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Re: Sharovipteryx an ornithodiran??
>Quoting david peters <firstname.lastname@example.org>:
>> There are dinosaurs and there are crocodiliforms (Scleromochlus nests
>> here) and together they comprise the sum total of the Archosauria
>> (birds + crocs). Pterosaurs and Sharovipteryx are way off yonder in
>> lizard land where the lateral digits are not reduced,
>Um, lateral digits most certainly are reduced in pterosaurs. Manual
>digit V is *gone*, and pedal digit V is long (in basal forms), but
>composed of only 2 phalanges, implying reduction and secondary
>Department of Linguistics
>University of Michigan
Nice try, Nick. But "implying" doesn't cut it.
Sure finger V of pteros is tiny, but that goes back to Macrocnemus. In fact the
relationship of IV to V is always much greater in every member of the
Macrocnemus > pterosaur clade than in any archosauriform.
Finger IV is still a lateral digit. Not THE lateral digit. A lateral digit. In
lizards long. In archosaurs small, smaller than III at least. Look for the
better match. That's what PAUP does.
Toe V in pterosaurs has fewer phalanges because two shorts fused to become one
long. There was no reduction. Look again at Sharovipteryx and Cosesaurus. They
both have elongated pedal Vs. You have to go back to Macrocnemus to find it
shortened -- and that seems to be an apomorphy within that clade -- because
everything around it has a long toe V, langobardisaurids and tanystropheids
Bottom line, it's better to 'show' than 'imply.'
In archosauriforms, as you know, toe V is always pretty short. Again, look for
the best match. Forget tradition and textbooks. Test it yourself. Benton 1985
did and look what he found. Even he didn't believe his own results, so you're
in good company.
The pattern is so different that, as I think I mentioned before, you put any
number of archosaurs into a cladogram, add the basal pterosaur MPUM 6009 and
two lizards, Varanus and Iguana, and the pterosaur will nest with the Iguana.
You don't even need the usual predecessors. Try it!
The strength of the paradigm is great. But it has to fall.