A SUBADULT MAXILLA OF A TYRANNOSAURIDAE FROM THE TWO MEDICINE FORMATION, MONTANA, UNITED STATES

• Main Author: RAFAEL DELCOURT
• Format: Article
• Language: English
• Published: Universidade de São Paulo
• Series: Papéis Avulsos de Zoologia
• Subjects: Daspletosaurus; Ontogeny; North America; Montana
• Online Access: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0031-10492017000900113&lng=en&tlng=en

ABSTRACT Daspletosaurus is a Campanian genus of Tyrannosauridae from North America. This genus occupied the same geographic area of Albertosaurus, but remains of Albertosaurus are more abundant than Daspletosaurus. Here is described a subadult maxilla (AMNH FARB 5477) of Daspletosaurus sp. from Montana (USA) and possibly from the Two Medicine Formation. The description is based on Carr (1999) that described cranial ontogenetic variations in tyrannosaurids. The maxilla belongs to the ontogenetic Stage 3 sensu Carr (1999), in which the maxilla is thick, the lateral surface of the bone well sculptured, and the maxillary fenestra is subcircular and well separated from the anterior edge of antorbital fossa. Possibly there were more than one species of Daspletosaurus and the locality of the here described subadult specimen suggests that Daspletosaurus species occurred more southern than Albertosaurus.