Description and Classification

Weewarrasaurus was a relatively small dinosaur, estimated to be about the size of a large dog or a modern wallaby. It walked on two legs and was a plant-eater. As an ornithopod, it belongs to a diverse group of herbivorous dinosaurs that included well-known animals like Iguanodon and the hadrosaurs or “duck-billed dinosaurs.”

Scientists classify Weewarrasaurus as a basal (early) member of the ornithopod group. Its exact relationship to other ornithopods is still being studied, but it shares some similarities with other small Australian ornithopods discovered from Cretaceous rocks, such as Fulgurotherium and Atlascopcosaurus. These dinosaurs were part of a unique group that lived in the high-latitude regions of ancient Australia, sometimes referred to as “polar dinosaurs.”

Distinguishing Features

Since Weewarrasaurus is known only from parts of its lower jaw (dentary) and teeth, its distinguishing features are mostly related to these bones. Some of these features helped scientists identify it as a new genus:

• It had a unique pattern of small openings for nerves and blood vessels on the outer surface of its lower jawbone.
• The jawbone itself was relatively straight and housed up to 12 tooth positions.
• Its teeth were leaf-shaped with ridges, suitable for shredding and grinding tough plant material, which is typical for herbivorous ornithopods.
• It did not have a diastema, which is a toothless gap often seen between the front beak (if present) and the cheek teeth in some other plant-eating dinosaurs.

Paleoenvironment and Diet

Weewarrasaurus lived in an environment that, during the Cenomanian stage of the Late Cretaceous, was a vast floodplain with meandering rivers. The landscape was covered with conifer forests, ferns, and other lush vegetation. This area, known as the Griman Creek Formation, was located at high southern latitudes. This means it would have experienced cooler temperatures and periods of extended twilight or darkness during the winter months, unlike regions closer to the equator. This ancient environment supported a diverse ecosystem.

As a herbivore, Weewarrasaurus would have fed on the local plant life. It likely browsed on low-growing ferns, cycads, and possibly young conifer shoots. Its small size suggests it might have been a nimble dinosaur, able to move easily through the dense undergrowth to find food. It shared its world with other dinosaurs, including other small ornithopods, and potentially various theropods (meat-eating dinosaurs). Fossils of turtles, crocodiles, and lungfish have also been found in the same rock layers, painting a picture of a rich, river-dominated habitat.

Significance and Ongoing Research

The discovery of Weewarrasaurus is important because it adds to our knowledge of dinosaur diversity in Australia. It particularly sheds light on the small ornithopods that appear to have been quite common on the continent during the Cretaceous period. Like many other fossils found in the Lightning Ridge area, the remains of Weewarrasaurus are preserved in opal, which is Australia’s national gemstone. This makes these fossils not only scientifically valuable but also uniquely beautiful.

Ongoing research focuses on finding more complete remains of Weewarrasaurus. More fossils would help scientists learn more about its full anatomy, how it behaved, and its precise evolutionary relationships with other ornithopods, such as the larger Australian dinosaur Muttaburrasaurus or other ornithopods from the ancient supercontinent Gondwana. Each new discovery from locations like Lightning Ridge helps scientists piece together the fascinating story of life in ancient polar Australia and understand how these animals adapted to their distinctive high-latitude environments. This research also contributes to our broader understanding of how ornithopod dinosaurs evolved and spread across the world during the Mesozoic Era.