New Tiny Tyrannosaur Species Fills Gap in T. rex Origin Story

The newly-discovered, small tyrannosaur, Suskityrannus hazelae, circles a pair of Zuniceratops, a small and ancient relative of Triceratops. (Credit: Andrey Atuchin) In 1902, famed fossil hunter Barnum Brown was prospecting in Montana when he discovered the first documented remains of a Tyrannosaurus rex. The creature was nearly 40 feet long with banana-sized teeth, warranting its name, “king of the tyrant lizards.” Finds since then have only reinforced T. rex’s status as one of the planet’s most ferocious predators ever. We now know that — in a world of large plant-eaters — these hunters didn’t just rely on their enormous size, they had keen senses and were surprisingly smart. But a new mystery has recently emerged. Tyrannosaurs – the family that includes T. rex and dozens of its ancestors and relatives — lived on Earth for roughly 100 million years. And for most of that time, they were relatively tiny carnivores in a world dominated by much larger meat-eaters. The oldest known species, Proceratosaurus, was shorter than a human. So, how did these featherweights rise to become kings? Answering that question has been a major challenge for paleontology thanks to a troublesome gap in the fossil record created when sea levels rose during the Late Cretaceous period (80 million to 66 million years ago) and destroyed many fossils from the preceding era. This gap left scientists with a handful of tiny, ancient tyrannosaur fossils from early on, and a large number of super-sized tyrannosaur fossils from the dinosaurs’ final years. But in between was a question mark. Now scientists are making significant strides toward filling that gap thanks to two new tyrannosaurs from the American Southwest that lived more than 90 million years ago. The details of a small tyrannosaur from this era, discovered in Utah, were published earlier this year. A second find, this one from New Mexico, was published Monday in the journal Nature Evolution & Ecology.