Characters that Support the Great Ape Clades

Anyone familiar with the current state of great ape phylogeny knows that the following structure is well-supported:

• Great apes are a clade.
• Orangutans are a subclade of great apes.
• African great apes are a subclade of great apes.
• Gorillas are a subclade of African great apes.
• Mangani are a subclade of African great apes.
• Humans are a subclade of mangani.
• Chimpanzees are a subclade of mangani.

And most such people probably know that the primary evidence for this structure is molecular. But there has to be morphological data to back this up, right?

Great Apes

I've been trying to hunt down such morphological data, but it's been a bit hard. There really aren't that many morphology-based cladistic studies of primates, and the few that exist either exclude humans or focus on stem-humans more than living great apes.

An example of a study that looks at a wide array of fossil and living primates, but fails to include humans:

• Rossie & Seiffert (2006). Continental paleobiogeography as phylogenetic evidence. Pages 469–522 in Lehman & Fleagle (eds.) Primate Biogeography: Progress and Prospects. Springer, New York. 546pp. isbn:0387298711

An example of a study that includes some living great apes, but focuses on stem-humans:

• Strait & al. (1997). A reappraisal of early hominid phylogeny. Journal of Human Evolution 32(1):17–82. pmid:9034954

I've compiled some shared character lists from these:



CHARACTERS SHARED BY CHIMPANZEES AND HUMANS, BUT NOT GORILLAS (Strait & al. 1997):

• Inferior orbital margin never rounded laterally
• Sagittal crest not present in males*
• Postorbital constriction moderate or slight
• Narrow supraglenoid gutter width
• External auditory meatus positioned medially (not laterally)
• Consistently small mandibular cross-section area at M₁
• Narrow mandibular extramolar sulcus
• Very small premolar crown area
• Very small molar crown area

* Fossils show this to be a convergence.

CHARACTERS SHARED BY CHIMPANZEES AND GORILLAS, BUT NOT ORANGUTANS OR GIBBONS (Rossie & Seiffert 2006):

• Upper premolar cusp heteromorphy reduced
• P₃ MD length narrow
• M₁-M₂ waisting present
• M₁-M₂ crown tapering distal
• Talon size large relative to trigon
• Radial head outline smaller flat area
• Dorsal ridge on radius present
• Os centrale fused*
• Metacarpal dorsal ridges present
• Hamate hamulus distally projecting
• Posterior calcaneoastragular joint faces dorsally
• Supraorbital region strong inflated tori
• Frontal sinus present*

* I've verified that these are present in humans, too. I'm sure most or all of the others are as well, but I haven't had time to check.

CHARACTERS SHARED BY CHIMPANZEES, GORILLAS, AND ORANGUTANS, BUT NOT GIBBONS (Rossie & Seiffert 2006):

• I₂ cingulum present
• P₄ crown shape sub-ovoid
• P₄ MD length narrow
• p₃ mesiolingual beak present
• p₃ sectoriality poor
• p₄ length very broad
• m₁-m₃ distal fovea wide
• Transverse process inclination dorsally and caudally inclined
• Transverse processes on pedicle
• Four lumbar vertebrae
• Deltoid insertion on distal half
• Radial styloid process reduced
• Trapezium-MC1 joint sellar
• MC1 prox articulation lateral extension
• Hamate distolateral edge interrupted by ligament pit
• Tibial condylar facets medial larger
• Femoral condyles medial larger
• Talar head width greater than height
• Anterior calcaneal length less than one third
• Heel tubercle present
• Infraorbital surface of maxilla slopes anteroinferiorly
• Snout length protruding
• Palate shape parallel to tooth rows
• Orbit inferior margin flush with cheek
• Orbit position high
• Nasal shape narrow superiorly
• Horizontal palatine process narrow

What I'd like to do eventually is synthesize these into easily-readable lists of characters supporting the major great ape clades (great apes, African great apes, mangani). The lists are in pretty sloppy form right now, though. Things left to do:

1. Double-check against the character matrices.
2. Find the human state for the relevant characters in Rossie & Seiffert 2006.
3. Weed out the symplesiomorphies and homoplasies.
4. Translate these into less technical language, insofar as possible.