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Re: The most important fossil discovery in 2004 (your opinions?)
Amtoine Grant wrote-
> which makes the question "how can we be sure it is THE[of the species
> we know] basal tyrannosaurid, and not something else".
We can't, but it is more parsimonious than other hypotheses given the
published data. Tyrannosauroid synapomorphies include- fused nasals; nasals
anteriorly convex in section; pneumatic articular; preacetabular notch in
> Which brings to mind the allosaurs to tyrannosaurs theory. I actually
> lost my 'Predatory Dinosaurs of the World' at the airport before I got
> to that section. Uh, could someone break down or point to an article
> online where it discusses this. Because last I checked tyrannosaurs
> were considered coelurosaurs that attained their size independent of
> the allosaurs, similar to the spinosaurids. Aren't allosaurs considered
> carnosaurs, on a serperate branch from the coelosauria?
Tyrannosauroids have been considered coelurosaurs by all(?) published
numerical phylogenetic analyses where this has been tested. Allosaurids are
by definition carnosaurs. Paul (2002) lists only a few features to justify
placing tyrannosauroids in Carnosauria - deep, anterodorsally directed
cultriform process; broad squamosal-quadratojugal bar; third metatarsal
L-shaped in proximal view. These seem more likely to be avetheropod
symplesiomorphies, and are far outnumbered by the coelurosaurian characters
of tyrannosauroids. Dilong does have a few carnosaurian characters, but it
resembles basal coelurosaurs far more.
> While we're at
> it, how does allosaur hind-limb morphology differ from tyrannosaurs in
> terms of gracility?
Allosaurids are less gracile than similarly sized tyrannosaurids.
Undergraduate, Earth and Space Sciences
University of Washington
The Theropod Database - http://students.washington.edu/eoraptor/Home.html