Predatory behaviour in mosasaurid squamates inferred from tooth microstructure and mineralogy

Abstract

Dental morphology, microstructure and chemistry provide unique insights into various aspects of the evolutionary history and ecology of extinct clades. However, most studies have focused exclusively on the morphological aspects of teeth, while there are significantly fewer detailed accounts of tooth microstructure and mineralogy. Here we provide a full description of the enamel and dentine microstructure of mosasaurid squamates based on an assessment of isolated teeth belonging to two distantly related mosasaurid taxa, i.e., a russellosaurinan and a mosasaurine, from the ?Coniacian–Santonian and Maastrichtian of Belgium. The obtained data are further explored with regard to their value for inferences of mosasaurid predatory behaviour. SEM observations have shown that the Schmelzmuster consists of columnar enamel with an outer layer of parallel crystallites; transmitted light observations have further revealed the presence of mantle dentine cushioning between enamel and orthodentine, and electron microprobe analyses have demonstrated the unaltered enamel chemistry and heterogeneous diagenetic alteration of dentine. Columnar enamel allows minute movements without rupture under bending stress, and together with the presence of shock-absorbing mantle dentine and possibly elevated Fe contents in the enamel, which increase its hardness and enhance acid resistance, it is suggestive of a good ability of the teeth to withstand severe mechanical damage. Such properties of teeth indicate adaptation to shaking and tearing large and resisting prey.