The palaeoecology of three Late Cretaceous snakes is evaluated. Pachyophis woodwardi Nopcsa, 1923 and Pachyrhachis problematicus Haas, 1979, are Cenomanian in age and are found in carbonate rocks deposited in marine inter-reef basin environments of the European and African Tethys Sea. Dinilysia patagonica Woodward, 1901, Coniacian in age, is considered closely allied to living anilioid snakes, and is found in clastic rocks deposited in a terrestrial inter-dune basin environment in northern Patagonia, Argentina. All three snakes are known from well preserved and articulated specimens found in sediments where detailed sedimentological and taphonomic analyses are possible. Pachyophis and Pachyrhachis were laterally compressed, have pachyostotic ribs and vertebrae, and small, narrow heads. These two snakes are interpreted as aquatic predators living in and around the margins of reef mounds on a shallow water carbonate platform. Dinilysia was a large bodied snake with a relatively large head, and is interpreted here as a terrestrial predator that lived in a dry, interdune basin environment dominated by aeolian sedimentation. Sedimentary units preserve ichnological evidence of burrowing insects and rooting plants.

Key words: Key words: Dinilysia, Pachyrhachis, Pachyophis, snakes, phylogeny, palaeoecology, palaeobiogeography, palaeoenvironment, Cretaceous.

Michael W. Caldwell [mw.caldwell@ualberta.ca], Departments of Earth and Atmospheric Sciences & Departments of Biological Sciences, CW-405 Biological Sciences Building University of Alberta, Edmonton, Alberta, Canada, T6G 2E9; Adriana M. Albino [aalbino@mdp.edu.ar], Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Dpto Biología, Universidad Nacional de Mar del Plata, Funes 3250, 7600 Mar del Plata, Argentina.