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New Refs: JVP 19 (3)
Hey, everybody!
The latest issue of Journal of Vertebrate Paleontology is out, and (as
usual) full of great stuff. Besides the abstract volume for this year's SVP
meeting, there's a number of good papers.
First and foremost, in the
no-longer-"in-press"-;-out-there-where-everyone-can-read-it category (or the
"patience is finally rewarded" category):
Carr, T.D. 1999. Craniofacial ontogeny in Tyrannosauridae (Dinosauria,
Coelurosauria). JVP 19:497-520.
The LONG awaited analysis of changes in growth of tyrannosaur faces, with
implications for the validity of "Nanotyrannus". Among other things:
I. The Field Museum "Albertosaurus" is almost certainly a specimen of
_Daspletosaurus torosus_. The skull has been greatly reconstructed, and _G.
libratus_ features added to it (unintentionally: back when this was an AMNH
specimen _Daspletosaurus_ wasn't known). Furthermore, all the maxillary
teeth and about half the dentary teeth are restored: it is not at all
certain at present what the original tooth count was. One major drawback of
this: this specimen has been used repeatedly as the source for illustrations
of _Albertosaurus libratus_!
II. As _Gorgosaurus libratus_ (Carr uses _Albertosaurus libratus_) grows
various features change shape, including: size and position of the fenestrae
of face; cranial ornamentation; tooth count; tooth thickness.
III. "Nanotyrannus" is almost certainly a juvenile, as attested to by the
immature bone grain all over the surface of its face. Furthermore, it
shares with _T. rex_ (and _T. bataar_) a number of synapomorphies otherwise
unknown in tyrannosaurids. Carr thus considers "Nano" a juvenile (stage I)
_T. rex_.
IV. Truly excellent drawings of a young _G. libratus_, "Nanotyrannus", a
comparative young and adult picture of _T. rex_ skulls.
Good work, Thom!
Also in the volume, a short contribution by Wilson et al. concerning
titanosaur tails:
Wilson, J. A., R. N. Martinez & O. Alcober. 1999. Distal tail segment of a
titanosaur (Dinosauria: Sauropoda) from the Upper Cretaceous of Mendoza,
Argentina. JVP 19:591-594.
Confirms the presence of a series of short biconvex caudal central rather
than the whiplash condition in diplodocids.
Comment & reply:
Carrano, M. T. & C. A. Sidor. 1999. Theropod hind limb disparity
revisited: comments on Gatsey and Middleton (1997). JVP 19:602-605.
Gatsey, S. M. & K. M. Middleton. 1999. Theropod hind limb disparity
revisited: a response. JVP 19:606.
Concerns matters statistical and graphical with regards to Gatsey &
Middleton's ternary analyses of hind limb proportions in theropods.
Also of interest to many here:
Motani, R. 1999. Phylogeny of the Ichthyopterygia. JVP 19:473-496.
Part of Motani's ongoing work on the evolution of ichthyosaurs. Several new
taxonomic names are proposed. See also
http://www.ucmp.berkeley.edu/people/motani/ichthyo/index.html for a summary
of much of the information here.
Thomas R. Holtz, Jr.
Vertebrate Paleontologist
Department of Geology Director, Earth, Life & Time Program
University of Maryland College Park Scholars
College Park, MD 20742
http://www.geol.umd.edu/~tholtz/tholtz.htm
http://www.geol.umd.edu/~jmerck/eltsite
Phone: 301-405-4084 Email: tholtz@geol.umd.edu
Fax (Geol): 301-314-9661 Fax (CPS-ELT): 301-405-0796