Meet the tiny cousin of the Tyrannosaurus rex

Friday, 10 May, 2019

Meet the tiny cousin of the <em>Tyrannosaurus rex</em>

A new relative of the Tyrannosaurus rex — much smaller than the huge, ferocious dinosaur made famous in countless books and films — has been discovered and named by a palaeontologist from Virginia Polytechnic Institute and State University (Virginia Tech).

The newly named tyrannosauroid dinosaur — Suskityrannus hazelae — stood less than a metre tall at the hip and was about 2.7 metres in length, making the entire animal only marginally longer than the skull of a fully grown Tyrannosaurus rex. It is believed to have weighed between 20 and 40 kg, while the typical weight for a full-grown Tyrannosaurus rex was at least 8 tonnes.

Remains of the dinosaur were discovered by Sterling Nesbitt, now an assistant professor in the Virginia Tech College of Science, when he was a 16-year-old high school student participating in a dig expedition in New Mexico back in 1998. The milestone came one year after a partial skull of the dinosaur was found by geologist Robert Denton and others in the Zuni Basin of western New Mexico during an expedition organised by Zuni Paleontological Project Leader Doug Wolfe.

Nesbitt holds the partial skull of the tyrannosauroid Suskityrannus hazelae over the cast of a full-sized partial lower jaw of a Tyrannosaurus rex.

Nesbitt’s high school expedition, also led by Wolfe, saw the discovery of a more complete specimen at the New Mexico site, dating 92 million years to the Cretaceous period — a time when some of the largest dinosaurs ever found lived. The dinosaur was at least three years old at death, based on an analysis of its growth from its bones — yet for much of the 20 years since the fossils were uncovered, the science team did not know what they had.

“Essentially, we didn’t know we had a cousin of Tyrannosaurus rex for many years,” said Nesbitt. The team at first thought they had the remains of a dromaeosaur, such as Velociraptor, as close relatives Tyrannosaurus rex were simply were not known or not recognised during the late 1990s. More distant cousins of the species have been discovered since, which led Nesbitt and his team to re-examine the fossils. The results of their research have now been published in the journal Nature Ecology & Evolution.

The name Suskityrannus hazelae was derived from ‘Suski’, the Zuni Native American tribe word for ‘coyote’, from the Latin word ‘tyrannus’, meaning ‘king’, and ‘hazelae’ for Hazel Wolfe, whose support made possible many successful fossil expeditions in the Zuni Basin. Its diet likely consisted of the same as its larger meat-eating counterpart, with Suskityrannus hazelae likely hunting small animals — although exactly what it hunted is unknown.

An artist’s rendering of how Suskityrannus hazelae may have looked. Artwork by Andrey Atuchin.

Suskityrannus gives us a glimpse into the evolution of tyrannosaurs just before they take over the planet,” Nesbitt said. “It also belongs to a dinosaurian fauna that just precedes the iconic dinosaurian faunas in the latest Cretaceous that include some of the most famous dinosaurs, such as the Triceratops, predators like Tyrannosaurus rex and duckbill dinosaurs like Edmotosaurus.

Suskityrannus has a much more slender skull and foot than its later and larger cousins, the Tyrannosaurus rex. The find also links the older and smaller tyrannosauroids from North America and China with the much larger tyrannosauroids that lasted until the final extinction of non-avian dinosaurs.”

Top image caption: Nesbitt and fossil remains of Suskityrannus hazelae, which he found at age 16 in 1998.

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