One of the most iconic dinosaurs, Brontosaurus, is back on its own in the dino history books, having regained its status as a unique genus and species.

Paleontologists have spent the last century insisting the species and its name are invalid-that the first fossil was incorrectly or deceptively described, or what was called Brontosaurus is really another similar dinosaur, the Apatosaurus.

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The reclassification appears to resolve a long-standing debate over what to do with Brontosaurus, which looked a lot like Apatosaurus.

That similarity had caused paleontologists to rename Brontosaurus as Apatosaurus excelsus. In short, it was just considered to be another type of Apatosaurus. Gone was the cool name Brontosaurus, which means "thunder lizard" in Greek.

The fossils show enough skeletal differences from other specimens of Apatosaurus that they rightfully belong to a different genus.

There are seven specific bone differences that make the body of the original Brontosaurus its own species and genus, according to Emanuel Tschopp at the New University of Lisbon in Portugal.

Most of them are rather subtle. The tail vertebrae in dinosaurs related to Brontosaurus have spiny prominences called neural spines. These dinosaurs' spines project kind of backwards, but in Brontosaurus they're straighter up.

Brontosaurus's hips are unusual, with two bones (the ilium and pubis) meeting a curious junction. Its lower leg fibula meets its ankle bones in an equally unusual manner.

Tschopp examined bones in 18 different museums in the United States and Europe and studied photos and drawings from other specimens. The idea was to get a high-resolution family tree by examining many individual specimens, rather than focusing only on fossils that represent an entire species.

The study included six specimens of Apatosaurus excelsus, as Brontosaurus has been called since 1903.

"The differences we found between Brontosaurus and Apatosaurus were at least as numerous as the ones between other closely related genera, and much more than what you normally find between species," explained Roger Benson from the University of Oxford.

Brontosaurus has also undergone a minor image makeover as a result of the study. Because of its evolutionary history, the researchers believe the dinosaur probably had a head similar to that of Diplodocus.

The study appeared in the journal PeerJ.

TagsBrontosaurus Dinosaur Name Make a Come Back, Brontosaurus, Apatosaurus, Dinosaur era, ancient animal, dinosaur fossil, animal fossil