Megaraptorids, known as 'death hugs', were the dominant predators of South Australia during the Cretaceous. (Image credit: Artwork by Jonathan Metzger. Source: Museums Victoria)
Scientists in Australia have found fossils of two giant predators that lived alongside each other, changing our understanding of how ancient ecosystems worked less than 120 million years ago. The find included the oldest known large megaraptor.
Megaraptorids were a group of fearsome predators from the Cretaceous Period (145 to 66 million years ago). They inhabited the ecosystems of Australia and South America, which were connected by Antarctica in a huge southern landmass called Gondwana.
Lead author Jake Kotevski, a PhD student in palaeontology at the Museums Victoria Research Institute and Monash University in Australia, described megaraptorids as “predators that primarily stalk their prey,” with muscular forearms and long, curved claws for grabbing prey. They were effective at pulling their prey toward them for a “death hug,” he said in a video released by Museums Victoria.
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The fossils found by Kotevsky and his team belonged to an as-yet-unidentified 120-million-year-old megaraptorid that was 20 to 23 feet (6 to 7 meters) long, making it one of the largest theropods (two-legged dinosaurs, mostly carnivores) ever discovered in Australia. It also predates megaraptorids in South America by about 30 million years.
In a new study published Feb. 19 in the Journal of Vertebrate Paleontology, scientists also identified fossils of another group of large predatory dinosaurs known as Carcharodontosauria, which are also found in South America but have not previously been found in Australia.
Carcharodontosaurus fossils suggest that these dinosaurs reached lengths of 13 feet (4 m) in Australia, significantly shorter than their relatives in South America, which could grow up to 43 feet (13 m).
In other words, the roles of the two predatory dinosaurs appear to have been reversed in Victoria, with megaraptorids becoming large apex predators and carcharodontosaurs becoming small secondary predators. Australia's unique Cretaceous ecosystem thus had its dynamics “inverted,” according to a statement from Museums Victoria.
The newly discovered fossils were found in what were once the banks of a major river, similar to today's Ganges or Amazon, Kotevski told Live Science in an email. South Australia was close enough to the South Pole to be within the Arctic Circle during the Cretaceous, though the region was significantly warmer then than it is today.
The team examined fossils collected from the upper Strzelecki Formation of rock on the Victoria Coast in southern Australia between 1988 and 2022 using state-of-the-art 3D imaging techniques, including micro-computed tomography. This technique involves taking X-ray images of an object while rotating it 360 degrees to allow for a more detailed study.
Sourse: www.livescience.com
