Hesperosaurus

Filed under Jurassic dinosaurs · Types of Dinosaurs editorial team

Order: Ornithischia · Suborder: Thyreophora · Infraorder: Stegosauria · Family: Stegosauridae (family not firmly confirmed)

Hesperosaurus, whose name means "western lizard," was a stegosaurid dinosaur that lived during the Late Jurassic period in what is now North America. Discovered in the Morrison Formation, it was a close relative of the more famous Stegosaurus and reached an estimated length of around 20 feet (6 meters). Like its better-known cousin, Hesperosaurus was a four-legged herbivore that likely browsed on low-growing vegetation.

What distinguished Hesperosaurus from Stegosaurus was the character of its back plates. Rather than the tall, upright plates associated with Stegosaurus, those of Hesperosaurus were lower and proportionally longer, running in a double row along the spine. At the end of the tail, a set of spikes provided additional defense. Notably, at least one well-preserved specimen retained impressions indicating that the plates were covered in a horny sheath, offering rare direct evidence about the surface texture of these structures.

Hesperosaurus adds important depth to the understanding of stegosaur diversity during the Jurassic. Its presence alongside Stegosaurus in the Morrison Formation suggests that multiple stegosaurid species occupied the same broad ecosystem, each with subtly different anatomical features that paleontologists continue to study.

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Reference background: Natural History Museum, London — Dinosaurs; Smithsonian National Museum of Natural History — Dinosaurs; American Museum of Natural History — Dinosaurs & Fossils. Figures are typical published ranges; taxonomy follows the source era and modern consensus is noted where it differs. See our sources & fact-check policy.

Related dinosaurs

Other dinosaurs from the Stegosauridae family.