Steneosaurus edwardsi(Thalattosuchia: Teleosauridae), the largest known crocodylomorph of the Middle Jurassic

Abstract

Teleosaurids were a clade of marine crocodylomorphs that were globally distributed during the Jurassic Period. They evolved a wide range of body sizes, from small (?2–3?m) to very large (>?9?m). Until now, the largest known Middle Jurassic teleosaurid was ‘Steneosaurus’?obtusidens, from the Oxford Clay Formation of the UK. Here, we re-examine a very large Oxford Clay specimen (ilium, ischium, and femur) that had been tentatively attributed to ‘S.’?obtusidens. Based on comparative anatomical study with the ‘S.’?obtusidens holotype and referred specimens of Steneosaurus?edwardsi and Steneosaurus?leedsi, we conclude that this very large individual actually pertains to S.?edwardsi. Based on comparisons with the Machimosaurus?mosae neotype (which has a complete femur and skeleton), we estimate a total length in excess of 7?m for this large S.?edwardsi individual, making it the largest known Middle Jurassic teleosaurid. Therefore, along with the closely related genus Machimosaurus, this clade of large-bodied Middle–Late Jurassic teleosaurids were the largest species during the first 100 million years of crocodylomorph evolution.