A highly debated topic in eusuchian systematics has been the placement of “thoracosaurs,” an assemblage of Cretaceous–Paleogene longirostrine crocodylians from Europe and North America. The position of “thoracosaurs” varies from one study to the next, from being the sister taxon of the extant Gavialis to being excluded from the crown group Crocodylia entirely. Despite these issues, “thoracosaurs” have been understudied, with many taxa suffering from incomplete or outdated descriptions and dubious taxonomic assignment. Here, we provide a comprehensive study of Thoracosaurus isorhynchus from Maastrichtian–Danian deposits of northwestern Europe. We present and describe new material from the type locality of T. isorhynchus. In addition, we redescribe and figure the lectotype and paralectotypes of the species, as well as the material from the Maastrichtian type area, the Netherlands. Moreover, comparison of T. isorhynchus with the type material of Thoracosaurus “scanicus” of the Danian of southern Sweden indicates that the latter might be a junior synonym of T. isorhynchus, suggesting the survival of this species across the Cretaceous–Paleogene boundary. An array of phylogenetic analyses points to a close relationship between T. isorhynchus and the Cenomanian Portugalosuchus azenhae. This implies an early emergence of “thoracosaurs” and causes extensive ghost lineages within Gavialoidea, highlighting the stratigraphic inconsistency of this group and a need for a thorough revision of other “thoracosaurs.”
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RBINS Staff Publications 2026
Saniwa is an extinct genus of varanid squamate from the Eocene of North America and Europe. Up to now, only one poorly known species, Saniwa orsmaelensis Dollo, 1923, has been reported from Europe. Diagnostic material was limited to vertebrae with only preliminary description and no figure provided, except of one dorsal vertebra that was designated as the lectotype. New specimens from the earliest Eocene of Dormaal, Belgium and Le Quesnoy, France, including recently recovered skull ma-terial, are described and illustrated here. These fossils representing the oldest varanid squamate allow further comparisons with the type species, Saniwa ensidens Leidy, 1870, from the early and middle Eocene of North America and to propose a new diagnosis for S. orsmaelensis. Its arrival in Europe is probably linked to rapid environmental changes around the Paleocene Eocene Thermal Maximum (PETM). The occurrence of S. orsmaelensis is restricted to the early Eocene of northwest Europe and paleogeographic considerations regarding the distribution of the genus Saniwa Leidy, 1870 suggest an Asian origin, but an African origin cannot be completely excluded.
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RBINS Staff Publications 2022 OA
