Re: Miocene and Pliocene apes familiy tree?

Alex Duncan (
1 Aug 1995 03:49:52 GMT

In article <herwin-3007951710200001@> Harry Erwin, writes:
>1. Broad incisive fossa overhung by nasal-alveolar clivus, forming a steep
>drop to the floor of the nasal cavity,
>2. A number of detailed wrist and ankle modifications,
>3. Relatively reduced premolar size,
>4. Delayed dental eruption,
>5. Structure of heart and aorta,
>6. Specialized axillary organ,
>7. Preponderance of eccrine glands over body surface,
>8. Densely haired scalp,
>9. Lengthened small intestine and shortened colon,
>10. Earlobes,
>11. Frontal sinuses,
>12. Sutural patterns, and
>13. Foraminal positions.
>Most of this stuff doesn't fossilize well.

What Harry said.

One of the best skeletal characters are the premax/palate articulation
(#1 above). Its very derived in modern Homo, but in other hominids
(traditional) it is very similar to what is seen in Pan & Gorilla. This
is a very good example of the fossil record clarifying a trait that would
difficult to utilize otherwise.

Humans and chimps share a very early obliteration of the premax/maxillary
suture. This may be related to the fact that we're both relatively
orthognathic compared to gorillas and pongo.

All African hominoids (incl. Humans) have os centrale fused to scaphoid
(this is one of the features that would make up #2, above). This same
fusion occasionally happens in Pongo, but my understanding is that it
only occurs late in life.

All African hominoids have robust supraorbital tori and corresponding
sulci. Again, humans are so derived (expanded frontal) that the feature
is usually absent, but it was clearly present in most human precursors,
and the occasional modern human still has a substantial brow ridge. I
don't think the polarity of this character is clear at all, and is
confused by size issues. It is probably also associated w/ the hafting
of the neurocranium on the face (airo/klinorhychy). I suspect there are
two ways to transmit stresses generated during chewing through the upper
face. One way is to have a big brow ridge, and another is to have a
frontal that rises nearly vertically above the orbits. It may be that
neither buttressing system is necessary until a certain size is reached,
which may explain why we don't clearly see either one in Aegyptopithecus
or small Proconsul species.

There have been recent suggestions (see Gebo) that African 'noids share a
mode of locomotion that involves early heel strike, and that there are
modifications to the calcaneus that are associated. This trait is a
little controversial, I think. I've only scanned Gebo's article and its
critiques, so I'm not sure what to think.

One feature I've seen cited as a possible synapomorphy of chimps and
humans is "angle of ear bones over 90 degrees" (Peter Andrews, JHE).
I'm not sure what this means, or what ear bones he's talking about, or
about what the 90 degrees is relative to.

Another possible synapomorphy of human and chimp is "homomorphic upper
lateral incisors." Our lateral incisors are similar in size and shape to
the centrals. This is less true of Gorilla, and very much less true of

Alex Duncan
Dept. of Anthropology
University of Texas at Austin
Austin, TX 78712-1086