Triceratops horridus (Marsh, 1889)

Kenneth Carpenter & D. Bruce Young, 2002, Late Cretaceous dinosaurs from the Denver Basin, Colorado, Rocky Mountain Geology 37, pp. 237-254 : 247

Triceratops horridus

Figures 9 and 10

Material.— Currently uncataloged (formerly UCM 41777) skull, right dentary, 2 dorsal vertebrae, rib fragments, 10 caudal vertebrae, both ischia, left pubis(Laramie Formation, Loc. 4); and UCM 38473 nasal horn core, partial vertebrae, left humerus, right coracoid, scapula fragment, phalanges, brow horn core fragment, rib fragments (Laramie Formation, somewhere near Loc. 4).

Description and discussion. —A nearly complete skull is on display at the Weld County Court House in Greeley, Colorado. It was found resting on its right side ( Fig. 9 ) in overbank deposits of the Laramie Formation. The skull is about 1.5 meters long, with an orbit 11.25 cm long anteroposteriorly and 15 cm vertically; the longest horn measures 45 cm. The frill is incomplete and is restored in plaster ( Fig. 10 A ). The skull has the elongated rostrum and anteriorly curved horns characteristic of T. horridus as defined by Forster (1996). Postcranial material includes a few dorsals and mid-caudals ( Fig. 10B ), rib fragments, and left pubis and partial ischium ( Fig. 10 C, D ). Two of the caudals are pathologically co-ossified. Despite the relatively small size of the skull, the animal is an adult as indicated by fusion ofthe neural arches to their centra.

Figures

Figure 9, below. First complete skull of Triceratops from Colorado (uncata­ loged). It was found with partial skeleton in Laramie Forma­ tion. See Figure 10 for prepared speci­ men.

Figure 10. Fossils of Triceratops horridus from Laramie Formation after preparation (uncataloged; Weld County Court House). Skull in right lateral view (A), mid-caudal vertebrae in left lateral view (B), left pubis (C), and right partial ischium (D). Scale bars = 10 cm.