How Many Dinosaur Species Roamed Earth? It’s Surprisingly Hard to Know

Such taxonomic debates tend to hit the headlines most often where dinosaurs are involved. In the past two years, multiple studies have sought to clarify whether the animal known as Tyrannosaurus rex in fact represented a single species. Other research is weighing whether to split well-known taxa such as Velociraptor into multiple ones.

This isn’t just some esoteric academic debate. Some paleontologists argue that our estimates of prehistoric biodiversity are so far off base that they risk skewing our understanding of how life on Earth is faring today.

“The actual numbers of species lost in previous environmental catastrophes are probably always worse than we currently record because we’re probably lumping more than one species under one name.