The largest animals that ever walked the Earth were the long-necked, long-tailed dinosaurs known as sauropods, and the most famous of these giants was probably the “thunder lizard” Brontosaurus. For more than a century, scientists stopped using the genus name brontosaurus, but in 2015 researchers suggested that it was time to “resurrect” it. Why was Brontosaurus brought back from the dead, so to speak?

The skeleton of a long-necked, long-tailed dinosaur was found in Wyoming by paleontologist Othniel Charles Marsh in 1879, according to the Natural History Museum in London. Scientists later named the giant herbivore, which lived during the Jurassic period about 150 million years ago, brontosaurus (Brontosaurus excelsus), according to data from Yale University.

But the Museum of Natural History notes that in 1903, paleontologist Elmer Riggs discovered that B. excelsus was very similar to another dinosaur, Apatosaurus ajax, which Marsh discovered in Colorado in 1877. The differences between dinosaurs turned out to be so insignificant that scientists decided it would be better to classify them in the same genus or species group. Since Apatosaurus was first named, scientific naming conventions have retained the name, forcing scientists to abandon the name Brontosaurus.

More than 100 years later, researchers proposed resurrecting Brontosaurus as a separate genus. A sauropod study published in 2015 in the journal PeerJ found that the original fossils of Apatosaurus and Brontosaurus may have been different enough to classify them as separate groups.

The nearly 300-page study examined 477 physical features of 81 sauropod specimens. The initial aim of the study was to analyze the relationships among the species that make up the sauropod family known as Diplodocidae, which includes diplodocus, apatosaurs, and now brontosaurs.

In general, scientists found that Brontosaurus’ neck was higher, narrower and smaller than that of Apatosaurus, vertebrate paleontologist Emanuel Chopp, now at the University of Hamburg in Germany, told Live Science in an interview. They proposed three known species of Brontosaurus: B. excelsus, B. parvus, and B. yahnahpin.

“They call Brontosaurus ‘resurrected,'” says Jacques Gauthier, curator of reptiles at the Yale Peabody Museum of Natural History, who was not involved in the research. “I love the way it sounds. ‘Restored’ is certainly the correct term, but ‘resurrected’ is the official description of what they do.”

Chopp noted that they could not have made this discovery 15 or more years before their study; Only recently has the discovery of dinosaurs similar to Apatosaurus and Brontosaurus helped reveal what makes these groups unique.

Almost a decade has passed since the article was published, and Chopp noted: “Not everyone accepts such offers immediately. “There were, and still are, researchers who were not very confident in the results and continued to use the name Apatosaurus for what I call Brontosaurus.”

“You rarely get consensus from paleontologists on these questions, so the answer you get will depend on who you ask,” Mike Taylor, a vertebrate paleontologist at the University of Bristol in England who was not involved in the 2015 study, told Live Science in an email. “There were no objections in the official literature, but I heard some grumblings.”

Still, according to Taylor, the call to “resurrect” brontosaurus “seems like the smartest thing to do.” He noted that the 2015 study “provides strong arguments that most experts find quite convincing and not particularly surprising.” Taylor and colleagues repeatedly mentioned B. excelsus and B. parvus in their research.