Re: hypocleidium (an interclavicle???)

["David Marjanovic" <david.marjanovic@gmx.at>]

> WOW,
>     So you are saying that the theropod "hypocleidium" and the pygostylian
> hypocleidium may not be homologous (and therefore should probably be coded
> as separate characters)?

HP Jaime A. Headden does, I don't at the moment, because the absence of a
hypocleidium in *Archaeopteryx*, *Confuciusornis* and, BTW, *Beipiaosaurus*
could be convergence. In most phylogenies this is not most parsimonious, but
it is in mine :-)

> If so, is there any way to know which of these
> types is present in Protoavis??

Definintely the first, because the clavicles aren't even entirely fused!

>      I didn't know that the "hypocleidium" (the theropod type) was present
> in allosauroids or tyrannosauroids.  Aren't such structures uncommon among
> non-avian theropods, or perhaps they are common but just not often in
> ossified form?

They seem to be common when ossified and preserved (especially the latter is
rare). Judge for yourself at

Daniel J. Chure & James H. Madsen: On the presence of furculae in some
non-maniraptoran theropods, JVP 16(3), 573 -- 577 (September 1996)

Peter J. Makovicky & Philip J. Currie: The presence of a furcula in
tyrannosaurid theropods, and its phylogenetic and functional implications,
JVP 18(1), 143 -- 149 (March 1998)