With its three-horned head, the triceratops is one of the most famous species of dinosaur. They lived at the very end of the Cretaceous Period before the fatal mass-extinction triggered by the asteroid that caused the Chicxulub crater 65 million years ago.
These 30-foot long herbivores, weighing 12 tonnes, roamed in an area that is now to the East of the Rocky Mountains in North America, which then had a mild climate. They lived contemporaneously with, and were predated upon by, Tyrannoraurs rex. The horns and bony frill on the skull were probably used as a defense against this fearsome foe; although a recent theory has suggested that the frill may have been highly coloured and for ornamentaion, or even temperature regulation.
The first specimen discoved was a pair of horns that were mistaken for a Pliocene bison in 1887. Later realising his mistake the two species, horridus and prorsus, were described by Othniel Charles Marsh in 1889-90. The first mounted skeleton was reconstructed by the Smithsonian in 1905 and has remained on display ever since. For over a century the triceratops has remained one of the most easily recognised and iconic species of dinosaurs.