Paleontologists in Argentina have found fossil fragments from a new genus and species of rebbachisaurid sauropod dinosaur that walked the Earth more than 90 million years ago.
The newly-discovered dinosaur lived in what is now Argentina during the Cenomanian age of the Late Cretaceous epoch, between 96 and 93 million years ago.
Scientifically named Sidersaura marae, the ancient beast was up to 20 m in length, had an estimated mass of 15 tons, and had a very long tail.
The animal belongs to Rebbachisauridae, a large family of sauropod dinosaurs known from fragmentary fossil remains from South America, Africa, North America, Europe and Asia.
These dinosaurs are distinguished from other sauropods by their distinctive teeth. Some species had tooth batteries, similar to those of hadrosaur and ceratopsian dinosaurs.
“Rebbachisaurids were very important dinosaurs in Cretaceous ecosystems and disappeared in the middle of this period in an extinction event that took place 90 million years ago,” said Dr. Lucas Nicolás Lerzo, a paleontologist at Fundación Azara – Universidad Maimónides and CONICET, and his colleagues.
“Sidersaura marae is one of the last rebbachisaurids, but at the same time it belongs to an ancient lineage in evolutionary terms.”
“This shows us that at the end of their time some of early rebbachisaurids survived, and that these were the largest of their group, given that they could reach nearly 20 m in length.”
Sidersaura marae fossil. Image credit: Lerzo et al., doi: 10.1080/08912963.2023.2297914.
The fossilized bones of Sidersaura marae were recovered from rocks of the Huincul Formation of Neuquén province, Patagonia, Argentina.
“Among the remains found are vertebrae from the sacral area and the partially articulated tail, bones from the hind limbs, parts of the skull and vertebrae from the tail,” Dr. Lerzo said.
“Having several specimens that overlap anatomically allowed us to correlate them and better understand the characteristics of this new sauropod dinosaur.”
According to the team, one of the characteristics that distinguish Sidersaura marae from other dinosaurs is the star-shaped shape of the hemal arches (tail bones).
Furthermore, its skull bones are robust, unlike those of the rest of its closest relatives.
“Another cranial feature that differentiates Sidersaura marae from other rebbachisaurids is its frontoparietal foramen, which is basically a hole in the roof of the skull,” the paleontologists said.
“This trait brings it closer to dicraeosaurids, a family of sauropod dinosaurs known for having spines on their necks and backs.”
“The presence of an early species at Cenomanian-Turonian times, so close to the extinction of the group, implies that the evolutionary history of Rebbachisauridae was more complex than previously thought,” they concluded.
Their paper was published in the journal Historical Biology.
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Lucas Nicolás Lerzo et al. The last of the oldies: a basal rebbachisaurid (Sauropoda, Diplodocoidea) from the early Late Cretaceous (Cenomanian-Turonian) of Patagonia, Argentina. Historical Biology, published online January 3, 2024; doi: 10.1080/08912963.2023.2297914