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Cranial morphology of a juvenile Triceratops skull from the Hell Creek Formation, McCone County, Montana, with comments on the fossil record of ontogenetically younger skulls

By
Mark B. Goodwin
Mark B. Goodwin
Museum of Paleontology, University of California, Berkeley, California 94720-4780, USA
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John R. Horner
John R. Horner
Museum of the Rockies, Montana State University, Bozeman, Montana 59717-0040, USA
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Published:
January 2014

Here, we describe a juvenile Triceratops sp. skull, UCMP 136306, from the Hell Creek Formation, McCone County, Montana. The relative completeness and superb preservation of this skull contribute to an improved understanding of the cranial ontogeny, morphology, and individual variation in Triceratops. Total skull length is 120 cm long (est.). UCMP 136306 is one of the most complete Triceratops skulls of this ontogenetic stage yet known. The cranial sutures are patent, and most are overlapping with minimal sinuosity, modest interdigitation, and overlapping flat sutural surfaces. The following cranial elements are preserved and described in this study: epinasal, rostral, quadrate, quadratojugal, jugal, pterygoid, dentary, surangular, postorbital horn, parietal, squamosal, epiparietal, episquamosal, occipital condyle, supraoccipital, and exoccipital.

For decades following the initial description of Triceratops by O.C. Marsh in 1889, the typical collector attitude was “bigger is better.” Emerging scientific institutions and museums with newly constructed exhibit halls demanded the biggest and newest dinosaurs. We hypothesize that this historical practice, influenced by facies and taphonomic factors in the Upper Cretaceous Hell Creek Formation, Montana (and contemporaneous formations in neighboring states), resulted in the underrepresentation of nonadult Triceratops in museum collections. This practice contributed to the false notion that nonadult Triceratops specimens are rarely preserved in the fossil record, until now.

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GSA Special Papers

Through the End of the Cretaceous in the Type Locality of the Hell Creek Formation in Montana and Adjacent Areas

Edited by
Gregory P. Wilson
Gregory P. Wilson
Department of Biology and Burke Museum of Natural History and Culture, University of Washington, Seattle, Washington 98195-1800, USA
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William A. Clemens
William A. Clemens
Museum of Paleontology, University of California, Berkeley, Berkeley, California 94720-4780, USA
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John R. Horner
John R. Horner
Museum of the Rockies, Montana State University, Bozeman, Montana 59717-0040, USA
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Joseph H. Hartman
Joseph H. Hartman
Harold Hamm School of Geology and Geological Engineering, University of North Dakota, Grand Forks, North Dakota 58202-8358, USA
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Geological Society of America
Volume
503
ISBN print:
9780813725031
Publication date:
2014

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