Megacephalosaurus, new pliosaur from Cretaceous of Kansas

[Ben Creisler <bcreisler@gmail.com>]

From: Ben Creisler
bcreisler@gmail.com


A new paper in the JVP:



Bruce A. Schumacher, Kenneth Carpenter & Michael J. Everhart (2013)
A new Cretaceous Pliosaurid (Reptilia, Plesiosauria) from the Carlile
Shale (middle Turonian) of Russell County, Kansas.
Journal of Vertebrate Paleontology 33(3): 613-628
DOI:10.1080/02724634.2013.722576
http://www.tandfonline.com/doi/full/10.1080/02724634.2013.722576#.UYm9drXvtcQ


The Eulert pliosaurid remains (FHSM VP-321) housed at the Sternberg
Museum of Natural History (Kansas, U.S.A.) include one of the world's
best examples of a Cretaceous pliosaurid plesiosaur skull. The
specimen's original assignment to Brachauchenius lucasi was based
solely upon the skull (dorsal surface) and left lower jaw (lateral
view) because the specimen was embedded in a plaster mount. The
history of B. lucasi is similarly problematic, because the type and a
referred skull were formerly visible only in ventral and dorsal views,
respectively. Further preparation and comparison of these specimens
reveal new data about the arrangement of cranial elements. The Eulert
pliosaurid bears several distinct autapomorphies as compared with B.
lucasi, including cranial proportions (pretemporal length of palate
longer, shorter temporal fenestrae), configuration of skull roof
elements (frontals participate in premaxilla-parietal suture, suture
occurs further forward), and configuration of the palate (posterior
vomers not masked by medial alar extensions of the palatines, caudal
vomerian fenestrae positioned further posterior, long slit-like
anterior pteryoid vacuity present). Furthermore, FHSM VP-321 possesses
double-headed cervical ribs, a feature previously unknown in
Cretaceous pliosaurids. This combination of characters merits
separation of the Eulert pliosaurid and a referred specimen to a new
taxon, Megacephalosaurus eulerti. The type and paratype skulls of M.
eulerti are 1.5 m and 1.75 m in length, respectively, and thus 50% and
75% larger than the known 1-m-long skulls of B. lucasi, suggesting
that M. eulerti may attain larger size than B. lucasi.