Paleontologists have long believed that dinosaurs evolved from their early ancestors into the creatures we’re familiar with over the course of at least 10 million years. Now, a recent study suggests that this process may have occurred much faster than we thoughtwithin a period of less than 5 million years.

The paper, published in the Proceedings of the National Academy of Sciences, illustrates how Randall Irmis of the Natural History Museum of Utah and his colleagues used radioactive dating to analyze the rocks found around some of the earliest fossils of these ancient relatives to the dinosaur. The dating put the sediments somewhere between 234 million and 236 million years old, which would make the fossils the same age. 

The main differences between the dinosaurs and their predecessors were the dinosaurs' ball-and-socket hip joints and extra vertebrae at the end of their spines, which helped to strengthen their hips. Their early ancestors, which are part of the broad dinosauromorph group along with dinosaurs, have been dated by scientists before using a technique called biostratigraphy. The method employed in this most recent study is much more accurate, which is why the early dinosauromorphs have been found to live 5 to 10 million years earlier than paleontologists previously believed. These new findings suggest that the evolution of dinosaurs spanned a much shorter timeline.

According to the researchers, although the dinosaurs's emergence was rapid, their eventual domination over paleo-Earth progressed at a much slower pace. "You don't seem to see dinosaurs showing up and immediately taking over," Irmis told LiveScience. "It really emphasizes that there wasn't much special about the first dinosaurs. They were pretty similar to their early dinosauromorph relatives and probably doing very similar things." If that was indeed the case, a new question for scientists to explore would be what exactly caused the early dinosauromorphs to die out while dinosaurs grew stronger.