Re: Another Alxasaurus query (was: thanks and ...)

["Jaime A. Headden" <qilongia@yahoo.com>]

I wrote:

<<Okay, I am operating on the assumption that segnosaurs are
theropods.>>

Larry Dunn wrote:

<Aren't they considered to be?>

  The best published analysis of the group (the whole group, excluding
*Alxasaurus*) is Barsbold & Maryanska, 1990, in _the Dinosauria_. They
showed that because of the mosaic of characters evident in the bones,
they could not, at that time and analysis, be demonstrated as having
undoubted theropod, prosauropod, or even ornitrhschian affinities.
They placed them in Saurischia, but the authors showed that even that
was changable and mutable.

<The fourth toe is awfully odd, isn't it? Is there an analogy that can
be drawn in, say, extant mammals?>

  Of all animals that possess a hallux, only extant lepidosaurs and
crocodyloids had the ability to place it on the ground, at least
laterally, while the structure in birds is highly different from
_either_, though the digit, at least distally, touched the ground. But
the analogy is not comparable in any sense to extant forms, and we
_must_ use extinct ones to make any sort of inference. Well, I found
stegosaurs and prosauropods to be quite distinctively similar (in some
details). This is heavy weight-bearing, broad distal ends, and reduced
flexion/extension in the phalangeal bones. Lateral compression of the
claws is something I doubt _anyone_ has made a strong enough case for
the purpose of, but needless to say, there are no osteological
characters to assume webbed feet are evident, in that the pes is short
and the digits strongly shortened.

  Some of the pedal functions were popularly discussed in Norman, 1983
(_Encyclopedia of Dinosaurs_) and Lambert, 1993(?) (_Ultimate Dinosaur
Book_).

==
- Often, it is the man who is brought
  down the path to the end who does
  not see his own steps. -

Jaime A. Headden

Qilong, the website, at:
_________________________________________________________
DO YOU YAHOO!?
Get your free @yahoo.com address at http://mail.yahoo.com