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. Last Updated: 07/27/2016

Thais Unearth Oldest T. Rex Fossil

PHU WIANG, Thailand -- Dinosaur bones found in a Thai forest suggest the ferocious Tyrannosaurus rex, the king of dinosaurs that stalked pre-historic North America, originated in Asia.

A joint Thai-French team has discovered the fossilized remains of a dinosaur they think is the grandfather of all tyrannosaurs, 20 million years older than the oldest specimen of the fierce, meat-eating dinosaur previously found.

"We have found that many of the characteristics are the same as the tyrannosaurs though more primitive," Thai researcher Varavudh Suteethorn said of the dinosaur.

The creature has been dubbed Siamotyrannus isanensis, from Thailand's former name, Siam, and the name of the northeastern Isan region of the country where it was found.

"It has more similarities to the tyrannosaurs than any other carnivore; it's the same family," said Varavudh, Thailand's leading paleontologist, who works with the industry ministry's department of mineral resources.

The remains of the nearly complete skeleton, which is about 120 million years old, were found embedded in rock in a forest in the Phu Wiang national park in Khon Kaen province in 1994.

"We think the tyrannosaur evolved in this area and then dispersed to other areas," Varavudh said. "At that time all the continents were one, they had not separated yet, so we think it dispersed and then after that the continents separated."

The Tyrannosaurus rex has been found only in North America and lived some 50 million years after the Siamotyrannus isanensis.

The Thai creature was about 6.5 meters long, about half the size of the Tyrannosaurus rex, reflecting a natural tendency for all animals to grow in size as they evolve, as long as the conditions are right, Varavudh said.

Though the remains of some 10 different dinosaur species have been discovered in Thailand, most have been herbivorous sauropods -- plant-eating dinosaurs that walked on all four legs and had long necks and long tails.

The Siamotyrannus isanensis is the first near-complete fossilized carnivorous dinosaur found in Thailand. The animal was bipedal, walking mostly on its rear legs with a short neck and short forelegs, good for grabbing and holding prey.

The first dinosaur remains were discovered in Thailand by geologists prospecting for uranium in 1976. Systematic excavations by Thai-French teams were started in the early 1980s. Researchers soon realized that the best dinosaur remains in southeast Asia were dotted just below the surface of northeast Thailand.

The relative abundance of dinosaur remains in Thailand, as well as in parts of China and India, occurred because of an accident of geology.

"Only sedimentary rock can preserve fossils," Varavudh said, adding that such stone is found on, or just below, the top soil, across much of northeastern and northern Thailand.

In neighboring Kalasin province Varavudh and his team are excavating a site about the size of a tennis court that contains the remains of several herbivorous dinosaurs.

Varavudh hopes that one day a museum will be built where the fossils can be pieced together and exhibited but for the time being he and his team continue their digging and their search for more remains on a shoe-string.

"Paleontology does not get a big budget," he said.

Varavudh said the site must have been a bend in a prehistoric river where the carcasses of the dead animals drifted and were trapped and quickly covered by layers of silt.