Leaellynasaura
Encyclopedia
Leaellynasaura is a genus
of small herbivorous ornithischian dinosaur
from the Albian
stage of the Early Cretaceous
, first discovered in Dinosaur Cove
, Australia
. The type species is Leaellynasaura amicagraphica. It was described in 1989, and named after Leaellyn Rich, the daughter of the 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.
). The most recent assessment describes it as a non-iguanodontian ornithopod
. Unlike more advanced ornithischians, Leaellynasaura lacked ossified tendons in its tail. 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.
would have been within the Antarctic Circle
. Although this latitude is very cold today, it was less frigid in the mid-Cretaceous. However, because of the Earth's tilt, Leaellynasaura and its contemporaries would still have been living under conditions with extended periods of 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. This is particularly relevant to the fact that a skull fragment interpreted as being from Leaellynasaura shows enlarged eye
s and the suggestion of proportionally large optic lobes, as if it had evolved to be routinely active in low-light conditions. However, these characteristics of the skull are also commensurate with juvenile skull proportions, and this interpretation fails to incorporate the fact that these polar conditions would have also meant 6 months of annual near-ceaseless daylight where low-light optic adaptations would be somewhat moot.
.
Evolved cold-weather Leaellynasaura appeared (as leaellyns) in Stephen Baxter's "Evolution" in the chapter "The Last Burrow", although now carnivorous.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of small herbivorous ornithischian 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...
from the Albian
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 112.0 ± 1.0 Ma to 99.6 ± 0.9 Ma...
stage of the Early Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
, first discovered in Dinosaur Cove
Dinosaur Cove
Not to be confused with the children's book series of the same name.Dinosaur Cove in Victoria, Australia is a fossil bearing site in south-east of the continent where the Otway Ranges meet the sea to the west of Cape Otway, adjacent to Great Otway National Park .The inaccessible ocean-front cliffs...
, Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
. The type species is Leaellynasaura amicagraphica. It was described in 1989, and named after Leaellyn Rich, the daughter of the 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
National Geographic Society
The National Geographic Society , headquartered in Washington, D.C. in the United States, is one of the largest non-profit scientific and educational institutions in the world. Its interests include geography, archaeology and natural science, the promotion of environmental and historical...
for their support of Australian paleontology.
Description
Leaellynasaura is known from several specimens including two nearly complete skeletons and two fragmentary skulls. It has been variously described as a hypsilophodontid, a primitive iguanodontian and primitive ornithischian (GenasauriaGenasauria
Genasauria is an extinct clade of beaked, herbivorous dinosaurs. The group was first named by paleontologist Paul Sereno in 1986, and is typically split into Thyreophora, a group of armored dinosaurs; and Neornithischia, which included the horned and duck-billed dinosaurs...
). The most recent assessment describes it as a non-iguanodontian 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...
. Unlike more advanced ornithischians, Leaellynasaura lacked ossified tendons in its tail. 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.
Biology and ecology
Leaellynasaura was an Australian polar dinosaur. At this period in time, VictoriaVictoria (Australia)
Victoria is the second most populous state in Australia. Geographically the smallest mainland state, Victoria is bordered by New South Wales, South Australia, and Tasmania on Boundary Islet to the north, west and south respectively....
would have been within the Antarctic Circle
Antarctic Circle
The Antarctic Circle is one of the five major circles of latitude that mark maps of the Earth. For 2011, it is the parallel of latitude that runs south of the Equator.-Description:...
. Although this latitude is very cold today, it was less frigid in the mid-Cretaceous. However, because of the Earth's tilt, Leaellynasaura and its contemporaries would still have been living under conditions with extended periods of daylight and night. Depending on latitude
Latitude
In geography, the latitude of a location on the Earth is the angular distance of that location south or north of the Equator. The latitude is an angle, and is usually measured in degrees . The equator has a latitude of 0°, the North pole has a latitude of 90° north , and the South pole has a...
, 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. This is particularly relevant to the fact that a skull fragment interpreted as being from Leaellynasaura shows enlarged eye
Eye
Eyes are organs that detect light and convert it into electro-chemical impulses in neurons. The simplest photoreceptors in conscious vision connect light to movement...
s and the suggestion of proportionally large optic lobes, as if it had evolved to be routinely active in low-light conditions. However, these characteristics of the skull are also commensurate with juvenile skull proportions, and this interpretation fails to incorporate the fact that these polar conditions would have also meant 6 months of annual near-ceaseless daylight where low-light optic adaptations would be somewhat moot.
In popular culture
Leaellynasaura appeared on the fifth episode of Walking with DinosaursWalking with Dinosaurs
Walking with Dinosaurs is a six-part documentary television miniseries that was produced by BBC, narrated by Kenneth Branagh, and first aired in the United Kingdom, in 1999. The series was subsequently aired in North America on the Discovery Channel in 2000, with Branagh's voice replaced with that...
.
Evolved cold-weather Leaellynasaura appeared (as leaellyns) in Stephen Baxter's "Evolution" in the chapter "The Last Burrow", although now carnivorous.