Be startled, be very startled.
Have you ever seen a large rat and thought it was disgustingly large? Well it could be worse. take a look at the skull of this rodent:
Josephoartigasia monesi is an extinct species which is believed to be the largest rodent that ever lived. It's total body length is around 3 m long, with a skull of 53 cm long and a 30 cm incisor tooth. It's maximum weight estimate is highly variable, ranging from 350 kg to 2.5 tonne but is difficult to determine because the skeleton is mostly incomplete. It is known from only a single reasonably well preserved skull, although most of the teeth are missing.
Josephoartigasia monesi used to live in South America. It is believed to have gone extinct some time after North and South America were rejoined around 2 million years ago.There were several large rodents in South America which thrived in recent geological history.
Josephoartigasia monesi is actually more closely related to guinea pigs than rats. If you have ever seen the south park Pandemic episodes this is especially funny. It's closest relative, and the only surviving member of the family Dinomyidae, is the South American Pacarana.
Species: Josephoartigasia monesi