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THE MUSCULAR SYSTEM

     The Muscular Cladogram depicts a nested hierarchy of anatomical features of animal muscular systems.  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).

     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. 


 

 

MUSCULAR CLADOGRAM

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

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

--actin and myosin (Amos, 2004; Egleman, 2003). 

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)

--Twist expression first occurs in the entocodon, the mesoderm-like layer from which muscle tissue differentiates in cnidarians (Castanon, 2002).   The development of striated and smooth muscle from this third cell layer have led some to consider cnidarians as tribloblastic (Muller, 2003).

--In bilateran animals, some of the genes which are essential for the embryonic formation of muscle are members of the basic helix-loop-helix gene family (bHLH).  Jellyfish are known to possess at least four bHLH transcription factors.  The sequence, dimerization, and expression of the JellyD1 protein in striated muscle indicate that it is a homolog of MyoD in bilaterans.  Vertebrate MyoD genes, which can form both homodimers and heterodimers, can form dimers with JellyD.  This indicates that the striated muscle of jellyfish is homologous to that of bilaterans (Muller, 2003).

 

5.       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)

6.       A nemertine-like ancestor of complex bilateran animals

--all vertebrates and invertebrates ranging from nematodes to arthropods use troponin and tropomyosin. a homolog of titin is known in nematodes (Hoar, 1983, p. 325).

7.       Coelomate Ancestor

--Titin is known in arthropods (Champagne, 2000). 

8.       Deuterostome Ancestor

9.       Chordate Ancestor

--Tunicates do possess homologs of vertebrate genes involved in heart formation, but typically fewer members than contained in vertebrate gene families (Dehal, 2002

--myotomes since cephalochordates (Cameron, 2000)

 

10.   Craniate Ancestor

--hypobranchial musculature (Romer, p. 288)

--both fast and slow twitch muscles (Hardisty, p. 357).

--myotomes from head region of jawless and cartilaginous fish embryos suggest that the ancestral condition included pro-otic somites whose muscles produced the muscles which move the eye.  The first pro-otic somite forms the superior rectus, inferior rectus, internal rectus, and inferior oblique and is innervated by III.  The second pro-otic somite forms the superior oblique, IV.  The third becomes external rectus, abducens VI. (Weichert, 1970). 

 

11.   Vertebrate Ancestor

12.   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)

13.   Bony Fish Ancestor

14.   Sarcopterygian Fish Ancestor

15.   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)

--interspinalis muscles (Webster, 1974)

 

16.   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)

--extensions of the oblique muscles form the intercostal and scalene muscles of amniotes.  (Webster, 1974; Weichert, 1970, p.512).

--a longissimus coli and levatores costarum (Webster, 1974; Weichert, 1970, p.512).

--sphincter colli deep to the integument of the head (Weichert, 1970)

 

17.   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)

--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)

--intercostals are move developed (Webster, 1974; Weichert, 1970, p.512)

--the multifidus is a mammalian remnant of transversospinalis muscles in reptiles (Weichert, 1970, p. 513). 

--the ancestral single sheet of the latissimus dorsi divides to form the latissimus dorsi, the teres major and cutaneous maximus in mammals (Webster, 1974, p.139; Hartman, 1933).

--the pectoralis splits and also forms part of the cutaneous maximus. (Webster, 1974, p.139; Hartman, 1933).

-- remnants of the cranial portions of this ancestral rectus abdominis in head region include the sternohyoid, sternothyroid, geniohyoid, omohyoid, and thyrohyoid. (Weichert, 1970).  

--mammals the reptilian sphincter colli differentiates into facial muscles although they are poorly developed in most mammals.  The outer layer of the sphincter colli (the platysma layer) forms the auricularis frontalis, orbicularis oculi, mentalis, quadratus labii inferiors, and zygomatic.  The deep layer of the sphincter colli gives rise to muscles of the nose, the orbicularis oris, and buccinator muscles. (Weichert, 1970, 529).

18.   Therian Mammal Ancestor (Marsupials and Placentals)

19.   Placental Mammal Ancestor

20.   Primate Ancestor

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

--wider gluteal attachment on ilium (Gebo, 2008).

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

23.   Ape Ancestor

--caudal muscles converted into pelvic diaphragm

 -- flexor digitorum brevis is intermediate between humans and lower primates (Hartman, 1933,p 172). 

  -- usually lack the epitrochleo-anconeus of lower primates, which was originally derived from the flexor carpi ulnaris (Hartman, 1933, p. 137) 

--a deep head of the pronator teres  (Hartman, 1933, p. 138).

--a radial origin of flexor digitorum sublimis (Hartman, 1933, p. 138)

--vestiges of the muscles which are used in tailed primates to flex the tail usually exist (such as the sacrococcygeus anterior in humans).

 --the ancestral pubo-iliocaudalis is attached to the visceral organs and becomes the levator ani

-- the pectoralis minor inserts onto the coracoid process instead of the arm (Hartman, 1933)

 

 

23A. Higher Apes

—extensor indicis usually doesn’t insert on digit IV (Gibbs, 2002)

rectus femoris with 2 heads (variable in all but humans) (Gibbs, 2002)

articularis genus (Gibbs, 2002)

--extensor pollicis brevis (Hartman, 1933, p. 141)

--the latissimus dorsi developed an additional origin on the iliac crest.  (Hartman, 1933). 

 

24.   African Ape Ancestor

—origin of flexor pollicis brevis limited to flexor retinaculum and trapezium (Gibbs, 2002)

—flexor digitorum superficialis originates from intermuscular septum (Gibbs, 2002)

pronator teres obliquely oriented (Gibbs, 2002)

—flexor pollicis longus from anterior radius and interosseous membrane (Gibbs, 2002)

—extensor digitorum IV sends slips to digits III and V (Gibbs, 2002)

—origin of coroacobrachialis from intermuscular septum (Gibbs, 2002)

—anterior extension of coracobrachialis ussually present (Gibbs, 2002)

—origin of extensor pollicis brevis from ulna and interosseous membrane (Gibbs, 2002)

-- extensor indicis usually doesn’t insert on digit III (Gibbs, 2002)

teres minor inserts below greater tubercle (Gibbs, 2002)

—origin of subclavius on first rib only (Gibbs, 2002)

—origin of psoas major reaches S1 (Gibbs, 2002)

piriformis usually fused with gluteus medius (Gibbs, 2002)

—adductor magnus and quadratus femoris insertions meet (Gibbs, 2002)

peroneus brevis may insert onto digit V proximal and middle phalanges (Gibbs, 2002)

—origin of soleus frequently on tibia (Gibbs, 2002)

--although the peroneus tertius has frequently been described as a muscle which only exists in humans as an adaptation to bipedal locomotion, it occasionally occurs in gorillas and rarely in chimps (Hartman, 1933, p. 166).

--the deep extensor layer is reduced (Hartman, 1933)

--the  psoas minor may be absent in African apes but seems constant in other mammals (Hartman, 1933, p. 149). 

 

 

24B.  Humans and Chimps

—origin of extensor digitorum on antebrachial fascia (Gibbs, 2002)

—origin of lateral head of triceps from lateral intermuscular septum (Gibbs, 2002)

—extensor carpi ulnaris sometimes extends to proximal phalanx V(Gibbs, 2002)

Teres major and minor share an origin from intermuscular septum (Gibbs, 2002)

—reduction of clavicular origin of pectoralis major (Gibbs, 2002)

—proximal portion of tensor fascia lata fused to gluteus maximus (Gibbs, 2002)

—origin of extensor digitorum on crural fascia (Gibbs, 2002)

—insertion of abductor hallucis may include medial cuneiform (Gibbs, 2002)

—origin of flexor digitorum brevis on plantar aponeurosis (Gibbs, 2002)

--frequently a coronoid origin of the flexor digitorum sublimis; (Hartman, 1933, p. 138).