''Australotitan'' () is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of possibly

titanosauria Titanosaurs (or titanosaurians; members of the group Titanosauria) were a diverse group of Sauropoda, sauropod dinosaurs, including genera from all seven continents. The titanosaurs were the last surviving group of long-necked sauropods, with tax ...

somphospondylan Somphospondyli is an extinct clade of titanosauriform sauropods that lived from the Late Jurassic until the end of the Late Cretaceous, comprising all titanosauriforms more closely related to Titanosauria proper than Brachiosauridae. The remain ...

dinosaurs from the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the more recent of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''cre ...

Winton Formation The Winton Formation is a Cretaceous Formation (geology), geological formation in central-western Queensland, Australia. It is late Albian to early Turonian in age. The formation blankets large areas of central-western Queensland. It consists of ...

(

Cenomanian The Cenomanian is, in the International Commission on Stratigraphy's (ICS) geological timescale, the oldest or earliest age (geology), age of the Late Cretaceous epoch (geology), Epoch or the lowest stage (stratigraphy), stage of the Upper Cretace ...

–

Turonian The Turonian is, in the International Commission on Stratigraphy, ICS' geologic timescale, the second age (geology), age in the Late Cretaceous epoch (geology), Epoch, or a stage (stratigraphy), stage in the Upper Cretaceous series (stratigraphy), ...

) of southern-central

Queensland Queensland ( , commonly abbreviated as Qld) is a States and territories of Australia, state in northeastern Australia, and is the second-largest and third-most populous state in Australia. It is bordered by the Northern Territory, South Austr ...

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

. The genus contains a single species, ''A. cooperensis'', known from multiple partial skeletons. The genus ''Australotitan'' may be synonymous with '' Diamantinasaurus'', a contemporary relative.

Discovery and naming

3D Restorations of Australotitan Holotype

''Australotitan'' was discovered in 2005 in layers of the

in southwest

, Australia, near the town of Eromanga. Sandy Mackenzie, the discoverer, had already collected other bones on the land of his parents in 2004. The

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...

material was then prepared and excavated in conjunction with the

Queensland Museum The Queensland Museum Kurilpa is the state museum of Queensland, funded by the government, and dedicated to natural history, cultural heritage, science and human achievement. The museum currently operates from its headquarters and general museu ...

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". The

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

specimen, EMF102 ("Cooper"), consists of a partial skeleton, including an incomplete left

scapula The scapula (: scapulae or scapulas), also known as the shoulder blade, is the bone that connects the humerus (upper arm bone) with the clavicle (collar bone). Like their connected bones, the scapulae are paired, with each scapula on either side ...

, partial left and complete right

humeri The humerus (; : humeri) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius and ulna, and consists of three sections. The humeral upper extremity consists of ...

, right

ulna The ulna or ulnar bone (: ulnae or ulnas) is a long bone in the forearm stretching from the elbow to the wrist. It is on the same side of the forearm as the little finger, running parallel to the Radius (bone), radius, the forearm's other long ...

, the right and left pubes and

ischia Ischia ( , , ) is a volcanic island in the Tyrrhenian Sea. It lies at the northern end of the Gulf of Naples, about from the city of Naples. It is the largest of the Phlegrean Islands. Although inhabited since the Bronze Age, as a Ancient G ...

, and partial right and left

femora The femur (; : femurs or femora ), or thigh bone is the only bone in the thigh — the region of the lower limb between the hip and the knee. In many four-legged animals the femur is the upper bone of the hindleg. The top of the femur fits in ...

. An additional three specimens were referred to the genus: EMF164, nicknamed "George," (fragmented

femur The femur (; : femurs or femora ), or thigh bone is the only long bone, bone in the thigh — the region of the lower limb between the hip and the knee. In many quadrupeds, four-legged animals the femur is the upper bone of the hindleg. The Femo ...

, presacral

vertebra Each vertebra (: vertebrae) is an irregular bone with a complex structure composed of bone and some hyaline cartilage, that make up the vertebral column or spine, of vertebrates. The proportions of the vertebrae differ according to their spina ...

e, and

rib In vertebrate anatomy, ribs () are the long curved bones which form the rib cage, part of the axial skeleton. In most tetrapods, ribs surround the thoracic cavity, enabling the lungs to expand and thus facilitate breathing by expanding the ...

material), EMF105 (a complete femur), and EMF165 (a distal humerus). The

type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...

, ''Australotitan cooperensis,'' was named and described by Scott A. Hocknull, Melville Wilkinson, Rochelle A. Lawrence, Vladislav Konstantinov, Stuart Mackenzie and Robyn Mackenzie in 2021. The generic name, ''Australotitan'', combines the

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

word "australis", meaning "southern"—as it was found in Australia (which is sometimes referred to as "The Great Southern Land")—with the

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

word "Tιτάν" meaning "titan", in reference to the

mythological

Titans In Greek mythology, the Titans ( ; ) were the pre-Twelve Olympians, Olympian gods. According to the ''Theogony'' of Hesiod, they were the twelve children of the primordial parents Uranus (mythology), Uranus (Sky) and Gaia (Earth). The six male ...

and the dinosaur's gigantic size. The specific name, ''cooperensis'', refers to the

Cooper Creek The Cooper Creek (formerly Cooper's Creek) is a river in the Australian states of Queensland and South Australia. It was the site of the death of the explorers Burke and Wills in 1861. It is sometimes known as the Barcoo River from one of its ...

system near the initial location of the holotype, and the nickname given to the holotype when it was discovered. Australotitan cooperensis

Several of the fossils housed and studied by the Eromanga Natural History Museum were trampled and compressed during deposition. This was the result of multiple smaller sauropods walking in a single line. The trackway has a total length of approximately .

Description

''Australotitan'' represents the largest known Australian dinosaur. The femur of specimen EMF164 has a length of , similar in size to the femora of ''

Futalognkosaurus ''Futalognkosaurus'' ( ; meaning "giant chief lizard") is a genus of titanosaurian dinosaur. The herbivorous ''Futalognkosaurus'' lived approximately 87 million years ago in the Portezuelo Formation, in what is now Argentina, of the Coniacian st ...

'' and ''

Dreadnoughtus ''Dreadnoughtus'' is a genus of titanosaurian sauropod dinosaur containing a single species, ''Dreadnoughtus schrani''. ''D. schrani'' is known from two partial skeletons discovered in Upper Cretaceous (Campanian to Maastrichtian; approximately ...

'', though smaller than those of ''

Patagotitan ''Patagotitan'' is a genus of titanosaurian sauropoda, sauropod dinosaur from the Cerro Barcino Formation in Chubut Province, Patagonia, Argentina. The genus contains a single species known from at least six young adult individuals, ''Patagotita ...

''. The describing authors deliberately abstained from providing a size estimate, as it is notoriously difficult to obtain reliable results for sauropods. The discovery of ''Australotitan'' indicates that the gigantic

n sauropods were present during the mid-Cretaceous of eastern

Gondwana Gondwana ( ; ) was a large landmass, sometimes referred to as a supercontinent. The remnants of Gondwana make up around two-thirds of today's continental area, including South America, Africa, Antarctica, Australia (continent), Australia, Zea ...

Classification

In a

phylogenetic analysis In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical data ...

performed by Hocknull et al. (2021), ''Australotitan'' was recovered as a

titanosaur Titanosaurs (or titanosaurians; members of the group Titanosauria) were a diverse group of sauropod dinosaurs, including genera from all seven continents. The titanosaurs were the last surviving group of long-necked sauropods, with taxa still thr ...

. In eleven out of fourteen analyses, it was placed in a clade with the contemporaneous titanosaur '' Diamantinasaurus'', which, depending on the dataset, also included other

sauropods ''

Wintonotitan ''Wintonotitan'' (meaning " Winton titan") is a genus of titanosauriform dinosaur from Cenomanian (Late Cretaceous)-age Winton Formation of Australia. It is known from partial postcranial remains. Description and history Fossils that are no ...

'' and ''

Savannasaurus ''Savannasaurus'' is a genus of titanosaurian sauropoda, 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 ...

'', and sometimes also ''

Sarmientosaurus ''Sarmientosaurus'' is a genus of titanosaurian sauropod dinosaur belonging to the Titanosauria. It lived in what is now South America, specifically Argentina, during the Upper Cretaceous Period (geology), Period about 95 million years ago. The ...

'', ''

Baotianmansaurus ''Baotianmansaurus'' is an extinct genus of somphospondylian sauropod. Its fossils were discovered in the Late Cretaceous Gaogou Formation of Henan Province, China. The type and only species is ''B. henanensis'' — named after the province in ...

'', ''

Dongyangosaurus ''Dongyangosaurus'' is a genus of titanosaurian sauropod dinosaur from the Late Cretaceous. The only species is ''Dongyangosaurus sinensis'', from which only a single fragmentary skeleton is known, coming from the Zhejiang province of eastern Chin ...

'', ''

Erketu ''Erketu'' (meaning "Erketü Tengri") is a genus of somphospondylan dinosaur that lived in Asia during the Late Cretaceous roughly between 96 million and 89 million years ago. It is known from the Bayan Shireh Formation of Mongolia and its fossil ...

'', and '' Pitekunsaurus''. This places it in the clade

Diamantinasauria Diamantinasauria is an extinct clade of somphospondylan titanosauriform sauropod dinosaurs with close affinities to the Titanosauria, known from the early Late Cretaceous (Cenomanian-Turonian) of South America and Australia. It was named by Poro ...

sensu ''Sensu'' is a Latin word meaning "in the sense of". It is used in a number of fields including biology, geology, linguistics, semiotics, and law. Commonly it refers to how strictly or loosely an expression is used in describing any particular co ...

Poropat et al. (2021). 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 that ''Australotitan'' shares several similarities with the contemporary ''Diamantinasaurus'' that were not recognized in its original 2021 description. Beeston et al. failed to find sufficient

autapomorphies In phylogenetics, an autapomorphy is a distinctive feature, known as a derived trait, that is unique to a given taxon. That is, it is found only in one taxon, but not found in any others or outgroup taxa, not even those most closely related to ...

, or distinct features, to distinguish it from ''Diamantinasaurus'', and, as such, proposed that it can likely be considered as a

junior synonym In taxonomy, the scientific classification of living organisms, a synonym is an alternative scientific name for the accepted scientific name of a taxon. The botanical and zoological codes of nomenclature treat the concept of synonymy differently. ...

of the latter. However, since the ''Australotitan'' only shares one autapomorphy with ''Diamantinasaurus'', and three

synapomorphies In phylogenetics, an apomorphy (or derived trait) is a novel character or character state that has evolved from its ancestral form (or plesiomorphy). A synapomorphy is an apomorphy shared by two or more taxa and is therefore hypothesized to ...

(shared traits) of the Diamantinasauria, they regarded it as an indeterminate member of this clade. Beeston et al. (2024) reviewed the relationships of diamantinasaur specimens in a phylogenetic analysis, and recovered the clade as the

sister taxon In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and ...

to the

Titanosauria Titanosaurs (or titanosaurians; members of the group Titanosauria) were a diverse group of Sauropoda, sauropod dinosaurs, including genera from all seven continents. The titanosaurs were the last surviving group of long-necked sauropods, with tax ...

within the

Somphospondyli Somphospondyli is an extinct clade of titanosauriformes, titanosauriform sauropods that lived from the Late Jurassic until the end of the Late Cretaceous, comprising all titanosauriforms more closely related to Titanosauria proper than Brachiosau ...

. The ''Australotitan'' holotype was found to be most closely related to ''Diamantinasaurus''. Their results are displayed in the

cladogram A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...

below:

References

{{Taxonbar, from=Q107141748 Macronaria Dinosaur genera Turonian dinosaurs Winton Formation Taxa named by Scott Hocknull Fossil taxa described in 2021 Dinosaurs of Australia