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Re: Lewisuchus, a Dinosauriform
Adam Yates wrote-
> Not all early sauropodomorphs have such a phalanx on the fifth digit.
> The most primitive of all Saturnalia and Thecodontosaurus do not have
> one (this is based on complete articulated feet for both taxa, and the
> pointed shaped of the distal mt V). As Ornithischians, Guiabasaurus,
> Theropods, Marasuchus and Lagereton all lack one as well I think that a
> good case can be made that this is the ancestral state and for the
> convergent re-aquisition of a phalanx in derived sauropodomorphs and
> Herrerasaurus (probably related to broadenening of the foot). Do we
> actually know the state for Eoraptor?
How very interesting. That's what I get for assuming all basal
sauropodomorphs were alike. Checking Rauhut (2000) indicates the state is
unknown for Eoraptor. In light of this evidence, I would have to agree that
it is most parsimonious to assume phalanx V-1 was lost in Dinosauromorpha
and regained in both Herrerasaurus and the Plateosaurus+Sauropoda clade.
The absence of the phalanx in basal sauropodomorphs really throws a wrench
in George's basis for his hypothesis.