Torosaurus Marsh, 1891
publication ID |
https://doi.org/ 10.5281/zenodo.3675277 |
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https://doi.org/10.5281/zenodo.3681086 |
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https://treatment.plazi.org/id/A810F277-741B-D021-FAE8-F65C930FBB21 |
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Jeremy |
scientific name |
Torosaurus Marsh, 1891 |
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Order Ornithischia
Suborder Ceratopsia
Family Ceratopsidae
Genus Torosaurus Marsh, 1891
Remarks.— There are three shapes to the frills of ceratopsia with fenestrated parietals, 1) triangular, found in Protoceratops , Chasmosaurus , and Pentaceratops , 2) figure-8, found in Brachyceratops , Monoclonius , Styracosaurus and presumably Pachyrhinosaurus , 3) broad frill with elliptical or circular fenestrae, found in Anchiceratops , Arrhinoceratops , and Torosaurus . Triceratops, except for a few “sports,” lacks fenestrae but is related to the last group. Considering the third group, in dorsal view Anchiceratops and Arrhinoceratops have rectangular frills with well developed epoccipitals. Torosaurus has a cardioid frill, has weakly developed epoccipitals, thinner parietals, and reduced vascular sulci. Since Torosaurus arose from an Arrhinoceratops- like form, a complete fossil record would show a gradation between forms and primitive torosaurs should be intermediate in character. Such a situation seems to exist in the case of Torosaurus utahensis .
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