[Taxacom] Chororapithecus and bad science (for morphologists only)

[John Grehan]

Ken implied some criticism of my reading of the paper on
Chororapithecus. I have therefore provided some detailed notes below for
his or anyone else's assessment (those who do not believe in morphology,
please do not read any further).

I have to make particular note of Ken's implication that paleontologists
"who named and have carefully studied these fossils" are somehow above
question. For Chororapthecus in particular, the authors admit that there
is no evidence that one of their paratypes cannot be associated with the
holotype. Is that bad science or am I misunderstanding something?

John Grehan

Is Chororapithecus a Gorilla relative?

The 10 million year old fossil Chororapithecus, represented by a
collection of lower and upper teeth, is widely viewed as providing
evidence of it being a close Gorilla relative. A review by Dalton (2007)
quotes authors as saying the teeth "are collectively indistinguishable
from modern gorilla subspecies" in size, proportion and scan-revealed
internal structure. But Jay Kelley is also quoted as saying he is not
convinced that Chororapithecus is a gorilla (presumably he means a
gorilla relative).

When the text of Suwa et al (2007) examined in detail, the necessary
definitive features required to support a closer phylogenetic
relationship between Chororapithecus and Gorilla than with other
primates appears to lacking.

The argument seems to rest principally on the notion that the teeth are
gorilla sized and that Chororapithecus "may" be a basal member of the
gorilla clade (p. 222). They make it clear that Chororpatitheucs is
distinct from Gorilla in having lower molar crown and cusps, thicker
enamel, upper molars with less distinct crista oblique, lower molars
lacking buccolingual infolding of the buccal occlusal margin (this is, a
lack of extremely elongated shearing crests). 

The dentition is described as "gorilla-sized" and combines distinct
shearing crests with think enamel on its "functional' side cusps with a
"relatively flat cuspal enamel-dentine junction". An enhanced shear
between the medial protocone crest and distal occlusal slope of the
metaconid is seen to be similar is seen to be "similar" to that of
Gorilla and the fossil taxa Rangwapithecus, Nyanzapithecus, and
Oreopithecus, although no comparative data is cited with respect to
these or other living and fossil taxa.

The straight to weakly concave mesial protocone crest in the
enamel-dentine junction of CHO-BT4 (right upper second molar), -BT5
(right upper third molar) and -BT6 (right upper third molar) is also
described as "gorilla like".

However, the "low relief of the 'functional' side cusps endowed with
thick enamel...is reminiscent of the three-dimensional enamel
distribution patterns seen in Pongo..."

In addition the list of paratypes includes a right upper third molar
(CHO-BT 11) that the authors admit in the supplementary information some
uncertainty and raise the possibility that it represents another taxon.
They conclude that "its fragmentary status and lack of diagnostic
morphological signals caution against further speculation at this
rudimentary stage of knowledge". But to retain the tooth as a paratype
even though there is nothing to link it to the holotype is bad taxonomy
and systematics.



-----Original Message-----
From: taxacom-bounces at mailman.nhm.ku.edu
[mailto:taxacom-bounces at mailman.nhm.ku.edu] On Behalf Of Kenneth Kinman
Sent: Thursday, April 28, 2011 10:35 PM
To: taxacom at mailman.nhm.ku.edu
Subject: Re: [Taxacom] Hominoid classification (was: incertae sedis)

John,
       I don't know if you are trying bait me into one of your arguments
or if you haven't read the original articles which actually described
and named Nakalipithecus and Chororapithecus.  The paper on the original
description (and naming) of Nakalipithecus discusses its similarity to
Ouranopithecus , and suggests that Nakalipithecus is close to what might
be regarded as the immediate ancestor to the Gorilla-Pan-Hominid clade.
Ouranopithecus (which they regard as a bit more derived) could arguably
be sister group of Nakalipithecus, an exgroup of genus Nakalipithecus,
or part of the gorilla-chimp-hominid clade.  One paper even suggested
Ouranopithecus is close to the Australopithecus-Homo clade (my Family
Hominidae), but that is perhaps a bit of a stretch in that it is mainly
based on evidence from milk teeth.         
       And also note that the paper which originally described and named
Chororapithecus suggested that it could very well be a basal member of
the gorilla clade.       
       So are you suggesting that I ignore the opinions of those
paleontogists who carefully studied and named those new genera, and
instead follow your interpretation?  Thick molar enamel in particular,
which you frequently cite, is probably very labile evolutionarily
(depending on diet, which can easily and quickly shift).  
       So I"m afraid I have to go with the paleontologists who named and
have carefully studied these fossils.  Your concerns with the thickness
of tooth enamel in hominoid evolution seem to be too heavily weighted in
my opinion.  I like to look at a broader range of data and weight them
differently.     
        As for whether more fossil material is the solution, it only
takes one unusually complete specimen at the right place
(phylogenetically) to clarify which characters are synapomorphic and
which are plesiomorphic.  Don't underestimate the value of such special
fossils just because they cannot yield molecular evidence.  Of course,
we are more likely to get results from whole genome analysis before we
get lucky enough to stumble such rare special fossils.  
          -------Ken Kinman       

--------------------------------------------------------
John Grehan wrote: 
       As noted in the past, I have no objections to Ken expressing his
opinion about his preferred classification, but in the absence of
supporting evidence also being presented, the classification is
scientifically meaningless. 
Chororapithecus has nothing definitively gorilla, and contradictorily
the molars have thick enamel!                
          I have not seen any evidence that Ouranopithecus and
Nakalipithecus are closely related. I would be interested to know what
Ken would cite in support that would place Ouranopithecus closer to
Nakalipithecus than various other orangutan relatives as demonstrated by
Grehan & Schwartz (2009). 
         More fossil material is not the solution in of itself. Early
hominids (australopiths) for example, clearly have orangutan as well as
human-orangutan apomorphies, but no one wants to recognize that reality.

        A whole genome analysis isn't going to accomplish anything for
fossil hominids of course. 


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