"It's about ten times the size of the largest living rodent"

'Guinea-zilla' or to give it its scientific name Phoberomys pattersoni is a distant relative of the humble guinea pig (Cavia porcella). Weighing around one ton (or 700 kilograms), around ten feet (three metres) long and four feet tall with a long tail for balancing on its hind legs and six-inch long teeth, it represented the biggest rat the world has ever seen.

Fortunately there is no need to build a bigger mousetrap or worry about the state of your wainscotting as 'Guinea-zilla' was last seen alive some eight million years ago, and its existence has only recently come to light after the discovery of its fossilized remains.

"Urumaco was a place of giants eight million years ago"

The first ninety percent complete fossil was actually discovered in the May of 2000 in some brown shale and coal beds near the town of Urumaco, 250 miles west of Caracas in Venezuela. But the research team held back from publishing their results until they had found a second specimen with more extensive skull features so that they could establish a formal classification. It was christened Phoberomys pattersoni, after a palaeontologist by the name of Brian Patterson who worked in the Urumaco region in the 1970s.

Although now semi-desert, eight million years ago the Paleo-Oronoco-Amazon river system ran through Urumaco, draining water from the South American continent into the Caribbean Sea. At the end of the Miocene Epoch it was therefore a lush semi-tropical area capable of sustaining a wide variety of life. The area is of great interest to paleantologists since South America had, at the time been isolated for tens of millions of years, (since it wasn't joined to the rest of the Americas until around three million years ago) and therefore a source of a number of weird and wonderful creatures.

Not only was it inhabited by giant guinea pigs, but giant crocodiles, the world's largest ever turtles, ten foot long fish as well and lion-sized marsupial cats. The 'Guinea-zilla' was probably semi-aquatic and dined on sea grasses and other vegetation that grew around the lagoons and bays that comprised its natural habitat.

It is suggested that 'Guinea-zilla' ran around in huge packs in order to afford some protection from the aforementioned crocodiles and cats not mention carnivorous birds. Given its size, it would not have been able to carry out the standard rodent threat avoidance routine of scurrying down the nearest burrow and hiding and it would have been too big and slow to run away. (Mind you with six inch long incisors, it may have been able to deliver a nasty nip.)

No one knows what happened to 'Guinea-zilla', or why indeed there are no giant rodents wandering about the world today; perhaps something bigger and faster came along and ate them.

Second in an occasional series on giant sized creatures.


Quotations by Marcelo Sanchez-Villagra from the sources listed below.

Jonathan Amos 'Giant rodent astonishes science
BBC News Online

Carin L. Cain 'A Guinea Pig the Size of a Horse'
National Public Radio online

American Association for the Advancement of Sciencesemi-aquatic Press Release

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