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      New Horned Dinosaurs from Utah Provide Evidence for Intracontinental Dinosaur Endemism

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          Abstract

          Background

          During much of the Late Cretaceous, a shallow, epeiric sea divided North America into eastern and western landmasses. The western landmass, known as Laramidia, although diminutive in size, witnessed a major evolutionary radiation of dinosaurs. Other than hadrosaurs (duck-billed dinosaurs), the most common dinosaurs were ceratopsids (large-bodied horned dinosaurs), currently known only from Laramidia and Asia. Remarkably, previous studies have postulated the occurrence of latitudinally arrayed dinosaur “provinces,” or “biomes,” on Laramidia. Yet this hypothesis has been challenged on multiple fronts and has remained poorly tested.

          Methodology/Principal Findings

          Here we describe two new, co-occurring ceratopsids from the Upper Cretaceous Kaiparowits Formation of Utah that provide the strongest support to date for the dinosaur provincialism hypothesis. Both pertain to the clade of ceratopsids known as Chasmosaurinae, dramatically increasing representation of this group from the southern portion of the Western Interior Basin of North America. Utahceratops gettyi gen. et sp. nov.—characterized by short, rounded, laterally projecting supraorbital horncores and an elongate frill with a deep median embayment—is recovered as the sister taxon to Pentaceratops sternbergii from the late Campanian of New Mexico. Kosmoceratops richardsoni gen. et sp. nov.—characterized by elongate, laterally projecting supraorbital horncores and a short, broad frill adorned with ten well developed hooks—has the most ornate skull of any known dinosaur and is closely allied to Chasmosaurus irvinensis from the late Campanian of Alberta.

          Conclusions/Significance

          Considered in unison, the phylogenetic, stratigraphic, and biogeographic evidence documents distinct, co-occurring chasmosaurine taxa north and south on the diminutive landmass of Laramidia. The famous Triceratops and all other, more nested chasmosaurines are postulated as descendants of forms previously restricted to the southern portion of Laramidia. Results further suggest the presence of latitudinally arrayed evolutionary centers of endemism within chasmosaurine ceratopsids during the late Campanian, the first documented occurrence of intracontinental endemism within dinosaurs.

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          Most cited references21

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          On the Classification of the Fossil Animals Commonly Named Dinosauria

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            Tectonic, stratigraphic, and sedimentologic significance of a regional discontinuity in the upper Judith River Group (Belly River wedge) of southern Alberta, Saskatchewan, and northern Montana

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              Dinosaurs, dragons, and dwarfs: the evolution of maximal body size.

              Among local faunas, the maximum body size and taxonomic affiliation of the top terrestrial vertebrate vary greatly. Does this variation reflect how food requirements differ between trophic levels (herbivores vs. carnivores) and with taxonomic affiliation (mammals and birds vs. reptiles)? We gathered data on the body size and food requirements of the top terrestrial herbivores and carnivores, over the past 65,000 years, from oceanic islands and continents. The body mass of the top species was found to increase with increasing land area, with a slope similar to that of the relation between body mass and home range area, suggesting that maximum body size is determined by the number of home ranges that can fit into a given land area. For a given land area, the body size of the top species decreased in the sequence: ectothermic herbivore > endothermic herbivore > ectothermic carnivore > endothermic carnivore. When we converted body mass to food requirements, the food consumption of a top herbivore was about 8 times that of a top carnivore, in accord with the factor expected from the trophic pyramid. Although top ectotherms were heavier than top endotherms at a given trophic level, lower metabolic rates per gram of body mass in ectotherms resulted in endotherms and ectotherms having the same food consumption. These patterns explain the size of the largest-ever extinct mammal, but the size of the largest dinosaurs exceeds that predicted from land areas and remains unexplained.
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                Author and article information

                Contributors
                Role: Editor
                Journal
                PLoS One
                plos
                plosone
                PLoS ONE
                Public Library of Science (San Francisco, USA )
                1932-6203
                2010
                22 September 2010
                : 5
                : 9
                : e12292
                Affiliations
                [1 ]Utah Museum of Natural History and Department of Geology and Geophysics, University of Utah, Salt Lake City, Utah, United States of America
                [2 ]Raymond M. Alf Museum of Paleontology, Claremont, California, United States of America
                [3 ]School of Earth and Environmental Science, James Cook University, Townsville, Queensland, Australia
                [4 ]Department of Biological Sciences, George Washington University, Washington, D. C. United States of America
                [5 ]Grand Staircase-Escalante National Monument, Bureau of Land Management, Kanab, Utah, United States of America
                Paleontological Institute, Russian Federation
                Author notes

                Conceived and designed the experiments: SDS MAL AAF. Performed the experiments: SDS MAL AAF ER CF JS AT. Analyzed the data: SDS MAL AAF ER CF. Wrote the paper: SDS MAL AAF.

                Article
                10-PONE-RA-19007R1
                10.1371/journal.pone.0012292
                2929175
                20877459
                8435d234-bbfc-42fe-b6e8-f2b5ac8b5760
                Sampson et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
                History
                : 18 May 2010
                : 20 July 2010
                Page count
                Pages: 12
                Categories
                Research Article
                Ecology/Evolutionary Ecology
                Evolutionary Biology/Evolutionary Ecology
                Evolutionary Biology/Paleontology

                Uncategorized
                Uncategorized

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