Guide Note

Apatosaurus is a species of sauropod dinosaur that existed approximately 140 million years ago during the Late Jurassic period.¹ Apatosaurs are distinguished by their long neck and tail, great size, and small head.²

Fast Facts

1. Pronounced: ah-PAT-uh-SAWR-us
2. Meaning: Deceptive lizard
3. Diet: Herbivore
4. Family: Diplodocae
5. Order: Saurischia
6. Height: 30 feet¹
7. Length: 75 feet¹
8. Weight: 33 tons¹
9. Time Period: Jurassic

Apatosaurus was classified by Othniel Charles Marsh in 1877. Two years later, Marsh named a larger sauropod dinosaur "Brontosaurus." The new species was the largest dinosaur discovered at that time and captured the popular imagination. Paleontologist Elmer Riggs determined in 1903 that the specimen classified as Apatosaurus was actually a juvenile Brontosaurus. In accordance with established practice, the name first given to the species became its official designation: Apatosaurus.³

The tail of Apatosaurus makes up nearly half its entire length. Three feet wide at the base, the tail tapers to less than an inch wide at the tip. Since the turn of the century, scientists have wondered what advantage a long, whip-like tail gave the animal.

Paleontologist Philip J. Currie, working in 1997 with a Microsoft research scientist, created a detailed computer model of Apatosaurus physiology in an attempt to solve the mystery. Their model showed it was physically possible for Apatosaurus to move its tail exactly like a whip to produce a two hundred decibel crack, a sound loud as a naval cannon blast.

All non-avian dinosaurs have been extinct for over 65,000,000 years, so there is no way to prove Apatosaurus actually used its tail in this manner, or if it did, why. However, fossil evidence shows adaptations necessary to create the whip motion exist in more male than female specimens, leading to speculation that the whip crack may have been a sexual display.⁴