[Waltzing] Matilda’s (from the Banjo Paterson song which was written and first performed in the Winton area) Diamantina [River] lizard
Middle Cretaceous (100–95 Mya)
Discovery and publication
Found on Elderslie station (near Winton), Queensland, in 2005 by the property owner, Sandra Muir. The site was dubbed the “Matilda” site and was excavated by the Australian Age of Dinosaurs Museum of Natural History from 2006–2010. Diamantinasaurus was named and described in 2009 by Dr Scott Hocknull and others, and revised with description of newly prepared specimens in 2015 by Dr Stephen Poropat and others. The remains of this sauropod were found intermingled with the theropod Australovenator, as well as bones of crocodylomorphs and turtles, lungfish tooth plates, and isolated bivalves.
Diamantinasaurus was established on the basis of a skeleton (nicknamed “Matilda”) which preserves both forelimbs, the right hind limb, the shoulders and pelvis, and several back vertebrae and ribs. Approximately 30% of the skeleton of “Matilda” has been recovered, making it the most complete Cretaceous sauropod ever found in Australia (only the Jurassic-aged Rhoetosaurus comprises a greater quantity of material). Diamantinasaurus is unique among Australian sauropods, and somewhat of a rarity among sauropods worldwide, because its bones were found scattered and intermingled with those of a theropod dinosaur, now known as Australovenator.
At the shoulder, Diamantinasaurus would have been 2.5–3m tall, Based on comparisons with other related sauropods from around the world, Diamantinasaurus was probably 15–16m long, with a robust build and a long neck and tail. A reassessment of Diamantinasaurus’ place on the sauropod family tree suggests that it was a titanosaur, and therefore the most advanced (derived) sauropod yet found in Australia.
Sauropods from the titanosauriform group would typically have had small heads and delicate, pencil-like teeth, big nostrils, broad shoulders and somewhat narrower hips, robust forelimbs with elongate metacarpals (embedded in the “palm” of the hand), and a reduced number of bones in each finger. Some advanced titanosaurs had bony plates in their skin called osteoderms; however, no titanosaur osteoderms have yet been found in Australia (despite a mistaken report). No osteoderms were found with the Diamantinasaurus skeleton either, suggesting that this sauropod lacked them.
Another Diamantinasaurus specimen, nicknamed “Alex”, was found at the Elliot site in 2004, but was not officially recognised as a Diamantinasaurus until 2016. Although “Alex” was smaller than “Matilda”, anatomically it is nearly identical. Importantly, “Alex” preserves bones not present in the “Matilda” specimen, including bones from the neck. However, the most exciting part of “Alex” is a large piece of the skull known as the braincase, which allows scientists to investigate the shape of the brain. This is the only sauropod skull known from Australia.