Pterosphenus

Pterosphenus belong to the Palaeophiid snakes, a clade which includes all snakes outside of blind and thread snakes. Its closest relative is Palaeophis, of which both belong to the subfamily Palaeopheinae.

While only known from partial remains, enough has been found of Pterosphenus to suggest it was a large reptile over 4 metres. It body was laterally compressed as an adaptation to pelagic life.

A marine ocean dweller, Pterosphenus lived in the shallow seas of the future eastern US, such as Texas, Louisiana, Mississippi, and Arkansas, up north to New Jersey. Pterosphenus was a top predator of the ecosystem, likely preying on fish and molluscs found in the same area.

It is certain that Pterosphenus would have encountered basal cetaceans like Zygorhiza and Basilosaurus, though its likely a mixed of niche partitioning and living in different areas in the case of Basilosaurus would prevent competition between the species.