Konishi, T. & Caldwell, M. (2006) Re-diagnosis of Platecarpus planifrons (Cope, 1874) (Squamata; Mososauridae) and a revised taxonmy of the genus. JVP 26(3) Abstracts pp.87

One of the most enigmatic species of Platecarpus from the Western Interior Seaway of North America (Upper Santonian-Lower Campanian), P. planifrons, has been re-diagnosed based on the one of the most completely-preserved cranial specimens of the genus, UALVP 24240, along with the other less complete specimens that are assignable to the species. The species is definitively distinguishable from any other congener from North America according to the following diagnosis: clear separation of prefrontal and postorbitofrontal on ventral surface of frontal, transverse distance of preorbital region of frontal greater than interorbital distance, dorsal surface frontal planar lacking mid-sagittal keel, presence of paired posteromedian flanges on frontal, anterodorsal border of quadrate distinctly notched posteriorly, and stapedial pit narrow and keyhole shaped. In addition, UALVP 24240 provides the first evidence of the presence of a pair of septomaxillae in the genus, posteriorly forming the floor of the nasal cavity.

Once concidered nomen vanum, the newly gained osteological data based on these specimens of P. planifrons not only re-establish the validity of the taxon, but also provides some opportunity to re-examine the current taxonomy of the genus found in the seaway. Based on our data, we support the synonymization of P. coryphaeus with P. ictericus, while retaining the latter taxon as a distinct species from the generic type, P. tympaniticus, which lacks a significant amount of diagnosable characters to the species level. Platecarpus cf. P. somenensis from the Pierre Shale Formation is tentatively retained for its taxonomical recognition; in consequence, we recognize four species of Platecarpus in North America.

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