A new genus and species of sauropod dinosaur has been identified from a fossilized bone found in China almost 30 years ago.
Life restoration of Mamenchisaurus youngi, the best-known member of the family Mamenchisauridae. Image credit: Steveoc 86 / CC BY-SA 2.5.
The new dinosaur species roamed Earth during the Late Jurassic epoch, approximately 155 million years ago.
Scientifically named Rhomaleopakhus turpanensis, the animal was up to 25 m (82 feet) in length.
It was a member of the family Mamenchisauridae, a group of sauropod (herbivorous long-necked) dinosaurs known from the Jurassic and Early Cretaceous of Asia and Africa.
“These dinosaurs added extra vertebrae to their necks to elongate them, and in addition to this made each individual neck vertebra longer,” Professor Paul Barrett, a paleontologist in the Department of Earth Sciences at University College London and the Department of Earth Sciences at the Natural History Museum, London, said in a statement.
“We don’t know why they did this, but we presume it was either a feeding adaptation or sexual selection.”
Holotype right forelimb of Rhomaleopakhus turpanensis with individual elements in approximate anatomical position, shown in anterior view. Scale bar – 200 mm. Image credit: Upchurch et al., doi: 10.1080/02724634.2021.1994414.
A nearly complete forelimb of Rhomaleopakhus turpanensis was recovered from the lower part of the Kalazha Formation in Turpan Basin, the Xinjiang Uyghur Autonomous Region, China.
“Rhomaleopakhus turpanensis was formally described as a specimen of another similar dinosaur called Hudiesaurus sinojapanorum, but it has a number of features that are not seen in any other sauropod,” Professor Barrett said.
“For example, it has perhaps the stockiest arms of any known sauropod of this age.”
“That means it would have been really heavily-set in comparison to the other sauropods it lived alongside. If it was a rugby player, it would be a prop forward.”
In addition, Rhomaleopakhus turpanensis had an extremely robust ulna (more medial of the two long bones of the forearm).
“We think that an unusually large chunky projection at the top of its ulna is associated with a more strongly flexed forelimb, so that the forelimb is held habitually in a slightly bent, rather than straight pose,” Professor Barrett said.
“We think this means that the forelimb was not just propping the large animal up, but that they might have been doing something interesting with it.”
A paper describing the findings was published in the Journal of Vertebrate Paleontology.
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Paul Upchurch et al. Re-assessment of the Late Jurassic eusauropod dinosaur Hudiesaurus sinojapanorum Dong, 1997, from the Turpan Basin, China, and the evolution of hyper-robust antebrachia in sauropods. Journal of Vertebrate Paleontology, published online December 13, 2021; doi: 10.1080/02724634.2021.1994414
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