The name “Brontosaurus” has a double life. In one, the name paints giant, long-necked dinosaurs harmlessly munching on leaves in the Jurassic of our minds. In the other, the genus Brontosaurus is the center of a taxonomic tug-of-war.
The bones that would become Brontosaurus excelsus — the great thunder lizard — were named in 1879. But just a few decades later in 1903, paleontologist Elmer Riggs concluded that the Brontosaurus fossils were close enough to another diplodocid dinosaur genus discovered earlier, Apatosaurus, that the public’s beloved stomper should be renamed. Brontosaurus excelsus became Apatosaurus excelsus, and like Pluto, the former status of Brontosaurus remained only in our hearts.
Published today in the journal PeerJ, a new analyses of diplodocid dinosaurs — giant sauropods like Diplodocus and Apatosaurus — from , , and
The tentative reinstatement is just one of the results from a huge undertaking. Tschopp and his team wanted to sort out the true family tree of diplodocids, with a focus on species of Apatosaurus and Diplodocus. They did so with a dino-sized amount of data — five-years worth of digital fossil scans from 20 museums in the US and Europe. Tschopp took this data and categorized 477 anatomical distinctions in 81 individual dinosaurs. The idea was that by using all the diplo-data they could find, the team could lend further support to the family tree scientists have been crafting for over a century. For the most part, that’s what happened…and then Brontosaurus popped out. Again.
If researchers took the time to analyze every fossil they found by hand, they might turn into fossils themselves before they were done. Today, paleontologists take advantage of scanners and algorithms that can rapidly image and compare bones from organisms long gone. In Tschopp’s study, algorithms compared those 477 traits across the individual dinosaurs to see where they differed. If a specimens differed by 20 percent or more among the traits, they would be placed in a different genus, or the taxonomic group that is a grouping of species, like Homo is for Homo sapiens.
The Apatosaurus species were still in the evolutionary tree, as they were expected to be, but two skeletons stood out from them. One was the very same skeleton that generated the name Brontosaurus in the first place, and the other was a skeleton that matched it on a species level. In other words, a deeper look at the original bones had brought Brontosaurus back to life.
These findings aren’t just a simple reinstatement either. Placing a set of dinosaur bones in a new genus is like taking a set of human bones and re-classifying them as Australopithecus. Brontosaurus may live for now, but more research will be needed to further solidify the fossils. Tschopp and his co-authors will now go back for more data and double-check their dinos. After all, the taxonomic tug-of-war is inevitable in a situation like this, where evolutionary trees can change based on very subtle differences among very old bones. The rules that set apart ancient species and genera are not nearly as clear as the rules that demoted Pluto.
Even if the name does stand, and our Brontosaurus can again lumber across our hearts, our understanding of these incredible animals will have to evolve with our understanding of what they left behind.
“That’s the thing to remember,” says Brian Switek, award-winning author of the book My Beloved Brontosaurus, “even if we have the name Brontosaurus back, the animal didn’t look like Littlefoot – or even the old version of the dinosaur. It would still look like an Apatosaurus.”
IMAGE: StudioAM, CC BY 4.0