Lesothosaurus

Lesothosaurus was a genus of omnivorous ornithischian dinosaur from South Africa and Lesotho. 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
Temporal range: Early Jurassic
~199–189 Ma
Lesothosaurus diagnosticus
Lesothosaurus diagnosticus skull
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Ornithischia
Clade: Genasauria
Genus: Lesothosaurus
Galton 1978
Species:
L. diagnosticus
Binomial name
Lesothosaurus diagnosticus
Galton 1978
Synonyms
  • Stormbergia dangershoeki Butler 2005

Description

Lesothosaurus NT
Size compared to a human

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.[1][2] 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.[3] 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.[4]

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.[1]

Discoveries of Lesothosaurus in the Upper Elliot Formation suggest that this early ornithischian dinosaur may have lived in groups.[5]

Classification

Lesothosaurus diagnosticus
Lesothosaurus diagnosticus reconstruction

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.[6]

The species Stormbergia dangershoeki (named by Richard Butler in 2005), named for fossils found in the Upper Elliot Formation, almost certainly represents the adult form of Lesothosaurus.[7] Stormbergia was named for the Stormberg Series of rocks in southern Africa, which includes the Elliot Formation, and the location (Dangerhoek Farm) in South Africa at which the type specimen was found. The holotype and referred specimens of Stormbergia had been mentioned in the scientific literature as a 'large fabrosaurid' for at least 20 years prior to description.[8] A study published in 2017 by Baron, Norman & Barrett demonstrated that the differences between Stormbergia and Lesothosaurus are most likely related to the animal's growth. The authors argued that Stormbergia is a junior subjective synonym of Lesothosaurus and should be regarded as invalid.[2]

References

  1. ^ a b Palmer, D., ed. (1999). The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals. London: Marshall Editions. p. 134. ISBN 1-84028-152-9.
  2. ^ a b Matthew G. Baron; David B. Norman; Paul M. Barrett (2016). "Postcranial anatomy of Lesothosaurus diagnosticus (Dinosauria: Ornithischia) from the Lower Jurassic of southern Africa: implications for basal ornithischian taxonomy and systematics". Zoological Journal of the Linnean Society. in press. doi:10.1111/zoj.12434
  3. ^ Benton, Michael J. (2012). Prehistoric Life. Edinburgh, Scotland: Dorling Kindersley. p. 271. ISBN 978-0-7566-9910-9.
  4. ^ Sciscio L, Knoll F, Bordy EM, de Kock MO, Redelstorff R. (2017). Digital reconstruction of the mandible of an adult Lesothosaurus diagnosticus with insight into the tooth replacement process and diet. PeerJ, 5: e3054 https://doi.org/10.7717/peerj.3054
  5. ^ Barrett, P. M., Butler, R. J., Yates, A. M., Baron, M. G., & Choiniere, J. N. (2016). New specimens of the basal ornithischian dinosaur Lesothosaurus diagnosticus Galton, 1978 from the Early Jurassic of South Africa.
  6. ^ Butler, Richard J.; Upchurch, Paul; Norman, David B. (2008). "The phylogeny of the ornithischian dinosaurs". Journal of Systematic Palaeontology. 6 (1): 1–40. doi:10.1017/S1477201907002271.
  7. ^ Knoll, F.; Padian, K.; de Ricqles, A. (2009). "Ontogenetic change and adult body size of the early ornithischian dinosaur Lesothosaurus diagnosticus: implications for basal ornithischian taxonomy". Gondwana Research. 17 (1): 171–179. doi:10.1016/j.gr.2009.03.010.
  8. ^ 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 (2): 175–218. doi:10.1111/j.1096-3642.2005.00182.x.

Bibliography

  • P. M. Galton. 1978. Fabrosauridae, the basal family of ornithischian dinosaurs (Reptilia: Ornithischia). Paläontologische Zeitschrift 52(1/2):138-159
  • 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.
Albertadromeus

Albertadromeus is an extinct genus of orodromine parksosaurid dinosaur known from the upper part of the Late Cretaceous Oldman Formation (middle Campanian stage) of Alberta, Canada. It contains a single species, Albertadromeus syntarsus.

Averostra

Averostra, or "bird snouts", is a clade that includes most theropod dinosaurs that have a promaxillary fenestra (fenestra promaxillaris), an extra opening in the front outer side of the maxilla, the bone that makes up the upper jaw. Two groups of averostrans, the Ceratosauria and the Orionides, survived into the Cretaceous period. When the Cretaceous–Paleogene extinction event occurred, ceratosaurians and two groups of orionideans within the clade Coelurosauria, the Tyrannosauroidea and Maniraptoriformes, were still extant. Only one subgroup of maniraptoriformes, Aves, survived the extinction event and persisted to the present day.

Avetheropoda

Avetheropoda, or "bird theropods", is a clade that includes carnosaurians and coelurosaurs to the exclusion of other dinosaurs.

Cerapoda

Cerapoda ("ceratopsians and ornithopods") is a clade of the dinosaur order Ornithischia.

Dinosauriformes

Dinosauriformes is a clade of archosaurian reptiles that include the dinosaurs and their most immediate relatives. All dinosauriformes are distinguished by several features, such as shortened forelimbs and a partially to fully perforated acetabulum, the hole in the hip socket traditionally used to define dinosaurs. The oldest known member is Asilisaurus, dating to about 245 million years ago in the Anisian age of the middle Triassic period.

Eocursor

Eocursor (meaning "dawn runner") was a primitive genus of dinosaur. It was an ornithischian which lived in what is now South Africa. Remains of this animal have been found in the Lower Elliot Formation and might be the most complete known from a Triassic ornithischian, shedding new light on the origin of this group.The exact age of this taxon is uncertain. It was originally interprereted as living during the Late Triassic (Norian age), around 210 million years ago; however, Olsen, Kent & Whiteside (2010) stated that there is no independent geochronological support for its assumed age, and the available data makes it impossible to conclusively determine whether Eocursor is of Triassic or Early Jurassic (potentially as young as Sinemurian) age. Eocursor was subsequently interpreted as a taxon of Early Jurassic age by Mcphee et al. (2017).Fossils of Eocursor were originally collected in 1993, but were not formally described until fourteen years later. The type species, Eocursor parvus, was described in 2007 by Richard J. Butler, Roger M. H. Smith, and David B. Norman. Eocursor was one of the earliest known ornithischians, and sheds some light on early dinosaur relationships because early dinosaurs are known from mostly incomplete skeletons. Eocursor is known from partial skeletal elements, including skull fragments, spinal elements, pelvis, long leg bones, and unusually large grasping hands.

Evolution of dinosaurs

This article gives an outline and examples of dinosaur evolution. For a detailed list of interrelationships see Dinosaur classification.

Dinosaurs evolved within a single lineage of archosaurs 243-233 Ma (million years ago) from the Anisian to the Carnian ages, the latter part of the middle Triassic. Dinosauria is a well-supported clade, present in 98% of bootstraps. It is diagnosed by many features including loss of the postfrontal on the skull and an elongate deltopectoral crest on the humerus.In March 2017, scientists reported a new way of classifying the dinosaur family tree, based on newer and more evidence than available earlier. According to the new classification, the original dinosaurs, arising 200 million years ago, were small, two-footed omnivorous animals with large grasping hands. Descendants (for the non-avian dinosaurs) lasted until 66 million years ago.

Fabrosauridae

The Fabrosauridae is an obsolete group of basal ornithischian dinosaurs from the Early to Middle Jurassic, originally proposed by Galton (1972). Recent studies indicate the Fabrosaurs are not a natural grouping of dinosaurs, and instead consist of unrelated genera.The proposed "Fabrosaurs" descended from a Lesothosaurus-like animal. Proposed fabrosaurids were 1–2 meters long, and were lightly built and bipedal. Their skulls were triangular and had very large eye sockets. They were herbivorous and would have used agility to escape predators.

Fabrosaurids are known from southern Africa in the Upper Triassic and Lower Jurassic, as well as in China from the Middle and Upper Jurassic periods. Fabrosaurids bear a semblance to many other members of Ornithischia, and have attracted much interest in phylogenetic studies. However, most genera that were previously referred to as Fabrosauridae are only known from fragmented and partial remains, with most based on no more than isolated teeth, and their place in Fabrosauridae is questionable.Galton in 1972 originally proposed the creation of Fabrosauridae based on the finding of cheek teeth. The successive discovery (1990) of a Middle Jurassic primitive ornithischian, Agilisaurus louderbacki, found in the Xiashaximiao Formation of Zigong, Sichuan Basin, China, has led to paleontologists learning more about the phylogeny of fabrosaurids.

Fabrosaurids have many characters that are unique to their physiology, particularly unique tooth morphology and structure, and short forelimb lengths compared to hindlimbs. Unlike many other primitive Ornithischians, such as heterodontosaurids and hypsilophodontids, the teeth of fabrosaurids are very thinly and uniformly enameled. Compared to Agilisaurus, Fabrosaurus is much more primitive in that it has six premaxillary teeth, and a stout prepubis. Agilisaurus differs from Fabrosaurus in that it appears to be larger and more well developed in structure.The Upper Jurassic ornithischian dinosaur, Gongubusaurus, from China, is thought to be more closely related to fabrosaurids than hypsilophodontids. The type species, G. shiyii, is from the Shangshaximiao Formation in the Rongxian County in Sichuan Basin, has been classified from only a few scattered teeth.

Fabrosaurus

Fabrosaurus ( FAB-ro-SAWR-əs; meaning "Fabre's lizard" in honor of Jean Fabre, a French geologist and a colleague of Ginsburg on the expedition that collected the fossil in Basutoland, Southern Africa ; Greek sauros "lizard")) was a genus of herbivorous dinosaur which lived during the Early Jurassic (Hettangian to Sinemurian stages 199 - 189 mya).

Genasauria

Genasauria is a clade of extinct beaked, primarily herbivorous dinosaurs. Paleontologist Paul Sereno first named Genasauria in 1986. The name Genasauria is derived from the Latin word gena meaning ‘cheek’ and the Greek word saúra (σαύρα) meaning ‘lizard.’ Genasauria is the most inclusive clade within the order Ornithischia. According to Sereno (1986), Genasauria represents all ornithischians except for the most primitive ornithischian, Lesothosaurus. Sereno’s formal definition is, “Ankylosaurus, Triceratops, their most recent common ancestor and all descendants.” It is hypothesized that Genasauria had diverged from Lesothosaurus by the Early Jurassic. Cranial features that characterize Genasauria include a medial offset of the maxillary dentition, a sprout-shaped mandibular symphysis, moderately sized coronoid process, and an edentulous (without teeth) anterior portion of the premaxilla. A distinguishing postcranial feature of Genasauria is a pubic peduncle of the ilium that is less robust than the ischial peduncle.

Genasauria is commonly divided into Neornithischia and Thyreophora. Neornithischia is characterized by asymmetrical distributions of enamel covering the crowns of the cheek teeth, an open acetabulum, and a laterally protruding ischial peduncle of the ilium. Neornithischia includes ornithopods, pachycephalosaurs, and ceratopsians. Thyreophora is characterized by body armor and includes stegosaurs, ankylosaurs, Scelidosaurus, and Scutellosaurus.

Laquintasaura

Laquintasaura is a genus of Venezuelan ornithischian dinosaur containing only the type species Laquintasaura venezuelae. The species is the first dinosaur to have been discovered in Venezuela. Found in the Lower Jurassic, Hettangian, La Quinta Formation from which it takes its name, the bipedal species was about a meter long and 25 centimeters high. L. venezuelae, which is believed to have lived in herds, was primarily herbivorous, although it may have also eaten large insects and other small animals.A phylogenetic analysis by Baron et al. (2017) recovered Laquintasaura as the sister-taxon to Scutellosaurus, within the clade Thyreophora.

List of African dinosaurs

This is a list of dinosaurs whose remains have been recovered from Africa. Africa has a rich fossil record, but it is patchy and incomplete. It is rich in Triassic and Early Jurassic dinosaurs. African dinosaurs from these time periods include Coelophysis, Dracovenator, Melanorosaurus, Massospondylus, Euskelosaurus, Heterodontosaurus, Abrictosaurus, and Lesothosaurus. In the Middle Jurassic, the sauropods Atlasaurus, Chebsaurus, Jobaria, and Spinophorosaurus, flourished, as well as the theropod Afrovenator. The Late Jurassic is well represented in Africa, mainly thanks to the spectacular Tendaguru Formation. Veterupristisaurus, Ostafrikasaurus, Elaphrosaurus, Giraffatitan, Dicraeosaurus, Janenschia, Tornieria, Tendaguria, Kentrosaurus, and Dysalotosaurus are among the dinosaurs whose remains have been recovered from Tendaguru. This fauna seems to show strong similarities to that of the Morrison Formation in the United States and the Lourinha Formation in Portugal. For example, similar theropods, ornithopods and sauropods have been found in both the Tendaguru and the Morrison. This has important biogeographical implications.

The Early Cretaceous in Africa is known primarily from the northern part of the continent, particularly Niger. Suchomimus, Elrhazosaurus, Rebbachisaurus, Nigersaurus, Kryptops, Nqwebasaurus, and Paranthodon are some of the Early Cretaceous dinosaurs known from Africa. The Early Cretaceous was an important time for the dinosaurs of Africa because it was when Africa finally separated from South America, forming the South Atlantic Ocean. This was an important event because now the dinosaurs of Africa started developing endemism because of isolation.

The Late Cretaceous of Africa is known mainly from North Africa. During the early part of the Late Cretaceous, North Africa was home to a rich dinosaur fauna. It includes Spinosaurus, Carcharodontosaurus, Rugops, Bahariasaurus, Deltadromeus, Paralititan, Aegyptosaurus, and Ouranosaurus.

Neornithischia

Neornithischia ("new ornithischians") is a clade of the dinosaur order Ornithischia. They are the sister group of the Thyreophora within the clade Genasauria. Neornithischians are united by having a thicker layer of asymmetrical enamel on the inside of their lower teeth. The teeth wore unevenly with chewing and developed sharp ridges that allowed neornithischians to break down tougher plant food than other dinosaurs. Neornithischians include a variety of basal forms historically known as "hypsilophodonts", including the Parksosauridae; in addition, there are derived forms classified in the groups Marginocephalia and Ornithopoda. The former includes clades Pachycephalosauria and Ceratopsia, while the latter typically includes Hypsilophodon and the more derived Iguanodontia.

Orionides

Orionides is a clade of tetanuran theropod dinosaurs from the Middle Jurassic to the Present. The clade includes most theropod dinosaurs, including birds.

Ornithischia

Ornithischia () is an extinct clade of mainly herbivorous dinosaurs characterized by a pelvic structure similar to that of birds. The name Ornithischia, or "bird-hipped", reflects this similarity and is derived from the Greek stem ornith- (ὀρνιθ-), meaning "of a bird", and ischion (ἴσχιον), plural ischia, meaning "hip joint". However, birds are only distantly related to this group as birds are theropod dinosaurs.Ornithischians with well known anatomical adaptations include the ceratopsians or "horn-faced" dinosaurs (e.g. Triceratops), armored dinosaurs (Thyreophora) such as stegosaurs and ankylosaurs, pachycephalosaurids and the ornithopods. There is strong evidence that certain groups of ornithischians lived in herds, often segregated by age group, with juveniles forming their own flocks separate from adults. Some were at least partially covered in filamentous (hair- or feather- like) pelts, and there is much debate over whether these filaments found in specimens of Tianyulong, Psittacosaurus, and Kulindadromeus may have been primitive feathers.

Sinemurian

In the geologic timescale, the Sinemurian is an age and stage in the Early or Lower Jurassic epoch or series. It spans the time between 199.3 ± 2 Ma and 190.8 ± 1.5 Ma (million years ago). The Sinemurian is preceded by the Hettangian and is followed by the Pliensbachian.In Europe the Sinemurian age, together with the Hettangian age, saw the deposition of the lower Lias, in Great Britain known as the Blue Lias.

Technosaurus

Technosaurus (meaning "Tech lizard", for Texas Tech University) is an extinct genus of Late Triassic dinosauriform, from the Late Triassic Bull Canyon Formation (Dockum Group) of Texas, United States.

For about 20 years after its description, it was thought to be a basal ornithischian dinosaur, but better remains of other Triassic archosaurs have cast doubt on this interpretation. As named, it was a chimera of different animals.

Thyreophora

Thyreophora ("shield bearers", often known simply as "armored dinosaurs") is a group of armored ornithischian dinosaurs that lived from the early Jurassic Period until the end of the Cretaceous.

Thyreophorans are characterized by the presence of body armor lined up in longitudinal rows along the body. Primitive forms had simple, low, keeled scutes or osteoderms, whereas more derived forms developed more elaborate structures including spikes and plates. Most thyreophorans were herbivorous and had relatively small brains for their body size.

Thyreophora includes various subgroups, including the suborders Ankylosauria and Stegosauria. In both the suborders, the forelimbs were much shorter than the hindlimbs, particularly in stegosaurs. The clade has been defined as the group consisting of all species more closely related to Ankylosaurus than to Triceratops. Thyreophora is the sister group of Cerapoda within Genasauria.

Xiaosaurus

Xiaosaurus ("dawn lizard", ), is a genus of small herbivorous dinosaur from the middle Jurassic, approximately 169 to 163 mya. Xiaosaurus lived in what is now the Sichuan Basin of China.

In 1979 and 1980, two specimens were discovered of a small herbivorous dinosaur during excavations near Dashanpu in Sichuan. In 1983 Dong Zhiming and Tang Zilu named the fossils under the type species Xiaosaurus dashanpensis. The generic name is derived from Chinese xiáo, 曉, "dawn", a reference to the age of the fossil. The specific name refers to Danshanpu.The holotype, IVPP V6730A, was found in the lower Xiashaximiao Formation of which the age is uncertain: both the Bajocian and the Bathonian–Callovian have been proposed. It consists of a partial skeleton including a jaw fragment with a single tooth, two cervical vertebrae, four caudal vertebrae, a humerus, a partial left femur and a complete right hindlimb. The paratype IVPP V6730B is a second partial skeleton including a right femur, a dorsal vertebra, two sacral vertebrae, a phalanx, a rib and two teeth.

In 1992 Peng Guangzhao renamed Agilisaurus multidens He & Cai 1983 (now Hexinlusaurus) into a second species of Xiaosaurus: Xiaosaurus multidens, but this has not been accepted.

Xiaosaurus was a small bipedal animal with an estimated length of one metre. The femur is 11 centimetres (4.3 in) long.

The remains are too fragmentary to easily classify the genus. The describers assigned it both to the Fabrosauridae and the Hypsilophodontidae, considering it an evolutionary link between Lesothosaurus and Hypsilophodon. Xiaosaurus has sometimes been considered a nomen dubium and an ornithischian of uncertain affinities, possibly a basal cerapod or marginocephalian. However, Paul Barrett et al. in 2005 concluded it to be provisionally valid, as it possessed a single unique derived trait or autapomorphy: a mediolaterally (seen from the front) straight humerus.

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