quote:
quite -- i just don't think we can go dashing off calling all theropods "birds" willy-nilly.
I completely agree. But I don't know of anyone who is refering to some theropods as flightless birds without good reason. Note that I don't necessarily subscribe to this idea; just playing devil's advocate.
quote:
the primary feature i look for in calling something "bird" is the clawless, fused digits of a bird wing.
Very well. That's still very much a subjective choice, as I'm sure you will agree. Other scientists might chose another apomorphy by which to identify birds. Still others would rather describe birds based on their relationships to other groups (i.e. stem- or node-based definitions).
quote:
but if it's a feather, it's still kind of strange.
There has certain been much literature on the issue. For the pros, see:
Jones, T.D., J.A. Ruben, L.D. Martin, E.N. Kurochkin, A. Feduccia, P.F.A. Maderson, W.J. Hillenius, N.R. Geist, and V. Alifanov. 2000.
Nonavian feathers in a Late Triassic archosaur. Science 288: 2202-5.
The cons:
R.R. Reisz, H.-D. Sues. The "feathers" of Longisquama. Nature 408:428.
As far as I'm concerned, even if the 'feathers' of
Longisquama and birds were one and the same (which I don't think they are), the rest of the skeleton just doesn't compare at all between the two.
Longisquama definitely isn't a contender, at least as far as bird ancestry is concerned (which I know isn't what you're contending, arachnophilia).