A large pholidosaurid in the <scp>P</scp>hu <scp>K</scp>radung <scp>F</scp>ormation of north‐eastern <scp>T</scp>hailand

Abstract

Abstract In the early 1980s, the remains of a large crocodilian, consisting of a nearly complete lower jaw, were referred to a distinct species of S unosuchus , S . thailandicus . The specimen was recovered from a road‐cut near N ong B ua L amphu, north‐eastern T hailand, in the upper part of the continental P hu K radung F ormation, and then considered E arly to M iddle J urassic in age. Since then, this age has been revised and most of the formation is now considered E arly C retaceous, although a L ate J urassic age is possible for its lowermost part. Here, we report for the first time cranial elements associated with mandibular remains assignable to ‘ S ’. thailandicus . An attribution to P holidosauridae is proposed on the basis of premaxillary morphology, and the original referral of this taxon to the goniopholidid S unosuchus is discarded. A new genus name C halawan now designates the originally described material of S . thailandicus . Nevertheless, the newly described specimen shares a characteristic with both ‘traditional’ G oniopholididae and P holidosauridae: the presence of a depression located on the lateral wall of the maxilla and jugal. A phylogenetic analysis confirms the inclusion of both G oniopholididae and P holidosauridae into a common clade, C oelognathosuchia tax. nov. Although the new Thai skull is much fragmented, its original shape is reconstructed and is compared with other pholidosaurid genera, namely E losuchus , M eridiosaurus , O ceanosuchus , P holidosaurus , S arcosuchus and T erminonaris . The presence of the genus S unosuchus being highly questionable in T hailand, it cannot be used as evidence to link the C hinese and I ndochinese blocks. Instead, the recognition of a freshwater pholidosaurid in a continental formation of the I ndochinese block suggests that early in their evolutionary history, these crocodilians, already known from E urope, A frica and S outh A merica, were more widely distributed along the northern margin of the T ethys than previously recognized.