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Mosasauroids of Big Bend region,Texas



From: Ben Creisler
bcreisler@gmail.com

A new online paper:

Gorden L. Bell Jr., Kenneth R. Barnes and Michael J. Polcyn (2013)
Late Cretaceous mosasauroids (Reptilia, Squamata) of the Big Bend
region in Texas, USA.
Earth and Environmental Science Transactions of the Royal Society of
Edinburgh (advance online publication)
DOI: http://dx.doi.org/10.1017/S1755691013000406
http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=9016650&fulltextType=RA&fileId=S1755691013000406

Upper Cretaceous marine rocks of the Big Bend Region of trans-Pecos
Texas preserve a number of marine-adapted mosasauroids. At least three
unnamed taxa of basal mosasauroids are represented by remains from
shaly limestones in the middle Turonian portion of the Boquillas
Formation. These occur along with remains of larger derived mosasaurs
referable to Russellosaurina and an undescribed tylosaurine. Derived
mosasaurs from the middle to late Coniacian include the first report
of Tylosaurus kansasensis outside of Kansas, T. nepaeolicus,
Platecarpus planifrons, and Platecarpus aff. P. planifrons. Clidastes
liodontus is found in the latest Coniacian or early Santonian part of
the Pen Formation. An undescribed species of Ectenosaurus, Clidastes
sp. and an indeterminate plioplatecarpine occurs in the middle
Santonian to early Campanian interval of the Pen Formation. The
mosasaur fauna from the Big Bend region is quite similar to that from
the Smoky Hill Chalk of Kansas, a thousand kilometres to the north. We
refine the position of the Cenomanian–Turonian boundary within the
Ernst Member of the Boquillas Formation, based on ammonite faunas. We
also corroborate previous interpretations describing the
time-transgressive nature of the onset of deposition of the Pen
Formation based on a west-to-east descending level of the Inoceramus
(Cremnoceramus) undulatoplicatus FAD.