A NEW SPECIES OF PROGNATHODON (SQUAMATA, MOSASAURIDAE) FROM THE MAASTRICHTIAN OF ANGOLA, AND THE AFFINITIES OF THE MOSASAUR GENUS LIODON ANNE S. SCHULP 1 , MICHAEL J. POLCYN 2 , OCTÁVIO MATEUS 3 , LOUIS L. JACOBS 2 , and MARIA LUÍSA MORAIS 4 1 Natuurhistorisch Museum Maastricht, De Bosquetplein 6/7, NL-6211KJ Maastricht, The Netherlands, Corresponding author - anne.schulp@maastricht.nl; 2 Roy M. Huffington Department of Earth Sciences, Southern Methodist University, Dallas, TX, 75275, USA; 3 Dept. Earth Sciences (CICEGe), Universidade Nova de Lisboa, Faculdade de Ciências e Tecnologia, Monte de Caparica, Portugal and Museu da Lourinhã, Lourinhã, Portugal; 4 Universidade Agostinho Neto, Departamento de Geologia, Luanda, Angola. ABSTRACT: Here we describe a new species of the mosasaurine genus Prognathodon from the Maastrichtian of Namibe, Angola, on the basis of five specimens which represent most of the cranial skeleton including the diagnostic quadrate. Phylogenetic analysis shows this new taxon, P. kianda nov. sp., to be the sister taxon to all other species of Prognathodon. It is unique amongst Prognathodon in possessing a high marginal tooth count and relatively small pterygoid teeth. The tooth morphology in the new taxon is reminiscent of some species of the genus Liodon, allowing association of Liodon-like dentition with otherwise Prognathodon-like crania, and thus resolves the long-standing question of the phylogenetic affinities of Liodon. INTRODUCTION Fieldwork in 2005 through 2007 at outcrops of Maastrichtian strata in southern Angola has yielded a rich fauna of mosasaurs, fishes, turtles, plesiosaurs and other marine vertebrates (Jacobs et al., 2006). The material described herein was collected near the village of Bentiaba, Namibe Province, southwestern Angola (Fig. 1). An overview of the geology of the Namibe (formerly Moçâmedes) area was presented by de Carvalho (1961), including the first record of mosasaur teeth from this area. Antunes (1964) recorded a diverse fauna of Maastrichtian marine vertebrates, based primarily on shed teeth, at outcrops near the village of Bentiaba (formerly São Nicolau). For a discussion of the geology of Maastrichtian deposits at Bentiaba, and a more detailed account of previous work, see Jacobs et al. (2006). Among the material recovered during the 2005 reconnaissance fieldwork are remains of two individuals of a new species of Prognathodon, of which a preliminary description was presented in Schulp et al. (2006). Following preparation of additional material collected in 2006 and 2007, we can now provide a more detailed description and formally name this new taxon. For the sake of completeness, relevant portions of the description given in Schulp et al. (2006) are repeated here. Institutional abbreviations - BMNH: The Natural History Museum, London, UK; MGUAN: Museo Geológico da Universidade Agostino Neto, Luanda, Angola; MNHN: Muséum National d’Histoire Naturelle, Paris, France; NHMM: Natuurhistorisch Museum Maastricht, Maastricht, The Netherlands. NEW MATERIAL One relatively complete skull with disarticulated postcranial elements was referred to by its preliminary registration number 07 in Schulp et al. (2006) and now registered at the Museo Geológico da Universidade Agostino Neto collection as MGUAN PA 129 (PA denoting the PaleoAngola Project). Additional material referred to the same taxon includes cranial material from the same locality (field number 05 in Schulp et al. [2006]; now registered as MGUAN PA 128). A braincase and incomplete frontal-parietal (MGUAN PA149, MGUAN PA150, respectively) of the same taxon were recovered from near PA129, and are tentatively assigned to the same individual. Dentaries, frontal, parietal, postorbital and squamosal of the same taxon exposed in a nearby wash (PA151) allow confident referral of skull roof and temporal arcade to the new taxon. SYSTEMATIC PALEONTOLOGY Order SQUAMATA Oppel, 1811 Superfamily MOSASAUROIDEA Gervais, 1853 (nom. transl. Camp, 1923) Family MOSASAURIDAE Gervais, 1853 Subfamily MOSASAURINAE Gervais, 1853 (nom. transl. Williston, 1897) Tribe GLOBIDENSINI Russell, 1967 (sensu Bell, 1997) PROGNATHODON Dollo, 1889 PROGNATHODON KIANDA nov. sp. Proceedings of the Second Mosasaur Meeting - 2008 p. 1-12