Early Cretaceous predator discovered

Palaeontologists digging through red sandstone and clay in northern Thailand have unearthed a new species of carnivorous dinosaur.

Duangsuda Chokchaloemwong from Nakhon Ratchasima Rajabhat University in Thailand, and colleagues, described the new dinosaur species – Siamraptor suwati – from skull, backbone, hip and leg fossils of four separate individuals.

The remains were found in northern Thailand, in the dinosaur-rich Khok Kruat Formation. These deposits were formed by an ancient river basin that dates to the early Cretaceous, between 125 and 113 million years ago.

Only fragmentary remains were found, so it’s not known exactly how big Siamraptor was. But a rough skeletal reconstruction suggests it could have measured almost eight metres from head to tail – that’s about two-thirds the size of the iconic Tyrannosaurus rex.

Siamraptor’s features suggest that it was an early-evolving member of a group of dinosaurs known as carcharodontosaurs.

The carcharodontosaurs were among the largest predators of the early and middle Cretaceous. By the late Cretaceous – some 90 million years ago – they were gone, replaced by other three-toed theropod dinosaurs including the tyrannosaurids.

Its location and age suggests this group of carnivorous dinosaurs became widespread early in their evolutionary history. At the time, carcharodontosaurs were also living in Europe and the parts of Gondwana that would later become Africa.

The discovery is described in the journal PLoS ONE.