Lesothosaurus

Taxobox
name = "Lesothosaurus"
fossil_range = Early Jurassic


regnum = Animalia
phylum = Chordata
classis = Reptilia
superordo = Dinosauria
ordo = Ornithischia
genus = "Lesothosaurus"
genus_authority = Galton, 1978
subdivision_ranks = Species
subdivision = "L. diagnosticus" Taxobox_authority | author = Galton | date = 1978

"Lesothosaurus" is a member of the herbivorous clade of dinosaurs, the Ornithischia. It was named by paleontologist Peter M. Galton in 1978, the name meaning "lizard from Lesotho". The genus is monotypic, meaning there is only one valid species, "Lesothosaurus diagnosticus", within the genus.

"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.cite journal |last=Butler |first=Richard J. |coauthors=Upchurch, Paul; and Norman, David B. |title=The phylogeny of the ornithischian dinosaurs|journal=Journal of Systematic Palaeontology |volume=6 |issue=1 |year=2008 |pages=1–40 |doi=10.1017/S1477201907002271]

Description

"Lesothosaurus" was a small (one meter in length), bipedal plant-eater. Skeletal remains suggest that it was a fast runner; it would have resembled a large lizard walking bipedally.

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. The skull was mounted on a short neck.

The hind limbs of "Lesothosaurus" were much longer than the forelimbs, which were quite short with small, five-fingered 'hands'. The length of the rear legs indicates "Lesothosaurus" was a fast, agile runner. The distinctive femur has a unique femoral head not seen in other dinosaurs.

"Lesothosaurus" lived in the hot, arid conditions of Lesotho and South Africa, during the Early Jurassic. Remains of "Lesothosaurus" have been collected from the Upper Elliot Formation, dating it to the Hettangian to Sinemurian portions of the Early Jurassic.

References

Butler, R.J., 2005. "The 'fabrosaurid' ornithischian dinosaurs of the Upper Elliot Formation (Lower Jurassic) of South Africa and Lesotho." "Zoological Journal of the Linnean Society" 145: 175-218.