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Re: Upstroke of *Archaeopteryx* and *Confuciusornis* was Re: Science feather strength debate

David Marjanovic <david.marjanovic@gmx.at> wrote:

> Archie further lacks an ossified sternal keel, and so do most specimens of
> *Confuciusornis*. Tim Williams has way exaggerated what *C.* has: Chiappe et
> al. (1999) counted _two_ specimens that had a faint ridge on the caudal half
> of the sternum, out of several hundred; in all others, the sternum is
> completely flat.

The situation is potentially more complicated, because Chiappe et al.
(1999) raise the prospect that this bony ridge might have anchored a
larger, cartilaginous keel.  If this is the case, then it implies that
a cartilaginous keel was present in all _Confuciusornis sanctus_.

So although it is true that only two _C. sanctus_ specimens (GMV-2147
& SMFAv-423) show a bony 'keel' (more of a sagittal ridge), the
flesh-and-blood animals might have had a substantially larger keel
made out of cartilage.  Only in some animals was the bony anchor point