File:Torosaurus latus (ceratopsian dinosaur) (Hell Creek Formation, Upper Cretaceous; Fergus County, Montana, USA) 4.jpg

English: Torosaurus latus Marsh, 1891 - fossil ceratopsian dinosaur frill from the Cretaceous of Montana, USA. (MOR 1122, Museum of the Rockies, Bozeman, 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 the dorsal (top) surface of a Torosaurus latus frill ("shield") from Montana's Hell Creek Formation of near-latest Cretaceous age. Some researchers consider Torosaurus to be synonymous with Triceratops, but they are probably separate genera (Scannella & Horner, 2010; Longrich & Field, 2012). The large openings are called "fenestra" - their presence reduced the weight of the skull.

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From exhibit signage:

Torosaurus had one of the largest skulls of land animal. This skull measures nine feet in length and six feet across the shield.

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From exhibit signage:

The neck shield (parietal bone) of Torosaurus latus

The neck shields of Torosaurus and all other horned dinosaurs are indented with branching blood-vessel channels. On the front side of the shield, large indented vessels seem to be directed into the hole openings, while on the rear side, these vessels seem to pass through the holes, terminating at the outer rim of the shield. The blood supply appears to have come from the head and gone out to the epoccipital bones on the ourter time of the shield.

Histological sections (paper-thin slices) cut from the inside of the bony shield reveal tiny bundles of Sharpey's fibers. These microscopic structures are often observed in bone where muscle, ligaments, or hard keratin attaches to bone.

Studies of ceratopsian shields by Jack Horner and post-doctoral student Cynthia Marshall provided evidence to suggest that bones with indented vessels and internal Sharpey's fibers were overlain by hard keratin. In birds, indented vessels and internal Sharpey's fibers are found under keratin beaks and on the bones of keratin-covered claws.

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Classification: Animalia, Chordata, Vertebrata, Reptilia, Archosauria, Dinosauria, Ornithischia, Marginocephalia, Ceratopsia, Ceratopsidae

Stratigraphy: Hell Creek Formation, Maastrichtian Stage, Upper Cretaceous

Locality: undisclosed site ("Toro 2") in Fergus County (apparently near the town of Valentine; = Museum of the Rockies locality # HC-258), Montana, USA

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References cited:

Scannella & Horner (2010) - Torosaurus March, 1891, is Triceratops March, 1889 (Ceratopsidae: Chasmosaurinae): synonymy through ontogeny. Journal of Vertebrate Paleontology 30: 1157-1168.

Longrich & Field (2012) - Torosaurus is not Triceratops: ontogeny in chasmosaurine ceratopsids as a case study in dinosaur taxonomy. Public Library of Science One 7(2): e32623. 10 pp.

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Info. at:

en.wikipedia.org/wiki/Torosaurus