Abstract October 1, 2008, Philip J. Currie, Wann Langston, Jr., and Darren H. Tanke unveiled for the first time the name of a newly discovered horned dinosaur species. In the first monographic treatment of a horned (ceratopsid) dinosaur in almost a century, this monumental volume presents one of the closest looks at the anatomy, relationships, growth and variation, behavior, ecology and other biological aspects of a single dinosaur species. The research, which was conducted over two decades, was possible because of the discovery of a densely packed bone bed near Grande Prairie, Alberta. The locality has produced abundant remains of a new species of horned dinosaur (ceratopsian), and parts of at least 27 individual animals were recovered. This new species of Pachyrhinosaurus is closely related to Pachyrhinosaurus canadensis, which is known from younger rocks near Drumheller and Lethbridge in southern Alberta, but is a smaller animal with many differences in the ornamental spikes and bumps on the skull. The adults of both species have massive bosses of bone in the positions where other horned dinosaurs (like Centrosaurus and Triceratops) have horns. However, juveniles of the new species resemble juveniles of Centrosaurus in having horns rather than bosses. Skull anatomy undergoes remarkable changes during growth and the horns over the nose and eyes of the Pachyrhinosaurus juveniles transform into bosses; spikes and horns develop on the top of and at the back of the frill that extends back over the neck. No cause has been determined for the apparent catastrophic death of the herd of Pachyrhinosaurus from the Grande Prairie area, but it has been suggested that such herds may have been migratory animals. In addition to the main descriptive paper, the volume includes information on the distribution of bones within the bone bed itself, and a cutting-edge digital treatment of CT-scan data of the fossils to reveal the anatomy of the animal’s brain! See below to view the Pachyrhinosaurus braincase, fading away to reveal the brain within. Courtesy of Witmer & Ridgely, Ohio University.

Abstract A densely packed bone bed near Grande Prairie, Alberta, has produced abundant remains of a new species of ceratopsid. A minimum number of 27 individuals is represented in the part of the bone bed that has been excavated so far. The new animal— Pachyrhinosaurus lakustai sp. nov.— is closely related to the centrosaurine Pachyrhinosaurus canadensis, which has been recovered from younger beds in southern Alberta. It differs from the geologically younger species in having a relatively shorter nasal boss that is well separated from the supraorbital bosses. Juveniles of the new taxon resemble juveniles of Centrosaurus and other centrosaurines. However, the cranial morphology underwent a remarkable ontogenetic change, in which the nasal and supraorbital horns of the juveniles transformed into a huge nasal boss and smaller supraorbital bosses, and the frill became adorned with spikes and horns on top of and at the back of the parietal. Although there is some indication that the species may have been sexually dimorphic at maturity, it is not possible to separate sexual variation from individual and ontogenetic variation without a much larger sample. It is quite clear that the nasal boss supported some sort of keratinous structure, although it is not possible to determine its shape and function. No cause has been determined for the apparent catastrophic demise of a herd of P. lakustai. Key words : Dinosauria, Ceratopsia, Pachyrhinosaurus lakustai , Late Cretaceous, Alberta, Canada.