BOULDER, Colo. (AP) _ The fossil remains of a rare, meat-eating dinosaur that predated the more famous Tyrannosaurus Rex but rivaled it in size and ferocity have been discovered in Colorado, a scientist said Wednesday.

The dinosaur, named Epanterias amplexus, weighed about four tons and measured about 50 feet long, and had a long, powerful tail that probably allowed it to bounce along like a kangaroo, said University of Colorado paleontologist Robert Bakker.

The Epanterias could eat about 40 tons of meat a year and its ''claws seem to be the longest and the strongest of any meat-eating dinosaur that ever lived,'' he said.

''Because of its jaw structure, Epanterias could have swallowed a 1,400- pound Hereford cow with no trouble,'' Bakker said.

The first bones of the latest Epanterias site were found west of Fort Collins in northern Colorado by a team headed by Bakker.

Epanterias walked on its hind legs like Tyrannosaurus Rex, but was built lower, or ''slinkier'' to the ground, Bakker said, adding that T. Rex came along some 66 million years after Epanterias.

So far the dig has recovered a jawbone, neck and tail vertebrae and chest bones, he said.

''There's more still in the ground but it's the hardest dig I've ever made, like digging porcelain imbedded in concrete,'' he said.

The site is mountainous and a transitional zone between sage and pine. When Epantarias roamed the region 135 million years ago at the end of the Jurassic period, it was a vast flat floodplain stretching east and west from Nevada to South Dakota and north and south from Alberta, Candad, to New Mexico, Bakker said.

The only other two known Epantarias sites were discovered in 1877 near Canon City, Colo., and in 1934 in the Oklahoma panhandle.

Bakker hopes that by assembling bones from all three sites, a nearly complete composite Epanterias can be assembled.

''Since these discoveries only seem to come along about every 50 years, we still have a lot to learn about Epanterias. Even though this animal was as long as Tyrannosaurus Rex and heavier than the average circus elephant, it's rarely mentioned in standard dinosaur textbooks,'' Bakker said.