Re: pteroid trouble

[Augusto Haro <augustoharo@gmail.com>]

If Unwin turns to be right in that the pteroid articulated with the
proximal syncarpal, it would be expected it articulated on the
preaxial "radiale territory", which would fit well with homologating
the pteroid with the prepollex, which usually contacts the radiale in
embryos, when present.

I was just looking at Feduccia and Nowicki's (2002) paper and find
that the presumptive "first finger" actually seems to contact the
radiale as well (or at least, is just preaxial and distal to the
radiale) so that this may represent support for your idea that the
first condensation of the ostrich is actually the prepollex, and that
no frameshift is necessary.

Thus, the prepollex can represent both the first, normally absorbed
condensation of birds, and the pteroid of pterosaurs. The prepollex
seems to be absent in crocodiles according to Müller and Alberch
(1990), but present in Lacerta (Steiner, 1934), so that the lack of
praepollex can represent just a crocodylian apomorphy, and its
ossification and persistance an apomorphy of pterosaurs, shared with
talpids (the os falciforme of moles derive from the embryonic
prepollex, Holmgren, 1952).