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Re: Questions of Various Kinds
I'll take a punt at a few of these. Feel free to criticise if these
answers are way off the mark.
Rachel Clark wrote:
> 5) Do specimens of _Allosaurus_ suggest any kind of sexual dimorphism?
All in the eye of the beholder. It's clear that Morrison allosaurs
come in two morphs - gracile and robust - but there's differing
views over whether these morphs constitute two distinct species
or two sexes of a single, sexually dimorphic species. In _Predatory
Dinosaurs of the World_ Greg Paul asserts that there were two
sympatric species, and calls the gracile allosaur _A. fragilis_ and
the more robust species _A. atrox_ (after _Creosaurus atrox_). The
fact that the former is a much rarer species - it is unknown from the
Cleveland-Lloyd Quarry - tends to support the idea of two distinct
I've also heard the view that "_A. atrox_" is a distinct genus from
_Allosaurus_ - not yet officially named but both "_Creosaurus_" and
"_Madsenius_" have been proposed. ("_Madsenius_" is one of Bakker's
proposed genera; in the view of he and many others, the lectotype of
_Creosaurus atrox_ is indeterminate therby invalidating further usage
of the name.).
> 12) Is _Ornitholestes_ closely related to _Allosaurus_?
I don't believe so. _Ornitholestes_' allosaur-like characters
(recognised by Greg Paul - "box-like" braincase, decidedly non-
cursorial hindlimbs, etc) may be "holdovers" - _Ornitholestes_ is a
primitive coelurosaur, so not too far removed from the group's
divergence from the Allosauroidea.
> 14) Is _Albertosaurus_ the valid generic name for the species "A. libratus"?
The type species for _Albertosaurus_ (_A. sarcophagus_) is a
fragmentary skull which some researchers believe is too poorly
preserved to diagnose a valid genus. This throws the referral of all
other _Albertosaurus_ species into doubt. Apparently the whole
_Albertosaurus_ mess is being sorted out at the moment, and a paper
is (reputedly) in the pipeline.