Maastrichtian marine reptiles of the Mediterranean Tethys; a palaeobiogeographical approach

A global comparison of coeval Maastrichtian marine reptiles (squamates, plesiosaurs, chelonians and crocodyliformes) of Europe, New Jersey, northwestern Africa and Middle-East has been performed. More than twenty outcrops and fifty species (half of them being mosasaurids) have been recorded. PEA and Cluster Analysis have been performed using part of this database and have revealed that marine reptile faunas (especially the mosasaurid ones) from the Mediterranean Tethys are clearly segregated into two different palaeobiogeographical provinces: 1) The northern Tethys margin province (New Jersey and Europe), located around palaeolatitudes 30-40 degrees N and developing into warm-temperate environments, is dominated by mosasaurid squamates and chelonioid chelonians; it is characterized by the mosasaurid association of Mosasaurus hoffmanni and Prognathodon sectorius. 2) The southern Tethys margin province (Brazil and the Arabo-African domain), located between palaeolatitudes 20 degrees N-20 degrees S and developing into intertropical environments, is dominated by mosasaurid squamates and bothremydid chelonians; it is characterized by the mosasaurid association of Globidens phosphaticus as well as by Halisaurus arambourgi and Platecarpus (?) ptychodon (Arabo-African domain). These faunal differences are interpreted as revealing palaeoecological preferences probably linked to differences in palaeolatitudinal gradients and/or to palaeocurrents. On a palaeoecological point on view and concerning mosasaurids, the mosasaurines (Prognathodon, Mosasaurus, Globidens and Carinodens) prevail on both margins but with different species. The ichthyophageous plioplatecarpines Plioplatecarpus (Northern margin) and Platecarpus (?) ptychodon (Southern margin) characterise respectively each margin. The halisaurine Halisaurus is present on both margins but with different species. Of importance, the tylosaurines remain currently unknown on the southern Tethys margin and are restricted to higher palaeolatitudes. Chelonians (bothremydids and chelonioids) are respective of each margin, which probably indicates lower dispersal capabilities compared to mosasaurids. The relative scarcity of plesiosaurs and crocodyliformes could be linked to different ecological preferences. The noteworthy crocodyliforme diversity increase in the Palaeogene is probably linked to mosasaurid extinction during the biological crisis of the K/Pg boundary.