[Taxacom] Orrorin a hominid?

[John Grehan]

I would agree with Orrorin being a hominid. I missed Strait and Jungers
2008 so I will take a look. But in the forthcoming hominid analysis (now
about four weeks from publication) Schwartz and I present four 'hominid'
characters (i.e. features otherwise unique to australopiths-Homo) in
Orrorin - presence of a linea aspera, inferiorly thickened femoral neck,
femoral shaft outwardly angled, and thick molar enamel.  

The thick molar enamel is mentioned by Ken, but if he believes in the
chimpanzee theory of origin then thick enamel is uninformative since it
is also shared by the orangutan. But placing Orrorin within a
hominid-oranutan clade thick enamel is certainly congruent with the
other morphological evidence.

Describing the canine of Orrorin as 'chimp-like' is not informative
unless it is chimp-like in a uniquely shared aspect. Is it?

As for Ardipithecus - its nothing much more than a metaphysical entity
because the holotype is not openly accessible for inspection - contra
zoological rules of nomenclature.

John Grehan

> -----Original Message-----
> From: taxacom-bounces at mailman.nhm.ku.edu [mailto:taxacom-
> bounces at mailman.nhm.ku.edu] On Behalf Of Kenneth Kinman
> Sent: Wednesday, May 13, 2009 2:05 PM
> To: taxacom at mailman.nhm.ku.edu
> Subject: [Taxacom] Orrorin a hominid?
> 
> Dear All,
>       One paper which indicates that Orrorin should be placed near
> Australopithecus in Hominidae (sensu stricto) is Richmond and Jungers
> paper (March 2008 in the journal Science) on the femoral structure of
> Orrorin.  They make a good case that it was bipedal.  I believe the
case
> for bipedality in Ardipithecus is still based on single toe bones (and
> that argument seems more of a stretch to me).
>       And of course, we know that Orrorin also had thicker tooth
enamel,
> like Australopithecus, whereas Ardipithecus has thinner enamel like
> chimps.
>       The one thing that still troubles me about Orrorin is its canine
> tooth, which is very chimp-like.  I just wonder if perhaps the
earliest
> hominids might have been sexually dimorphic in this character.
Perhaps
> males of Orrorin still retained a chimp-like canine, but the females
had
> already begun the reduction of this tooth.  As far as I know, we still
> only have a single canine tooth from Orrorin, but I am hoping for more
> material to be discovered.
>             ---------Ken Kinman
> 
> 
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