From: firstname.lastname@example.org [mailto:email@example.com]On Behalf Of Mickey_Mortimer11
>Foster, Holtz and Chure, 2001. Contrasting patterns of diversity and community structure in the theropod faunas of the Late
>Jurassic and Late Cretaceous of Western North America. JVP 21(3) 51A.
>The main point of this talk was that the Morrison Formation has a wide size range of theropods, with several taxa in the
>largest size range (500+ kg), while the Hell Creek has fewer theropod taxa, only one of which is over 500 kg. Oddly,
>Ceratosaurus was said to be much smaller than Allosaurus, presumedly based on the subadult holotype.
Nope. While there are apparently fully adult Ceratosaurus out there (see Britt et al.'s poster from 2000, for example), these are still smaller than the larger (and, sadly, unmounted) Allosaurus fragilis specimens.
>"What about Albertosaurus?!" :-)
Quite. Incidentally, even if there were a mid-sized tyrannosaurid in the Hell Creek, it doesn't make a difference to the big pattern we were describing: namely, the extreme taxonomic diversity and even size distribution in the Morrison versus the more restricted taxonomic diversity and very uneven size distribution (all big carnivores being tyrannosaurids) in the Hell Creek, Judith River, and the like.
>Holtz, 2001. Pedigree of the tyrant kings: New information on the origin and evolution of the Tyrannosauridae. JVP 21(3) 62A-
>Holtz had a phylogeny of theropods with 85 taxa and 642 characters with the following topology-
> `-+-"Szechuanosaurus" zigongensis
> | |-Lourinhanosaurus
> | |-Sinraptor
> | |-Allosaurus
> | |-+-Fukuiraptor
> | | `-Siamotyrannus
> | `-+-Neovenator
> | `-+-Acrocanthosaurus
> | `-+-Carcharodontosaurus
> | `-Giganotosaurus
> | |-Dryptosaurus
> | `-+-Eotyrannus
> | `-+-+-Alectrosaurus
> | | `-Bayn Tsav material
> | `-+-Alioramus
> | `-+-+-Albertosaurus
> | | `-Gorgosaurus
> | `-+-+-Daspletosaurus
> | | `-new long snout taxon
> | `-+-Tarbosaurus
> | `-Tyrannosaurus
> | `-+-Avimimus
> | `-Oviraptorosauria
Actually, the Two Medicince Form (which comes out as the sister to Daspletosaurus torosus) is not a particularly long-snouted form. This is the form considered by Horner et al. (1992) to be transitional between Daspletosaurus and T. rex.
>Notice the paraphyletic Ceratosauria sensu lato, basal position of "Szechuanosaurus" zigongensis like Rauhut 2000, odd
Take that one with a grain of salt: it is on just one character. However, it is interesting given the somewhat similar distribution in time and space...
>Dryptosaurus in the Tyrannosauroidea and Coelurus being more derived than other "basal coelurosaurs". Also, Avimimus is
>an oviraptorosaur, Protarchaeopteryx a paravian and there is no evidence for secondary flightlessness. What an interesting
>cladogram, I wish I could have copied the rest of the taxa.
Actually, the rest just elaborates the ingroup relationships of the various maniraptoriform clades, and these are being worked out in greater detail by other scientists. Indeed, there are a few specimens and analyses to be published within a few months (I expect) which will really help to clarify some of these relationships.
Thomas R. Holtz,