''Leaellynasaura'' (meaning "Leaellyn's lizard") is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

of small

herbivorous A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthpar ...

ornithischian Ornithischia () is an extinct order of mainly herbivorous dinosaurs characterized by a pelvic structure superficially similar to that of birds. The name ''Ornithischia'', or "bird-hipped", reflects this similarity and is derived from the Greek st ...

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...

s from the

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 ...

stage of the Early

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...

(dated to between 118 and 110 million years agoHoltz, Thomas R. Jr. (2012) ''Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages,'
Winter 2011 Appendix.
/ref>), first discovered in Dinosaur Cove,

Australia Australia, officially the Commonwealth of Australia, is a sovereign country comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands. With an area of , Australia is the largest country by ...

. 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 Thomas Rich (born c. 1940), generally known as Tom Rich, is an Australian palaeontologist. He is, as of 2019, Senior Curator of Vertebrate Palaeontology at Museums Victoria. Education and career *He was a student of Professor Ruben Arthur Stirt ...

and

Patricia Vickers-Rich Patricia Arlene Vickers-Rich (born 11 July 1944), also known as Patricia Rich, is an Australian Professor of Palaeontology and Palaeobiology, who researches the environmental changes that have impacted Australia (including the ancient super c ...

who discovered it. The specific name, ''amicagraphica'', translates to "friend writing" and honours both the Friends of the Museum of Victoria and the

National Geographic Society The National Geographic Society (NGS), headquartered in Washington, D.C., United States, is one of the largest non-profit scientific and educational organizations in the world. Founded in 1888, its interests include geography, archaeology, ...

for their support of Australian paleontology.Rich, T. and Rich, P. (1989). “Polar dinosaurs and biotas of the Early Cretaceous of southeastern Australia.” ''National Geographic Research'', 5(1): 15–53.

Description

Leaellynasaura-amicagraphica-ornithischian-dinosaur-fossil-p-185992-p-185993-350891-large

Leaellynasaura-amicagraphica-dinosaur-skull-p-185990-1330079-large

''Leaellynasaura'' is a relatively small dinosaur, about 90 centimeters (3 feet) in length. 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

hadrosaur Hadrosaurids (), or duck-billed dinosaurs, are members of the ornithischian family Hadrosauridae. This group is known as the duck-billed dinosaurs for the flat duck-bill appearance of the bones in their snouts. The ornithopod family, which includ ...

s.Herne, M. (2009). "Postcranial osteology of ''Leaellynasaura amicagraphica'' (Dinosauria; Ornithischia) from the Early Cretaceous of southeastern Australia." ''Journal of Vertebrate Paleontology'', 29(3): 33A. 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''.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 Leaellynasaura fossils

Classification

''Leaellynasaura'' has been variously described as a hypsilophodontid, a primitive iguanodontian or a primitive ornithischian (

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'' (� ...

). Recent studies have not found a consensus; some analyses describe it as a non- iguanodontian

ornithopod Ornithopoda () is a clade of ornithischian dinosaurs, called ornithopods (), 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 w ...

,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) whereas others describe it as a basal

neornithischia Neornithischia ("new ornithischians") is a clade of the dinosaur order Ornithischia. It is the sister group of the Thyreophora within the clade Genasauria. Neornithischians are united by having a thicker layer of asymmetrical enamel on the ins ...

n. A 2019 study recovered it as a member of Elasmaria. Position according to Herne ''et al.'', 2019:

Biology and ecology

''Leaellynasaura'' was an Australian polar dinosaur. At this period in time,

Victoria Victoria most commonly refers to: * Victoria (Australia), a state of the Commonwealth of Australia * Victoria, British Columbia, provincial capital of British Columbia, Canada * Victoria (mythology), Roman goddess of Victory * Victoria, Seychelle ...

would have been within the

Antarctic Circle The Antarctic Circle is the most southerly of the five major circles of latitude that mark maps of Earth. The region south of this circle is known as the Antarctic, and the zone immediately to the north is called the Southern Temperate Zone. So ...

. 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 In geography, latitude is a coordinate that specifies the north– south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from –90° at the south pole to 90° at the north ...

, 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.Rich, T. H. and Vickers-Rich, P. (2002). ''Dinosaurs of Darkness''. Bloomington: Indiana University Press. However, the relatively large orbits of this specimen were more recently interpreted as representing characteristically large eyes of a juvenile individual, rather than any low-light adaptation.

References

* Marthon, Antony, "Dinosaurs Down Underground", Australasian Science Magazine, Oct 2009. {{Taxonbar, from=Q131179 Ornithischian genera Early Cretaceous dinosaurs of Australia Albian life Fossil taxa described in 1989 Taxa named by Patricia Vickers-Rich Paleontology in Victoria Ornithopods Taxa named by Tom Rich