(CN) — A study published Thursday in Current Biology found a brand new species of dinosaur with similar features to the iconic Tyrannosaurus Rex. Found in Patagonia, Argentina, Meraxes gigas gave researchers even more insight into the build of large carnivores.
Like the T. rex and other giant theropod dinosaurs, Meraxes has a large body with small arms. However, scientists made it clear that there is no relation between T. rex and Meraxes — they went extinct about 20 million years before T. rex became a species. This, along with the evidence of solid arm muscles, leads researchers to believe there must have been an evolutionary benefit to the mini-arm trend and they didn't become smaller over time due to lack of use.
"I'm convinced that those proportionally tiny arms had some sort of function. The skeleton shows large muscle insertions and fully developed pectoral girdles, so the arm had strong muscles," said lead study author Juan Canale.
After decades of research, it's widely accepted that the larger the head of dinosaurs like Meraxes, the smaller the arms. Researchers also note that the arms weren't for hunting and that the dinosaur's head carried out most predator behaviors. It isn't easy to hypothesize exactly the arms' primary use.
"They may have used the arms for reproductive behavior such as holding the female during mating or support themselves to stand back up after a break or a fall," Canale said.
The fossils also shed light on Meraxes skull decorations and how they progressed over their lifespan. For example, Meraxes' skulls were adorned with furrows, bumps, hornlets and crests — all things that developed late in life and are thought to attract mates.
"Sexual selection is a powerful evolutionary force. But given that we cannot directly observe their behavior, it is impossible to be certain about this," Canale noted.
Scientists also got a good idea of what this Meraxes' life was like from the bones it left behind — at eleven meters long and weighing over four tons, this dinosaur was 45 years old and had a large family. Meraxes also hit peak diversity and were flourishing shortly before they went extinct. With the fossils in such excellent condition, Canale is looking forward to getting more questions answered with further research.
"We found the perfect spot on the first day of searching, and M. gigas was found. It was probably one of the most exciting points of my career," Canale said.