Leaellynasaura: A dinosaur that called the South Pole home

A drawing of the South Poles resident dinosaur Leaellynasaura
Image Credit: El fosilmaníaco, https://commons.m.wikimedia.org/wiki/User:El_fosilman%C3%ADaco

It’s hard to imagine any land based animal living at the South Pole. The frozen wastes, completely prevents any significant plant growth, complete darkness covers the area for about half the year, and temperatures are nearly always well below freezing. This results in an environment where the largest life-form is no more than microscopic. However for a sizeable chunk of earth’s history there was no permanent ice cap at the South Pole. Instead temperate forests covered the continents that were located there. During the Early to Mid-Cretaceous period, (around 105-110 million years ago), a landmass that would eventually break up to become Antarctica and Australia was present at the south pole of our planet. If you trekked through this land, often with only the southern lights illuminating the landscape, you might be able hear the chirps of a small, unassuming little dinosaur piercing the otherwise silent frozen forest. These sounds belonged to an ornithopod known as Leaellynasaura amicagraphca (Latin for “Leaellyn’s lizard”, with “amicagraphica” referring to the friends of Museum Victoria who helped with the research).

When a prehistoric animal is given its scientific name, the usual procedure is to either; 1. Name it because of a distinguishing feature; 2. Name it after the area it was discovered in; or 3. Give it an eye catching name that involves the words “terror” or “massive” or “weird”. However Leaellynasaura bucks this trend by instead being named after Leaellyn Rich, the young daughter of Palaeontologists Thomas and Patricia Rich, who first discovered Leaellynasaura in 1989 (a great present for any person!). The fossils were found at a place known as Dinosaur Cove, which is located just outside of Melbourne, Australia. This site, and others in Australia, have shown that Leaellynasaura lived alongside a wide range of other animals. This included other dinosaurs, such as the large vegetarian iguanodontid Muttaburrasaurus and the mid-sized hunting theropod Australovenator, as well as a giant 5 metre long amphibian named Koolasuchus. Fans of the hit BBC documentary “Walking with Dinosaurs” might recognise some of the names I’ve just mentioned. This is because the fifth episode, titled “Spirits of the Ice Forest”, is actually based on this fossil assemblage.

A selection of Leaellynasaura amicographica fossils.
Image Credit: Kumiko, https://www.flickr.com/photos/kmkmks/8086848566/

Leaellynasaura itself was a small dinosaur, with estimates varying between 1-3 metres. It is unclear what specific group of Ornithopod Dinosaurs it belonged to, however it is similar in anatomy to the Hypsilophodontids (try saying that five times fast!). These dinosaurs are characteristically small, bipedal, nimble herbivores, using their beaks to browse vegetation, all whilst scampering between larger herbivores (the best modern analogue might be modern day Gazelles). When you look at the skeleton of Leaellynasaura a few features stand out. Firstly it had large eye sockets relative to its skull. Combined with a large optic lobes in its brain cavity this suggests that Leaellynasaura had excellent eyesight, allowing it to spot predators and locate juicy plants to eat. Secondly its tail was very long, nearly 3/4 of its entire length! This tail contained over 70 vertebrae and lacked many of the ossified tendons involved in stiffening and strengthening the tail of other dinosaurs. This means that Leaellynasaura probably possessed a remarkably flexible tail, capable of a wide variety of movement (maybe even curling round up and around its body). The function of this long tail is unclear at the moment, though it has been theorised that it was involved in display, especially when combined with any feather covering that it likely possessed.

Size comparison between Leaellynasaura amicagraphica and an adult human. Note Leaellynasaura’s proportionally long tail that takes up 2/3rds of its total length!
Image Credit: Slate Weasel, https://en.m.wikipedia.org/wiki/File:Leaellynasaura_Size.svg

The biggest challenge that Leaellynasaura would have faced would have certainly been surviving the elements. As Dinosaur Cove was located well within the Antarctic Circle it would have endured the same seasonal variations that Antarctica does today; 6 months of near permanent sunshine followed by 6 months of near permanent darkness. So how could a dinosaur possibly have coped with these long periods of darkness, where temperatures would’ve regularly dropped well below freezing? This is where its key distinguishing features come into play. Its large eyes would have allowed it to see well in the dim light, key for spotting what little edible plant matter could be found in the frozen ground. Its long flexible tail could potentially have been wrapped round itself when the animal rested in order to keep itself warm (rather like your pet cat does when it is taking a nap!). Another strategy to protect itself against the cold could have been taking shelter in burrows. Fossil burrows have been found at Dinosaur Cove and it has been suggested they could have been made by Leaellynasaura. Support for this theory comes from fossils in Montana of a close cousin, named Oryctodromeus. Fossilised remains have been found preserved in the burrows that they lived in. Also because of fossil evidence from ancestral relatives (such as Tianyulong) it has been suggested that Leaellynasaura was covered in feathers. Speculations range from simple velvety fuzz to a multi-layered fluffy coat according to different reconstructions. The feathered coat makes sense considering the cold climate, certainly allowing it a much greater degree of insulation than traditional reptilian scales.

It may not be the biggest, or possess giant claws, bone clubs or spines, but Leaellynasaura in its own way was just as remarkable a dinosaur as any that have ever existed, perfectly adapted to an environment that was previously thought to be impossible for a reptile to live in. Also, especially if we assume it did possess a thick fluffy coating of feathers with its big eyes and long tail, Leaellynasaura would have certainly been a contender for the cutest dinosaur to ever exist! If it were alive today dog grooming shows would have serious competition from Leaellynasaura grooming shows!

References/Further Reading

Article on Australian Dinosaurs (including Leaellynasaura) and Dinosaur Cove

Udurawane, Vasika, “Dinosaurs down under”, Earth Archives, 2016, eartharchives.org/articles/dinosaurs-down-under/

A 2017 study by Sharp et al. which put a Leaellynasaura fossil through a CT scanner

Sharp, Alana & Regalado Fernandez, Omar & Siu, Karen & Rich, Tom. (2017). Revealing the skeleton of the polar dinosaur Leaellynasaura amicagraphica using synchrotron computed tomography, Society of Vertebrate Paleontology (SVP) 77th Annual Meeting.

The Western Australian Museum’s article about Leaellynasaura, talking about its anatomy, size and growth.

“Leaellynasaura”, Western Australian Museum, 2014, museum.wa.gov.au/explore/dinosaur-discovery/leaellynasaura

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