page_title: Hesperosaurus
section_title: Phylogeny
hierarchical_section_title: Hesperosaurus / Phylogeny
caption_attribution_description: English: Hesperosaurus with sleeping Othnielia.
context_page_description: Hesperosaurus is an herbivorous stegosaurian dinosaur from the Kimmeridgian epoch of the Jurassic period, approximately 156 million years ago.
  Fossils of Hesperosaurus have since 1985 been found in the state of Wyoming and Montana in the United States of America. The type species Hesperosaurus mjosi was named in 2001. It is from an older part of the Morrison Formation, and so a little older than other Morrison stegosaurs. Several relatively complete skeletons of Hesperosaurus are known. One specimen preserves the first known impression of the horn sheath of a stegosaurian back plate.
  Hesperosaurus was six to seven metres long and two to three tonnes in weight. It was a member of the Stegosauridae, quadrupedal plant-eaters protected by vertical bony plates and spikes. It was closely related to Stegosaurus and was similar to it in having two rows of, possibly alternating, plates on its back and four spikes on its tail end. The plates on its back were perhaps not as tall, but were longer. It possibly had a deeper skull than Stegosaurus.
context_section_description: In 2001 Carpenter performed a cladistic analysis showing that Hesperosaurus was rather basal and related to Dacentrurus:
  Carpenter was aware that his analysis was limited in scope.
  More extensive phylogenetic studies by Maidment recovered Hesperosaurus as a very derived stegosaurid, and the sister species of Wuerhosaurus. The position of Hesperosaurus in the stegosaurid evolutionary tree according to a study from 2009 is shown by this cladogram:
  In a 2019 re-evaluation of dacentrurine stegosaurids, Costa and Mateus suggested that, based on their revised diagnosis for the clade Dacentrurinae, Hesperosaurus appears to heave been closely related to Dacentrurus after all, though they refrained from formally re-assigning it to that group pending the completion of an expanded phylogenetic analysis.
caption: Life restoration with Othnielia
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