Thoracosaurs are a polyphyletic group of Cretaceous–Paleogene longisrostrine crocodylians from Europe and North America. Traditionally perceived as gavialoids, phylogenetically closer to Gavialinae than to Tomistominae, they play a key role in the gharial problem: their old age and seemingly close relationship to Gavialinae is inconsistent with molecular clock estimates indicating a far younger origin of Gavialoidea. Moreover, the phylogenetic position of thoracosaurs is debated, as recent studies suggested thoracosaurs are non-crocodylian eusuchians instead. Here we describe thoracosaur material from Mont-Aimé, France, rediscovered in the collections of the Musée d’Histoire Naturelle de Lille. The Mont-Aimé is famous for its richness in fossil vertebrates, among which the longirostrine species Thoracosaurus isorhynchus (formerly T. macrorhynchus). Confusion about the age of the vertebrate layers has recently been solved, indicating that they are Maastrichtian in age instead of Danian. The new material most likely belongs to T. isorhynchus based on a flexure in the ectopterygoid–pterygoid suture, a distinctive character found in adults of this taxon. Our study reveals new characters not visible on previously known material. An example is the short posterior non-dentigerous process of the maxilla, a character shared with early Paleogene longirostrines and tomistomines but not with gavialines. Furthermore, microCT data of the skull reveal for the first time endocranial characters of this taxon, such as the presence of an internal recess in the parietal. Together with redescribed T. isorhynchus material from the Muséum d’Histoire Naturelle, Paris, this leads to an updated phylogenetic position of this taxon.
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RBINS Staff Publications 2023
A total of 225 specimens - representing three orders, four families, 12 genera, 44 species and one variety - collected in the shallow-waters of Kenya and Pemba Island (Tanzania) - are investigated. Bohadschia cousteaui, B. similis, Holothuria (Metriatyla) albiventer; Pearsonothuria graeffei, Thelenota anax, Euapta godeffioyi, Opheodesoma grisea, 0. spectabilis and Synaptula recta are new records for Kenya and from Pemba Island (Tanzania). H. (M) timana is a new record for the western Indian Ocean. Diagnostic characters and descriptions (including some brief notes on the ecology) are given for most species. Identification keys up to the species level are also included. The results are compared to the shallow-water holothuroid biodiversity of the western Indian Ocean. This study stresses the richness of the holothuroid biodiversity of Kenya and Pemba Island. The holothuroid fauna of Kenya (with Pemba Island) is now represented by 48 species.
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