Planet Earth


An artist’s rendering of a cow-size guinea pig that lived in South American swamps 8 million years ago. It was 10 times the size of the largest rodent alive today. | Carin Cain/Science


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Prehistoric Guinea Pig Weighed Nearly a Ton

Like its modern guinea pig cousins, Phoberomys pattersoni loved to nibble on grass. The toothy rodent was anything but cuddly, however. Last September, zoologist Marcelo Sánchez-Villagra of the University of Tübingen in Germany unveiled the “exceptionally complete skeleton” of an 8-million-year-old swampland forager that was by far the largest rodent ever known: roughly nine feet long and more than 1,500 pounds. Even with a sturdy tail to help balance its formidable weight, Phoberomys had heavy hind legs and was clearly not much of a scamperer. That ungainliness may have contributed to its demise. The predators that were unearthed in the same fossil burial ground, 240 miles west of Caracas, Venezuela, include 30-foot-long crocodiles, marsupial cats as big as lions, and monstrous flesh-eating birds called phorusrhacoids.

Charles Hirshberg

Regal Kin of T. rex Turns Up in India

The skeleton had moldered in a closet for nearly two decades. In August paleontologists Paul Sereno of the University of Chicago and Jeffrey Wilson of the University of Michigan announced they had unearthed a brand-new species of dinosaur from a jumbled collection of fossils stored in Jaipur, India. After sorting through hundreds of bones excavated by paleontologists Suresh Srivastava and Ashok Sahni during a 1983 expedition in the Narmada River valley in western India, Sereno and Wilson realized they were looking at the braincase, parts of a hip, a vertebra, and a tailbone of a distant cousin of Tyrannosaurus rex. They named the new species Rajasaurus narmadensis, which means a “regal dinosaur from the Narmada.”

The approximately 4-ton, 30-foot-long predator lived 67 million years ago during the end of the Cretaceous Period, an epoch marked by intense volcanic activity and the extinction of the dinosaurs. Its bones resemble parts of dinosaurs found in Madagascar, Africa, and South America. So what made these bones stand out as a new species? “The roof of the skull has a raised lip, an indication of a horn. We’re not sure of the exact shape of it, though it was probably a low, blunt horn,” says Wilson. “There is nothing else in the world like this.”

Michael W. Robbins

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