Osteology of Monjurosuchus splendens (Diapsida: Choristodera) based on a new specimen from the Lower Cretaceous of western Liaoning, China

The discovery of a new specimen of Monjurosuchus splendens, a taxon that has remained a taxonomic conundrum since the 1940s, from the Lower Cretaceous Yixian Formation in western Liaoning, has allowed a new and accurate interpretation of the skull roof. Comparison of the new fossil with several specimens of the same taxon from the type Lingyuan area clarifies several anatomical ambiguities, thus providing valuable information for assessment of the phylogenetic relationships within the Choristodera of this problematic taxon. Monjurosuchus and its sister taxon Philydrosaurus are the two known genera in the Monjurosuchidae, and the latter family occupies a basal position outside the Neochoristodera. Determination of the relationship of the Monjurosuchidae with another basal clade, the Hyphalosauridae, requires a better understanding of the cranial morphology of the latter group, and an extensive survey of character distribution among all other choristoderan clades.