Skull material of an Early Cretaceous hadrosauriform dinosaur (Ornithopoda) from Salas de los Infantes (Burgos, Spain)

Skull remains of an ornithopod dinosaur, identified as MDS-LTASI, from the Los Terreros-Altollano site in Salas de los Infantes (Burgos, Spain) are described. The site is located in the upper Barremian-Aptian Castrillo de la Reina Formation (Cameros Basin). The fossils are part of a single individual and consist of a predentary, a dentary and a set of isolated teeth, four of which (three maxillary teeth and one tooth from the dentary) are described here. The combination of characters observed in MDS-LTASI (septa of the alveoli shaped to accommodate the teeth; ventral deflection of the rostral zone; coronoid process forming an obtuse angle with the craniocaudal axis of the mandibular ramus; medial surface of the adductor fossa with an oval foramen—a character shared with Portellsaurus-; maxillary teeth without or with few secondary ridges) differentiates it from other non-hadrosaurid styracosternans, but the fragmentary nature of the material does not advise the erection of a new taxon. A phylogenetic analysis suggests that the Los Terreros-Altollano taxon is a basal hadrosauriform more derived than Iguanodon, but more basal than Proa. This find extends the diversity of ornithopods from the Cameros Basin, as well as the Iberian record of non-hadrosaurid styracosternans.