New mosasaurs from Northern Italy.

A series of mosasaur specimens has been discovered in northern Italy thanks to the quarrying operations in the local Upper Cretaceous limestones. These carbonate rocks belong to the Scaglia Rossa Veneta Formation and in particular to a unit informally referred to as the “Lastame”. The Lastame is a lithotype loosely dated to the uppermost Turonian-lowermost Santonian (Lozar and Grosso, 1997), however, a recent analysis of the rocky matrix of one of the mosasaurs (MPPS-IGVR 42224) allowed us to date the specimen more precisely to the early Santonian.So far five mosasaur specimens (NHMV-V7481, MPPS-IGVR 45301, MPPS-IGVR 42224, MPPS-IGVR 45299 and THF-IGVR 64108) have been recovered from quarries located north of Verona: NHMV-V7481 is represented only by isolated skull bones, including the two maxillary bones, the left dentary, the frontal, and the posterior end of the left mandibular ramus; MPPS-IGVR 42224 is a well preserved but fragmentary skull represented by two complete mandibular rami, the left maxilla, the right jugal, the two quadrates, one cervical vertebra, and a series of uncertainly identified bony fragments. The left quadrate of MPPS-IGVR 42224 has been prepared free of the matrix and compares closely with the quadrate of Russellosaurus coheni (Polcyn and Bell, 2005); MPPS-IGVR 45301 consists of an incomplete skull and some postcranial material, which unfortunately is poorly preserved. However, on the basis of the similar anatomy of some skull bones and the identical marginal dentition, it is possible to conclude that it very probably belongs to the same species of MPPS-IGVR 42224; MPPS IGVR 45299 is represented only by a poorly preserved series of vertebrae belonging to the dorsal and proximal caudal regions. However, the size and morphology of the preserved elements show a clear resemblance to the vertebrae belonging to MPPS-IGVR 45301. Adding all available data together (morphology, identical locality and horizon) we consider these last three specimens to be congeners, if not conspecific; THF-IGVR 64108 is the most recently found mosasaur of the series, and consists of an almost complete skull (inclusive of jaws, braincase, squamosals, pterygoids, ectopterygoids, and quadrates) and about half of the vertebral column exposed in ventral view.These mosasaurs have some anatomical characters in common with Russellosaurus coheni, but the presence of some distinctive features suggests placement in a new genus and possibly two distinct species. A preliminary phylogenetic analysis of the Mosasauroidea based on a modified version of the data matrix published by Caldwell and Palci (2007) places these new mosasaurs in a clade that is in the sister group to the Plioplatecarpinae and Tylosaurinae.ReferencesCALDWELL M.W., & PALCI A. (2007). A new basal mosasauroid from the Cenomanian (U. Cretaceous) of Slovenia with a review of mosasauroid phylogeny and evolution. Journal of Vertebrate Paleontology 27: 863–880.LOZAR F., & GROSSO F. (1997). Biostratigrafia della successione cretacica del margine dei Lessini occidentali (Provincia di Verona, Italia). Bollettino del Museo Regionale di Scienze Naturali, Torino 15: 111–136.POLCYN M. J., & BELL G.L.Jr. (2005). Russellosaurus coheni n. gen., n. sp., a 92 million-year-old mosasaur from Texas (USA), and the definition of the parafamily Russellosaurina. Netherlands Journal of Geosciences 84: 321–333.