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Fossil of bull-sized mouse found

London: A rodent the size of a bull? Well, researchers claim to have discovered the remains of a one-tonne beast that thrived in the estuaries and forests of South America four million years ago.

The giant mouse fossil was found in a broken boulder on the coast of Rio de La Plata in Uruguay and studied by Andres Rinderknecht and Ernesto Blanco of Museum of Natural History and Institute of Physics, respectively, in Montevideo. “We report the discovery of an exceptionally well preserved fossil skull of a new species of rodent, by far the largest ever recorded,” the team wrote in the Proceedings of the Royal Society, Biological Sciences journal. “The creature weighed between 1-1.4 tonnes. Its skull is half-a-metre long and reached a length of around three metres, assuming its body was barrel-shaped like that of a capybara. “The incisors of the mega rodent were around four inches and characteristics of its teeth suggest that it dined on aquatic plants, perhaps even fruit,” The Daily Telegraph quoted Dr Blanco as saying.

Rodents are a very successful group of mammals — accounting for four in every 10 species of mammal — but they are usually small, less than 1 kg, with the capybara only reaching 60 kg, a lightweight compared with the new find.

There are various theories to explain why rodents grew so big millions of years ago in South America, according to Dr Blanco. “One possibility is to avoid predation. In South America at the time this rodent was living, there were giant predatory birds [terror birds] and sabre-toothed marsupial carnivores. Rodents are not good at running, and their only effective weapons are their teeth, then big size is a good way to intimidate predators,” he said.

The giant rodent has been named Josephoartigasia monesi after the South American rodent expert Alvaro Mones and is a member of the family that today includes the pakarana (Dinomys branickii), a poorly studied rodent that grows up to approximately 15 kg.

The size of its skull suggests that it is twice as big as Phoberomys, which was reported previously as the largest rodent that ever existed with a weight of 700 kg.

Unearthed in the town of Urumaco, in an arid region of Venezuela 400 km west of Caracas, Phoberomys may have even grazed in herds.

The creature was described by Prof Marcelo Snchez, now at the University of Zurich, Switzerland, as “a weird guinea pig, but huge, with a long tail for balancing on its hind legs and continuously growing teeth”. — PTI

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