Re: Lewisuchus, a Dinosauriform

[AM Yates <Adam.Yates@bristol.ac.uk>]

On Mon, 23 Jul 2001, Mickey Mortimer wrote:

> Now, you're correct in stating that "lagosuchians" (Lagerpeton, Marasuchus)
> lack phalanges on pedal digit V, while basal dinosaurs (Eoraptor,
> herrerasaurids, basal sauropodomorphs, sauropods) have a phalanx.  Of

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?
PS Mike Keesey asked who said that Herrerasauridae was basal to
Eoraptor. It was Max Langer at SVPCA, and I think he's right.

cheers

Adam Yates