A new species of Maomingosuchus from the Eocene of the Na Duong Basin (northern Vietnam) sheds new light on the phylogenetic relationship of tomistomine crocodylians and their dispersal from Europe to Asia

Abstract

Maomingosuchus acutirostris sp. nov. is a new tomistomine crocodile from the middle–upper Eocene deposits (late Bartonian–Priabonian age, 39–35 Ma) of the Na Duong Basin in northern Vietnam. M. acutirostris can be differentiated from the type species Maomingosuchus petrolicus by having an acute anterior tip of the premaxilla. Both species differ from another Maomingosuchus from Krabi (Thailand) by differences in the surangular–dentary suture and maxillary alveoli. According to our phylogenetic results, M. acutirostris seems to be the sister species to the group M. petrolicus + Krabi-Maomingosuchus. The close relationship between those three tomistomines is supported in the present phylogenetic analysis by three synapomorphies. In our phylogenetic analysis, Maomingosuchus was retrieved in a basal position forming the sister group to Paratomistoma + Gavialosuchus + Melitosaurus + Tomistoma, including the extant Tomistoma schlegelii. This phylogeny indicates three different dispersal events of Tomistominae from Europe towards eastern Asia: 1) for the stem lineage of Maomingosuchus, no later than the late Eocene; 2) for the stem lineage of Penghusuchus pani + Toyotamaphimeia machikanensis, no later than the early–middle Miocene; and (3) for the stem lineage of T. schlegelii, during the Neogene. http://zoobank.org/urn:lsid:zoobank.org:pub:19B27C1E-0A3F-4425-AA8C-F904277DF327