Remarkably well-preserved in-situ gut-content in a specimen of Prognathodon kianda (Squamata: Mosasauridae) reveals multispecies intrafamiliar predation, cannibalism, and a new mesosaurine taxon

In this contribution we report a spectacularly well-preserved, semi-articulated specimen of Prognathodon kianda containing three partial mosasaurs in its stomach region. The discovery is from the lower Maastrichtian (~71.5Ma) “Bench 19 Bonebed” at Bentiaba, Angola. Each of the three mosasaurs found in the gut region is a unique taxon, one being the first documented occurrence of cannibalism in mosasaurs, and another representing a new mosasaurine genus and species, Bentiabasaurus jacobsi gen. et sp. nov., a taxon closely related to Mosasaurus. Trophic interactions at the “Bench 19 Bonebed” locality appear to be controlled in part by relative size of the predator and the prey, all prey taxa falling between 43 and 57% of the predator’s body length. Prey items are all dismembered to some degree and individual parcels approach the estimated maximum sizes that can pass the gullet. Tooth and bone modification, and other aspects of prey processing are discussed. Though the sample is small, the observed range of modalities suggests prey processing, digestive biology, and methods of elimination in mosasaurs was diverse.