The first (�horn-faced�) dinosaur remains were found in the 1870s by the American paleontologi.... horn neck

The first inkling that there had been horned dinosaurs did not emerge until the late 1880s with the discovery of a large horn core, first mistaken for that of a . Correlated with the various arrays of head horns in the different taxa was the unusually large size of ceratopsian heads. Several hypotheses have been proposed to explain this frill structure: a protective shield to cover the neck region, an attachment site of greatly enlarged jaw muscles, an attachment site of powerful neck muscles for wielding the head horns, or a sort of ornament to present a huge, frightening head-on profile to potential attackers. An exception to this pattern was Triceratops , which had a solid and relatively short frill, but Triceratops is so well known that its frill is often mistakenly considered typical of ceratopsians. The open frill of other ceratopsians would have provided only poor protection for the neck region and only a modest area of attachment for jaw or neck muscles. The Ceratops! ia are divided into groups that mirror their evolutionary trends through time: the primitive , such as ; the protoceratopsids, including Protoceratops of Asia and of North America; and the ceratopsids, encompassing all the advanced and better-known kinds such as the chasmosaurines Triceratops and Torosaurus as well as the centrosaurines such as Centrosaurus (or Monoclonius )all from North America. Psittacosaurus , however, possessed a beak, the beginnings of a characteristic neck frill at the back of the skull, and teeth that prefigured those of the more advanced ceratopsians. The ceratopsian skull was disproportionately large for the rest of the animal, constituting about one-fifth of the total body length in Protoceratops and at least one-third in Torosaurus . Protoceratops also displayed a short but stout horn on the snout due to development of the nasal bones; this too was a precursor of the prominent nasal horns of ceratopsids such as Centrosaurus , Chasmosaurus , Styr! acosaurus , Torosaurus , and Triceratops . These advanced cera! topsids are sometimes divided into centrosaurines, which had a prominent nose horn but small or absent eye horns, and chasmosaurines, which had larger eye horns but reduced nose horns. This mixed posture was perhaps related to the large horned head and its role in combat, the bent forelegs providing a wide stance and stable base for directing the horns at an opponent and resisting attack. The first joint of the neck was unusual in that the bone at the base of the skull formed a nearly perfect sphere that fit into a cuplike socket of the fused neck vertebrae. horn neck