Brontosaurus was once one of the most famous dinosaurs. However, in 1903, researchers concluded that there was not enough evidence to support the idea that this animal – as we knew it – ever lived, and the creatures were reclassified in the Apatosaurus group. Now, a new study suggests Brontosaurus should be reinstated as their own genus among dinosaurs.

Paleontologists decided over a century ago that the anatomical differences between Apatosaurus and Brontosaurus were minor enough to combine the two in a single genus. Since Apatosaurus was the older classification, the Brontosaurus name was nullified.

Dinosaur species were discovered by the dozens during the 1870s, including the two long-necked sauropods. These discoveries were fueled in part by a vigorous competition between two paleontologists, Othniel Marsh and Edward Cope. During this period, Marsh uncovered two similar dinosaur skeletons, without skulls, which he shipped to the Yale Peabody Museum where he was employed.

Marsh named one of these creatures Apatosaurus ajax (deceptive lizard), and the second Brontosaurus excelsus (noble thunder lizard). The paleontologist developed a model skull for Brontosaurus, designed after the similar-sized Camarasaurus that also lived in the western United States.

Soon after the death of Marsh, paleontologist Elmer Riggs showed that most of the observed differences between Apatosaurus and Brontosaurus were due to growth. Later research also revealed that the highly rectangular skull created by Marsh was incongruous with the bones of the actual animals.

During the 1970s, paleontologists discovered the Apatosaurus was more closely related to Diplodocus than it was to Camarasaurus. This dinosaur was noted for its slender skull, and researchers theorized that the dinosaur with an identity crisis likely exhibited a similar horse-shaped skull. This led to decades of thinking that the creature was an Apatosaurus with an unusual head.

"Our research would not have been possible at this level of detail 15 or more years ago. In fact, until very recently, the claim that Brontosaurus was the same as Apatosaurus was completely reasonable, based on the knowledge we had," said Emanuel Tschopp from the Universidade Nova de Lisboa in Portugal.

Both Apatosaurus and Brontosaurus were members of the family of Diplodocidae, which walked on short legs with long necks and tails resembling powerful whips. The large size of these animals forced researchers to depend on small details in bones to determine how the animals were related to one another.

Now, newly revealed features in the bones of the dinosaur once known as Brontosaurus are believed to be significant enough to bring the once-popular genus back into the popular nomenclature.

"Numerous new sauropods have been discovered and named in the last couple of decades, new techniques have been developed, and we simply have a more sophisticated understanding of sauropods now," said Louis Jacobs of Southern Methodist University. "Good for them, and bully for Brontosaurus!" 

This study was published in the journal PeerJ.

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