Re: Claws of Baryonyx and Sinosauropteryx

["Mickey_Mortimer11" <Mickey_Mortimer11@email.msn.com>]

Fam Jansma wrote-

> If in higher mairaptorans the pedal claws are important in some groups
> (Dromeosaurs e.g.), why is it shrinking than in later genera like
> Achillobator and Adasaurus? It's like reversing evolution when you have
> this great tool to slice those poor Hypsies to shred and than to
re->evolve
> into something that makes a scap on it's toe or whatever.

You're assuming that Adasaurus and Achillobator had large clawed ancestors.
The only analysis I know of containing them is Norell et al.'s (2001), which
has them in a polytomy with dromaeosaurids, Utahraptor and Unenlagia.  My
analysis has never been very precise in the eumaniraptoran area, but
Achillobator being further from birds than dromaeosaurids is certainly a
possibility.  Also, I'm not convinced the supposed second pedal ungual of
Achillobator isn't from the hand.

> Here's one "just-so" scenario to explain the "shrinking" sickle-claw:
> "Mid-sized" dromaesoaurids _Deinonychus_ and _Velociraptor_ needed a
> particular large sickle-claw because they targeted prey of comparable (or
> even larger) size than themselves.  The preferred prey of larger
> dromaeosaurids (like _Utahraptor_ and _Achillobator_), by contrast, was
> relatively smaller than themselves: the importance of the sickle-claw
> declined, since the predator could rely more on physical strength to
subdue
> prey.  The sickle-claw of _Microraptor_ was rather undersized too,
compared
> to _Deinonychus_ and _Velociraptor_.
>
> (As for _Adasaurus_, I didn't think it was very big.)

As Utahraptor has comparatively large pedal unguals, I don't think the size
differences can explain it.  Adasaurus wasn't very big- only about 2.5
meters long for the old holotype.

Mickey Mortimer