Scientists have just stumbled upon something huge, and it could totally change our understanding of the evolution of dinosaurs. Researchers have identified a massive crocodile known as Teleocrater rhadinus that was seven to 10 feet long and walked on all fours as potentially one of the earliest known dinosaur relatives, and it’s completely different than what kind of species they thought gave rise to dinosaurs 245 million years ago.

The findings, which were published in the journal Nature recently, could completely  upend scientists’ understanding of the origins of dinosaurs, and also of many other reptiles. Dinosaurs are a member of a larger group called archosaurs, which are split into a bird-line branch of reptiles that includes both dinosaurs and birds. The crocodilian branch was always thought to be separate, giving rise to crocodiles and alligators, according to a National Science Foundation statement.

Scientists have struggled to figure out what early bird-line reptiles look like after splitting with crocodilians because there are big gaps in the fossil record about 230 million years ago. This new discovery could blow the lid off that mystery.

“The discovery of such an important new species is a once-in-a-lifetime experience,” said Sterling Nesbitt, a paleobiologist at Virginia Tech and lead author of the Nature paper.

“It’s so exciting to solve puzzles like Teleocrater, where we can finally tease apart tricky mixed assemblages of fossils and shed light on broader anatomical and biogeographic trends in an iconic group of animals,” said Michelle Stocker, a paleobiologist at Virginia Tech and co-author of the paper.