[N] 2006 New Ceratopsian from the Upper Horseshoe Canyon Formation, Alberta
Wu, X-C., Brinkman, D. & Eberth, D. (2006) A new Ceratopsian dinosaur (Ornithischia) from the Upper Horseshoe Canyon Formation, Alberta, Canada. JVP 26(3) Abstracts pp. 142
Southern Alberta is uniquely famous for its richness of dinosaurian and other fossil vertebrates in the late Cretaceous. ceratopsians, or horned dinosaurs, are one of the best represented dinosaur groups in the region and one of the last non-avian dinosaur groups to become extinct. Ceratopsians are well represented in the Lower Horseshoe Canyon Formation (Upper Campanian) and Lower Scollard Formation (Upper Maastrichtian, roughly equivalent in age to the Frenchman Formation of southern Saskatchewan and the Hell Creek and Lance Formations of USA), but are rare in the Upper Maastrichtian Upper Horseshoe Canyon Formation and its equivalent deposits in neighboring areas. A new ceratopsian dinosaur skeleton was collected from the Upper Horseshoe Canyon Formation in the Dry Island-Buffalo Jump Provincial Park, southern Alberta in the field season of 2001. Although dinosaurs have been collected from this interval for approximately a century, this is the first associated specimen of vertebrate fossils found within the top 20 m of the Horseshoe Canyon Formation.
The new ceratopsian is diagnosable primarily on the basis of a combination of features in the premaxilla, nasal horn core, squamosal frill, and epijugal. The most striking of those features include an extremely dorsoventrally broadened narial process of the premaxilla, a rostrally positioned premaxillary process extending into the interpremaxillary fenestra, the presence of greatly elongate epoccipitals of the squamosal frill, a deep fossa on the rostroventral surface of the squamosal frill, the epijugal sharply triangular in lateral view, and the presence of a transverse and a oblique vascular trace on the rostral surface of the nasal horn core. Our preliminary study suggests that the new form is a chasmosaurine and nested within a clade including Triceratops, Diceratops and Torosaurus, which are all from the late Maastrichtian deposits. The new ceratopsian fills the stratigraphical/chronological gap that currently exists between the late Campanian and the late Maastrichtian ceratopsian dinosaurs.