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Re: Therizinosaur track from Denali National Park, Alaska



Anthony Docimo <keenir@hotmail.com> wrote:

>> There is at least one other group of Cretaceous theropods that have
>> four forward-facing toes. The flightless bird _Patagopteryx_ has a
>> "pamprodactyl" foot,
>
> um, just out of curiosity, how many species is _Patagopteryx_ held to
> presently have?


Unless something has changed, _Patagopteryx_ currently has only one
species.  _Alamitornis_ has been regarded as a close relative by
Agnolin and Martinelli (doi 10.1016/j.jsames.2008.09.003), but it's
smaller and more gracile, and it's not known if it was flightless.


> (if less than two, how is that a third group?)


By the "other group" I meant birds in general.  Sorry for not making
that clear.  Pamprodactyly has evolved several times in the Avialae.
In modern birds this pedal morphology is associated with clinging to
vertical trunks or branches in certain arboreal birds.  In these
birds, all four toes point forward and insert on the metatarsus at
about the same level (i.e., the hallux is incumbent).
_Epidendrosaurus_ has a similar morphology.  The very terrestrial
_Patagopteryx_ is pamprodactyl in the sense that all four toes are
directed cranially; but the first toe is not incumbent.  The foot is
therefore more similar to therizinosaurs than to vertical-clinging
birds.







Cheers

Tim