Diamantinasaurus matildae was a genus of lithostrotian titanosaur, found in the earliest late Cretaceous (Cenomanian) period in the Winton Formation of central Queensland.
ETYMOLOGY: (Waltzing) Matilda’s Diamantina (River) Lizard
GEOLOGY: Winton Formation, central western Queensland
AGE: Earliest Late Cretaceous (Cenomanian) 98–95 million years ago
The partial humerus of a sauropod dinosaur was discovered in June 2005 on Elderslie Sheep Station, northwest of Winton. A team from the Australian Age of Dinosaurs Natural History Museum (The Museum) excavated the site, now designated AODL 85 or the "Matilda site", in 2006, and discovered several more bones, including the remainder of the humerus. The remains of a theropod dinosaur were discovered intermingled with the bones of the sauropod. Between 2006 and 2009, annual digs recovered further remains of the two dinosaurs which were officially published in 2009. The sauropod remains, collectively designated AODF 603, were made the holotype of D. matildae, named for the Diamantina River (located several kilometres west of the site) and the famous song "Waltzing Matilda", written by Australian poet Andrew Barton "Banjo" Paterson on a property near Winton in 1895. In 2016 the sauropod nicknamed Alex first found in 1999 by David Elliott was also assigned to D. matildae. The theropod remains, designated AODF 604, were made the holotype of Australovenator wintonensis. Excavation of the site continued in 2010, when more remains of the same skeletons were discovered. Preparation of fossiliferous concretions from the "Matilda site" continues at the Museum to this day.
The holotype specimen of D. matildae was originally reported to comprise several cervical and dorsal ribs, the right scapula, the right sternal plate, the left and right humeri, the right ulna, left metcarpal I, right metacarpals II-V, a manual ungual, three manual phalanges, the left ilium, both pubes, both ischia, the right femur, the right tibia, the right fibula and the right astragalus. Subsequent excavations and continued preparation of previously excavated concretions has yielded yet more remains, including two dorsal vertebrae, a partial sacrum, the right radius, and an additional manual phalanx.
The element previously identified as the right sternal plate was found to actually comprise part of the right coracoid. The remains were recovered from the mid-Cretaceous Winton Formation. The site was originally interpreted to date to the upper Albian, but subsequent zircon dating of the site has demonstrated that it is in fact Cenomanian in age, since the site lies to the west of the Cork Fault.
In 2016 Dr Poropat and colleagues announced the first sauropod skull ever found in Australia. This skull, and the partial skeleton with which it was associated, has been assigned to D. matildae. “This new Diamantinasaurus specimen has helped to fill several gaps in our knowledge of this dinosaur’s skeletal anatomy,” said Poropat. “The braincase in particular has allowed us to refine Diamantinasaurus’ position on the sauropod family tree.”
Left: Comparison between the holotype scapula of Diamanatinasaurus and the new Diamantinasaurus specimen scapula (AODF 836). Middle: Neck vertebrae and skull of the new Diamantinasaurus specimen (AODF 836). Right: A partially prepared Diamantinasaurus rib, 2014.
Dr Poropat collaborated with British sauropod experts Dr Philip Mannion (Imperial College, London) and Professor Paul Upchurch (University College, London), among others, to work out the position of S. elliottorum (and refine that of D. matildae) on the sauropod family tree. “Both S. elliottorum and D. matildae belong to a group of sauropods called titanosaurs. This group of sauropods includes the largest land-living animals of all time,” said Dr Mannion. “S. elliottorum and the new D. matildae specimen have helped us to demonstrate that titanosaurs were living worldwide by 100 million years ago.”
Poropat and his colleagues suggest that the arrangement of the continents, and the global climate during the middle part of the Cretaceous Period, enabled titanosaurs to spread worldwide. “Australia and South America were connected to Antarctica throughout much of the Cretaceous,” said Professor Upchurch. “Ninety-five million years ago, at the time that D. matildae and S. elliottorum were alive, global average temperatures were warmer than they are today. However, it was quite cool at the poles at certain times, which seems to have restricted the movement of sauropods at polar latitudes"
ANATOMY AND HABITS
Like all sauropods, D. matildae must have been a herbivore. The preserved ribs demonstrate that the body was barrel-shaped to accommodate enlarged guts for processing plant matter, and the columnar limb bones were clearly not adapted for speed; rather, they were adapted for supporting the animal's body mass on land. The fore and hind limb bones are massively built, and scars on their surfaces show where huge leg muscles would have attached. The forelimb of D. matildae was shorter than the hind limb, and the metacarpals were more than 60% the length of the radius. The structure of the front foot of D. matildae was typical of sauropods, with the metacarpals held upright, bound tightly together at the wrist, but splayed out at the base, allowing the weight of the body to be dispersed. The thumb claw (an unusual feature for a titanosaur) may also have been used in defence against marauding predators like A. wintonensis. Among titanosaurs, D. matildae was relatively small: 15–18 metres long and 2.5 metres tall at the hip. D. matildae was originally identified as a lithostrotian titanosaur based on analyses run from two independent datasets, closely related to Opisthocoelicaudia skarzynskii. In a subsequent analysis, D. matildae was found to occupy a more basal position outside Titanosauria, and in one analysis in a less-derived position than its Winton Formation contemporary Wintonotitan wattsi. However, the description of new remains of D. matildae, coupled with a revision of its anatomy, restored D. matildae to a position as a lithostrotian titanosaur, based on two separate phylogenetic datasets.
FOR MORE INFORMATION WE RECOMMEND READING...
Scientific papers, Diamantinasaurus matildae (Matilda).
Wikipedia, Diamantinasaurus matildae.
Australian Museum, Diamantinasaurus matildae.