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fact file

Pronounced: HESS-pur-oh-SAWR-us

Name means: Western Reptile


Species: mjosi

Range: Late Jurassic (Tithonian, 155 MYA) from Wyoming,  Montana

Size estimate: 15-20 ft length, 3 tons

Discovery: Carpenter, Miles and Cloward 2001

Classification: dinosauria, ornithischia, thyreophora, stegosauria, stegosauridae

A close relative of Stegosaurus, Hesperosaurus lived at the same time and some of the same places. The two creatures are so similar that some scientists have suggested that they represent males and females of the same species, but certain features of their bodies suggest that they are distinct. Hesperosaurus was slightly smaller than Stegosaurus, with fewer and more rounded plates on its back, and a different number of back vertebrae. The two tended to live separate but overlapping regions in both geography and time, also indicating separateness of the genera.


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