A new mosasaurine from the Maastrichtian (Upper Cretaceous) phosphates of Morocco and its implications for mosasaurine systematics

ABSTRACT

A new mosasaur, Eremiasaurus heterodontus, gen. et sp. nov., from the Maastrichtian phosphates of Morocco is described based on the basis of two specimens: one consisting of a nearly complete skull, vertebral column, and isolated appendicular elements, and the other a nearly complete skull with associated vertebral column. This new mosasaur exhibits a high degree of heterodonty and a large number of pygal vertebrae, the latter feature expressed to a greater degree only in Plotosaurus from the Maastrichtian of California. Analysis of a data matrix of 135 characters and 32 terminal taxa resulted in three equally most parsimonious trees, and recovered E. heterodontus as the sister taxon to Plotosaurini. A second analysis incorporating five species of the globidensine mosasaur Prognathodon recovered 252 most parsimonious trees. This second analysis also recovered E. heterodontus as the closest relative to the Plotosaurini, a position supported by the presence of an internarial bar keel, exclusion of the prefrontals from the narial borders, narial embayments in the frontal, and the presence of a quadrate ala groove. A change in the positions of several key character-state changes in the second analysis not only supports the exclusion of E. heterodontus from the globidensine mosasaurs, but also calls into question the monophyly of the Globidensini and the suite of quadrate and dental characters used to diagnose this group.

ACKNOWLEDGMENTS

We would like to thank A. Lindoe for his outstanding preparation of UALVP 51744, and M. Schmidt for assisting with the University of Alberta's acquisition of the specimen. We also thank the technical team of the OCP Geological Service at Khouribga Mine for preparation of OCP DEK/GE 112. We also thank L. Chiappe for assistance to A.L. and M.C. during a visit to LACM, and N. Klein and A. Folie for assisting A.L. during visits to RFWUIP and IRScNB. A.L. would also like to thank A. Palci and the other members of the M. Caldwell, P. Currie, and M. Wilson laboratories for critical discussion and help with the manuscript. We also thank T. Cook for identifying selachian remains associated with UALVP 51744. The manuscript was greatly improved by the comments and suggestions of A. S. Schulp, J. Lindgren, and F. R. O’Keefe. Support for this project came from an NSERC CGSM to A.L. and from an NSERC Discovery Grant (no. 238458-01), Chair's Research Allowance, and Museum's Grants via the University of Alberta Annual PaleoGala and Fundraiser, to M.C. Additional support came from a National Geographic Society grant (no. 6627-99) and a CNRS-CNRST French-Moroccan International Program of Scientific Collaboration (AC no. 18567 and MARPIC no. 4892) to N.B. The work of N.B. is part of a French-Moroccan Palaeontological Convention of Collaboration between the Muséum National d’Histoire Naturelle/Centre National de la Recherche Scientifique (Paris), the Office Chérifien des Phosphates (Casablanca), the Ministère de l’Energie, des Mines, de l’Eau et de l’Environnement (Rabat), and the Universities Cadi Ayyad (Marrakech) and Chouaîb Doukkali (El Jadida).

Handling editor: F. Robin O'Keefe