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Skeleton reconstruction of Hesperosaurus mjosi

Skeleton reconstruction of Hesperosaurus mjosi

Temporal occurrence
Upper Jurassic ( Oxfordium )
163.5 to 157.3 million years
Pelvic dinosaur (Ornithischia)
Scientific name
Carpenter , Miles & Cloward, 2001
  • Hesperosaurus mjosi Carpenter, Miles & Cloward, 2001

Hesperosaurus is a genus of the shield-bearing dinosaurs (Thyreophora) in the stegosauria group from the Upper Jurassic of North America (163.5 to 157.3 mya ).


Hesperosaurus reached an estimated length of 6.5 meters and a weight of 3.5 tons. Like all stegosaurs, it had a double row of bone plates ( osteoderms ) along its back. These bone plates were elongated and oval compared to those of Stegosaurus . At the tip of its tail it had two pairs of long, pointed spikes. The limbs of this dinosaur are unknown, the skull was slightly shorter and wider than that of other stegosaurs. Like all stegosaurs, Hesperosaurus had small teeth that were adapted to a vegetable diet.

Discovery and naming

Fossils of hesperosaurus were in the Morrison Formation in the State of Wyoming found and 2001 by Kenneth Carpenter et al. first described . It is a complete skull (cranium) and most of the body skeleton (postcranium) of an individual, only limbs and shoulder blades are missing. The name Hesperosaurus means "western lizard" (from the ancient Greek ἑσπερο- / hespero- "evening, western" and σαῦρος / sauros "lizard"). The authors named the genus after its location in the western United States. The only species and thus type species is H. mjosi . The species addition honors Ronald G. Mjos, responsible for collecting the fossils and the skeletal reconstruction of the new species. The finds are dated to the early Upper Jurassic ( Oxfordian ).

After Stegosaurus, Hesperosaurus is the second genus of stegosaurs known from North America.


Hesperosaurus is considered to be a rather primitive representative of the stegosauria. Phylogenetically , the genus is classified as a basal representative of the Stegosaurinae, the more highly developed Stegosauria (see systematics of the Stegosauria ). The validity as an independent genus is disputed by some paleontologists, since the only species H. mjosi shows great similarity to Stegosaurus . In contrast, in 2016 Paul pointed out the differences in the anatomy of the skull , which made a genus separate from Stegosaurus necessary.


Individual evidence

  1. a b c Gregory S. Paul : The Princeton Field Guide To Dinosaurs. Princeton University Press, Princeton NJ et al. 2010, ISBN 978-0-691-13720-9 , p. 224, preview Google Books .
  2. ^ A b Kenneth Carpenter, Clifford A. Miles, Karen Cloward: New Primitive Stegosaur from the Morrison Formation, Wyoming. In: Kenneth Carpenter (Ed.): The armored dinosaurs. Indiana University Press, Bloomington IN 2001, ISBN 0-253-33964-2 , pp. 55-75. PDF
  3. Thomas Holtz : Dinosaur Genus List (as of 2012), p. 39. Updated appendix to the book: Thomas Holtz: Dinosaurs (2007). Genus List for Holtz (2007) Dinosaurs (Appendix)