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Triceratops and Pachycephalosaurus Skulls

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Triceratops and PachycephalosaurusThese late Cretaceous (about 70 million years old) dinosaurs were found in 1994 on a Sierra College paleontological field trip. They are from the Hell Creek Formation at Fort Peck Reservoir in Montana. This is the same area where skeletons of Tyrannosaurus rex have been found. The Pachycephalosaurus skull is probably the largest of its kind found. Originally when this specimen was found by Frank DeCourten it was mistaken for a ball joint of a dinosaur femur. Upon going back to the site a year later, the "femur" was actually the back half of a skull with a missing eye socket. Although another field trip was taken to the area the following summer, the nose or any other portions of the skull could not be found. The nose portion was later sculpted by artist Ken Kirkland.

Pachycephalosaurus skullPachycephalosaurus was a bipedal herbivore with strong hind limbs and smaller "arms" with grasping hands. Its name means thick-headed reptile. The domed portion of the skull can be as much as 10 inches thick. There is much debate as to why this feature evolved. It may have butted heads like today's bighorn sheep, but the fragility of the neck vertebrae does not support this. Also the roundness of the head would make for glancing blows and not solid hits like bighorn sheep. Perhaps they swung their heads like giraffes do. In this case the head becomes a wrecking ball. Could this be how our specimen lost its eye? It may never be known whether it was lost in a fight or the eye socket simply eroded away. The skull was on loan to another museum and a study of bone growth was conducted.

Triceratops occipital condyleThe Triceratops skull was found by students Jeanine Ingram and Janet Olson. It is an incomplete skull of this horned dinosaur. The skull is torqued out of shape from the pressure of burial. Triceratops is the largest of the horned dinosaurs. Like most other herbivores, including modern bison and rhinoceros, it may have traveled in herds and used its horns for protection. Only the right one-third of the the frill was preserved. It was found crushed under the main portion of the skull. The occipital condyle was also found. This is the ball joint that connects to the vertebral column. The nose portion was missing. The nose portion on display was sculpted by artist Ken Kirkland.

In the summer of 2002 professor Dick Hilton found a juvenile Triceratops skull in the same area. It is now under study by Mark Goodwin, University of California, Berkeley, and Jack Horner, the Museum of the Rockies. The Sierra College Natural History Museum will receive a cast of the skull.

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