circuit; no ductus arteriosus connecting pulmonary and systemic circuits in adult (Kardong)

--sinus venosus smaller but still contains SA node. 

--a pulmonary trunk and at least one systemic aortic trunk leave the heart (Kadong 467)

--partial division of ventricles (Kardong 467)

--posterior cardinal veins of embryo remain in adults only as azygos veins (Romer 475)

--reduction of renal portal system (Romer 475)

--lymphatic cisterns or lymphatic sites at same sites as true lymph nodes in mammals and some water birds (Kardong, 484)

--hearts create higher pressure, greater cardiac output, and separate oxygenated from deoxygenated blood. (Kardong 467).

--Conduction system of heart in amniotes; (in more primitive vertebrates, muscles contracted in a wave (Romer, 482)

-- conus arteriosus present in embryo only; makes up portions of vessels leaving the Heart (Romer 488)

17.     Mammal Ancestor

--interventricular septum creates right and left ventricles

--an AV node in heart (Kardong, 461)

--bone marrow more important in hematopoeisis (birds as well) (Romer 450)

--some lymphocyte proliferation (lymph nodes) & production (thymus) occurs outside bone marrow (Romer 450)

--complex coiled masses of vessels called rete mirable; occur in many mammalian tails, perhaps as heat-saving device; humans still have the coccygeal glomus in their tail (Romer 455)

--valves (present in primitive lymph “hearts”) in lymphatic vessels (also in birds) (Romer 458)

--loss of lateral head veins;  internal jugular veins replace them (Romer 472-3)

--loss of renal portal system (Romer 475)

--iliac veins empty into the posterior vena cava (as opposed to the lateral abdominal veins or renal portal veins)

--loss of carotid duct connecting carotid artery to dorsal aorta which is retained in some amphibians and reptiles (Romer)

--true lymph nodes (Kardong, 484)

--anucleate red blood cells (3)

18.     Therian Mammal Ancestor (Marsupials and Placentals)

--spleen more compact (Romer 452)

--although the embryonic external carotid artery is small and the stapedial artery is large, as in the condition in non-therian adult vertebrates, the external carotid grows into the branches of the stapedial artery which is subsequently reduced or absent (Romer 468)

--umbilical arteries (4)

--umbilical vein; empties into both the liver and the hepatic vein (4)

--foramen ovale diverts most blood from lungs during fetal development (4)

19.     Placental Mammal Ancestor

--sinus venosus only present as SA node after embryonic development (Kardong, 475)

--in many mammals, including humans, left common cardinal vein disappears (473)

--embryonic lateral abdominal veins become umbilical veins (Romer 477)

--in many mammals, left common cardinal vein degenerates in embryonic development; there is only one resultant anterior/superior vena cava (Romer)

--ductus arteriosus is functional in embryo but becomes the ligamentum arteriosum in adults. (Kardong 479)


20.     Primate Ancestor

21.     Anthropoid Primate Ancestor (monkeys, apes, and humans)

--ABO blood groups (some prosimians have B-like antigens); M blood antigen (3)


22.     Catarrhine Primate Ancestor (Old World Monkeys, apes and humans)

--cranial venous drainage pattern in which internal jugular receives major supply (4)


23.     Ape Ancestor

  --N blood antigen (5)

24.     African Ape Ancestor

25.     Human Ancestor

--greater asymmetry in cranial venous drainage (6)

--occipito-marginal venous system enlarged (6)





  1. LUCA—Last common ancestor of all modern life on earth
  2. Ancestor of Protists, Plants, Fungi, and Animals
  3. Ancestor of Animals
  4. Ancestor of Animals with Tissues

--nerve cells

--bipolar and multipolar neurons (Hickman, 138)

--some neurons are capable of secretion (Hickman)

--sensory, motor, and association neurons; motor and association neurons deep to epithelia

(Beklemishev  vol. 2, p. 75)

--interneuronal and neuromuscular synapses (Hyman, p.)

--neurosensory cells of the epithelia synapse with the nerve net. (Hickman) 

--giant fibers linking the senses to the muscles are similar to the giant fibers of many invertebrates (Fretter, p. 68).  

--ganglia can control the regular rhythms of (Fretter, 68 & 94). 

--slight centralization in some instances Beklemishev, vol. 2 p. 79-80, (Hyman)

  1. Ancestor Bilateran Animals

--axons different from dendrites (Beklemishev  vol. 2, p. 75).

--action potentials in one direction only (can proceed in either direction in coelenterates ((Hyman, p. 377)

--cerebral ganglion (“brain”)

--longitudinal nerve chords (although not present in all Beklemishev, vol. 2, p. 80)

--brain associated with sensory structures at anterior end of animal (Beklemishev, vol. 2, p. 50-1). 

--2 main nerve chords (Rhabdocoela; Hickman)

--nerves from brain (Hickman)

--unipolar neurons (Hassler, p. 260)

  1. A nemertine-like ancestor of complex bilateran animals

--greater cephalization and centralization (Beklemishev, vol. 2, p. 83)

--the nervous tissue migrate deeper into the body away from epithelia (Beklemishev, vol. 2, p. 83)

--greater complexity of behavior (Beklemishev, vol. 2, p. 83)

  1. Coelomate Ancestor
  2. Deuterostome Ancestor

--dorsal nerve cord (as opposed to ventral as in many invertebrates); (2)

  1. Chordate Ancestor

--atria of tunicates homologous to the otic vesicles of craniates (Ahlberg, p. 62)

--tunicate larvae have gene expression in nerve chord homologous to vertebrates (such as Otr, Hox1, Hox5, Pax2/5/8 (Ahlberg, p. 21)

--while Amphioxus lacks neural crest cells, many important neural crest genes of vertebrates are expressed on the neural plate and non-neural ectoderm; the same is true of cranial placodes (Ahlberg, p.25)

-- paired nerves leaving the CNS (at least anterior end) (Willey, p. 82). 

--dorsal and ventral roots leaving nerve chord (Willey, p.83-4)

--dorsal and ventral rami  (Willey, p.85)

 --ventral roots carry muscle fibers only (Willey, p.86)

--parasympathetic innervation of gut (Romer p. 553)

 --visceral fibers which may contain sympathetic input (Willey, p. 86).

--cerebral vesicles (Willey, p.90)

--anterior midbrain (Ahlberg, p. 15)

--medulla (Willey, p.91) 

--otoliths in tunicates (Willey, p. 10)

--hollow nerve cord (3)

--nerve cord continuous with a hollow cerebral vesicle in head region (3)

--a type of glial cell (in nervous system) called ependymal cell (3)

--nerves separate into upper and lower branches; mixed spinal nerves (have both sensory and motor components);  (4)

-- sensory, motor, and integrative neurons in nerve cord (thus making it a “spinal cord” as opposed to an “axonal cord”) (4)

--neurons innervating segmented trunk muscles more abundant in ventral portion of trunk cord (4)

--frontal organ with pigmented eyes (in cephalochordates there are pigmented cells homologous to eyes; the area where cephalochordates process visual information may be

homologous to an area of the vertebrate  midbrain called the tectum) (4)

--cells homologous to pineal and hypothalamus (4)


  1. Craniate Ancestor

--medulla has choroid plexus (Hardisty, p. 312-3)

--medulla contains the nuclei of cranial nerves V through X (Hardisty, p. 312-3)

--there are chromaffin cells in both jawless fish but they are located in the heart(in lampreys as well) (Hardisty, p. 359)

--autonomic fibers in the vagus nerve (Romer p. 547)

--autonomic innervation of the gut: ACh stimulates the gut while NE inhibits it (Hardisty, p. 360).

--dorsal and ventral roots of spinal chord join (but not in lampreys) (Romer p. 547)

-- collateral ganglia (Kardong, p. 628)

--the major regions of the cerebrum are present: the pallium (both the medial/hippocampal region and the dorsal & lateral/cortex region) and the subpallium (both the sriatum and septum) (Kardong, p. 646).

--one semicircular canal (Romer, p. 526)

in forebrain, rostral cerebral hemispheres and caudal diencephalon (2)

--medulla, olfactory bulb,  optic tectum (2)

--pineal body (2)

--neural crest (2)

--neurogenic epidermal placodes (2)

--olfactory, oculomotor, trigeminal, facial, glossopharyngeal, and vagus cranial nerves (2)

--autonomic nervous system (although fragmentary) (2)

  1. Vertebrate Ancestor

-- a single meninx (Hardisty, p. 308)

--neural crest cells (unknown if hagfish have) (Ahlberg, p. 23)

--cerebellum forms at the anterior end of fourth ventricle (Hardisty 312) as in the embryos of higher vertebrates (Hardisty, p. 327)

--cells similar to Purkinje fibers (Hardisty, p. 312)

--midbrain contains the nuclei of cranial nerves III and IV (which departs the brain dorsally) (Hardisty, p. 311)

--the diencephalon can be divided into a thalamus, hypothalamus, and epithalamus and it contains a pineal body and a habencular nucleus (Hardisty, p. 310)

--olfactory bulbs

--bipolar neurons connect the olfactory bulbs to the olfactory epithelia and the olfactory pathway is structured similarly to that of higher vertebrates (Hardisty, p. 316)

--hippocampus, corpus striatum, and part of the pallidum.  Olfactory pathways connect to the hippocampus.   (Hardisty, p. 316)

the geniculate primordium of the thalamus receives visual input (Hardisty, p. 319)

--the hypothalamus contains the preoptic nucleus, mammillary body, and neurons capable of secretion. (Hardisty, p. 320-1)

--tectum processes visual information (Hardisty p. 326)

--glial cells (Hardisty, p. 335)

 --the spinal cord contains spinocerebellar and tectospinal tracts ((Hardisty, p. 328)

--GABA is an inhibitory neurotransmitter while glutamate is excitory (Hardisty, p. 328)

--in the spinal chord, the dorsal root is more restricted to sensory information and there are dorsal root ganglia (Hardisty, p. 357)

--oculomotor and trochlear nerves which control eye muscles (hagfish lack these but their eyes are degenerate) (Hardisty 355-7).

--ANS more developed in lampreys (Hardisty, p. 359)

-- the heart is innervated by the vagus (although ACh and vagal stimulation stimulate the heart, unlike the situation in higerh vertebrates (Hardisty, p. 358).

--the hypothalamus integrates visceral input (Romer p. 586).

--anterior commissure connects cerebral hemispheres (Romer, p. 594)

--enteric ANS plexuses (Kardong, p. 628).

--two semicircular canals (Romer, p. 526)

--rods in eye (Kardong, p. 665)

--3 semicirular canals (Kardong, p. 682)

--corpus striatum (4)



  1. Gnathostome Ancestor

--distinct gray and white matter in spinal cord; horns of spinal cord (which are not present in lampreys, Hardisty p.313—check sharks)

--ANS input to blood vessels(Romer p.554) and

--autonomic ganglia along the spinal cord (Romer p.554) 

--increased the non-olfactory regions of the cerebrum (Romer p. 588)

--pyramidal cells (in hippocampus at first) (Hassler, p. 117)

--bed nucleus of anteriorhippocampal commissure (Hassler, p. 121)

--smooth muscle in iris (Romer, p. 508)

--lens attached (Romer, p. 509)

--primitive eyelids (Romer, p. 516)

--saccule and utricle in the inner ear (Romer, p. 526)

--forebrain no longer composed solely of olfactory lobe  (6)

--tectum main association area (6)

--basal ganglia (6)

--suspensory ligaments of eye (6)

--otoliths (6)


  1. Bony Fish Ancestor

 --autonomic gray rami and sympathetic chains (Romer p.554)

--the ophthalmicus profundus is always part of the trigeminal (Romer p. 560).

--chromaffin cells separate from ganglia (Kardong, p. 628).

--lens attaches to ciliary body (Romer, p. 510)

--collateral ganglia (9)

  1. Sarcopterygian Fish Ancestor

--hippocampus along medial and dorsomedial wall of evaginated cerebral hemisphere (Hassler, p. 117)

--fornix connects hippocampus and septal region (Hassler, p. 122)

--olfactory tubercle with same subdivisions as observed in mammals (Hassler, p. 122)

--paleostriatal and nestriatal areas (Hassler, p. 127)

--lagena from vestibule detects sound (9)

--ANS fibers travel only through ventral roots (9)

  1. Tetrapod Ancestor

--inferior colliculus (Romer p. 585)

--increased the non-olfactory regions of the cerebrum (Romer p. 588)

--first touch receptors in which dendrites form part of a corpuscle (Romer, p. 497)

--first proprioceptors (Romer, p. 498)

--vomeronasal organ (Romer, p.504)

--movable eyelids (Romer, p. 517)

--lacrimal canals in eye (Romer, p. 517)

--hair cells involved in hearing (Romer, p. 532)

--auditory ossicle involved in hearing (the stapes) (Romer, p.532)

--papilla basilaris may be primitive organ of Corti in amniotes (Kardong, p. 684)

--neural plate, groove, and folds (as opposed to the neural keel of fish) (5)

--sensory fibers processed in forebrain (5)

--same homeobox gene expression in all tetrapod basal ganglia (5)

--pallidal subdivision of basal ganglia (5)

--striato-tegmental-tectal pathway (5)

--amygdala (5)

--2 meninges over spinal cord (5)

--cervical and lumbar enlargements (5)

--nictitating membrane (5)

  1. Amniote Ancestor

--both the cerebrum and tectum (as opposed to the tectum alone)are important association (Romer p. 585)

--loss of giant fibers which exist in invertebrates, Amphioxus, fish, salamanders, and frog tadpoles (Willey, p. 94)

--hypothalamus is involved in temperature (Romer p. 586).

--increased importance of thalamus as sensory relay center for cerebrum (Romer p. 586-7)

--posterior column—medial lemniscus pathway (Hassler, p.319)

--nucleus gracilis and nucleus cuneatus in medulla (Hassler, p.319)

--spinal nerves are incorporated into the brain, forming cranial nerves XI and XII (Kardong, p. 618).

--taste buds no longer on skin (Romer, p.498)

--olfactory epithelium on superior part of nasal cavity (Romer, p.503)

--lens flexible, allowing accomodation (Romer, p.510)

--lateral line system lost (Romer, p. 518)

---cartilage surrounding external auditory meatus (Romer, p.531)

--organ of Corti in ear (Kardong, p. 684)

--most striatal neurons contain GABA and project outside striatum (9)

--2 groups of thalamic nuclei project to striatum (9)

--substancia nigra receives input from basal ganglia and projects onto tectum (9)

--pallidotegmental pathway (9)

--modifications of dorsal thalamus (9)

--thalamic reticular nucleus (9)

--lagena forms a tube (9)

  1. Mammal Ancestor

--the tectum is reduced as the cerebrum is the main association center (Romer p. 585)

--the tectum becomes less important in visual processing and many visual fibers proceed to the thalamus (Romer p. 585).

--the facial nerve expands its area of innervation (Romer p. 560).

--hypothalamus has roles in heartbeat, respiration, blood pressure, and sleep (Romer p. 586).

--fornix (Romer, p. 590)

--corticospinal tract (Hassler, p. 321)

--olfactory region of cerebrum inferior to rhinal fissure (Romer 592)

--specialized muscle fibers in spindles for proprioception (Romer, p. 498)

--taste buds concentrated on tongue (as opposed to pharynx; reptiles and birds have few taste buds on tongue) (Romer, p.498)

--most modern mammals are not responsive to color, suggesting the first mammals adapted to nocturnal life (Romer, p. 514)

--not all optic fibers cross at chiasm (Romer, p. 516)

--space for inner ear expands into the mastoid bone (Romer, p.530)

--pinna of external ear (Romer, p. 531)

--–increased brain size (2)

--cerebellum expanded (2)

--pons develops (3)

--pineal body no longer used for light sensing (3)

--cerebrum main association area (3)

--superior and inferior colliculi (3)

--sensory and motor maps of the body; they are fused (3)

--massive cortical input to striatum from all cortical areas (3)

--external auditory meatus elongated (3)

--lagena coils to form cochlea (3)

--modifications of dorsal thalamus (3)


  1. Therian Mammal Ancestor (Marsupials and Placentals)

--lagena coiled to form cochlea (Romer, p.535)

--lagenar macula lost in ear (Romer, p.532)

--vertical tympanic membrane (4)

--sensory and motor maps separate (4)

--separation of claustrum from cerebral cortex (4)

--presence of  a complete sensory somatic sensory region of the cerebral cortex (4)


  1. Placental Mammal Ancestor

--end of midbrain exposure (Romer p. 592)

--gyri and sulci increase surface area of cerebrum in most placentals (Romer, p. 593)

--6 cellular layers in the neopallium (Romer, p. 594)

--corpus callosum (Romer, p. 594)

--hippocampus shifts posteriorly (Hassler, p. 119)

--increase in digital dexterity (1)

--fibers of dorsal lateral olfactory tract pass through accessory olfactory formation (also in rodents) (1)

--corpus callosum connects cerebral hemispheres (5)

--no oil droplets in retinal cone receptors (5)


  1. Primate Ancestor

--increased size of neocortex (and also at following nodes) (Ankel-Simons, p. 175)

--increased visual areas (Ankel-Simons, p. 175)

--central sulcus (in other placental groups this sulcus may or may not be present) (Romer, p. 595)

--sylvian fissure in cerebrum (Ankel-Simons, p. 187)

--cerebral hemisphere extends over part of olfactory bulb (Ankel-Simons, p. 187)

--fovea in eye (Ankel-Simons, p.376)

--septum velum narrows (Hassler, p. 398)

--changes in tectal connections to retinas (Dermoptera) (1)

--highly developed sight (2)

--general increase in brain size: body size (2)

--changes in the corticospinal tract in the ventralmost lamina receiving synapses and the lamina receiving densest synapses (2)

--large pulvinar nucleus (2)

--equivalent tectopetal connections to the anterior colliculus of one side from both retinas (2)


  1. Anthropoid Primate Ancestor (monkeys, apes, and humans)

--(and tarsiers) 4 cell layers in thalamic geniculate body  (Ankel-Simons, p. 182)

--orientation of lateral geniculate nucleus ventral and rotated (Ankel-Simons, p. 188)

--septum pellucidum (Hassler, p. 398)

--(and tarsiers) olfactory area reduced (Ankel-Simons, p.189)

--greater development of gyri (Ankel-Simons, p. 190)

--stereoscopic vision (Ankel-Simons, p. 190)

--enhanced sense of touch (Ankel-Simons, p. 190)

--greater specialization of lateral geniculate nucleus (Ankel-Simons, p.190)

--large integration areas develop in all 4 lobes of brain (Ankel-Simons, p. 191)

--(and tarsiers) rhinarium lost (Ankel-Simons, p. 350)

--(and tarsiers) upper lips lose some of their attachments and more free to move (Ankel-Simons, p.350)

--(and tarsiers) no tapetum lucidum (Ankel-Simons, p. 375)

--cones outnumber rods (Ankel-Simons, p. 377)

--mirroring of sensory body map in isocortex (3)

--neocortex no longer smooth; contains gyri and sulci (unlike some insectivores and prosimians)  (3)

--large association areas within frontal, parietal, temporal, and occipital lobes (3)

--optic areas highly developed, olfactory areas reduced (3)

--a common sulcal pattern (one of the two groups of NW monkeys, Cebidae, resemble OW) (3)

--retina has both rods and cones; cones outnumber rods (3)

--fovea and macula densa (3)

--optical axes roughly parallel (3)

  1. Catarrhine Primate Ancestor (Old World Monkeys, apes and humans)

--vomeronasal organ much reduced in adults (Ankel-Simons, p. 354)

--ability to taste the protein thaumatin (from African berries) as sweet; other primates don’t taste  (Ankel-Simons, p. 359)

--long, bony auditory meatus (Ankel-Simons, p. 369)

--accessory olfactory bulb reduced or absent (Hassler, p.387)

  1. Ape Ancestor

--ability to recognize mirror reflection of self (5)

--language ability (sign or spoken) (5)

--cerebral asymmetries that exist in apes (larger one given): left sylvian fissure,  left occipital lobe, left lateral ventricle (5)


  1. African Ape Ancestor

--tool usage (especially common in chimps: sticks for termites, wad of chewed leaves to remove water from tree holes, stout sticks to dig up ant, bee, or termite nests, leafy branches for sandals or gloves, leaf cushions to protect from thorny branches, bone picks to extract bone marrow, leaf napkins to clean themselves and infants, leaves to scoop water, natural objects to carry water, mortar and pestle to smash palm) (5)

--learning of human sign language (chimps, gorillas, orangs) (5)

--use of signs to communicate in wild (chimps) (5)

--the ability to paint representationally (only shown after chimps could name their paintings) (5)

--culture?—not all chimp populations have the same practices/tool usage, this is passed down in each population as a learned behavior (5)


  1. Human Ancestor

--main olfactory bulb greatly reduced in size (6)

--damage to Broca’s area leads to loss of speech (in other primates voluntary sound production apparently unaffected) (6)

--septum increase (6)

--increase in cells in thalamic limbic system (6)

--pulvinar nucleus largest thalamic nucleus (6)




  1. LUCA—Last common ancestor of all modern life on earth
  2. Ancestor of Protists, Plants, Fungi, and Animals
  3. Ancestor of Animals
  4. Ancestor of Animals with Tissues

--musculo-epithelial cells in circular, longitudinal, and sometime oblique layers (Fretter 56-8)

--some musculo-epithelial cells are striated and some insert into mesoglea (Hickman, p. 137) 

--ctenophores possess true muscle cells (Hickman, p. 181).

Hagfish and lampreys possess both fast and slow twitch muscles (Hardisty, p. 357).

  1. Ancestor Bilateran Animals

--subepidermal and mesenchymal muscle which is more similar to the muscle of higher animals (Hickman). --in addition to moving the body, muscle serves both the mouth and reproductive structures. Beklemishev, vol.  2)

--peristalsis  (Beklemishev, vol.  2)

  1. A nemertine-like ancestor of complex bilateran animals
  2. Coelomate Ancestor
  3. Deuterostome Ancestor
  4. Chordate Ancestor
  5. Craniate Ancestor

--hypobranchial musculature (Romer, p. 288)

  1. Vertebrate Ancestor
  2. Gnathostome Ancestor

--horizontal septum divides epaxial and hypaxial (dorsal and ventral) musculature (Romer, p. 282)

--eye muscles standardized (Romer, p. 291)

--dorsal and ventral fin musculature (Romer, p. 292)

--branchiomeric musculature well developed (Romer, p. 306)

--cucullaris (trapezius of tetrapods; the only branchial bar levator which tetrapods retain) (Romer, p. 307)

--hyoid arch and its musculature modified (becomes operculum) (Romer, p. 309)

--adductor mandibulae (will divide in tetrapods to form the temporalis, masseter, and pterygoid muscles) (Kardong, p. 393; Romer, p. 312)

--epihyoideus (contributes to mammalian facial musculature including platysma) (Kardong, p. 393)

  1. Bony Fish Ancestor
  2. Sarcopterygian Fish Ancestor
  3. Tetrapod Ancestor

--external oblique produces serratus anterior, levator scapulae, and rhomboid muscles (Romer, p. 287)

--hypobranchial musculature produces glossus and hyoid groups of muscles (Kardong, p. 378; Romer, p. 288-9)

--pectoralis, coracobrachialis, biceps brachii, brachialis (Romer, p. 295)

--puboischiofemoralis internus (becomes psoas, iliacus, and pectineus muscles in mammals) (Kardong 387; Romer, p. 297)

--ambiens or iliotibialis (sartorius in mammals) (Kardong, p. 387; Romer, p. 297)

--triceps femoris of ampibians (iliotibialis and femortibialis in reptiles; quadriceps in mammals) (Romer, p. 297)

--gluteal muscles (iliofemoralis in reptiles) (Romer, p. 297)

--puboischiofemoralis externus (develops into obturator externus and quadratus femoris in mammals) (Kardong, p. 387; Romer, p. 297)

--ischiotrochantericus (develops into obturator internus and gemellus in mammals) (Kardong, p. 387; Romer, p. 297)

--gracilis muscles (puboischiotibialis in reptiles) (Romer, p. 298)

--gastrocnemius (Romer, p. 300)

--operculum lost and hyoid arch musculature expands into neck (Romer, p. 309)

--iliofemoralis (tensor fascia latae, pyriformis, and gluteus muscles of mammals) (Kardong, p. 387)

--depressor mandibulae (retained only as stapedius in mammals) (Kardong, p. 393)

--levatores arcuum (sternomastoid and cleidomastoid in mammals (Kardong, p. 386)

--latissimus dorsi, triceps, pectoralis (Kardong, p. 386)

--hip and leg muscles: tibialis anterior, peroneus longus, extensor digitorum longus, peroneus brevis, extensor digitorum brevis, caudofemoralis (Kardong, p. 386)

--dorsalis scapulae and procoracohumeralis longus (acromiodeltoid and scapulodeltoid in mammals) (Kardong, p. 386)

--arm muscles: extensor digitorum communis, extensor carpi radialis, extensor carpi ulnaris, extensores digitorum breves, supinator, dorsal interossei, flexor carpi radialis, palmaris longus, flexor carpi ulnaris, pronator profundus (quadratus), flexor palmaris (digitorum) profundus (Romer, p. 302-3)

  1. Amniote Ancestor

--dorsalis trunci divides into medial, intermediate, and lateral groups (Romer, p. 283; Kardong 382)

--(and fossil amphibians) external and internal intercostal muscles develop from the external and internal obliques (Romer, p. 284)

--subvertebral muscles become more developed (Romer, p. 284)

--levator palpebrae superioris for eyelid (and nictitating membrane in some) (Romer, p. 291)

--latissimus dorsi and deltoid prominent (Romer, p. 293)

--subcoracoscapularis (subscapularis in mammals) (Romer, p. 294)

--scapulohumeralis (teres minor in mammals) (Romer, p. 294)

--musculature of the dorsal forearm fairly standardized (Romer, p. 294)

--adductor femoris (Romer, p. 298)

--flexor tibialis externus and internus (hamstrings in mammals) (Romer, p. 298)

--pubotibialis (adductor longus in mammals) (Romer, p. 298)

--caudofemoralis (Romer, p. 298)

--sternomastoid and cleidomastoid develop from trapezius (Romer, p. 309)

--interhyoideus (forms digastric in mammals) (Kardong, p. 393; Romer, p. 310)


  1. Mammal Ancestor

--epaxial musculature less segmented in nature; includes sacrospinalis (Romer, p. 284)

--rectus abdominis produces the diaphragm (Romer, p. 290)

--caudal muscles reduced (Romer, p. 290)

--scapular origin of deltoid on the spine (Romer, p. 293)

--teres major produced from the latissimus dorsi (Romer, p. 293)

--dermal panniculus carnosus from pectoralis (Romer, p. 295)

--the reptilian supracoracoideus divides to become the supraspinatus and infraspiantus (Romer, p. 296)

--homologue of reptilian iliofibularis often lost (Romer, p. 297)

--hyoid arch musculature expands to form facial muscles (Romer, p. 310)

--depressor mandibulae lost (Romer, p. 310)

--pectoralis muscle splits to form the pectoralis major, pectoralis minor, pectoantebrachialis, and xiphohumeralis (Kardong, p. 387 )

--biceps with two heads (from the fusion of two ancestral muscles) (Kardong, p. 387)

--reptilian gastrocnemius internus forms gastrocnemius medialis and flexor hallucis longus in mammals (Kardong, p. 388)

--reptilian gastrocnemius externus forms gastrocnemius lateralis, soleus, and plantaris in mammals (Kardong, p. 388)

  1. Therian Mammal Ancestor (Marsupials and Placentals)
  2. Placental Mammal Ancestor
  3. Primate Ancestor
  4. Anthropoid Primate Ancestor (monkeys, apes, and humans)
  5. Catarrhine Primate Ancestor (Old World Monkeys, apes and humans)
  6. Ape Ancestor

--caudal muscles converted into pelvic diaphragm

  1. African Ape Ancestor
  2. Human Ancestor





  1. LUCA—Last common ancestor of all modern life on earth
  2. Ancestor of Protists, Plants, Fungi, and Animals
  3. Ancestor of Animals

--cutaneous respiration (which still performs some gas exchange in modern vertebrates, especially amphibians and bats but including humans) (Kardong, p.403)

  1. Ancestor of Animals with Tissues

--mouth (Fretter)

--gastrovascular cavity(Fretter)

--digestive enzymes secreted into cavity (Fretter)

--gut lined by endoderm; glands endodermal (Fretter)

--cilia move particles which are caught in mucus (Fretter)

--muscle cells surround the gastrovascular cavity and may be present in multiple layers (Hickman 185)

--some have a pharynx and ctenophores have anal canals (Hickman 185)

--digestive enzymes include a trypsin-like digestive enzyme that functions in an alkaline environment. (Hyman, 393)


  1. Ancestor Bilateran Animals (the following traits are not found in the most primitive flatworms, Order Acoela)

--muscular pharynx which performs peristalsis (Fretter)

--pharynx is ciliated, with longitudinal and circular muscle layers (Dougherty, p. 197, Beklemishev 2, p. 196)

 --microvilli increase the surface area of the intestine (Hickman)

 --many unicellular glands are present in intestine (Beklemishev 2, p. 196)

--in flatworm orders Macrostomida & Notandropora digestion is extracellular and a stable epithelial gut lining exists (Beklemishev 2, p. 192)


  1. A nemertine-like ancestor of complex bilateran animals

--a complete digestive system, with a mouth and an anus (Hickman)

--mouth is located on the anterior end of the animal (except in a few species (Hickman, p. 227)

--food is moved primarily through ciliary movement and is digested both extracellulary and intracellulary. (Hickman)


  1. Coelomate Ancestor


--in some primitive coelomates (Phoronida), mesenteries support the intestine.  (Hickman, p. 288)

  1. Deuterostome Ancestor

--blood vessels to pharyngeal slits for gas exchange  (Harris)

--second embryonic opening of the digestive tract becomes the mouth, rather than the anus (Romer, p. 325)

  1. Chordate Ancestor

--(urochordates, 9A) blood vessels to pharyngeal slits more extensive  (Harris)

--internal gills around pharynx, distinct from external gills in other invertebrates (Romer, p. 348)

--(cephalochordates, 9B) aortic arches carry oxygenated blood to the dorsal aorta (Willey, 49)

--(cephalochordates, 9B) gelatinous rods in walls around gill clefts (cartilage of vertebrate pharyngeal arches will compose structures such as the hyoid, trachea, and larynx) (Willey, 28)

--(cephalochordates, 9B) liver (Willey, 54)

----(cephalochordates, 9B) hepatic portal system in which blood from intestines brought to a capillary network in liver before the hepatic vein returns it to general circulation (Willey, 54)

--skeletal muscle in anal sphincter (Willey, p. 35)

  1. Craniate Ancestor

--extensions of the dorsal mesentery (mesentery, mesocolon, greater ommentum; absence of mesentery in lamprey may be secondary loss) (Romer, p. 318-9)

--pancreas (although pancreatic tissue is dispersed, similar to the multiple units of the embryonic pancreas) (Romer, p. 393-5)

--liver no longer for enzyme production and food absorption as in Amphioxus (Romer, p. 390)

--only posterior portion of stomodeum (anterior embryonic invagination which unites with digestive tube) contributes to mouth (Kardong, p. 490)

  1. Vertebrate Ancestor

--(maybe hagfish as well) coelom forms from mesoderm after it separates from other tissues (it is not formed from segmented pouches from the gut as in echinoderms and lancets) (Romer, p. 315)

--oral glands; some secrete mucus (Romer, p. 329)

  1. Gnathostome Ancestor

--stomach (Romer, p. 378)

--dermal denticles which are homologous to teeth (Romer, p. 333)

--gills no longer involved in feeding (as in lower chordates, lamprey larvae, and fossil ostracoderms) (Romer, p. 357)

--hypophyseal pouch of stomodeum incorporated into mouth (Kardong, p. 490)

--pancreas units unites, exocrine and endocrine regions together (Kardong, p. 519)

--stomach with  pylorus and fundus (6)

--rectum (6)

--gall bladder (6)


  1. Bony Fish Ancestor


--although advanced actinopterygians (teleosts) possess a swim bladder, the earliest actinopterygians possess lungs (such as Polypterus) whose texture is similar to amniote lungs.  The gar pike and Amia will suffocate without atmospheric air; as will sarcopterygian lungfish (Romer, p. 360, 364) 

--the fossil placoderm Bothriolepis possessed a pair of sacs connected to digestive tube of unknown function (Kardong, p. 403)

--lungs develop as an outpocket of digestive system (Romer, p. 362; Dutta p. 241)

--lung epithelium is endodermal (as is that of digestive tract) (Romer, p. 363)

--bilobed lungs (Polypterus) (Romer, p. 363)

--surfactant for lungs (Dutta, p. 254)

--first true enamel in teeth (Romer, p. 338)

--muscular mechanisms of gulping food which are similar to breathing (Dutta, p. 138)

  1. Sarcopterygian Fish Ancestor

--pericardial cavity no longer opens into coelom around digestive organs (the early pericardial cavities were continuous with the general coelom and even in cartilaginous fish and primitive actinopterygians a connection remains) (Romer, p. 317)

--the pulmonary artery develops as a branch of aortic arch VI which also services gills before emptying into the dorsal aorta through the ductus arteriosus (amphibians have the same) (Kardong)

--pulmonary vein carries oxygenated blood from lungs to left atrium (Kardong p. 465).

--lungs paired (Romer, p. 364)

--alveoli (Romer, p. 364)

--ridges of connective tissue increase respiratory surface area (Romer, p. 366)

--internal naris (Romer, p. 325)

--nasal placodes from stomodeum incorporated into mouth (Kardong, p. 490)

  1. Tetrapod Ancestor

--intestine coils, as does mesentery around it (Romer, p. 318-9)

--tongue muscles from hypobranchial muscles (from gill arches) anchored to the hyoid (which is composed of the fused cartilage of several gill arches) (Romer, p. 328)

--salivary glands (Romer, p. 329)

--a short trachea in some (Romer, p. 370; Dutta, p. 246)

--esophagus more prominent (Romer, p. 378)

--loss of intestinal spiral valve (present in gnathostome fish and perhaps lampreys) (Romer, p. 387)

--ileocecal valve separating a small and large intestine (Romer, p. 388)

--duodenum (Kardong, p. 512)

--lungs with simple squamous epithelia, collagen, and smooth muscle (Dutta, p. 248)

--larynx (5)



  1. Amniote Ancestor

--a completely separate pulmonary circuit; no ductus arteriosus connecting pulmonary and systemic circuits in adult (Kardong)

--increased internal complexity of lungs; septa further divide lungs  (Romer, p. 363; 366)

--trachea lengthens (Romer, p. 366)

--bronchi (Romer, p. 370)

--ribs attach to sternum and function in pulmonary ventilation

--in embryonic development, a large yolk sac distorts gut (even in mammals which lack yolk) (Romer, p. 374)

--cecum (Romer, p. 388)

--intercostal and abdominal muscles used in breathing (Kardong, p. 421-2)

--negative pressure used to inflate lungs (9)

--no cutaneous respiration (9)

--pleural membranes (9)


  1. Mammal Ancestor

--pleural cavities (also present in some reptiles) (Romer, p. 320)

--hard and soft palate (Romer, p. 327)

--fleshy lips and cheeks (Romer, p. 326)

--loss of palatal teeth (Romer, p. 328)

--taste buds primarily on tongue (Romer, p. 328)

--diaphragm (Romer, p. 368)

--vocal cords and resultant voice (Romer, p. 370)

--cardiac region of stomach (Romer, p. 382)

--stomach enzymes and acid are produced by two separate cell types rather than the same cell type as in reptiles (Romer, p. 382)

--intestinal villi prominent (Romer, p. 386)

--rectum derived from cloaca (Romer, p. 389)

--teeth embedded in sockets (thecodont condition) (Kardong, p. 497)

--teeth replaced only once

--occlusion of teeth in upper and lower jaws


  1. Therian Mammal Ancestor (Marsupials and Placentals)
  2. Placental Mammal Ancestor

--loss of cloaca (except in most primitive placentals such as some insectivores)

  1. Primate Ancestor
  2. Anthropoid Primate Ancestor (monkeys, apes, and humans)

--lower portion of duodenum attached by a special ligament (3)

  1. Catarrhine Primate Ancestor (Old World Monkeys, apes and humans)

--dental formula of 2133/2133

  1. Ape Ancestor

--appendix (Ankel-Simons, p. 385)

  1. African Ape Ancestor

--characteristics of spleen (Ankel-Simons, p. 385)

  1. Human Ancestor

--jaw protrudes less, affecting shape of pharynx and sound production

--in throat, pharynx lengthens which enhances sound production but makes choking a greater hazard (Kardong, p. 496)




  1. LUCA—Last common ancestor of all modern life on earth
  2. Ancestor of Protists, Plants, Fungi, and Animals

--meiosis and sexual reproduction

  1. Ancestor of Animals
  2. Ancestor of Animals with Tissues

--first gonads although not organs; may simply be aggregates of cells (Beklemishev vol. 2, Hickman, Hyman)

--ctenophores first ducts for gametes, although gametes released from mouth  (Beklemishev vol. 2, p. 393)

--sex cells migrate to gonads (Hyman, p. 431, Hickman)

  1. Ancestor Bilateran Animals

--the first excretory structures (although osmoregulation is primary function); absent in Acoela (Hickman)

--in advanced flatworms, compact ovaries and oviducts (Beklemishev vol. 2

--in some acoela, oocytes surrounded by folicular cells which nourish (Beklemishev vol. 2

  1. A nemertine-like ancestor of complex bilateran animals

--excretory tubules associated with blood vessels (Hickman)

  1. Coelomate Ancestor

--Metanephridia transport water, waste, gametes (Hickman 289)

--gonads lined by epithelium  (Hickman)

  1. Deuterostome Ancestor
  2. Chordate Ancestor

--podocytes (which are often mistakenly called flame cells) (Romer, p. 403)

--excretory structures in a segmental series (Romer, p. 403)

  1. Craniate Ancestor

--archinephritic duct unites series of excretory tubules (Romer, p. 404)

--archinephros releases waste to cloaca (Romer, p. 404)

--pronephros (anterior excretory tubules which are functional only in adult hagfish; in vertebrates they degenerated during embryonic development) (Romer, p. 405)

--spermatogonia and oogonia produced in yolk sac rather than gonads (Romer, p. 421)

  1. Vertebrate Ancestor

--regulation of body osmolarity (in hagfish, body fluids similar ion concentrations as seawater) (Romer, p. 401)

--mesonephros and metanephros (together called the opistonephros) not segmented after embryonic development (Romer, p. 405)

  1. Gnathostome Ancestor

--fenestrations in kidney glomeruli   (Hardisty 251)

--urea is the most abundant nitrogenous waste (Romer, p. 398 )

--renal corpuscle, proximal collecting tubule, distal collecting tubule (Romer, p. 398-400)

--increase in number of excretory tubules (Romer, p. 409)

--part of mesonephros used to transport sperm; sperm no longer released into coelom (Romer, p. 409)

--bladder (in females only) (Romer, p. 416)

--oviduct (although ova still released into coelom) (Romer, p. 426)

--ciliated infundibulum to “catch” ova (Romer, p. 427)

--gonads paired (Kardong, p. 551)


  1. Bony Fish Ancestor

--bladder in both males and females (Romer, p. 416)

  1. Sarcopterygian Fish Ancestor
  2. Tetrapod Ancestor

--archinephritic ducts are only used to transport sperm (Romer, p. 414)

  1. Amniote Ancestor

--renal corpuscle reduced in size to conserve water (Romer, p. 400)

--males no longer retain Muellerian ducts (as in some amphibians and lungfish) (Romer, p. 427)

--the metanephros is the primary kidney in adults (Kardong, p. 532)

--ovary joined to oviduct (Romer, p. 427)

--portions of oviduct specialize to become uterus and vagina (Romer, p. 429)

--(and cartilaginous fish) epididymis (Romer, p. 434)

--corpora cavernosa, glans penis, and clitoris (Romer, p. 441)

--corpora cavernosa becomes engorged with blood during sexual activity (Kardong, p. 562)

  1. Mammal Ancestor

--(and birds) loop of Henle in kidney (Romer, p. 400)

--mesonephros no loner functional after birth (Romer, p. 406)

--increase in the number of kidney tubules (Romer, p. 412)

--renal pelvis (Romer, p. 413)

--renal cortex and medulla (Romer, p. 413)

--kidney usually bean shaped (Romer, p. 413)

--loss of renal portal system (Romer, p. 414)

--ureters enter the bladder (rather than to the cloaca) (Kardong, p. 569)

--corpus luteum (Romer, p. 422)

--many mammals posses seminal vesicles, prostate glands, and bulbourethral glands (Romer, p. 434)

--cloaca begins to subdivide (Romer, p. 437)

--monotreme penis transitional between that of reptiles and higher mammals (Romer, p. 441)

--corpora spongiosum of penis (Kardong, p. 563)

  1. Therian Mammal Ancestor (Marsupials and Placentals)

--modifications of oviduct (Romer, p. 431)

--penis outside body in most mammals (Romer, p. 441)

--cloaca reduced (Kardong, p. 566)

  1. Placental Mammal Ancestor

--most placentals have a bipartite or bicornuate uterus rather than the primitive uterus duplex (w completely separate tubes) (Romer, p. 431)

--cloaca lost in most placentals but ventral portion retained in females as the vestibule (Romer, p. 439)

--testes descend into scrotum in most placentals (Romer, p. 441)

--testes are retained in the body cavity in monotremes, some insectivores, edentates, and elephants; a muscular pouch which is not a true scrotum exists in many rodents, some insectivores, and hyenas (Kardong, p. 559)

--single glans penis (forked in marsupials) (Kardong, p. 563)

  1. Primate Ancestor
  2. Anthropoid Primate Ancestor (monkeys, apes, and humans)
  3. Catarrhine Primate Ancestor (Old World Monkeys, apes and humans)
  4. Ape Ancestor
  5. African Ape Ancestor
  6. Human Ancestor