A new psittacosaur from Inner Mongolia and the parrot-like structure and function of the psittacosaur skull |
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Authors: | Paul C. Sereno Zhao Xijin Tan Lin |
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Affiliation: | 1.Department of Organismal Biology and Anatomy, University of Chicago, 1027 East 57th Street, Chicago, IL 60637, USA;2.Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, 100044 Beijing, People''s Republic of China;3.Long Hao Institute of Geology and Paleontology, Bureau of Land and Resources, 010010 Hohhot, People''s Republic of China |
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Abstract: | We describe a new species of psittacosaur, Psittacosaurus gobiensis, from the Lower Cretaceous of Inner Mongolia and outline a hypothesis of chewing function in psittacosaurs that in many respects parallels that in psittaciform birds. Cranial features that accommodate increased bite force in psittacosaurs include an akinetic skull (both cranium and lower jaws) and differentiation of adductor muscle attachments comparable to that in psittaciform birds. These and other features, along with the presence of numerous large gastroliths, suggest that psittacosaurs may have had a high-fibre, nucivorous (nut-eating) diet.Psittacosaurs, alone among ornithischians, generate oblique wear facets from tooth-to-tooth occlusion without kinesis in either the upper or lower jaws. This is accomplished with a novel isognathous jaw mechanism that combines aspects of arcilineal (vertical) and propalinal (horizontal) jaw movement. Here termed clinolineal (inclined) jaw movement, the mechanism uses posteriorly divergent tooth rows, rather than kinesis, to gain the added width for oblique occlusion. As the lower tooth rows are drawn posterodorsally into occlusion, the increasing width between the upper tooth rows accommodates oblique shear. With this jaw mechanism, psittacosaurs were able to maintain oblique shearing occlusion in an akinetic skull designed to resist high bite forces. |
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Keywords: | psittacosaur parrot-beaked dinosaurs jaw mechanics cranial kinesis mesowear nucivorous |
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