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Avaceratops lammersi: A New Ceratopsid from the Judith River Formation of Montana

Peter Dodson
Proceedings of the Academy of Natural Sciences of Philadelphia
Vol. 138, No. 2 (1986), pp. 305-317
Stable URL: http://www.jstor.org/stable/4064910
Page Count: 13
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Avaceratops lammersi: A New Ceratopsid from the Judith River Formation of Montana
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Abstract

A recently discovered dinosaur bonebed in the Upper Cretaceous (Campanian) sediments of south central Montana constitutes the southern-most concentration of dinosaurs in the Judith River Formation, and also the richest dinosaur discovery ever made in this formation in Montana. The fauna includes disarticulated remains of young juvenile dinosaurs of several kinds. The most important specimen in the quarry is that of a young ceratopsid whose length is estimated at 2.3 m. Preserved material includes much of the skull, most of the appendicular skeleton, and representative vertebrae and ribs. The specimen is described as a new genus and species, Avaceratops lammersi. It is a short-squamosaled ceratopsid, but the form of the parietal and of the squamosal contrast sharply with other Judithian short-squamosaled ceratopsids: Monoclonius, Centrosaurus, and Styracosaurus. Although it has the limb proportions of ceratopsids five or ten m long, early fusion of the occipital condyle and a tapering shape of the unguals suggest it may have reached a smaller adult size than that of typical Judithian ceratopsids.

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