The
difference between a pubic boot and a "hypopubic cup" is that they have
identical morphology (at least between derived non-avian maniraptorans and basal
birds). However, because those people who use the term "hypopubic cup"
know a priori that these are non-homologous structures, they have to
give them a different name.
Note
that there is a LOT of diversity in pubic boot morphologies among theropods:
compare the little knob of coelophysoids to the somewhat larger structure of
true ceratosaurs to those of basal tetanurines to those of derived carnosaurs
like Allosaurus and Neovenator and Giganotosaurus to
the (proportionately) enormous pubic boots of some basal coelurosaurs like
Aristosuchus and Coelurus to (whew) those of tyrannosaurids,
ornithomimosaurs, oviraptorosaurs, basal alvarezsaurids, mononykines, basal
therizinosaurs, derived therizinosaurs, dromaeosaurids, basal avialians, basal
enantiornithines, and so on.
Thomas R. Holtz,
Jr. |