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New Torosaurus paper



Out today:

Sullivan, R. M., A. C. Boere & S. G. Lucas. 2005. Redescription of the
ceratopsid dinosaur _Torosaurus utahensis_ (Gilmore, 1946) and a revision of
the genus. Journal of Paleontology 79 (3): 564-582.

"The holotype of the ceratopsid dinosaur Torosaurus (=Arrhinoceratops?)
utahensis (Gilmore, 1946) consists of a right squamosal, jugal, quadrate,
quadratojugal, epijugal, lacrimal, and postorbital horncore/orbital region.
Some elements previously described by Gilmore (1946), notably the
epoccipitals and parietals, were not originally included, so they cannot be
considered part of the holotype. Associated elements (lower jaws and
others), which may pertain to the holotype, are described for the first
time; they, too, are not formally considered part of the type material, but
they provide additional information regarding the osteology of this rare
chasmosaurine.

Torosaurus utahensis differs from T. latus (type species) in having a
squamosal that is shorter and squared-off at its distal end and an unusually
expanded horncore base that lies above and anterior to the orbit. In
contrast, T. latus has unusually long, attenuated triangular squamosals and
a more restricted horncore base. The otic notch is more open in T. utahensis
than T. latus. The genus Torosaurus is distinguished from other
chasmosaurine genera by a combination of characters including a broad, thin,
sheetlike parietal with relatively small, nearly circular fenestrae and
broad median parietal bar; convex posterior margin of parietal; and
relatively straight postorbital horncores that are oval (elliptical) in
cross section.

Bona fide records of T. latus from Montana, South Dakota, and Wyoming are
from strata of Lancian (late Maastrichtian) age. Previous reports of
Torosaurus from the Naashoibito Member of the Ojo Alamo Formation (Lehman,
1981, 1985, 1996) in the San Juan Basin and the McRae Formation (Lucas et
al., 1998), New Mexico, as well as the single Torosaurus record from
Saskatchewan (Tokaryk, 1986), are based on specimens that can at best be
identified as Chasmosaurinae genus indeterminate, because they lack derived
features of the taxon. Putative Torosaurus specimens from the Big Bend
region of Texas (Lawson, 1976; Lehman, 1996) are also considered as
indeterminate chasmosaurines. All records of Torosaurus are Maastrichtian in
age, but records of T. utahensis appear to be older than those of T. latus."

The same edition of Journal of Paleontology also includes a review (on pp.
625-627) by S. C. Bennett of "Posture, Locomotion, and Paleoecology of
Pterosaurs" by Chatterjee & Templin, and "Evolution and Palaeobiology of
Pterosaurs" edited by Buffetaut & Mazin.
    The most notable part of the review, I thought, was the significant
gaffe Bennett caught Chatterjee and Templin out on in regards to the ecology
of _Pteranodon_, which is suggested as dipping fish while swimming
(pelican-style, I'm guessing), but is regarded three pages earlier as
probably not being able to take off from water. To quote Bennett "perhaps
this explains the large numbers of Pteranodon specimens in the Niobrara
Formation" :-).

    Kia Ora,

        Christopher Taylor