Diamantinasaurus

*Diamantinasaurus matildae*

James Gurney Artwork

Diamantinasaurus, meaning ("Diamtina River Lizard") is a genus of derived titanosaurian dinosaur from the Albian Stage of the Early Cretaceous age rocks of Australia. It is known from partial postcranial remains.

## History of discovery

*Diamantinasaurus* was quite a big stocky dinosaur: it had a huge bulky, barrel-shaped body up to 52 feet (16 metres) long, thick, stout front and back limb bones which were just about the same length, and a box-shaped skull ant the end of its long neck similar to that of *Camarasaurus*. Diamantinasaurus is based on a partial skeleton including a right shoulder blade, a sternal plate, much of the forelimbs, much of the hindlimbs except the feet, partial hips, and ribs. *Diamantinasaurus* was unusual for a derived titanosaurian in retaining a thumb claw. Many titanosaurids are known to have had small armour plates, however, it is not known whether *Diamantinasaurus* had them.

Diamantinasaurus was described in 2009 by Scott Hucknoll and colleagues. The type species is *D. matildae*, in reference to the folk song "Waltzing Matilda", which was written by Banjo Paterson in nearby Winton where another Sauropod had been found called Wintonotitan. A phylogenetic analysis found *Diamantinasaurus* to be a lithostrotian titanosaurian sauropod, in the same clade as sauropods such as Opisthocoelicaudia and Saltasaurus. The discovery has been nicknamed "Matilda" after "Waltzing Matilda" and is probably the biggest Sauropod dinosaur in Australia.

## Description

*Diamantinasaurus* is based on AODL 603, a partial skeleton including a right shoulder blade, a sternal plate, much of the forelimbs, much of the hindlimbs except the feet, partial hips, and ribs. *Diamantinasaurus* was unusual for a derived titanosaurian in retaining a thumb claw. The limb bones were stout. *Diamantinasaurus* was described in 2009 by Scott Hocknull and colleagues. The type species is *D. matildae*, in reference to the folk song "Waltzing Matilda", which was written by Banjo Paterson in nearby Winton. A phylogenetic analysis found *Diamantinasaurus* to be a lithostrotian titanosaurian sauropod, in the same clade as sauropods such as *Opisthocoelicaudia* and *Saltasaurus*. The discovery has been nicknamed "Matilda" after "Waltzing Matilda", and is described as a stocky herbivore about 52 feet (16 m) in length.

## Classification

When it was originally described, Diamantinasaurus was assigned to Lithostrotia incertae sedis. In both phylogenies it was placed in, Diamantinasaurus was either just outside Saltasauridae or the sister taxon of Opisthocoelicaudia within the family. In a 2014 study, it was found that the genus was placed as a lithostrotian in both large phylogenies, in a relatively derived position in Titanosauria. Their first phylogeny was modified from that of Carbadillo and Sander (2014), the matrix being indirectly based on Wilson's 2002 phylogeny. In that cladogram, Diamantinasaurus was found to be sister taxon to Tapuiasaurus, their relationship outside of Saltasauridae. In this phylogeny, the Bremer support for each group was at most 1. Five features of the skeleton supported the placement of Diamantinasaurus in Lithostrotia.

In the same study, the relationships using the Mannion et al. (2013) matrix were tested. These resolved with Diamantinasaurus as a saltasaurid, sister to Opisthocoelicaudia, with Dongyangosaurus as the next closest. Two characters were found to support the placement of Diamantinasaurus in Lithostrotia, and a third could not be evaluated.
Another phylogenetic analysis in 2016, partially reproduced below, found it as a non-lithostrotian titanosaur and the sister taxon of the contemporary Savannasaurus.

The 2021 study recovered a similar topology, finding a close relationship with Savannasaurus as well as Sarmientosaurus from the early Late Cretaceous of Patagonia, which skull had similarities to the referred cranial material of Diamantinasaurus. The clade containing these taxa was dubbed Diamantinasauria.

## Paleobiology

In 2011, the smallest positively identified titanosaur embryo was described. Although it was uncovered in Mongolia, the embryo shares the most features with Diamantinasaurus and Rapetosaurus. The embryo, from a relatively spherical 87.07–91.1 millimetres (3.428–3.587 in) egg, was identified as persisting to a lithostrotian. The embryo was slightly robust, intermediate between the robustness of Rapetosaurus and Diamantinasaurus. The egg is part of an entire nesting site for lithostrotian titanosaurs. Dating of the region also suggests that this egg predates those of Auca Mahuevo in Argentina, and the eggs were laid in the Early Cretaceous.

## Paleoecology

The incomplete partial skeleton was found about 60 kilometres (37 miles) northwest of Winton, near Elderslie Station. It was recovered from the lower part of the Winton Formation, dated to the latest Albian. The incomplete partial skeleton was found in a clay layer between sandstone layers, interpreted as an oxbow lake deposit. Also found at the site were the type specimen of the theropod *Australovenator*, bivalves, fish, turtles, crocodilians, and plant fossils. The Winton Formation had a faunal assemblage including bivalves, gastropods, insects, the lungfish *Metaceratodus*, turtles, the crocodilian *Isisfordia*, pterosaurs, and several types of dinosaurs, such as the theropod *Australovenator*, the sauropod *Wintonotitan*, and unnamed ankylosaurians and hypsilophodonts. *Diamantinasaurus* bones can be distinguished from *Wintonotitan* bones because *Diamantinasaurus* bones are more robust. Plants known from the formation include ferns, ginkgoes, gymnosperms, and angiosperms. Like other sauropods, *Diamantinasaurus* would have been a large quadrupedal herbivore.

## Appearance in other media

### *Jurassic Park*

Diamantinasaurus is mentioned in the entry for the Winton Formation and the *Australovenator* in Jurassic World Evolution 2.

## References

1. ↑ Template:Cite journal
2. ↑ Template:Cite web
3. ↑ Template:Cite web