One ton rodent with a bite like a tiger’s related to modern-day guinea pig

The largest fossil rodent ever found was an animal that weighed 1,000 kilograms, had huge front tusk-like teeth, and a bite as powerful as that of a tiger’s, researchers from York in England reported. It is believed to be the ancestor of some types of modern-day guinea pigs.

The rodent, called Josephoartigasia monesi (family: Dinomyidae; Rodentia: Hystricognathi: Caviomorpha), probably used its front teeth in the same way a modern elephant uses its tusks, scientists from The Hull York Medical School (HYMS) and the University of York wrote in the Journal of Anatomy.

Josephoartigasia monesi is dedicated to the Uruguayan palaeontologist Álvaro Mones for his studies on South American rodents.

The buffalo-sized creature, with a bite force of about 1,400 N (newtons), would rival the forces of today’s tigers or lions, while its incisors would have been able to withstand nearly three times that force.

Compared to what exists today, J. monesi was a super-giant. In general, modern rodents have body masses smaller than 1 kilogram. The largest rodent today, the carpincho or capybara (Hydrochoerus hydrochaeris), which lives in South America, has a body mass of about 60 kilograms.

Dr. Philip Cox, who works at the Centre for Anatomical and Human Sciences, a joint research centre of the University of York and HYMS, used computer modeling to calculate the rodent’s bite.


Dr. Andres Rinderknecht, of The Museo Nacional de Historia Natural, and Dr Ernesto Blanco, of Facultad de Ciencias, Instituto de Fisica, both in Montevideo, Uruguay, who first described the fossil in 2008, also estimated the animal’s bite force.

Dr Cox said:

“We concluded that Josephoartigasia must have used its incisors for activities other than biting, such as digging in the ground for food, or defending itself from predators. This is very similar to how a modern day elephant uses its tusks.

The study involved CT scanning the Josephoartigasia monesi specimen and performing a virtual reconstruction of its skull. It was then subjected to an engineering technique, known as finite element analysis, that predicts stress and strain in a complex geometric object.