Hesperosaurus, meaning “western lizard,” is a genus of herbivorous dinosaur from the Kimmeridgian and Tithonian stages of the Late Jurassic Period (150 million years ago). It was discovered in the US state Wyoming in the Morrison Formation.

Hesperosaurus was described in 2001 by Kenneth Carpenter, and named it for its location in the western United States. It is known from a nearly complete skull and much of the skeleton. The only species known is H. mjosi.

Hesperosaurus was a type of stegosaurid. It had alternating plates on its back and four spikes on its tail. The back plates were not as tall, but were longer, than in the closely related Stegosaurus. Its skull was shorter and broader than Stegosaurus as well. Hesperosaurus is most closely related to Dacentrurus.

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