Re: Sphenochians and birds

["Larry Febo" <larryf@capital.net>]

-----Original Message-----
From: Jean-michel BENOIT <Jean-Michel.BENOIT@gemplus.com>
To: dinosaur@usc.edu <dinosaur@usc.edu>
Date: Wednesday, November 08, 2000 3:51 AM
Subject: Sphenochians and birds


>Hi all,
>
>I was re-reading recently a _quite_ old but interesting book written by the
Cserkases with help from Olson. It spoke of a possible origin of birds
within the sphenosuchians, the fossil called *protoavis*, having elongated
forelimbs thus thought to have had a arboricole ( is this the correct
word? ) life but found with no evidence of feathers. It was thought to be
derived from animals like *terretrisuchus* placing the first bird-like
reptiles back to the triassic period. The text said that embryology showed
that the missing fingers in birds were not the same as in theropods but were
the same to those of crocodilians. I'm not very sure I've understood all the
scientific explanations but it seemed very convincing to me. How about this
theory? Is it still debated or has it been abandonned for ever?


Funny,...I just started reading that book myself ("Dinosaurs...a Global
View"). It sits open on my table,...got as far as the "Jurrassic" section.
Anyways,....aside from the debate on digit count (which seems still
unresolved), Terrestrisuchus, being crocodylian, probably had the normal
crocodile ankle, which would preclude it from being a dinosaur ancestor. A
key characteristic of Ornithodirans, (including dinosaurs) would be the
advanced mesotarsal ankle. The croc ankle is too derived from this
condition, and would require a reversal for crocs to be considered dino ( or
bird) ancestors.