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

Re: Digit Loss



> What about the hyperphalangy in ichthyosaurs? And isn't the pteroid bone
in
> pterosaurs analogous to the panda thumb, also an altered (meta)carpal?
>
> Raymond Thaddeus C. Ancog
> Mines and Geosciences Bureau
> Philippines

Hyperphalangy is the phenomenon that the digits have more phalanges than
usual, not that there are more digits; this is very common in sea-living
tetrapods (sauropterygians, whales). The pteroid bone... hm. Might be the
ossified base of a tendon; it is not a metacarpal.

Someone wrote (can't find the post) that *Protoavis* had 5 fingers per hand.
If that what Chatterjee identifies as a hand is one (the first 3 metacarpals
+ digits + carpals look quite like a herrerasaurian foot, and the fingers
are shorter than in any other tetanuran I know), then it has 3 fingers and 4
metacarpals. Metacarpal IV is a rod that according to Chatterjee supported
the wing feathers and bears no phalanges; mc V is totally absent. If this
stuff is really articulated (looks so on the photo) and really a hand, it
might belong to a very basal tetanuran or a derived ceratosaur, off the top
of my head, or lots of tetanurans reduced their mc's IV lots of times
independently.

Details On forthcoming, sometime during the summer holidays... :-|