RE: The mystery of the furcula

[Nick Longrich <longrich@alumni.princeton.edu>]

> Second, as already mentioned, HELL YES we know what the fercula is used for.
> In FACT it was do to paleontology that it was finally nailed down.
> Jenkins, F. A,. Jr., Goslow G. E. Jr., and Dial K. P., 1987, Mechanics of an
> avian wing: The wishbone is a spring: Journal of Vertebrate Paleontology, v.
> 7, supplement to n. 3, Abstracts of Papers, Forty-Seventh Annual Meeting,
> Society of Vertebrate Paleontology, The University of Arizona, Tuscon,
> Arizona, October 22-24, p. 19a.


	In some birds, at least part of what it is doing is serving 
as a spring (ribs are also really bendy and may be up to something 
similar). Not all birds have the same kind of furculae, though. Some 
tend to have very thin, bendy ones, like the starlings Jenkins et al. 
were looking at. Others tend to have very robust, boomerang-shaped 
ones, e.g. eagles if I recall, that can't be working in the same way. 
Some are V-shaped, some U-shaped, some have a great deal of 
anteroposterior curvature, some don't. Most all flying birds have 
furculae, some don't, most flightless birds don't, but some do have 
reasonably well-developed ones, for example penguins.
	Besides serving as a spring, the avian wishbone may be 
serving as a strut and may be serving as an important site of origin 
for the pectoralis.

	Something I think is intriguing is that, to my knowledge, 
though lots and lots of theropods now turn out to have furculae 
(Allosaurus, tyrannosaurids, Syntarsus, Coelophysis, oviraptorids, 
dromaeosaurids e.g.) there's one group known from quite a few good 
skeletons which as far as I know has never been found with one, and 
that's the ornithomimids. Maybe they were trying to free up the 
shoulder girdle to give some more flexibility to the shoulders?