Stable isotopes, niche partitioning and the paucity of elasmosaur remains in the Maastrichtian type area

Remains of elasmosaurid plesiosaurs are exceedingly rare in the type-Maastrichtian strata ( Late Cretaceous, southeast Netherlands and northeast Belgium), in stark contrast to relatively common skeletal remains of mosasaurs. Here, we present an analysis of delta C-13 stable isotope values for tooth enamel of two elasmosaur teeth from the type Maastrichtian. The delta C-13 signal is a proxy for foraging area, trophic level and diving behaviour, the net value of which in these rare elasmosaurs turns out to be not noticeably different from that for the much commoner mosasaurs in the type Maastrichtian. Therefore, the rarity of elasmosaurs in the area probably reflects a primary near-absence of such reptiles during the latest Cretaceous, rather than a taphonomic artefact.