Alberta Palaeontological Society Tenth Annual Symposium 38 Sixty years of pachyrhinosaur (Dinosauria: Ceratopsidae) discoveries in North America Darren H. Tanke Royal Tyrrell Museum of Palaeontology INTRODUCTION Ceratopsian or horned dinosaurs have been known for over 115 years (Dodson, 1996). Despite many discoveries across western North America, it was not until 1946 that the first pachyrhinosaur, Pachyrhinosaurus canadensis, was discovered. Interest in pachyrhinosaurs has waxed and waned since then, but has enjoyed a resurgence since the mid 1980s with a number of new discoveries across west- ern North America. For this paper, the term “pachyrhinosaur” is used to collectively describe those Late Cretaceous short-frilled “centrosaurine” horned dinosaurs, in which the adults bear a nasal or fronto-nasal “boss” in lieu of the enlarged nasal horncore as seen in other members of the subfamily (e.g. Centrosaurus, Einiosaurus, Styracosaurus). Here are reviewed the North American occurrences of pachyrhinosaurs and relevant technical literature, selected popular literature, history of their discoveries, and other details. An extensive reference list is provided. Eighteen sites/occurrences are reviewed from north to south, starting in northern Alaska and ending in northern Montana. Institutional abbreviations: CMN—Canadian Museum of Nature, Ottawa, ON; GPRC—Grande Prai- rie Regional College, Grande Prairie, AB; GSC—Geological Survey of Canada, Ottawa, ON; TMP— Royal Tyrrell Museum of Palaeontology, Drumheller, AB. COLVILLE RIVER, ALASKA A number of pachyrhinosaur discoveries have been made on the North Slope of Alaska, consisting of isolated bones, isolated skulls and a pachyrhinosaur-dominated bonebed. All were derived from the Prince Creek Formation (Campanian–Maastrichtian). he sites are treated separately here, but all share a common references section following the Alaska entry. 1. he first specimen, a partial skull, was found and collected by J. Howard Hutchinson on August 4, 1988. It is usually known as the “Berkeley specimen” or “Berkeley pachyrhinosaur”. A 1997, a 53.5 minute documentary entitled “Dinosaur: he Arctic Expedition” covering the collection and preparation of this skull and other Alaskan dinosaur material was produced. It is still available for sale (Anonymous, 2005a). A website (Anonymous, 2005a) provides site photographs and a picture of the skull undergoing preparation. he specimen consists of a large portion of a skull, but lacking the premaxillae, jugals, and frill. It shares many osteological similarities to the pachyrhinosaur from Pipestone Creek, near Grande Prairie, AB. he specimen has yet to be formally described, awaiting the published results of the Pipestone Creek, AB pachyrhinosaur bonebed research. 2. Parrish et al.(1987, p. 383) describe and figure a horn core they ascribe to a parietal frill spike and compare it to southern Alberta specimens of Pachyrhinosaurus. his assignment appears correct. In the same paper, an occipital condyle found in the area compared most closely to Anchiceratops, but