New dinosaur discovery may be the closest relative to Tyrannosaurus rex, scientists say

Paleontologists have discovered a new species of dinosaur that could be the closest-known relative of the famed Tyrannosaurus rex.

The jaw of the dinosaur was found in 1983 by civilians boating in the Elephant Butte reservoir in Las Cruces, New Mexico, Spencer Lucas, curator of paleontology at the New Mexico Museum of Natural History and Science, told ABC News. After boaters alerted the museum to their finding, a subsequent search of the area by paleontologists uncovered additional dinosaur bones, and another dig in the 1990s led to the findings of even more, Lucas said.

The scientists initially assumed that the fossils they found, the jaw and part of the skull, belonged to Tyrannosaurus rex, the famed large theropod dinosaur that existed 66 million to 68 million years ago during the Late Cretaceous period. But in the last 20 years, further study of the jaw indicated that it was a new species entirely, Lucas said.

The new species has since been dubbed Tyrannosaurus mcraeensis, according to a paper published Thursday in Scientific Reports.

The general shape of the jaw of the new species of Tyrannosaurus is similar to the T. rex, but there are two key components in which they are different, Anthony Fiorillo, executive director of New Mexico Museum of Natural History and Science, told ABC News. The jaw of the Tyrannosaurus mcraeensis is much more slender than what you see in the robust lower jaw of the T. rex, which implies a different way of processing food, Fiorillo said.

The other difference lies in the prominent ridge, postorbital bone, the bone around the eye, which could have something to do with how the species attracted mates, Fiorillo said.

"Those are some pretty key biological differences," he said.

Further tests also indicated that this species of Tyrannosaurus existed 70 to 73 million years ago, up to five million years earlier than T. rex, leaving scientists to ponder whether it could possibly be a predecessor to the ferocious predator, Fiorillo said.

The researchers hope to gather more data to get a precise geologic age of the fossil, Lucas said.

The fossil is also unique in that it was found at least 100 miles away from sea coasts, Lucas said, adding that most of the dinosaur fossils of this age that are found in the Western United States, were of animals that lived right near the sea coast -- within 1 mile or 10 miles, sometimes 50 miles away from the sea.

"We're looking at a dinosaur fauna that's living in a rather unique environment," he said.

Lucas described the discovery of new dinosaur species as "the joy of paleontology."

"When you go over the hill, and you find that fossil, you're the first human being that's ever seen that animal in millions and millions of years," he said. "On top of it, in this case, we've got a whole new species of animal that was not known to science before."

On Thursday, the fossil was put on display for the public at the New Mexico Museum of Natural History and Science in Albuquerque.

"So for anybody who wants to see the actual fossil, they can come here and see it," Lucas said.