15 September 2011

Soft Tissue Characters Supporting the Great Ape Clades

In my last post, I took a look at some morphological cladistic analyses of hominoids (apes) and tried to compile list of characters that supported the major clades: great apes, African great apes, and mangani (chimpanzees + humans). Unfortunately the studies I looked at only considered skeletal characters (and one of them only craniodental characters). Fortunately, a reader (Dartian) suggested some studies that look at soft tissue characters. I've just skimmed this paper:
  • GIBBS, S., COLLARD, M. & WOOD, B. (2002). Soft-tissue anatomy of the extant hominoids: a review and phylogenetic analysis. Journal of Anatomy 200:349. doi:10.1046/j.0021-8782.2001.00001.x
The authors compiled a matrix of 171 soft tissue characters and found strong support for the topology produced by earlier molecular studies (gibbons, (orangutans, (gorillas, (humans, chimpanzees)))). Below, I've compiled lists of character states that unambiguously support the major clades:

Great ape synapomorphies (orangutans and African great apes):
  • Apical lingual gland present in at least some specimens
  • Most common pattern of insertion of extensor indicis does not involve digit IV (digit II and possibly III only)
  • Origin of gluteus minimus is discontinuous or variably continuous
  • Rectus femoris has two heads in at least some specimens
  • Articularis genus present in at least some specimens
  • Ratio of nipple position to horizontal height index of nipple position between 1.0 and 1.8

African great ape synapomorphies (gorillas and mangani):
  • Conical filiform predominate over cylindrical filiform
  • Radial head of flexor pollicis brevis originates from flexor retinaculum and trapezium only
  • Humeroulnar head of flexor digitorum superficialis takes origin from intermuscular septum
  • Palmaris longus not present in all specimens
  • Orientation of pronator quadratus moderately or weakly oblique
  • Flexor pollicis longus originates from anterior radius and interosseous membrane
  • Slips from extensor digitorum tendon for digit IV to digits III and V
  • Coracobrachialis origination from intermuscular septum in at least some specimens
  • Anterior extension of insertion of coracobrachialis present in most specimens
  • Extensor pollicis brevis origination from ulna and interosseous membrane
  • Most common pattern of insertion of extensor indicis does not involve digit III (digit II only)
  • Teres minor insertion extends onto shaft below greater tubercle
  • Subclavius takes origin on first rib only
  • Extent of clavicular origin of pectoralis major: 1/3 to 1/2 (less than 2/3)
  • Origin of psoas major does not extend to S1 in all specimens
  • Piriformis normally fused with gluteus medius
  • Quadratus femoris not split at insertion or variable
  • Adductor magnus insertion into inferior border of quadratus femoris insertion
  • Peroneus brevis may insert onto first and second phalanges of digit V
  • Soleus often has tibial origin
  • Cephalic vein sometimes limited to forearm
  • Origin of radialis indicus may include first palmar metacarpal artery
  • Point at which radial artery enters palm: dorsum of first interosseous space
  • Superior ulnar collateral artery may originate from brachial artery
  • Lateral thoracic artery normally an independent branch of axillary artery
  • Superior thoracic artery
  • Most common form of branches from aortic arch is E (Keith, 1895)
  • Lateral plantar artery dominant in at least some specimens
  • Normally 3.5 digits supplied by median nerve
  • Psoas minor innervated by femoral nerve
  • Muscular branches of tibial nerve includes flexor digitorum longus
  • Average body hair density moderate to low
  • Sternal glands
  • Axillary organ
  • Transverse rugae of vagina

Mangani synapomorphies (humans and chimpanzees):
  • Extensor digitorum originates from antebrachial fascia
  • Lateral head of triceps brachii originates from lateral intermuscular septum
  • Extension of extensor carpi ulnaris to first phalanx of digit V in some specimens
  • Teres minor shares origin from intermuscular septum with teres major
  • Latissimus dorsi may originate from inferior scapular angle
  • Extent of clavicular origin of pectoralis major: 1/2
  • Tensor fascia latae normally fused proximally with gluteus maximus
  • Origin of short head of biceps femoris: posterolateral femur and lateral intermuscular septum*
  • Extensor digitorum longus originates from crural fascia
  • Peroneus longus does not originate from lateral tibial condyle*
  • Plantaris often present
  • Extensor digitorum brevis tendon to digit V not normally present*
  • Slip from abductor hallucis into base of MI
  • Abductor hallucis may insert onto medial cuneiform
  • Medial and lateral heads of flexor hallucis brevis not separated by septum*
  • First dorsal interosseous originates from MI and MII
  • Flexor digitorum brevis originates from plantar aponeurosis
  • Origin of posterior interosseous artery: common interosseus (not brachial artery)
  • Dorsalis indicis and dorsal metacarpal branches of ulnar artery absent*
  • Superficial palmar artery may pass over thenar muscles
  • Dorsalis pollicis
  • Profunda brachii may originate from brachial artery*
  • No perforating branch of peroneal artery anastomoses with anterior lateral malleolar artery*
  • Inferior medial and inferior lateral genicular branches of popliteal artery*
  • Medial femoral circumflex artery may originate from profunda femori
  • Muscular branches of profunda femoris for hamstrings
  • Gangliform enlargement at junction of radial and posterior interosseous nerves
  • Axillary nerve does not innervate subscapularis*
  • Muscular branches of obturator nerve may include pectineus
  • Superficial peroneal nerve supplies medial side of digit II
  • Average body hair density low
  • Scrotum normally postpenial
  • Scrotum semidependent or dependent (never nondependent)
  • Relative testes size (ratio of observed/predicted body testes size) greater than 0.4
* also in gibbons

I'll be honest, I barely know what most of these are. But I intend to find out!


  1. This is my favorite post of all time on 3lb MB. Well done!

  2. These are just notes -- wait until I finish the synthesis!

    I was unfamiliar with the term "axillary organ" before today. I looked it up and apparently it's the fancy way of saying "armpit bush". So pungent, hairy armpits are a synapomorphy of African great apes. I had no idea!