Leaellynasaura

*Leaellynasaura amicagraphica*

**Leaellynasaura** was a small herbivorous ornithopod dinosaur of about 60–90 cm in length from the earliest Cretaceous, first discovered in Dinosaur Cove, Australia. Strangely enough, at this period in time, Victoria would have been well within the Antarctic Circle, which is now very cold. This means that Leaellynasaura was living and apparently thriving much further south than any reptile could today. This is particularly relevant due to Cryolophosaurus being discovered in Antarctica, thus further suggesting the idea that dinosaurs could live under conditions which were once thought unsuitable for their kind. It is possible that the sun would not have risen for several weeks or months in the winter, depending on latitude, which means that Leaellynasaura would have had to live in the dark for perhaps months at a time, possibly having a dormancy until Spring. This is particularly relevant to the fact that Leaellynosaura had very big eyes and its brain had large optic lobes, as if it had evolved to be routinely active in the dark. Regardless, the fact that it lived in extremely cold temperatures led many scientists to believe that Leaellynasaura was warm-blooded. It was preyed on by the Koolasuchus.

The type species is Leaellynasaura amicagraphica. It was described in 1989; It was named after Leaellyn Rich, the daughter of the palaeontologist couple Tom Rich and Patricia Vickers-Rich who discovered it. Leaellynasaura was a hypsilophodont, a rather basal ornithopod. Like all ornithopods, it was a herbivore. So far, no complete skeletons have been found of Leaellynasaura. It stood at about one metre (3 feet).

## Description

   *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 hadrosaurs. 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*.

## Classification

*Leaellynasaura* 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, whereas others describe it as a basal neornithischian. 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 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. 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.

## JPInstitute.com Description

Leaellynasaura is one of the rare dinosaurs discovered in Australia. At the time this little dinosaur lived, what is now Australia was almost at the South Pole! The winters were fairly warm compared to what they are today that far south, but there would have been long, dark nights. This dinosaur had some very large eyes that may have evolved to help it see better during the long winter nights when there may have only been a couple hours of daylight. There have been suggestions that a dinosaur living so close to a pole would not only have had to adapt to darkness, but may have needed to be warm-blooded to survive the colder climate too.

Remains of an Antarctic hypsilophodont were found that might be closely related to Leaellynasaura. Associated with this material in the frozen south were shells, tree trunks, ferns, and tree leaves.

## Links

https://web.archive.org/web/20030813055841/http://www.jpinstitute.com/dinopedia/dinocards/dc\_leall.html#
https://web.archive.org/web/20080706035144/http://kids.yahoo.com/dinosaurs/219--Leaellynasaura