Reconstructing the trophic structure of Maastrichtian elasmobranch communities in Morocco using calcium isotopes

Abstract

The diversification of elasmobranchs through time is accompanied by an incredible diversity of feeding ecologies reflecting every trophic position and placing elasmobranchs as cornerstone organisms of the marine food webs. Quantifying their trophic ecology in the fossil record brings precious insights about their successes and the evolution of trophic structure through deep time. Here we quantitatively describe the trophic organization of a rich Maastrichtian elasmobranch assemblage from Morocco presenting taxa from all the trophic levels using the calcium isotopes of their teeth. We highlight overall similarities with modern trophic food webs presenting batomorphs at the lower trophic levels including the first estimate of diet in the extinct suborder of sclerorhynchid and large selachimorphs as apex predators. Moreover, δ44/42Ca values in Squalicorax pristodontus reveal peculiar feeding behavior underlining that apex elasmobranchs were already divided into two categories including large piscivorous predators and tetrapod feeders.