Mahajangasuchus insignis (Crocodyliformes: Mesoeucrocodylia) cranial anatomy and new data on the origin of the eusuchian-style palate

ABSTRACT

New material of the fossil crocodyliform taxon Mahajangasuchus insignis from the Upper Cretaceous Maevarano Formation is described. The holotype lacked cranial remains but the new material includes an almost complete skull as well as at least two additional partial skulls. These new specimens add important information and allow us to diagnose Mahajangasuchus insignis as a derived mesoeucrocodylian crocodyliform distinguished by the following combination of characters (autapomorphies indicated with an asterisk): broad platyrostral snout; laterally compressed and serrated teeth; dorsally arched mandible; prominent caudofemoralis flange on femur; surangular with prominent lateral expansion anterior to glenoid fossa; supraocciptial excludes the parietal from occipital margin; massive choanal septum*; anterior margins of choanal septum contact ventral lamina of pterygoid, enclosing internal choanae*; strongly arched jugal with depression below orbit*; three prominent ridges running longitudinally on dorsal surface of snout*; fused nasals.* The new specimen offers new information to explore the phylogenetic relationships of Mahajangasuchus insignis and bears important information for understanding the evolutionary history of the crocodyliform palate and the adaptive significance of the modern eusuchian-style palate. The phylogenetic analysis conducted results in the discovery of monophyly of the traditional Peirosauridae and a derived position for Mahajangasuchus and Stolokrosuchus as successive sister taxa to Neosuchia. Inclusion or exclusion of Trematochampsa taqueti, a fragmentary taxon from Africa, greatly affects the phylogenetic relations of Mahajangasuchus.