Apatosaurus louisae

Artwork depicting an apatosaurus dinosaur

NPS/Bob Walters Tess Kissinger


Apatosaurus louisae is a species of sauropod dinosaur from the Late Jurassic of North America found in the Morrison Formation, and its remains are present on the Wall of Bones at Dinosaur National Monument. Apatosaurus grew up to 69 ft (21 m) long and ate plants. You may have heard it referred to by its scientifically incorrect name, Brontosaurus. This sauropod (long necked dinosaur) was discovered and named Apatosaurus, or "false lizard," because of its unbelievably large size. After Apatosaurus was named, other sauropod specimens were named Brontosaurus. It was later determined that both names actually referred to the same animal, Apatosaurus. In science the first used name is the official name.

A skeleton of Apatosaurus louisae was the first dinosaur to be excavated at the quarry by Earl Douglass, and was found by eight vertebrae sticking out of the rock. The species "louisae" was named after Andrew Carnegie's wife, Louise. Carnegie financed most of the excavations of the quarry at Dinosaur and had many of the specimens sent to Pittsburgh, Pennsylvania, where they still stand in the museum that bears his name.

Only one Apatosaurus skull has ever been found, and it came from Dinosaur National Monument!
Only one Apatosaurus skull has ever been found, and it came from Dinosaur National Monument.

The "Discovery Bones" that led to the discovery of the Carnegie Quarry were tail vertebrae (back bones) of Apatosaurus louisae. This specimen, a nearly complete skeleton with a skull, became the type specimen of Apatosaurus louisae. This means that it was the first of its species ever found and scientifically described.

Like many sauropods and dinosaurs in general, Apatosaurus skulls are extremely rare. The skull bones are thin and easily crushed. Skulls are mostly hollow to hold soft tissues that cannot be preserved. Fine sediments compress the skull to flatten it the way you might step on an empty tin can. These skulls may be preserved, but some of the three-dimensional structure is lost.

The only Apatosaurus skull in the world was found in the Carnegie Quarry because the sand-sized sediment preserves bone in great detail without compressing it. Today a cast of the Apatosaurus skull is still on display with the rest of the specimen at the Carnegie Museum of Natural History in Pittsburgh, Pennsylvania. The real skull is not on display due to the fragile nature of the bone.


Last updated: May 23, 2019

Park footer

Contact Info

Mailing Address:

4545 Hwy 40
Dinosaur, CO 81610


435 781-7700

Contact Us