[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Sphenochians and birds

Jean-michel BENOIT" <Jean-Michel.BENOIT@gemplus.com> writes:

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,

This theory (which walker supported for a time) is now widely discredited. Sphenosuchians like Terrestrisuchus (which you mention) are basal crocodylomorphs.

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.

Protoavis is thought by Chatterjee to possibly arboreal and undoubtedly volant (i.e. able to fly). The idea that Protoavis is a bird has received very little support in the paleontological community. The true identity of Protoavis is still uncertain - it may be made up of bones from more than one species.

It was thought to be derived from animals like *terretrisuchus* placing the first bird-like reptiles back to the triassic period.

Even Chatterjee believes birds to have evolved from dinosaurs, not crocodilians.

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.

This is probably not correct. Certain opponents of the birds-from-dinosaurs theory claim that the homology of the fingers differs betewwn theropods and birds (I-II-III vs II-III-IV). The embryological basis for this in birds is controversial, but I think it's fair to say that the embryological evidence is reconcilable with the I-II-III origin of the digits in birds (as in theropods). There are some recent papers which discuss this.

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?

It has been largely abandoned, but never say forever!


Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com.

Share information about yourself, create your own public profile at http://profiles.msn.com.