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Re: Details on SVP 2001 Friday talks



Title: Re: Details on SVP 2001 Friday talks
Nick Longrich wrote-
Sinraptor also appears to have had a pubic foramen, unlike Allosaurus which lacks the foramen, as in coelurosaurs. If you threw more taxa into this matrix, and then a few more characters,  you'd probably start seeing several different carnosaur groupings.
 
Ah, the old idea of allosaurids being closer to coelurosaurs than sinraptorids and carcharodontosaurids.  Replaced by the new consensus of all three groups in a Carnosauria.  Sinraptor dongi has an open obturator notch, as do your more basal Acrocanthosaurus and Giganotosaurus.  On the other hand, the Santana compsognathid has an obturator foramen in one pubis.  Confusing situation, as usual.  Then there's your placement of carcharodontosaurids by sinraptorids, not allosaurids, opposite of the current consensus.  Personally, I like a Carnosauria including sinraptorids and a carcharodontosaurid-allosaurid clade, with torvosaurs and spinosaurs further down, but it's not like I've run an analysis.
 
I've seen no evidence that Afrovenator has either the maxillary fenestra or obturator process it's illustrated with, and therefore it's a good candidate for being a Torvosaurus relative.
 
How interesting...
 
Finally, it's useful because if one of your supposedly derived taxa actually turns out to be more basal, it can fall down the tree in its correct spot instead of being stuck in with a bunch of taxa it doesn't belong with.
 
Indeed.  Siamotyrannus is always falling to the base with Allosaurus in my trees.
 
        With respect to Deinonychosauria, there are a fair number of features holding this group together; they include things like a large triangular lateral exposure of the splenial, ventrally flattened and anteriorly forked chevrons, the enlarged ungual of pedal digit II, and a spine table on the dorsals. Some of these features are also known from things such as Rahonavis or Unenlagia as well. I think the case for dromaeosaurid monophyly is going to be pretty good, the Dromaeosaurus skull is pretty weird but the postcrania is pretty standard and in the details looks like a lot Velociraptor, Saurornitholestes, and Deinonychus. Look at the possibility that the most birdlike, "derived" dromaeosaur-type critters (e.g. Sinornithosaurus) are in fact the *primitive* ones.
 
I do have those characters in my analysis, but they're not making a Deinonychosauria that includes Troodontidae-
79. splenial exposed broadly laterally
124. apices of dorsal neural spines expanded transversely to form spine table
272. pedal ungual II enlarged
339. distal chevrons with caudal bifurcations
Perhaps these are symplesiomorphic troodontid+eumaniraptoran characters reversed in derived avialans.  What Dromaeosaurus postcrania are you using to compare to other dromaeosaurids?  The pedal phalanges? ;-)  I agree that dromaeosaurids seems secondarily primitive in several characters, with the more avian Bambiraptor being a more basal deinonychosaur.  Sinornithosaurus still comes out as an avialan though.
 
        Alvarezsaurs... still a problem. The hindlimbs seem to suggest an oviraptorosaur-grade theropod, the lack of similarly derived forelimbs could be a result of their highly specialized morphology, but it's hard to say. A complete Alvarezsaurus or Patagonykus will be crucial in figuring these things out, but I think that it's clear they're probably not avialan and definitely not ornithomimid, but are some sort of Maniraptora.
 
I agree here- non-eumaniraptoran paravians in my trees.
 
Mickey Mortimer