Description and Classification

Muttaburrasaurus was a medium-sized herbivorous dinosaur, estimated to be about 7 to 9 meters (23 to 30 feet) long and weighing around 2.8 metric tons (3.1 short tons). It primarily walked on its two strong hind legs (bipedal), but it may have also been capable of walking on all fours (quadrupedal) when foraging for low-lying vegetation. One of its most striking features was its skull, which was broad and featured an enlarged, hollow, bony bump or dome on its snout, just in front of its eyes. The purpose of this structure is not fully understood. Its mouth contained complex batteries of teeth designed for shearing and grinding tough plant material.

Muttaburrasaurus is classified as an ornithopod, a diverse group of herbivorous dinosaurs that includes well-known genera like Iguanodon and Hadrosaurus. Its exact placement within Ornithopoda has been debated. While sometimes considered a basal iguanodontian, other studies suggest it might be a rhabdodontomorph, part of a group of ornithopods primarily known from Europe and Gondwana. It represents a distinct lineage of ornithopods that thrived in Australia.

Distinguishing Features

Muttaburrasaurus possessed several characteristics that help differentiate it from other ornithopods:

• A prominent, convex, hollow bony structure (nasal boss) on the upper part of its snout. The function of this boss is debated but may have been used for display, to make sounds, or housed an enlarged nasal cavity.
• A somewhat less developed thumb spike on each hand compared to its relative Iguanodon. This spike was more conical and possibly used for defense or breaking open tough plant matter.
• Rows of shearing teeth that formed dental batteries, allowing it to efficiently process coarse vegetation.
• A relatively robust and heavily built body for an ornithopod of its size.

Paleoenvironment and Diet

Fossils of Muttaburrasaurus have been found in the Mackunda Formation and the Allaru Mudstone in Queensland, and also in New South Wales. During the Early to mid-Cretaceous, this region of Australia was located at higher southern latitudes than today and experienced a cooler, more seasonal climate, though generally warmer than present-day polar regions. The environment likely consisted of fern prairies, conifer forests, and riverine woodlands. Muttaburrasaurus shared this environment with other dinosaurs, including sauropods like Austrosaurus, ankylosaurs such as Kunbarrasaurus (formerly Minmi), and various theropods.

As a herbivore, Muttaburrasaurus would have fed on the available vegetation, likely including ferns, cycads, and conifers. Its powerful jaws and specialized teeth were well-suited for cropping and grinding tough plant material. The broad beak at the front of its mouth would have been used to snip off vegetation.

Significance and Ongoing Research

The discovery of Muttaburrasaurus was highly significant as it provided one of the most complete dinosaur skeletons ever found in Australia, offering crucial insights into the continent’s prehistoric life. It demonstrated the unique evolutionary paths taken by dinosaurs on the isolated Australian landmass, which was then part of the supercontinent Gondwana. The unusual nasal boss continues to be a subject of interest for understanding dinosaur anatomy, behavior, and communication.

Ongoing research focuses on further refining the classification of Muttaburrasaurus within the ornithopod family tree and comparing it with other Gondwanan ornithopods like those from South America and Antarctica. Paleontologists are also keen to learn more about its growth, social behavior, and the precise function of its unique cranial features. Future fossil discoveries in Australia may reveal more about Muttaburrasaurus and the diverse ecosystems it inhabited.