Leaellynasaura

Leaellynasaura (meaning "Leaellyn's lizard") is a genus of small herbivorous ornithischian dinosaurs from the Albian stage of the Early Cretaceous (dated to between 118 and 110 million years ago[1]), first discovered in Dinosaur Cove, Australia. The only known species is Leaellynasaura amicagraphica. It was described in 1989, and named after Leaellyn Rich, the daughter of the Australian palaeontologist couple Tom Rich and Patricia Vickers-Rich who discovered it. The specific name L. amicagraphica translates to "friend writing" and honours both the Friends of the Museum of Victoria and the National Geographic Society for their support of Australian paleontology.[2]

Leaellynasaura
Temporal range: Early Cretaceous,[1]118–110 Ma
Leaellynasaura
Life restoration
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Ornithischia
Genus: Leaellynasaura
Rich & Rich, 1989
Species:
L. amicagraphica
Binomial name
Leaellynasaura amicagraphica
Rich & Rich, 1989

Description

Leaellynasaura fossils
Fossils

Leaellynasaura is a relatively small dinosaur, about 90 centimeters (3 feet) in length.[1] It is known from several specimens including two nearly complete skeletons and two fragmentary skulls. Herne (2009) argued that, unlike more advanced ornithischians, Leaellynasaura lacked ossified tendons in its tail. He also argued that the tail is noteworthy as among the longest relative to its body size of any ornithischian: the tail was three times as long as the rest of the body combined; it also has more tail vertebrae than any other ornithischians except for some hadrosaurs.[3] However, in a subsequent revision of fossil material attributed to Leaellynasaura Herne (2013) could not confidently assign the postcranial skeletons with long tails (or indeed any fossils other than the holotype incomplete cranium MV P185991, right maxilla MV P186352 and left maxillary tooth MV P186412, all from late Aptian-early Albian Eumeralla Formation) to Leaellynasaura amicagraphica.[4]

Classification

Leaellynasaura BW
Older reconstruction depicting it with scales

Leaellynasaurus has been variously described as a hypsilophodontid, a primitive iguanodontian or a primitive ornithischian (Genasauria). Recent studies have not found a consensus; some analyses describe it as a non-iguanodontian ornithopod,[5] whereas others describe it as a basal neornithischian.[6]

Biology and ecology

Leaellynasaura reconstruction
Restoration of three Leaellynasaura with hypothetical protofeathers

Leaellynasaura was an Australian polar dinosaur. At this period in time, Victoria would have been within the Antarctic Circle. Although this latitude is very cold today, it was significantly warmer during the mid-Cretaceous. Because of the Earth's tilt, Leaellynasaura and its contemporaries would still have been living under conditions with extended periods of both daylight and night. Depending on latitude, it is possible that the sun might not have risen for several weeks or months in the winter, which means that Leaellynasaura would have had to live in the dark for perhaps months at a time. A skull fragment interpreted as being from Leaellynasaura has been reported as showing enlarged eyes and the suggestion of proportionally large optic lobes, implying an adaptation to low-light conditions.[7] However, the relatively large orbits of this specimen were more recently interpreted as representing characteristically large eyes of a juvenile individual,[5] rather than any low-light adaptation.

References

  1. ^ a b c Holtz, Thomas R. Jr. (2012) Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages, Winter 2011 Appendix.
  2. ^ Rich, T. and Rich, P. (1989). “Polar dinosaurs and biotas of the Early Cretaceous of southeastern Australia.” National Geographic Research, 5(1): 15-53.
  3. ^ Herne, M. (2009). "Postcranial osteology of Leaellynasaura amicagraphica (Dinosauria; Ornithischia) from the Early Cretaceous of southeastern Australia." Journal of Vertebrate Paleontology, 29(3): 33A."Archived copy" (PDF). Archived from the original (PDF) on 2010-07-15. Retrieved 2010-07-05.CS1 maint: Archived copy as title (link)
  4. ^ Herne, M. (2013). "Anatomy, systematics and phylogenetic relationships of the Early Cretaceous ornithopod dinosaurs of the Australian-Antarctic rift system" PhD Thesis. The University of Queensland
  5. ^ a b Federico L. Agnolin, Martın D. Ezcurra, Diego F. Pais and Steven W. Salisbury (2010). "A reappraisal of the Cretaceous non-avian dinosaur faunas from Australia and New Zealand: evidence for their Gondwanan affinities" Journal of Systematic Palaeontology, 8 (2) [1]
  6. ^ Clint. A Boy (2015). "The systematic relationships and biogeographic history of ornithischian dinosaurs". PeerJ. 3 (e1523): e1523. doi:10.7717/peerj.1523. PMC 4690359. PMID 26713260.
  7. ^ Rich, T. H. and Vickers-Rich, P. (2002). Dinosaurs of Darkness. Bloomington: Indiana University Press.
  • Marthon, Antony, "Dinosaurs Down Underground", Australasian Science Magazine, Oct 2009.
Albian

The Albian is both an age of the geologic timescale and a stage in the stratigraphic column. It is the youngest or uppermost subdivision of the Early/Lower Cretaceous epoch/series. Its approximate time range is 113.0 ± 1.0 Ma to 100.5 ± 0.9 Ma (million years ago). The Albian is preceded by the Aptian and followed by the Cenomanian.

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.

Elasmaria

Elasmaria is a clade of iguanodont ornithopods known from Cretaceous deposits in South America, Antarctica, and Australia.

Haya griva

Haya is an extinct genus of basal neornithischian dinosaur known from Mongolia.

Jeholosauridae

Jeholosaurids were herbivorous neornithischian dinosaurs from the Cretaceous Period (Aptian - Santonian, with a possible Campanian record) of Asia. The family was first proposed by Han et al. in 2012. The jeholosaurids were defined as those ornithischians more closely related to Jeholosaurus shangyuanensis than to Hypsilophodon foxii, Iguanodon bernissartensis, Protoceratops andrewsi, Pachycephalosaurus wyomingensis, or Thescelosaurus neglectus. The Jeholosauridae includes the type genus Jeholosaurus and Yueosaurus.

Jingshanosaurus

Jingshanosaurus (meaning "Jingshan lizard") is a genus of sauropodomorph dinosaurs from the early Jurassic period.

Melanorosauridae

The Melanorosauridae were a family of sauropodomorph dinosaurs which lived during the Late Triassic and Early Jurassic. The name Melanorosauridae was first coined by Friedrich von Huene in 1929. Huene assigned several families of dinosaurs to the infraorder "Prosauropoda": the Anchisauridae, the Plateosauridae, the Thecodontosauridae, and the Melanorosauridae. Since then, these families have undergone numerous revisions. Galton and Upchurch (2004) considered Camelotia, Lessemsaurus, and Melanorosaurus members of the family Melanorosauridae. A more recent study by Yates (2007) indicates that the melanorosaurids were instead early sauropods.

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.

Neotheropoda

Neotheropoda (meaning "new theropods") is a clade that includes coelophysoids and more advanced theropod dinosaurs, and the only group of theropods who survived the Triassic–Jurassic extinction event. Yet all of the neotheropods became extinct during the early Jurassic period except for Averostra.

Orionides

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

Orodrominae

Orodrominae is a subfamily of parksosaurid dinosaurs from the Cretaceous of North America and Asia.

Patricia Vickers-Rich

Patricia Arlene Vickers-Rich (born 11 July 1944), also sometimes known as Patricia Rich, is an Australian palaeontologist and ornithologist of American origin. She has published several award-winning books on popular science. She is married to palaeontologist Tom Rich. Together the couple described the small herbivorous dinosaur Leaellynasaura, naming it after their daughter, Leaellyn Rich.

Raeticodactylidae

Raeticodactylidae is a family of eudimorphodontoid eopterosaurian pterosaurs that lived in Switzerland during the Late Triassic. The family includes Caviramus, and the type genus Raeticodactylus, which are both known from the Kössen Formation, around 205 mya. Raeticodactylidae was first used in 2014 by Andres et al., as a group of all pterosaurs closer to Raeticodactylus than Eudimorphodon. The following phylogenetic analysis follows the topology of Andres et al. (2014).

Riojasauridae

Riojasauridae is a family of sauropod-like dinosaurs from the Upper Triassic. It is known primarily from the genera Riojasaurus and Eucnemesaurus. Sites containing Riojasauridae include the Lower Elliot Formation of Orange Free State, South Africa (where fossils of Eucnemesaurus have been found), and Ischigualasto, in La Rioja Province, Argentina ( where fossils of Riojasaurus have been recovered).

Walking with Dinosaurs

Walking with Dinosaurs is a six-part documentary television miniseries created by Tim Haines and produced by BBC Natural History Unit. The series first aired on the BBC in the United Kingdom in 1999 with narration by Kenneth Branagh. The series was subsequently aired in North America on the Discovery Channel in 2000, with Avery Brooks replacing Branagh. The programme explores ancient life of the Mesozoic Era, portraying dinosaurs and their contemporaries in the style of a traditional nature documentary.

Developed by Haines and producer Jasper James, Walking with Dinosaurs recreated extinct species through the combined use of computer-generated imagery and animatronics that were incorporated with live action footage shot at various locations. The Guinness Book of World Records reported that the series was the most expensive documentary series per minute ever produced. A re-edited version of Walking with Dinosaurs aired on Discovery Kids for the first season of Prehistoric Planet. It was made more appropriate for children by removing most of the graphic content and trimming down some footage to fit the run time.

The series received critical acclaim, winning two BAFTA Awards, three Emmy Awards and a Peabody Award in 2000. Walking with Dinosaurs began a franchise that was followed by two additional miniseries, several television specials, spin-offs, a live-theatrical show, and a feature film of the same name.

Xixiposaurus

Xixiposaurus is a genus of prosauropod dinosaur which existed in what is now Lower Lufeng Formation, China during the lower Jurassic period. It was first named by Sekiya Toru in 2010 and the type species is Xixiposaurus suni.

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