On snake-like dentition in mosasaurian lizards

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Abstract
Two features of mosasaur dentition suggest affinities with snakes. The crowns of the replacement teeth are initially recumbent, pointing horizontally backwards. They gradually swing upwards into the vertical, functional position. The teeth in mosasaurs are associated with distinct sockets, and are thus thecodont. These features are found in only one other squamate group, snakes, and are potential derived features (synapomorphies) uniting mosasauroids and snakes. There are, however, differences in the development of the recumbent teeth, and in the attachment of the tooth to the socket, in mosasauroids and snakes. Recumbent replacement teeth have been proposed to be functionally correlated with presence of long fang-like teeth. However, the occurrence of this feature in mosasauroids and primitive snakes (which have short teeth) contradicts this hypothesis, and the functional significance of recumbent replacement teeth remains unclear. The dental similarities, and some unusual features of the lower jaw, suggest that the idea of mosasauroid-snake affinities merits serious consideration.