Savannasaurus is a genus of titanosaurian sauropod dinosaur from the Late Cretaceous Winton Formation of Queensland, Australia. It contains one species, Savannasaurus elliottorum, named in 2016 by Stephen Poropat and colleagues. The holotype and only known specimen, originally nicknamed "Wade", is the most complete specimen of an Australian sauropod, and is held at the Australian Age of Dinosaurs museum. Dinosaurs known from contemporary rocks include its close relative Diamantinasaurus and the theropod Australovenator; associated teeth suggest that Australovenator may have fed on the holotype specimen. At 15 metres (49 ft) long, Savannasaurus was a medium-sized titanosaur. It is notable for its wide hips, which would have been over 1.1 metres (3 ft 7 in) wide at their widest points. This would have distributed its body weight more evenly, along with a robust humerus (upper arm bones) and possibly also the tall astragalus (ankle bone). Combined with a flexible vertebral column, these traits would have made Savannasaurus better at navigating the muddy ground of the floodplains that it lived on. Other titanosaur lineages also show some of these traits, which might have been independently acquired from similar environmental pressures. Various traits suggest that Savannasaurus was an early-diverging (or basal) member of the Titanosauria, but not a member of the more specialized group Lithostrotia. Among these are the absence of hyposphene-hypantrum articulations in its vertebrae, which was one of the flexibility-enhancing traits that may have appeared in multiple titanosaur lineages. Palaeobiogeographic analyses suggest that the ancestors of Savannasaurus and Diamantinasaurus were from either Asia or one of the southern Gondwanan continents; regardless, they likely migrated to Australia through Antarctica around 105–100 million years ago.
Discovery and naming
In March 2005, the first specimen of Savannasaurus was discovered by David Elliot, founder of Australian Age of Dinosaurs (AODF), along with his wife Judy and their children. The specimen, now catalogued as AODF 660, was found on the Belmont sheep station, 60 kilometres (37 mi) northeast of Winton, Queensland; the site was given the number AODF 82, and is informally called the "Ho-Hum site". Excavations by the Queensland Museum and hundreds of volunteers unearthed the specimen in July and September of that year. A siltstone concretion containing the specimen was split along gypsum-filled fractures using jackhammers and chisels, with the pieces being marked to facilitate reassembly. Preparation of the specimen took around a decade, with air scribes and micro-jacks being used. Adhesives, such as superglue and araldite, were then used to put the pieces back together. The marks allowed the orientation of the specimen as it was found to be reconstructed, which informed a three-dimensional site map constructed with photogrammetry. AODF 660 consists of around 40 bones: one cervical (neck), the third through tenth dorsal (trunk), at least four sacral (hip), and at least five caudal (tail) vertebrae; cervical and (fragmentary) dorsal ribs; portions of the shoulder girdle, including a fragmentary scapula, a left coracoid, and both sternal plates; parts of the forelimbs, including portions of both humeri, a fragmentary ulna, the left radius, and hand bones (the left first to fifth metacarpals, the right fourth metacarpal, and two phalanges); the fused hip bones, namely both the left and the right pubis and ischium; foot bones (the left astragalus and right third metatarsal); and other fragments. One of the foot bones was originally thought to have belonged to a theropod, while the metacarpals were initially also interpreted as having come from the opposite hands. The specimen is the most complete sauropod specimen known from Australia, and represents approximately 20% to 25% of the animal.
The bones were preserved over an area of less than 20 m2 (220 sq ft). While the dorsal vertebrae were not articulated, they were preserved in sequence in front of the hip bones, allowing for their identification. The ribs on the left side appear to have been crushed prior to fossilization, before all of them were fragmented further. The fifth dorsal vertebra and both humeri show signs of being trampled by other dinosaurs before fossilization, which may also explain the scattered bones; however, the bones were less scattered than other dinosaur specimens from contemporary rocks. A third excavation in September 2006 discovered no additional remains, but a partial centrum from a caudal vertebra was found on the surface in 2013. Having been nicknamed "Wade", AODF 660 was formally described and named in 2016 by Stephen Poropat and colleagues in a paper that also described a skull belonging to Diamantinasaurus. They identified AODF 660 as the holotype of a new genus and species, Savannasaurus elliottorum; the generic name of Savannasaurus, from Taíno zavana (the root of the word "savanna"), refers to the environment in which it was found, while the specific name elliottorum honours the Elliott family and their contributions to Australian palaeontology. The preliminary anatomical description of AODF 660 in this paper was supplemented in 2020 by another paper from many of the same authors, which provided a full description of its osteology.
Description
Savannasaurus was a medium-sized titanosaur that measured about 15 metres (49 ft) in length, with a weight of around 20 tonnes (22 short tons) and a shoulder height of around 3 metres (9.8 ft).
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