Selmasaurus

Selmasaurus is an extinct genus of marine lizard belonging to the mosasaur family. It is classified as part of the Plioplatecarpinae subfamily alongside genera like Angolasaurus and Platecarpus. Two species are known, S. russelli and S. johnsoni; both are exclusively known from Santonian deposits in the United States. Selmasaurus is unique among the mosasaurs in that its skull is unusually akinetic, meaning that it is incapable of widening to swallow larger prey. Most mosasaurs have skulls which possess "coupled kinesis" (mesokinesis and streptostyly), that is, parts of the jaw can open widely to accommodate large prey. Selmasaurus was a small predatory mosasaur at approximately 3–5 meters in length. It possesses a relatively low number of teeth for a mosasaur, the lowest of any known species at the time of its discovery. Originally classified as a plioplatecarpine mosasaur, it differs from all other plioplatecarpine mosasaurs in several respects, listed below as stated by Polcyn and Everhart (2008): Suprastapedial process descends to about half the quadrate height, and is in contact with but not fused to the peg-like infrastapedial process; elongate medially constricted, subrectangular parietal table, broadening anteriorally and constricting posteriorly forming narrow parasagittal ridges that diverge at their terminus; posteroventral median process of parietal meets supraoccipital in narrow elongate contact; anteromedial process of supratemporal clasped by medial excavations of the parietal rami for nearly entire length of rami; canals for the basilar arteries enter the basioccipital as two small foramina separated by a median septum, diverge within the basioccipital and cross the basisphenoid suture in a lateral and deeply ventral position. First recognized by geologist Samuel Wayne Shannon in his 1975 Master's thesis, "Selected Alabama Mosasaurs", the taxon remained a nomen nudum until it was officially described in 1988 in an article coauthored by Wright.