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Rhoetosaurus brownei
Rhoetosaurus brownei

[Image: ahighheeledd.jpg]
An artist’s impression of Rhoetosaurus brownei© Queensland Museum 2014. Credit: Konstantinov, Atuchin & Hocknull. Credit: University of Queensland

Temporal range: Middle Jurassic ~171–167 Ma 

Scientific classification
Kingdom:  Animalia
Phylum:  Chordata
Clade:  Dinosauria
Order:  Saurischia
Suborder:  †Sauropodomorpha
Clade:  †Sauropoda
Clade:  †Gravisauria
Genus:  †Rhoetosaurus  Longman 1926
Type species:  Rhoetosaurus brownei  Longman 1926

Rhoetosaurus (meaning "Rhoetos lizard"), named after Rhoetus, a titan in Greek Mythology, is a genus of sauropod dinosaur from the Jurassic Hutton Sandstone of what is now eastern Australia. Rhoetosaurus is estimated to have been about 15 metres (49 ft) long, weighing about 9 tonnes (8.9 long tons; 9.9 short tons). Subsequent authors have sometimes misspelled the name: Rhaetosaurus (de Lapparent & Laverat, 1955); Rheteosaurus (Yadagiri, Prasad & Satsangi, 1979).

Discovery and species
In 1924, Heber Longman, self-trained paleontologist at (and later director of) the Queensland Museum in Brisbane, learned of a large fossil reptile skeleton exposed in the Hutton Sandstone at the Durham Downs Station near Roma in central Queensland. The station manager, Arthur Browne, forwarded fragments of bone to Longman, and was honoured with the dinosaur's specific name brownei. The initial collection was of 22 tail vertebrae, including a series of 16 consecutive bones, and other fragmentary hindlimb pieces. Soon after Longman announced the new discovery, he visited the station and arranged for more material of the same skeleton to be sent to the Queensland Museum. These included additional vertebrae from the thoracic area, bits of rib, more caudals and more of the femur and pelvis as well as a cervical vertebra. Further material was collected by Mary Wade and Alan Bartholomai in 1975, and still more by Drs. Tom Rich, Anne Warren, Zhao Xijin, and Ralph Molnar. By 2012, prepared material comprised 40 vertebrae, five partial thoracic ribs, part of the sacrum, fragments of the ilia, an ischium, the left and right pubic bones, and much of the right hind limb (femur, tibia, fibula, astragalus, and pes). More bones are yet to be removed from rock.
Rhoetosaurus is among the best-known sauropods thus far discovered in Australia, as well as for the Jurassic of Gondwana.

Initially Longman, with advice from leading German paleontologist Friedrich von Huene, noted the primitive nature of Rhoetosaurus, and so for a long time, it was called a cetiosaurid. More recently, others have compared it to Shunosaurus, based on similar general age, but without justification. Given its supposed relationship to Shunosaurus, which had a clubbed tail, Rhoetosaurus has also been hypothesized to possess something similar. The form of the nearly complete hind foot at least suggests that lies outside the more derived Neosauropoda, but the material needs further study to determine its precise positioning in sauropod evolution.

A 'high-heeled' dinosaur that walked on its tiptoes

by University of Queensland

A 24-tonne dinosaur may have walked in a 'high-heeled' fashion, according to University of Queensland research.
UQ Ph.D. candidate Andréas Jannel and colleagues from UQ's Dinosaur Lab analysed fossils of Australia's only named Jurassic sauropod, Rhoetosaurus brownei, to better understand how such an enormous creature could support its own body weight.
"Looking at the bones of the foot, it was clear that Rhoetosaurus walked with an elevated heel, raising the question: how was its foot able to support the immense mass of this animal, up to 40 tonnes?" Mr Jannel said.
"Our research suggests that even though Rhoetosaurus stood on its tiptoes, the heel was cushioned by fleshy pad."
"We see a similar thing in elephant feet, but this dinosaur was at least five times as heavy as an elephant, so the forces involved are much greater."
Mr Jannel and his colleagues arrived at this conclusion by creating a replica of the fossil, and then physically manipulating it in an attempt to understand the movement between bones.
"We also used 3-D modeling techniques to assess the different foot postures that would have allowed Rhoetosaurus to support its weight," he said.
[Image: 1-ahighheeledd.jpg]
Right hind foot of the fossil specimen of Rhoetosaurus brownei (QM F1659), in dorsal view. The hind foot preserves the first four digits in completion, but is missing the fifth one. Credit: Jay P. Nair & Andréas Jannel.

"Finally, we looked at a range of sauropod footprints from around the world, many of which indicated the presence of a fleshy heel pad behind the toes, supporting what the bones were telling us.
"The addition of a cushioning pad that supports the raised heel appears to be a key innovation during the evolution of sauropods, and probably appeared in early members of the group some time during the Early to Middle Jurassic Periods.
"The advantages of a soft tissue pad may have helped facilitate the trend towards the enormous body sizes we see in these dinosaurs."
The fossils of the specimen R. brownei were found near Roma in southwest Queensland and are dated to 160–170 million years ago, when Australia was part of the supercontinent of Gondwana.
Mr Jannel is now using computer techniques to simulate how different foot postures and the presence of a soft tissue pad affect stress distributions within the bones.

[Image: 2-ahighheeledd.jpg]
A cross-section of an elephant’s foot alongside a human foot x-ray, revealing a striking skeletal likeness. Credit: University of Queensland

"In a nutshell, I'm using engineering tools to apply theoretical forces on the bones, assessing how stress is distributed within the feet of these giant dinosaurs, with the aim to provide mechanical evidence for the presence of such a soft tissue pad.
"It can be a tedious and time-consuming process, but I've always been fascinated by palaeontology, particularly the link between form and function in extinct animals," he said.
"There's so much more to know, but it's amazing to discover that becoming 'high-heeled' might have been an important step in the evolution of sauropod dinosaurs."

Journal Reference:
Andréas Jannel et al. "Keep your feet on the ground": Simulated range of motion and hind foot posture of the Middle Jurassic sauropod Rhoetosaurus brownei and its implications for sauropod biology, Journal of Morphology (2019). DOI: 10.1002/jmor.20989

The biomechanics of the sauropod dinosaur pes is poorly understood, particularly among the earliest members of the group. To date, reasonably complete and articulated pedes in Early Middle Jurassic sauropods are rare, limited to a handful of taxa. Of these, Rhoetosaurus brownei, from eastern Australia, is currently the only one from the Gondwanan Middle Jurassic that preserves an articulated pes. Using Rhoetosaurus brownei as a case exemplar, we assessed its paleobiomechanical capabilities and pedal posture. Physical and virtual manipulations of the pedal elements were undertaken to evaluate the range of motion between the pedal joints, under both bone‐to‐bone and cartilaginous scenarios. Using the results as constraints, virtual reconstructions of all possible pedal postures were generated. We show that Rhoetosaurus brownei was capable of significant digital mobility at the osteological metatarsophalangeal and distal interphalangeal joints. We assume these movements would have been restricted by soft tissue in life but that their presence would have helped in the support of the animal. Further insights based on anatomy and theoretical mechanical constraints restricted the skeletal postures to a range encompassing digitigrade to subunguligrade stances. The approach was extended to additional sauropodomorph pedes, and some validation was provided via the bone data of an African elephant pes. Based on the resulting pedal configurations, the in‐life plantar surface of the sauropod pes is inferred to extend caudally from the digits, with a soft tissue pad supporting the elevated metatarsus. The plantar pad is inferred to play a role in the reduction of biomechanical stresses, and to aid in support and locomotion. A pedal pad may have been a key biomechanical innovation in early sauropods, ultimately resulting in a functionally plantigrade pes, which may have arisen during the Early to Middle Jurassic. Further mechanical studies are ultimately required to permit validation of this long‐standing hypothesis.
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