Two new predatory megaraptor dinosaur species that were distantly related to Tyrannosaurus rex have been identified from fossils found in Thailand.
The specimens were first unearthed 30 years ago but their significance went unrecognised until researchers re-examined the museum-stored samples.
Both new dinosaurs would have been smaller and more primitive than T Rex, researchers said, but would have still made for deadly predators.
Scroll down for video
Two new predatory megaraptor dinosaur species that were distantly related to T. rex have been identified from fossils from Thailand. Pictured: an artist’s impression of the finds
Palaeontologists Adun Samathi and Martin Sander of the University of Bonn, Germany, and Phornphen Chanthasit of the Sirindhorn Museum in Thailand worked together to study the remains, bringing casts of the fossils to Bonn for further analysis.
They first identified the preserved bones of a new dinosaur that they estimate would have been around 20 feet (six metres) in length.
‘We were able to assign the bones to a novel megaraptor, which we baptised Phuwiangvenator yaemniyomi,’ explains Mr Samathi.
The name was derived from both the district in which the remains were unearthed, Phuwiang, and the discoverer of Thailand’s first dinosaur fossil, the late geologist Sudham Yaemniyom.
Megaraptors were a group of carnivorous, predatory dinosaurs that were distantly related to Tyrannosaurus rex.
Most of the P. yaemniyomi fossil bones were dug up by Phu Wiang Fossil Research Center and Dinosaur Museum staff member Preecha Sainongkham, in 1993, who presented the finds to the Sirindhorn Museum.
However, the fossils were never examined in detail until recently.
‘Five years ago I came across these finds during my research,’ Mr Samathi said.
The fossils had been first unearthed 30 years ago, but their significance went unrecognised until researcher led by Adun Samathi (pictured) re-examined the museum-stored samples
Mr Samanthi discovered a second unidentified raptor species in the Sirindhorn Museum collection while hunting for additional samples of P. yaemniyomi in Thailand.
Dubbed Vayuraptor nongbualamphuensis, this second dinosaur would have been slightly smaller in life, with an estimated length of around 15 feet (4.5 metres).
For comparison, T. rex typically grew to around 39 feet (12 metres) in length.
The V. nongbualamphuensis remains were excavated by one Paladej Srisuk at Phu Wat in 1988.
While the fossilised bones were too sparse to precisely determine V. nongbualamphuensis’ ancestry, researchers assume that the smaller dinosaur is also related to both P. yaemniyomi and T. rex.
Both newly-discovered dinosaur species would have been efficient predators, researchers determined, with P. yaemniyomi likely to have been a fast runner.
Like Tyrannosaurus, both of the new dinosaurs would have run on their hind legs.
Unlike their famous relative, however, P. yaemniyomi and V. nongbualamphuensis would have had strong arms that ended with long claws, as well as more delicate heads that would have ended in a long snout.
‘Perhaps the situation can be compared with that of African big cats,’ said Mr Samathi.
‘If Phuwiangvenator were a lion, Vayuraptor would be a cheetah.’
Unlike T. rex, P. yaemniyomi (artist’s impression, below, showing the bones found) and V. nongbualamphuensis (above) would have had strong arms that ended with long claws, as well as more delicate heads that would have ended in a long snout
To date, megaraptors have primarily been unearthed from Australia and South America.
‘We have compared the Thai fossils with the finds there,’ Mr Samathi said.
‘Various characteristics of Phuwiangvenator indicate that it is an early representative of this group,’ he added.
‘We take this as an indication that the megaraptors originated in Southeast Asia and then spread to other regions.’
The two new dinosaurs will go on display to the public on May 28, 2019, in celebration of the tenth anniversary of the Sirindhorn Museum.
The exhibit will be opened by the Princess Maha Chakri Sirindhorn, of the Thai royal family.
The full findings of the study were published in the journal Acta Palaeontologica Polonica.
Most of the P. yaemniyomi remains were unearthed from the Phu Wiang Mountain by museum staff member Preecha Sainongkham in 1993, while the V. nongbualamphuensis fossils were excavated by one Paladej Srisuk at Phu Wat in 1988
