Siamraptor suwati: 'Tantalizingly Rare' Fossils Reveal New Species of Dinosaur

Paleontologists say they have discovered an entirely new species and genus of predatory dinosaur that would have lived in south-east Asia during the Early Cretaceous period (145 million years ago to 100.5 million years ago)⁠—the Siamraptor suwati.

The Siamraptor belonged to a group called the carcharodontosaurs, a band of large carnivorous dinosaurs found around much of the globe during the Jurassic and Cretaceous Periods, existing in different ecosystems across multiple continents. Their largest members rivaled the T-Rex in size. However, evidence of their presence in Early Cretaceous Asia is lacking—a gap the Siamraptor may now fill.

This discovery is particularly noteworthy because of where it was found.

Siamraptor skull reconstruction.
Siamraptor skull reconstruction. Chokchaloemwong et al., 2019

"Although dinosaurs had a global distribution, their remains have been tantalizingly rare in some areas of the world," Paul Barrett, a Merit Researcher at the Natural History Museum in London, the UK, told Newsweek.

"One such area is South-East Asia, whose heavily forested landscape is very difficult to prospect for fossils."

Roger Benson, Professor of Palaeobiology at the University of Oxford, UK, also emphasized the importance of the location and the fossil.

While incomplete, the fossils described in the paper represents some of the best evidence that large predatory dinosaurs existed in the area at that time, Benson told Newsweek.

The discovery, described in the journal PLOS ONE, is based on remains found in the Khok Kruat geologic formation in Khorat, in central Thailand. The fossils include fragments of the skull, backbone, hips, and limbs of four individual dinosaurs.

Morphological comparison with known species suggests that it is an not only an entirely new species of dinosaur, but a new genus, the researchers say.

Meanwhile, phylogenetic analysis shows the new dinosaur is a basal member of the carcharodontosaurs—a term that means it split from the group very early, evolutionary-speaking. While close relatives of the newly discovered species can be found in continents across the world, the find suggests that Asia was more important in the early history of the group than previously appreciated, said Barrett. It also highlights the diverse nature of the larger predators that inhabited the ecosystems of Asia during the Cretaceous Period.

"Discoveries over the past 20 years have begun to reveal an interesting diversity of dinosaurs from the region, though most are known from fairly incomplete remains," Barrett said.

"This new dinosaur, Siamraptor, adds welcome new information on the types of dinosaurs living in the region around 140 million years ago."