Tyrannosaurus rex may actually be three separate species

T. rex may have had lips like a modern lizard's

The Ultimate Guide To Tyrannosaurs

New controversial study says the T. rex was actually three species

Controversial idea that T. rex was three species comes under fire

They Want to Break T. Rex Into 3 Species. Paleontologists Aren't Pleased. - The New York Times

T rex's keyhole eye sockets helped its bite, research suggests, Dinosaurs

10 Facts About Tyrannosaurus Rex, King of the Dinosaurs

Was the “Nanotyrannus” real? Or just a young T. rex? Does it matter?

Specimens of Tyrannosaurus - Wikipedia

Tyrannosaurus rex may have been three different species