[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
Re: The ground-nowhere hypothesis on the origin of bird flight
I just have a question by now with Fowler's hypothesis:
As far as I know, large unguals are restricted to dromaeosaurids among
paravians (as far as I know, troodontids and avialans have much
smaller claws), so it seems that killing subequally sized prey should
not be primitive for paravians, but just an apomorphy of
dromaeosaurids or a subgroup therein. So it seems difficult for me
that this predation mode can explain avian flight.
The paravian primitive condition seems to be a small ungual in pedal
digit II, perhaps for seriema-like killing of small vertebrates.
2009/10/8 T. Michael Keesey <firstname.lastname@example.org> wrote:
> Often when a new trait appears, it appears in great abundancy, and is
> later narrowed down and refined by new inhibitors. Look at the
> earliest "apo-pterygotan" insects, with 3 pairs of wings (one pair
> significantly smaller than the other two), or the earliest
> "apo-tetrapods", with 8 digits.
Agree with the insects and the correlations between intracorporal
homologues. However, the tetrapod polydactyly may represent a
reduction from an ancestral sarcopterygian condition with many more
rays than 8, as in dipnoans (if dipnoan fin rays are to be homologized
with digits, which appear likely; David Marjanovic may know better).