DescriptionTriceratops sp. (Hell Creek Formation, Upper Cretaceous; Montana, USA).jpg
English: Triceratops sp. - ceratopsian dinosaur rib bone from the Cretaceous of Montana, USA.
Ceratopsians are the "horned dinosaurs". They were large, quadrupedal, herbivorous dinosaurs having a beaked skull and a frill - an extension of bone behind the skull that partially covered the neck. Ceratopsian dinosaurs are known from the Jurassic and Cretaceous. The last members of the group died out at the Cretaceous-Tertiary boundary, 65 million years ago.
Seen here is an Triceratops rib bone from Montana's Hell Creek Formation of near-latest Cretaceous age. The ~vertical slices near the middle of the bone are theropod dinosaur teeth marks.
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