Here’s a quick quiz. Choose the one that doesn’t belong:
Yes, I know, you’re way too smart for this. You chose “C” because you remember that everybody’s favorite dinosaur, that 16-ton vegetarian with the long neck and the whip-like tail, is really named Apatosaurus. Scientists have long since declared that Brontosaurus was a taxonomic error and doesn’t technically exist.
In fact, it’s been 112 years since a paleontologist named Elmer Riggs first pointed out that Brontosaurus, described by Yale’s O.C. Marsh in 1879, was an awful lot like Apatosaurus, which Marsh himself had described just two years previously. Marsh thought the two species were different because one had more vertebrae than the other in the sacral region, at the base of the spine. But Riggs pointed out that the sacral vertebrae in four-limbed species, including humans, normally fuse as an individual matures. Marsh’s two specimens were thus no more than older and younger individuals of the same species.
That is, until this morning. In a paper published Tuesday in the journal PeerJ, a team of paleontologists declared that Brontosaurus is back, baby, and better than ever. They argue that Brontosaurus is different enough to be a separate genus from Apatosaurus, and that it deserves its own spot on the dinosaur tree of life.
This will come as a great relief to legions of long-suffering dinosaur enthusiasts. “Everyone knows the dinosaur’s name, and we want Brontosaurus to exist,” Brian Switek, a paleontological writer, declared in his book My Beloved Brontosaurus. Likewise, in his book Bully for Brontosaurus, paleontologist Stephen Jay Gould wrote that the dinosaur formerly known as Brontosaurus was “everyone’s typical sauropod—indeed the canonical herbivorous dinosaur of popular consciousness, from the Sinclair logo to Walt Disney’s Fantasia.” Gould thought this was logical, since the skeleton originally called Brontosaurus, now mounted in the Peabody Museum at Yale, is one of the most complete ever found. The first Apatosaurus specimen, on the other hand, was merely “a pelvis and some vertebrae.”
But scientists—and the rest of us—were stuck with Apatosaurus because the rules of scientific naming dictate that the name given to the first properly described specimen is the name that counts. Apatosaurus (“deceptive lizard”) wasn’t even a particularly memorable name, whereas Brontosaurus (“thunder lizard”) had what modern marketing types would call stickiness, sometimes literally: In 1989, the U.S. Postal Service issued a stamp with an image of the dinosaur labeled “Brontosaurus,” defending its name choice as “more familiar to the general population.”
The authors of the new paper did not set out to a join the popular movement to resurrect Brontosaurus. “We were surprised ourselves” at that result, said Emanuel Tschopp, a paleontologist at Universidade Nova in Lisbon and the lead author of the study. The research, which Tschopp undertook as part of his PhD studies, was spurred by a desire to sort out the fossils at a dinosaur museum in Aathal, Switzerland.
Tschopp soon realized that many species of diplodocids—the huge, herbivorous dinosaurs that include Apatosaurus and Brontosaurus—“were not so well defined,” he said. That led him and his coauthors on a worldwide trek to examine specimens at two dozen museums around the world and collect measurements of nearly 500 anatomical traits needed to better characterize the huge sauropods.
Separating one species from another is a tricky business even with living species. When you’re dealing with animals that have been extinct for 150 million years, it becomes exponentially harder. For one thing, skeletons are often jumbled together when they’re found, so it’s not always clear whether the bones you’re looking at all came from the same animal. Fossilized skeletons are also rarely complete, requiring extrapolation to cover the missing parts. Even with well-preserved specimens, the wear and tear from tens of millions of years can damage or deform bones in ways that can be “almost impossible to identify and least of all to quantify,” according to the new paper.
Despite these caveats, said Tschopp, Brontosaurus clearly deserves to be a separate genus from Apatosaurus. The article identifies several specific differences that can differentiate the two, most notably that “Apatosaurus has a wider neck than Brontosaurus,” Tschopp said. Many of the other differences are highly technical, he said, and too difficult to explain in nonscientific terms. For the moment, suffice it to say that the article describing them runs on for 298 pages.
Tschopp expects that the revived name will generate a lot of discussion, and perhaps also pushback. It took a while for people to accept that Brontosaurus wasn’t a valid name. Now, he said, “I guess it will also take some time” for people to accept that it’s back.
Some, however, are already embracing the new finding. “I’m just delighted that Brontosaurus is back,” said Jacques Gauthier, curator of vertebrate paleontology at the Yale Peabody Museum of Natural History. Louis Jacobs, a professor of paleontology at Southern Methodist University, has no horse in this race but also seemed pleased. “They certainly pulled together a big data set,” he said. “Their work looks to me like it was pretty careful and thorough.” Asked if the return of Brontosaurus made him happy, he quibbled: “It’s not a matter of being happy or not happy. It’s where it falls out.” Then he added: “And if it falls out in that place, who would not be happy?”
Geoffrey Giller contributed reporting to this column.