Brontosaurus—the "Thunder Lizard"—Is Back as Its Very Own Genus

The Brontosaurus—first named by Yale paleontologist O.C. Marsh in 1879—has captured imaginations and become a part of popular culture. A statue of the Brontosaurus stood at the 1964 World's Fair in New York; it appeared in movies, including Jurassic Park and King Kong; and it became the logo for the Sinclair oil company.

But for years it has been considered a misnomer. That's because scientists concluded in 1903 that the Brontosaurus excelsus and the Apatosaurus, which Marsh had named in 1877, were so similar that they should be considered members of the same genus. Since Marsh had coined Apatosaurus first, it became the scientific name of the genus and Brontosaurus was rendered technically incorrect. That didn't mean the Brontosaurus itself never existed—it remained a distinct species within the Apatosaurus genus, technically dubbed Apatosaurus excelsus. Popular culture references to the Brontosaurus never went extinct, though, despite the fact that the name was no longer scientifically valid.

More than a century later, a new study published Tuesday in the journal PeerJ has the Brontosaurus making a comeback as its very own genus. In the paper, researchers analyzed dozens of specimens from the Diplodocidae family and concluded that the Apatosaurus and Brontosaurus are in fact different enough that they should each be classified as a separate genus.

In other words, the Brontosaurus is back.

"We looked in very great detail at the anatomy of bones from a group called Diplodocidae," says lead author Emanuel Tschopp, a paleontologist at University Nova in Lisbon, Portugal, whose doctoral research served as the basis of the study. These are "long-necked dinosaurs that lived in the Late Jurassic period in what is now known as the United States," he says. Specimens from the family have also been found in Tanzania, Zimbabwe, Portugal and Spain, as well as possibly England and Georgia, according to the paper.

"Thanks to this very detailed study of this anatomy, we were able to recreate the family tree basically from scratch. By doing this, we were able to study the relationships of all the species known in this group in much deeper detail than what was known before," Tschopp says.

The study resulted in three key findings: the discovery of a new genus within the Diplodocidae family, which Tschopp and his colleagues propose be called Galeamopus; the combining of two very similar genera, Supersaurus and Dinheirosaurus, as one group to be called Supersaurus lourinhanensis; and finally, "the resuscitation of Brontosaurus as a distinct genus from Apatosaurus," according to the paper.

Beginning in 2010, the researchers visited and studied skeletons at more than 20 museums in the U.S. and Europe, including the British Museum of Natural History in London, the American Museum of Natural History in New York, the Carnegie Museum in Pittsburgh and the Yale Peabody Museum in New Haven, Conn.

For their analysis and comparisons among different skeletons, they looked at almost 500 anatomical characteristics, like the shapes of various bones. For example, "the most obvious and visual feature" that distinguishes between the Apatosaurus and the Brontosaurus, Tschopp says, "would be that Apatosaurus has a wider neck than Brontosaurus, which has a rather high instead of a wide neck. So even though both were very massively built animals, Apatosaurus was even more robust than Brontosaurus, especially in the neck." Many of the other anatomical characteristics considered were more minor and complicated to explain in simple terms, he adds.

Then, "we were able with computer software [and statistical methods] to see which of the skeletons included were more similar to each other than other skeletons," Tschopp says, and draw conclusions about their taxonomy. In a field where there is no standard that governs what amount of variation constitutes a separate species versus a genus, the team tried to draw distinct lines based on quantitative differences rather than judgments about the relative importance of particular differences among skeletons.

"It has had an element of arbitrariness," says Louis Jacobs, a vertebrate paleontologist and professor at Southern Methodist University. He is not affiliated with the research but served as an outside committee member on Tschopp's dissertation and has seen the new study's manuscript. The researchers, Jacobs explains, attempted to set an explicit threshold for classifying an animal as a different species versus a different genus.

If you "look at the whole history of that animal and how it has changed and changed and changed," says Jacobs, there are two things that could happen next. As more specimens are found and analyses conducted, the findings—including the resuscitation of the Brontosaurus genus—could be disproved or more strongly confirmed. "That's the way science works."

For now, however, Jacobs believes Tschopp and his fellow researchers are on solid ground with their reclassification of the Brontosaurus as a genus separate from the Apatosaurus in "a case where the science has advanced and the science is indicating that the original work [from the 19th century] was correct."

"I would say, 'Bully for Brontosaurus," Jacobs exclaims in response to the new findings, referencing Stephen Jay Gould's 1991 book of essays with the same name. In the title essay, the paleontologist, evolutionary biologist and writer explained why the Brontosaurus misnomer had persisted for so many years. But now, more than two decades after Gould's book was published, Tschopp and his colleagues have argued that the Brontosaurus should get its genus back.