Stormbergia
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Lesothosaurus Temporal range: Early Jurassic, 199–189 Ma |
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| Lesothosaurus diagnosticus skull | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Order: | †Ornithischia |
| Clade: | †Neornithischia |
| Genus: |
†Lesothosaurus Galton, 1978 |
| Species: | †L. diagnosticus |
| Binomial name | |
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Lesothosaurus diagnosticus Galton, 1978 |
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| Synonyms | |
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Lesothosaurus was a type of omnivorous ornithischian dinosaur. It was named by paleontologist Peter Galton in 1978, the name meaning "lizard from Lesotho". The genus has only one valid species, Lesothosaurus diagnosticus.
Lesothosaurus was a 2 metres (6.6 ft) long, bipedal omnivore. It was one of the earliest ornithischians. Its long slender legs, small arms with hands that would not have been able to grasp properly, and slender tail all suggest that it was a fast runner. Like all ornithischians, the tips of Lesothosaurus upper and lower jaws were horny, forming a beaklike structure. Behind the beak were leaf-shaped teeth that lined the jaws, and near the front of the upper jaws were 12 fanglike teeth. Analysis of its teeth has shown that Lesothosaurus sliced up its food with its beak and was not able to chew its food. Studies of the tooth wear have shown much less abrasion on the teeth than would be expected of a plant-eater feeding mainly on tough, arid-climate plants, and concluded that Lesothosaurus was probably an opportunistic omnivore, feeding primarily on small animals during seasons when softer plants were not available.
The small skull of Lesothosaurus was short and flat, with large eye sockets. It had large cavities for the eye and jaw muscles. It had a short, pointed snout, and the lower jaw may have ended in a beak. Its teeth were pointed with grooved edges. The skull was mounted on a short but flexible neck.
Discoveries of Lesothosaurus in the upper Elliot formation suggest that this early ornithischian dinosaur may have lived in groups.
Lesothosaurus was originally considered an ornithopod. However, more recent work by Paul Sereno has suggested that it may actually represent one of the most primitive of all known ornithischian dinosaurs. The taxonomic history of Lesothosaurus is complex and it has long been confused with Fabrosaurus, another small ornithischian from the same locality. In 2005, Richard J. Butler published a new phylogenetic study of ornithischians, in which he proposed that Lesothosaurus was a basal member of the clade Neornithischia, which includes pachycephalosaurs, ceratopsians and ornithopods. Alternatively, this dinosaur may be a very early thyreophoran, a member of the group including the armored stegosaurians and ankylosaurians.
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