What Is Torosaurus latus?

The sculpted eye of Torosaurus in progress.


Torosaurus, a horned dinosaur that lived at the end of the Cretaceous Period 66 to 65 million years ago, is a member of the group of frilled and horned dinosaurs known as ceratopsians that also includes the more familiar Triceratops. Ceratopsians were herbivorous dinosaurs that fed on cycads and other low-lying plants, using their tough beak to crop plants, and their well-developed cheek teeth to chew.

The title page and an illustration from O.C. Marsh’s 1892 description of Torosaurus.
Yale Peabody Museum Archives


Torosaurus latus is significant in the history of the Yale Peabody Museum. In 1891 two large skulls of an unidentified dinosaur were sent to Yale from Niobrara County in southeastern Wyoming. Yale professor O.C. Marsh first described and named Torosaurus later that year, formally establishing a new genus of ceratopsian, or horned, dinosaur that he named Torosaurus (Marsh, O.C., 1891. Notice of new vertebrate fossils. American Journal of Science 42).

Marsh further elucidated his description in January 1892 (Marsh, O.C., 1892. The skull of Torosaurus. American Journal of Science 43). Although Marsh recognized 2 species in this genus, most modern paleontologists consider only one of them, Torosaurus latus, to be valid.

The Meaning of Torosaurus


The full-scale model in progress.


It is likely that the root “toro” in Torosaurus is from the Greek toreo (“perforate, pierce”) and not from the Latin torus (“protuberance, bulge”), nor is it from either the Latin (taurus) or Greek (tauros) words for “bull.” Moreover, according to the classicist Ben Creisler: “The non-classical Spanish word toro, ‘bull,’ is not the correct derivation of the name, though Marsh might have used the similar spelling as a pun for a horned dinosaur.” Thus, based solely on the parietal fenestrae in the frill, it seems that “perforated lizard” is the correct meaning for the name Torosaurus.

For those of you who still may want to call the Peabody’s Torosaurus specimens “bull lizards,” hope is not lost. One leading expert on ceratopsians, Peter Dodson, suggests in his 1996 book The Horned Dinosaurs (Princeton University Press) that, based on their upright and divergent brow horns, the two Peabody specimens of Torosaurus are adult males. If true, they could, just like adult male cattle, elephants and moose, be called “bulls”!
Adapted from “What’s in a Name? The Meaning of Torosaurus,” by Daniel Brinkman, originally published in the Yale Peabody Museum’s November/December 2002 Explorer newsletter.

The Meaning of Torosaurus


The frill openings are clearly visible in the type specimen of Torosaurus latus on display in the Yale Peabody Museum’s Great Hall.


Torosaurus — like Bronotosaurus, Stegosaurus and Triceratops — is a classic dinosaur whose name is intimately linked to the Yale Peabody Museum. Yet, unlike those other famous Peabody dinosaurs, the meaning of the name Torosaurus has generated much confusion for professional paleontologists and amateur natural historians alike.

Several meanings for Torosaurus have been suggested over the years, including “bull lizard,” “bulging lizard,” “pierced lizard,” “piercing lizard” and “perforated lizard.” This confusion can be traced to Marsh’s original 1891 description of Torosaurus latus, in which he did not specify the etymology, or meaning, of the name. In his paper Marsh described the frill of Torosaurus as “perforated by a pair of large openings.” Unfortunately, a few sentences later Marsh wrote that the main horn-cores in Torosaurus “are placed well back of the orbit,” which has led some to concentrate on the brow horns instead of the perforations in the skull when deriving a meaning for the name.

However, in a later, more detailed paper on the skull of Torosaurus Marsh leaves little doubt that it is the perforations and not the brow horns that led to the name when he wrote: “The open perforations in the parietal which have suggested the name Torosaurus, readily separate this genus from all the gigantic species hitherto known in the Ceratopsidae.…” Today we realize that many kinds of ceratopsians have these openings, called the parietal fenestrae, in their frills.