Quick – think of a dinosaur! Palaeontologists aside, the rest of us probably conjure up a T. rex ... or maybe that iconic Flinstones' favourite, the Brontosaurus. It might be everyone's number one dinosaur, but poor Brontosaurus hasn't had much luck when it comes to, well, convincing the scientific community of its existence. But after a century, its luck might finally be changing. We'll let a palaeontologist explain why:

New dinosaur species are being discovered on an almost weekly basis from every corner of the globe. Each time a new one is named, we celebrate it as another insight into the lives of these fascinating animals. But what about lamenting the ones we’ve lost? What happens when we lose a cherished dinosaur?

During a period of scientific strife in the USA known as the 'Bone Wars', there existed two rival scientific camps: on one side, we had Othniel C. Marsh, and on the other, Edward D. Cope, both pre-eminent scientists and revolutionaries in the field of palaeontology.

In 1877, Marsh named a new dinosaur Apatosaurus ajax, a name meaning 'deceptive lizard' and a nod to the Greek hero, Ajax. A few years later, he discovered and named another new dinosaur fossil Brontosaurus excelsus (the 'noble thunder lizard'), this time a much more complete and bigger dinosaur than Apatosaurus.

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Brontosaurus artistic reconstruction Image: Davide Bonadonna

These finds came from the fossil graveyards of the mid-western USA. Both dinosaurs belonged to a group known as sauropods, renowned for their enormous body sizes, long sweeping necks and whiplashed tails. Unfortunately, the rivalries between Marsh and Cope escalated to the point that the naming, description and announcement of new dinosaur species were often rushed as the scientists sought to outdo each other to gain academic prestige.

In 1903, the scientific community decided that the naming of Brontosaurus had been too hasty, and that it was not distinct enough to stand on its own. Specimens belonging to Brontosaurus were instead classified as a species of Apatosaurus, and the beloved dinosaur’s name was declared invalid ... and that's been its status ever since.

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Paleontologists Emanuel Tschopp and Octávio Mateus measure a sauropod dinosaur femur. Image FCT-University NOVA of Lisbon / M. Ladeira

But now, the thunder lizard rises again! A new study claims to have resurrected Brontosaurus as a valid scientific genus and species. Published in the journal PeerJ, the new research was led by Emanuel Tschopp, a palaeontologist at the New University of Lisbon in Portugal. 

One of the reasons for the uncertainty surrounding the scientific naming of dinosaurs (and other animal groups, too) is that there aren’t any strictly set boundaries for defining one species apart from another. While scientists are as objective as possible in identifying and naming new species, that means there's always a hint of bias involved.

Tschopp and his team were astoundingly thorough in their research, however. In their effort to resurrect Brontosaurus, they provide nearly 300 pages of anatomical evidence investigating the evolutionary relationships between a group of sauropods known as diplodocids, which includes Apatosaurus and other well-known dinosaurs. And the researchers didn't just examine one specimen per species – they looked at all currently known diplodocid specimens, allowing them to consider variations not just between different species, but within the same species as well.

“Our research would not have been possible at this level of detail 15 or more years ago,” explains Tschopp. “In fact, until very recently, the claim that Brontosaurus was the same as Apatosaurus was completely reasonable, based on the knowledge we had.”

While the new findings might ruffle a few feathers in the scientific community, they're also a nice nod to how scientific research progresses. Sometimes, even hypotheses that have remained stable for 100 years can be overthrown based on new discoveries and new analytical methods. "It’s the classic example of how science works," notes Professor Mateus, a collaborator on the research. “Especially when hypotheses are based on fragmentary fossils, it is possible for new finds to overthrow years of research.”

Femke Holwerda, a sauropod researcher based in Munich, is delighted by the revival. “When I was younger, I used to correct my friends and family [about Brontosaurus] all the time. It’s going to be funny to say we were wrong. Brontosaurus is valid again, but I can use this to explain to them how palaeontology works as a science,” he says.

So Brontosaurus is back, and with that comes a whole new set of questions for palaeontologists to ask about the evolution of the greatest animals that ever walked the earth.