A new dyrosaurid crocodyliform from the Paleocene of Morocco and a phylogenetic analysis of Dyrosauridae

A new genus and species belonging to Dyrosauridae, Arambourgisuchus khouribgaensis, from the Thanetian (Palaeocene) of Morocco, is erected. Two more or less complete skulls and three mandibular fragments enable a reconstruction of the anatomical characteristics of this species. Dyrosaurid systematics is mainly based on mandibular characters. The comparison of this new material with several dyrosaurid species previously known provides new systematic data for this group. The width of the interfenestral bar, the shape and development of the occipital tuberosities and the shape of the supraoccipital and the basioccipital are of particular importance. A phylogenetic analysis of the dyrosaurids provides an outline of the relationships between the best known species. Chenanisuchus lateroculi is the most primitive dyrosaurid. Sokotosuchus ianwilsoni and Phosphatosaurus gavialoidesform a clade, more closely related to other dyrosaurids than to Chenanisuchus lateroculi. The relationships between Arambourgisuchus, Rhabdognathus, Congosaurus, and Hyposaurus are unclear, and the two latter taxa remain too poorly known to provide an uncontested phylogenetic result. The dyrosaurids are known from nearly all continents. The phylogenetic results suggest a North African range for basal members, and the wide distribution of Rhabdognathus and Hyposaurus confirms the possibility of transoceanic dispersal of these taxa. Unfortunately, many dyrosaurids are insufficiently known to be included in the analysis, and the present analysis considers mainly African forms. A better knowledge and the inclusion of other taxa from other geographic regions should significantly improve and modify the hypothesis