6" Dinosaur (Triceratops?) Rib Bone - Wyoming

About Triceratops

Triceratops is one of the most recognized and intriguing of the North American ceratopsid dinosaurs. They stomped around the Late Cretaceous (around 68-66 mya), brandishing their three-pronged and bony frilled skulls, chewing on fibrous plants. They struggled against large predators, stood their ground, and tried not to be devoured by the ferocious Tyrannosaurus rex.



The head on a Triceratops may have been an intimidating show rather than a stabbing, defensive trident and imposing shield for inter-species jousting. Researchers have given close scrutiny to the holes, or fenestrae, of other ceratopsid crests. In the past, the holes within the shield were used to confirm separate species.

Individual Triceratops are estimated to have reached up to 9 meters (29.5 feet) in length, 3 meters (9.8 feet) in height, and weighed up to 26,000 pounds. The largest known skull is estimated to have been 2.5 meters (8.2 feet) long and would have extended almost a third of the length of the mature individual. The pointed horns were approximately 1 meter (3 feet) long. With its sturdy build and powerful legs, Triceratops could have ripped open the predator that wanted this herbivore for dinner.

One of the most abundant of the large Cretaceous fauna, Triceratops plucked low growth with its beak-tipped jaws. Triceratops teeth were arranged in groups, called batteries, of 36 to 40 tooth columns, in each side of each jaw. Each column contained about 3 to 5 stacked teeth, depending on the individual’s size. This produced a range of 432 to 800 teeth, of which only a fraction were in use at any given time (due to tooth replacement). The great size and quantity of teeth suggests that they ate large volumes of fibrous plants. These were possibly palms, cycads, and ferns.



Triceratops was designated as the state fossil of South Dakota in 1988.

About The Lance Formation

The Lance Formation of Wyoming, which dates back to the Late Cretaceous period between 66 and 69 million years ago, is home to a wide variety of both dinosaur and assorted small vertebrate fossils. During the Cretaceous, this midwestern formation would have been comprised of streams connected to the large Western Interior Seaway that split continental North America in half down the midwest. As a result of the subtropical climate and frequent rainfall, life flourished both on land and in the sea. These wet environments created perfect scenarios for sediment deposition, making the resulting Lance Formation such a fertile fossil site.

Perhaps the most famous Lance resident would be Tyrannosaurus rex, the largest North American carnivore to ever live. However, other smaller theropods also roamed the American midwest in this subtropical coastal stream system, including the beaked Ornithomimus, a lanky running theropod with a build similar to a modern ostrich, as well as several small predatory troodonts such as Paronychodon and Pectinodon.

Herbivorous dinosaurs also took advantage of the abundance offered by this unique era. Armored ankylosaurs dwelt in herds, their safety assured by their numbers, their heavy bone plating protecting most of their bodies and even their eyelids, and huge bone clubs on the ends of their tails providing them with powerful offensive capabilities. Ceratopsians like the famous Triceratops also formed protective herds, guarding their necks with frills and horns. Their smaller relatives, the dome-headed pachycephalosaurs, were also well represented in the area. Hadrosaurs, duck-billed titans with huge batteries of plant-grinding teeth in elongated snouts, are also well known from the region.

In addition to dinosaurs, a wide variety of fishes, amphibians, lizards, snakes, turtles, champsosaurs, crocodilians, and pterosaurs have been found in the formation.