A juvenile chasmosaurine ceratopsid (Dinosauria, Ornithischia) from the Dinosaur Park Formation, Alberta, Canada

ABSTRACT

An articulated, 1.5 m long skeleton of a juvenile Chasmosaurus, lacking only the front limbs, pectoral girdles, and terminal caudal vertebrae, was collected from the Dinosaur Park Formation in Dinosaur Provincial Park, Alberta. The short, tall skull has a narrow frill that lacks a posterior embayment. Many of the cranial bones are co-ossified in spite of the small size of the specimen. The nasals form an incipient horncore, and the short, knob-like postorbital horncore lacks sinuses. The palpebral is not fused to the rest of the skull. The frontal fontanelle is keyhole-shaped. The triangular squamosal extends to the back of the parietals. Epiossifications are lacking, although the squamosal margin is thick and scalloped. The parietal has a pronounced midline sagittal crest. Parietal fenestrae, if present, would have been narrow and elongate. There are only 18 maxillary tooth positions. The syncervical comprises three co-ossified, but distinct vertebrae. Anterior caudal vertebrae support unfused caudal ribs. Ossified tendons in the neck, trunk, and sacrum do not extend into the tail. Hind limb proportions are comparable to those of adult ceratopsids. The pedal unguals are distally acute. Skin impressions are similar to those of mature chasmosaurines. Phylogenetic analysis, if all characters are coded as they are seen, suggests that the specimen is a basal chasmosaurine. When size or age dependent characters are recoded as ‘?,’ the specimen groups with other Chasmosaurus. These characters should only be used in phylogenetic analyses when all specimens are mature.

SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP

Citation for this article: Currie, P. J., R. B. Holmes, M. J. Ryan, and C. Coy. 2016. A juvenile chasmosaurine ceratopsid (Dinosauria, Ornithischia) from the Dinosaur Park Formation, Alberta, Canada. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2015.1048348.

ACKNOWLEDGMENTS

UALVP 52613 was discovered by the first author in 2010, who collected the specimen with C. Coy and A. Lindoe. Preparation was done by the last author. Casts and information on the juvenile Triceratops were provided by M. Goodwin (University of California, Berkeley). Specimen measurements were provided for some specimens by J. Scannella (MOR) and J. Campbell (Carleton University). Removing specimens from the badlands is never an easy task, so the help of L. Lucas is gratefully acknowledged. CT scans were done at Alberta Innovates Technology Futures (Edmonton) with the assistance of S. Cameron. Many of the photographs were taken by J. Ulan.