The first complete description of the holotype of Brachylophosaurus canadensis Sternberg, 1953 (Dinosauria: Hadrosauridae) with comments on intraspecific variation

Abstract

The holotype of Brachylophosaurus canadensis was collected by C.M. Sternberg in 1936 from the Oldman Formation (Upper Cretaceous) of Alberta, Canada, with a brief description focusing on the cranium following in 1953. A re-description of the holotype skeleton confirms its position as a hadrosaurine dinosaur exhibiting the following unique combination of characters: paddle-like solid nasal crest; posteriorly elongated prefrontal; only the anterior tip of the lacrimal contacting maxilla; extremely elongated anterior maxillary process; and a quadratojugal with a noncrescentic posterior margin variably forming a paraquadratic foramen with the quadrate. Comparison of the holotype with other specimens assigned to the taxon reveals numerous morphological differences. These variable features include the presence/absence of an accessory premaxillary foramen, the number of maxillary/dentary vertical tooth rows, the number of functional teeth per tooth row contributing to the dental occlusal surface, the bones forming the mandibular glenoid, the presence/absence of a nasal foramen, nasal crest morphology, the number of cervical vertebrae, and axis morphology.© 2010 The Linnean Society of London.