Re-evaluation of the Wealden crocodyliform Koumpiodontosuchus Sweetman et al. , 2015: new osteological and neuroanatomical data from micro-computed tomography resolves a phylogenetic dispute

Abstract Koumpiodontosuchus aprosdokiti is a small neosuchian crocodyliform recovered from the Wealden Supergroup (Lower Cretaceous: Berriasian—Aptian) of southern England. It was initially allied to Bernissartia within Bernissartiidae, a small but phylogenetically important Late Jurassic and Cretaceous clade traditionally considered the sister group to Eusuchia and thus integral to our understandings of the origins and early evolution of crocodylians. However, recent studies have posited differing phylogenetic hypotheses, either placing Bernissartiidae within Eusuchia or recovering disparate positions for Bernissartia and Koumpiodontosuchus. We resolve these contrasting topologies by redescribing the known cranial, vertebral, and integumentary (osteoderm) osteology of the holotype specimen (IWCMS 2012.203–204) via micro-computed tomography (microCT). Our virtual models allow previously hidden regions to be visualized (e.g. braincase), clarify the position of the secondary choana, and provide novel information on the endocranial and pneumatic systems of the skull, all of which improve phylogenetic scoring for this taxon. Our new data confirms the placement of Koumpiodontosuchus as the sister taxon of Bernissartia within Bernissartiidae and, additionally, support the position of bernissartiids as the eusuchian sister group. Our reconstruction of Koumpiodontosuchus’s endocranial anatomy also allows an updated palaeoecological interpretation, and we find that its neurosensory capabilities had much in common with those of extant crocodylians.