Triceratops

Triceratops became the first genus of horned dinosaur known to science when its skull was described by Othniel C. Marsh in 1889. The remains of its horns were originally attributed to the high-horned bison (Bison alticornis), and its occipetal condyle was originally named Ceratops montanus. In his preliminary description of the skull, Marsh named its owner Ceratops horridus and felt it was related to the stegosaurs. After the skull had been cleaned, Marsh changed the name to Triceratops horridus. Thirteen species of Triceratops have been described, but only one (or possibly two) species actually occurred in nature. Triceratops lived in western North America at the end of the Cretaceous, between 68 and 65 million years ago.

Characteristics
The most characteristic feature of the animal was its large, V-shaped head which terminated in an elongate frill. The skull can be more than 6 feet long (2.2 meters). Only whales have larger skulls. The frill allowed an animal to recognize members of the same species as well as members of the opposite sex. Since Triceratops had color vision, the frill was probably pigmented, and its ornamentation was designed for visual display and not for protection or to serve as a point of attachment for the jaw muscles. The head bore three horns that functioned in display, ritual combat, and protection frompredators. One short horn arose over the nose, and two others, the longest, arose over the eyes. Males had large, erect horns while females had smaller, somewhat forward-pointing horns. The large number of skulls that have been found indicates that Triceratops was an abundant, gregarious species. No complete skeletons are known. A composite, presumably female, skeleton on display at the Science Museum of Minnesota is 26 feet (7.9 meters) long and 9 feet, 7 inches (2.9 meters) high. With a weight of 8.5 metric tons (9.4 tons), Triceratops was three times heavier than a rhinoceros. The shin bone (fibia) was notably shorter than the thigh bone (femur). The size relationship between these two bones is the reverse of what is seen in animals that are fast runners. Evidence from ceratopsian trackways and the anatomy of its shoulder (the hind legs were located directly below the hips while the forelimbs sprawled outward and were not located below the shoulders) also indicates that Triceratops was rather slow. Its running speed has been estimated at about 4.2 kilometers per hour (2.6 miles per hour).