| Australotitan | |
|---|---|
 | |
| Rightfemur of the holotype | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | †Sauropodomorpha |
| Clade: | †Sauropoda |
| Clade: | †Macronaria |
| Clade: | †Somphospondyli |
| Clade: | †Diamantinasauria |
| Genus: | †Australotitan Hocknull et al.2021 |
| Species: | †A. cooperensis |
| Binomial name | |
| †Australotitan cooperensis Hocknull et al. 2021 | |
Australotitan (/ɔːˈstreɪloʊˈtaɪtən/) is anextinctgenus of possiblytitanosauriansomphospondylan dinosaurs from theLate CretaceousWinton Formation (Cenomanian–Turonian) of southern-centralQueensland,Australia. The genus contains asingle species,A. cooperensis, known from multiple partial skeletons. The genusAustralotitan may be synonymous withDiamantinasaurus, a contemporary relative.
Australotitan was discovered in 2005 in layers of theWinton Formation in southwestQueensland, Australia, near the town ofEromanga. Sandy Mackenzie, the discoverer, had already collected other bones on the land of his parents in 2004. Thefossil material was then prepared and excavated in conjunction with theQueensland Museum and the Eromanga Natural History Museum between November 2005 and April 2010. It was nicknamed "Cooper" after its discovery, being from the Cooper-Eromanga Basin, Cooper Creek system, "the Cooper Country".[1]
Theholotype specimen, EMF102 ("Cooper"), consists of a partial skeleton, including an incomplete leftscapula, partial left and complete righthumeri, rightulna, the right and leftpubes andischia, and partial right and leftfemora. An additional three specimens were referred to the genus: EMF164, nicknamed "George," (fragmentedfemur,ulna, presacralvertebrae, andrib material), EMF105 (a complete femur), and EMF165 (a distal humerus).[2]
Thetype species,Australotitan cooperensis, was named anddescribed byScott A. Hocknull, Melville Wilkinson, Rochelle A. Lawrence, Vladislav Konstantinov, Stuart Mackenzie and Robyn Mackenzie in 2021. The generic name,Australotitan, combines theLatin word "australis", meaning "southern"—as it was found in Australia (which is sometimes referred to as "The Great Southern Land")—with theGreek word "Tιτάν" meaning "titan", in reference to theGreek mythologicalTitans and the dinosaur's gigantic size. The specific name,cooperensis, refers to theCooper Creek system near the initial location of the holotype, and the nickname given to the holotype when it was discovered.[2]
Several of the fossils housed and studied by the Eromanga Natural History Museum were trampled and compressed duringdeposition. This was the result of multiple smaller sauropods walking in a single line. The trackway has a total length of approximately 100 metres (330 ft).[3]
Australotitan represents the largest knownAustralian dinosaur. The femur of specimen EMF164 has a length of 2.146 metres (7.04 ft), similar in size to the femora ofFutalognkosaurus andDreadnoughtus, though smaller than those ofPatagotitan. The describing authors deliberately abstained from providing a size estimate, as it is notoriously difficult to obtain reliable results for sauropods. The discovery ofAustralotitan indicates that the gigantictitanosaurian sauropods were present during the mid-Cretaceous of easternGondwana.[2]
In aphylogenetic analysis performed by Hocknull et al. (2021),Australotitan was recovered as atitanosaur. In eleven out of fourteen analyses, it was placed in a clade with the contemporaneous titanosaurDiamantinasaurus, which, depending on the dataset, also included otherWinton Formation sauropodsWintonotitan andSavannasaurus, and sometimes alsoSarmientosaurus,Baotianmansaurus,Dongyangosaurus,Erketu, andPitekunsaurus.[2] This places it in the cladeDiamantinasauriasensu Poropat et al. (2021).[4]
In 2024, Beeston et al. reviewed the sauropod fossil material found in the Winton Formation and described additional new material. Based on their analyses, they found thatAustralotitan shares several similarities with the contemporaryDiamantinasaurus that were not recognized in its original 2021 description. Beeston et al. failed to find sufficientautapomorphies, or distinct features, to distinguish it fromDiamantinasaurus, and, as such, proposed that it can likely be considered as ajunior synonym of the latter. However, since theAustralotitan only shares one autapomorphy withDiamantinasaurus, and threesynapomorphies (shared traits) of the Diamantinasauria, they regarded it as an indeterminate member of this clade.[5]
Beeston et al. (2024) reviewed the relationships of diamantinasaur specimens in a phylogenetic analysis, and recovered the clade as thesister taxon to theTitanosauria within theSomphospondyli. TheAustralotitan holotype was found to be most closely related toDiamantinasaurus. Their results are displayed in thecladogram below:[5]
| Somphospondyli |
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||
