Lesothosaurus
Encyclopedia
Lesothosaurus is an herbivorous
ornithischia
n dinosaur
. It was named by paleontologist Peter Galton
in 1978, the name meaning "lizard
from Lesotho
". The genus is monotypic, having 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 thyreophora
n, a member of the group including the armored stegosauria
ns and ankylosauria
ns. Stormbergia
may represent the adult form of Lesothosaurus.
al plant-eater. Its long legs, small arms, and slender tail all 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. Its teeth were pointed with grooved edges, and would have been ideal for chewing tough plant matter. The skull was mounted on a short but flexible neck.
The hind limbs of Lesothosaurus were much longer than the forelimbs, which were quite short with small 'hands'. The hand had four well-developed fingers and a smaller fifth finger. 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
.
Herbivore
Herbivores are organisms that are anatomically and physiologically adapted to eat plant-based foods. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in...
ornithischia
Ornithischia
Ornithischia or Predentata is an extinct order of beaked, herbivorous dinosaurs. The name ornithischia is derived from the Greek ornitheos meaning 'of a bird' and ischion meaning 'hip joint'...
n dinosaur
Dinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...
. It was named by paleontologist Peter Galton
Peter Galton
Peter M. Galton is a British vertebrate paleontologist working in America, who has to date written or co-written about a hundred papers in scientific journals or chapters in paleontology textbooks, especially on ornithischian and prosauropod dinosaurs.With Robert Bakker in a joint article...
in 1978, the name meaning "lizard
Lizard
Lizards are a widespread group of squamate reptiles, with nearly 3800 species, ranging across all continents except Antarctica as well as most oceanic island chains...
from Lesotho
Lesotho
Lesotho , officially the Kingdom of Lesotho, is a landlocked country and enclave, surrounded by the Republic of South Africa. It is just over in size with a population of approximately 2,067,000. Its capital and largest city is Maseru. Lesotho is a member of the Commonwealth of Nations. The name...
". The genus is monotypic, having only one valid species, Lesothosaurus diagnosticus, within the genus.
Lesothosaurus was originally considered an ornithopod
Ornithopod
Ornithopods or members of the clade Ornithopoda are a group of ornithischian dinosaurs that started out as small, bipedal running grazers, and grew in size and numbers until they became one of the most successful groups of herbivores in the Cretaceous world, and dominated the North American...
. However, more recent work by Paul Sereno
Paul Sereno
Paul Callistus Sereno is an American paleontologist from the University of Chicago who discovered several new dinosaur species on several continents. He has conducted excavations at sites as varied as Inner Mongolia, Argentina, Morocco, and Niger...
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
Fabrosaurus
Fabrosaurus ) was a genus of herbivorous dinosaur which lived during the Early Jurassic . As the only fossil known of it is a partial jawbone with three teeth, Fabrosaurus is a nomen dubium and may in fact be the same as Lesothosaurus.Fabrosaurus was around 1 meter long...
, 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 thyreophora
Thyreophora
The Thyreophora were a subgroup of the ornithischian dinosaurs...
n, a member of the group including the armored stegosauria
Stegosauria
Known colloquially as stegosaurs, the Stegosauria are a group of herbivorous dinosaurs of the Jurassic and Early Cretaceous Periods, being found mostly in the Northern Hemisphere, predominantly in what is now North America and China....
ns and ankylosauria
Ankylosauria
Ankylosauria is a group of herbivorous dinosaurs of the order Ornithischia. It includes the great majority of dinosaurs with armor in the form of bony osteoderms. Ankylosaurs were bulky quadrupeds, with short, powerful limbs. They are first known to have appeared in the early Jurassic Period of...
ns. Stormbergia
Stormbergia
Stormbergia is a genus of early ornithischian dinosaur known from the upper Elliot Formation of South Africa and Lesotho, named by Richard Butler in 2005...
may represent the adult form of Lesothosaurus.
Description
Lesothosaurus was a 1 metres (3.3 ft) long, bipedBiped
Bipedalism is a form of terrestrial locomotion where an organism moves by means of its two rear limbs, or legs. An animal or machine that usually moves in a bipedal manner is known as a biped , meaning "two feet"...
al plant-eater. Its long legs, small arms, and slender tail all 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. Its teeth were pointed with grooved edges, and would have been ideal for chewing tough plant matter. The skull was mounted on a short but flexible neck.
The hind limbs of Lesothosaurus were much longer than the forelimbs, which were quite short with small 'hands'. The hand had four well-developed fingers and a smaller fifth finger. The length of the rear legs indicates Lesothosaurus was a fast, agile runner. The distinctive femur
Femur
The femur , or thigh bone, is the most proximal bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in...
has a unique femoral head not seen in other dinosaurs.
Lesothosaurus lived in the hot, arid conditions of Lesotho and South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
, during the Early Jurassic
Jurassic
The Jurassic is a geologic period and system that extends from about Mya to Mya, that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic era, also known as the age of reptiles. The start of the period is marked by...
. Remains of Lesothosaurus have been collected from the Upper Elliot Formation
Upper Elliot Formation
The Upper Elliot Formation is a geological formation dating to roughly between 200 to 190 million years ago and covering the Hettangian to Sinemurian stages. The Upper Elliot Formation is found in South Africa and Lesotho and is a member of the Stormberg Group. It consists mainly of limestone,...
, dating it to the Hettangian
Hettangian
The Hettangian is the earliest age or lowest stage of the Jurassic period of the geologic timescale. It spans the time between 199.6 ± 0.6 Ma and 196.5 ± 1 Ma . The Hettangian follows the Rhaetian and is followed by the Sinemurian.In Europe stratigraphy the Hettangian is a part of the time span in...
to Sinemurian
Sinemurian
In the geologic timescale, the Sinemurian is an age or stage in the Early or Lower Jurassic epoch or series. It spans the time between 196.5 ± 2 Ma and 189.6 ± 1.5 Ma...
portions of the Early Jurassic
Early Jurassic
The Early Jurassic epoch is the earliest of three epochs of the Jurassic period...
.