Trophic interactions of sharks and crocodylians with a sea cow (Sirenia) from the Miocene of Venezuela

Abstract

Evidence of trophic interactions are not scarce in the fossil record, yet these are mostly represented by fragmentary fossils exhibiting marks of ambiguous significance. Differentiating between marks of active predation and scavenging events is therefore often challenging. Here, we report on a dugongine sea cow skeleton (partial skull and vertebrae) from the Lower to Middle Miocene Agua Clara Formation (Venezuela) with shark and crocodylian bite marks. The sirenian is identified as Culebratherium sp. and preserves crocodylian bite marks across the skeleton. The most conspicuous correspond to deep tooth impacts with dragging effect, concentrated in the rostrum of the specimen. We interpret these as the result of active predation because of the similarity with those produced when a crocodylian holds or rolls a prey. Additionally, shark bite marks can be observed throughout the skeleton, also evidenced by the finding of an isolated tiger shark (Galeocerdo aduncus) tooth associated with this skeleton. Because of the irregular distribution of the shark bite marks, these are interpreted as scavenging. Overall, these findings constitute one of the few records documenting multiple predators over a single prey, and as such provide a glimpse of the trophic networks during the Miocene in the region.