T. rex look-alike unearthed in Patagonia

Though not a close relative, Gualicho shared those puny arms


JUST LIKE REX A newly discovered dinosaur species had a T. rex’s stubby arms, and probably relied on a huge head with a mouthful of teeth for hunting. 

©Jorge Gonzalez

What had two puny arms, lived 90 million years ago and probably chowed down on other dinosaurs? (Hint: It’s not T. rex.)

A new dinosaur discovered in what is now Patagonia had the runty forelimbs of a Tyrannosaurus rex but is no cousin of the giant iconic predator, researchers report July 13 in PLOS ONE.

The new species, Gualicho shinyae, has a close relative in Africa, an analysis of fossils suggests. T. rex’s ancestors, on the other hand, came from Asia.

Gualicho is a “smaller, slimmer, trimmer version of a T. rex,” says study coauthor Peter Makovicky, a paleontologist at the Field Museum in Chicago. It probably weighed about a ton and was longer than a pickup truck.

The runty two-fingered arms of Gualicho shinyae, a new dinosaur found in Argentina, look just like those of a T. rex. Pablo Lara

In 2007, Makovicky’s team discovered Gualicho’s partial skeleton — including those impractical arms. The dinosaur probably caught prey with its huge head, Makovicky says. Though the researchers haven’t dug up a skull yet, tiny arms seem to be a trade-off for a big head. Finding Gualicho’s skull would help nail down that idea, he adds.

Gualicho may have fed on grazers called ornithopods, such as duck-billed dinosaurs. Or perhaps it fed on the long-necked, long-tailed sauropods, which were common in the region. But only the youngsters. Sauropod adults were gigantic, Makovicky says, definitely not prey for a (relatively) little guy like Gualicho.

Meghan Rosen is a staff writer who reports on the life sciences for Science News. She earned a Ph.D. in biochemistry and molecular biology with an emphasis in biotechnology from the University of California, Davis, and later graduated from the science communication program at UC Santa Cruz.

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