This tiny dinosaur is officially T. rex’s cousin | Science News for Students

This tiny dinosaur is officially T. rex’s cousin

Decades after it was discovered, this 92-million-year-old tyrannosaur finally has a family
Jun 11, 2019 — 6:45 am EST
an illustration of Suskityrannus hazelae

At about 1 meter (39 inches) tall at the hip, the newly identified Suskityrannus hazelae (illustrated) suggests tyrannosaurs gained fearsome traits before they got really big.

Andrey Atuchin

A tiny tyrannosaur has finally found its place in the dinosaur family tree. Named Suskityrannus hazelae (Sus-kit-eye-RAN-us Hay-ze-lay), its bones are helping scientists chart the rise of giant dinos. Among those giants: Tyrannosaurus rex.

Sterling Nesbitt was part of a team of paleontologists who dug up this species in New Mexico. That was more than 20 years ago. The two partial skeletons they found looked a lot like those of towering tyrannosaurs. One skeleton was even found with what looked like a partly eaten lizard skull.

But S. hazelae is several million years older than the first titanic tyrannosaurs. It is also much smaller — only about a meter (3 feet) tall at the hip. The scientists wondered whether the species truly was a tyrannosaur. Perhaps it instead was some relative of small meat-eating dinos known as velociraptors.

“There was enough of a skeleton to be super intriguing, but not enough to nail it down,” recalls Nesbitt, who works at Virginia Tech in Blacksburg. Fossils of other meat-eaters around this dinosaur’s size would have helped ID it. But back then, those were hard to come by, he explains.

The tyrannosaur family tree has since filled out thanks to recent discoveries of small species in Asia and North America. That allowed Nesbitt and his colleagues to pin down S. hazelae as one of T. rex’s kin. The team reported its findings online May 6 in Nature Ecology and Evolution.

Like the king of the dinosaurs, S. hazelae’s skull was built for a strong bite. And three of its foot bones were pinched together. This bone bundle is thought to strengthen the ankle. That would have given this dino powerful hind feet for running and holding down prey, says Robert Denton. He is a geologist at Terracon, an engineering firm in Ashburn, Va.

These features were probably crucial for the supersize tyrannosaurs. With tiny front arms, the beasts depended “on their hind feet and their enormous tooth-filled jaws,” Denton says. Spotting these in S. hazelae suggests that tyrannosaurs gained the traits while still on the small side.

Power Words

(more about Power Words)

colleague     Someone who works with another; a co-worker or team member.

dinosaur     A term that means terrible lizard. These ancient reptiles lived from about 250 million years ago to roughly 65 million years ago. All descended from egg-laying reptiles known as archosaurs.

ecology      A branch of biology that deals with the relations of organisms to one another and to their physical surroundings. A scientist who works in this field is called an ecologist.

engineering     The field of research that uses math and science to solve practical problems.

evolution     (v. to evolve) A process by which species undergo changes over time, usually through genetic variation and natural selection. These changes usually result in a new type of organism better suited for its environment than the earlier type. The newer type is not necessarily more “advanced,” just better adapted to the particular conditions in which it developed. 

family     A taxonomic group consisting of at least one genus of organisms.

fossil     Any preserved remains or traces of ancient life. There are many different types of fossils: The bones and other body parts of dinosaurs are called “body fossils.” Things like footprints are called “trace fossils.” Even specimens of dinosaur poop are fossils. The process of forming fossils is called fossilization.

kin     Family or relatives (sometimes even distant ones).

lizard     A type of reptile that typically walks on four legs, has a scaly body and a long tapering tail. Unlike most reptiles, lizards also typically have movable eyelids. Examples of lizards include the tuatara, chameleons, Komodo dragon, and Gila monster.

paleontologist     A scientist who specializes in studying fossils, the remains of ancient organisms.

prey     (n.) Animal species eaten by others. (v.) To attack and eat another species.

skull     The skeleton of a person’s or animal’s head.

species     A group of similar organisms capable of producing offspring that can survive and reproduce.

trait     A characteristic feature of something. (in genetics) A quality or characteristic that can be inherited.

tyrannosaur     A line of meat-eating dinosaurs that began during the late Jurassic Period, about 150 million years ago. These species persisted into the late Cretaceous Period, about 65 million years ago. The best known member of these species: the late Cretaceous’ Tyrannosaurus rex, a 12-meter (40 foot) long top predator of its time.

Tyrannosaurus rex     A top-predator dinosaur that roamed Earth during the late Cretaceous period. Adults could be 12 meters (40 feet) long.

Velociraptor     A genus of predatory bird-like dinosaurs with a relatively large brain and a long, sharp claw on each foot. Its fossils were first discovered in the 1920s in what is now Mongolia. The roughly meter-tall animal moved on two feet and slashed at prey with one of its sharp talons. It would not have been as daunting as its namesake portrayed in the Jurassic Park movie franchise. Many scientists believe that movie version was actually Deinonychus, a dinosaur twice its size and known from fossils unearthed in the United States during the 1960s.


Journal:​ ​​ S.J. Nesbitt et al. A mid-Cretaceous tyrannosauroid and the origin of North American end-Cretaceous dinosaur assemblages. Nature Ecology and Evolution. Vol. 3, May 6, 2019, p. 892. doi: 10.1038/s41559-019-0888-0.