Scott D. Sampson; Mark A. Loewen; Andrew A. Farke; Eric M. Roberts; Catherine A. Forster; Joshua A. Smith; Alan L. Titus

“ Of the 16 dinosaur taxa currently recognized from the Kaiparowits Formation, 10 can presently be identified to genus and species, and all members of this subset represent previously unknown forms.
The evolutionary radiation of ceratopsid dinosaurs was apparently restricted both temporally and geographically; taxa are known predominantly from sediments of latest Cretaceous age (Campanian and Maastrichtian; ∼80–65.5 Ma) in the Western Interior Basin (WIB) of North America, with one exception from the latest Cretaceous of China [10] . ”

“ The preceding Campanian stage, in contrast, has yielded an exceptionally diverse assemblage of dinosaur taxa that span a far greater latitudinal range (Alberta to Mexico) and are much better constrained both geographically and stratigraphically [7] , [9] , [27] , [25] . With a dense and relatively well sampled fossil record, the potential for high-precision geochronology, and faunas occupying a peninsular continent, the Campanian WIB represents arguably the best time and place to investigate major questions surrounding the ecology and evolution of Mesozoic terrestrial ecosystems. ”

“ The highly derived parietosquamosal frill of Kosmoceratops shares several derived features only with Vagaceratops irvinensis [20] , including a rostrocaudally abbreviated frill with small, caudally placed parietal fenestrae and the presence of 10 well developed hook-like processes (five per side: three on the parietal, ep1-3; one on the squamosal, s1; and another at the boundary of these two elements, esp) on the caudal frill margin, all formed by accessory ossifications. ”

“ Thus, the phylogenetic evidence implies that all northern taxa from the latest Campanian and Maastrichtian (e.g., Anchiceratops, Torosaurus, Triceratops) evolved from ancestral forms originally restricted to the southern region of the WIB. The combined evidence is most consistent with the following sequence of events pertaining to the origin, dispersal and evolution of Chasmosaurinae: 1) origin on Laramidia 90–80 Ma (the oldest member of the sister clade Centrosaurine dates to about 80 Ma [24] ) ; 2) dispersal of the clade throughout much of Laramidia prior to 77.0 Ma ”

“ The data presented herein suggest further that latitudinal zonation may have persisted for at least 1.5 million years, resulting in distinct endemic centers within the WIB. Additional fossil representatives from the newly discovered Kaiparowits Formation dinosaur fauna (e.g., centrosaurines, hadrosaurids, tyrannosaurids) will be subjected to similar analyses in order to test the hypothesis that other clades exhibit a parallel biogeographic pattern. ”

“ The holotype and referred specimens described here were recovered by field crews working with the Utah Museum of Natural History and the Bureau of Land Management. This work was conducted under Bureau of Land Management Assistance Agreements # JSA015003 and JSA071004. Many crew members—including Scott Richardson, discoverer of the holotype and referred materials of Kosmoceratops richardsoni n. gen. et n. sp.—were volunteers. The specimens were recovered using traditional field methods employed by vertebrate paleontologists, augmented by helicopter airlifts. ”

“ The authors have declared that no competing interests exist.Funding: This work was supported by grants from the National Science Foundation (EAR 0745454, 0819953; http://www.nsf.gov/funding/) , Bureau of Land Management (GSENM;http://www.blm.gov) , Discovery Quest (http://www.discovery.com) , and the University of Utah (http://www.utah.edu) . The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. ”

“ Currie, PJ & Koppelhus, E (2005) , “Ornithischian dinosaurs.”, Dinosaur Provincial Park: A spectacular ancient ecosystem revealed (Bloomington: Indiana University Press) : 312–348 ↑ Longrich, N (2010) , “Mojoceratops perifania, a new chasmosaurine ceratopsid from the late Campanian of western Canada.”, J Paleont 84: 681–694 ↑ Horner, JR ”