No memeber of the Dinosauromorpha possesses an interclavicle. This is a
distinct osseous element
that interjects between coracoids and between each of the clavicle bones;
the interclavicle has a
tri-radiate morphology, essentially Y-shaped in form, leading to the
confusion I'm sure that spawned the question. In the period of time that
the dinosaurian furcula of *Oviraptor* was offered as an interclavicle
since Osborn's 1924 description, it has since been the prevalent
scientific conclusion that this element is in fact a fusion or collection
of two clavicles without
an interclavicle, and no the interclavbicle itself. Even as recent as 1986,
the fusion of the clavicles was regarded as "fused clavicles" and not a
"furcula," and is still regarded as such by
the more resistant of the ornithologists (see Feduccia, 1996, for example).
The hypocleidium is a structure that appears early in the development of
theropods with furculae, appearing in allosauroids and tyrannosauroids, as
a distinct process. It appears to be an extension of the fusion of two
diaphyses, such as the ramal shafts of the paired clavicles. It
is lost in early birds, such as *Archaeopteryx* and *Confuciusornis*, but
is derived in higher
groups, so that nearly all modern birds possess it. Rather than
re-expression, it is likely that
the hypocleidium in higher birds is probably a neomorph structure adapted
based on tendon
attachment, rather than the ends of two fused diaphyses.
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Jaime A. Headden
Aaaaaaaaaaaaaaaaaaaahhhhhhhhhhhhhhhhhhr-gen-ti-na
Where the Wind Comes Sweeping Down the Pampas!!!!
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