Rodents are troublesome creatures. They can damage property, spread disease, and just look creepy in general, which is why so many people hate them.

This class of animals comes in many shapes and sizes, ranging from mice and rats up to the more beefy capybara, but even the largest rodents today are fairly small when compared with humans.

If you start looking at the fossil records, however, you’ll quickly see that there were some rodents that were bigger. A lot bigger.

The largest rodent ever to walk the Earth is called the Josephoartigasia monesi. It was first described in 2008, but the fossilized skull of the animal was discovered in 1987. It was dug up in Uruguay and donated to the National History and Anthropology Museum.

The museum didn’t know what it had, so it just sat there for 20 years before a curator took an interest in it and got some experts to investigate further.

They found that the fossil was between 2 and 4 million years old based on the geological formation in which it was found. Analysis says that it would have looked something like a modern pacarana (Dinomys branickii), which is a rodent found in South America.

Of course, this one would have been a lot bigger.

Originally, experts said that it likely weighed anywhere from 468 kilograms (1032 pounds) to 2586 kilograms (5661 pounds), which means the bigger ones could have been bigger than rhinos.

A more recent study says that these numbers are likely too big and says that the animal was more than likely around 480 kilograms (1058 pounds). In the study, Russell K Engelman explained why these more modest numbers are likely more accurate:

“High estimates in previous studies appear to be due to the unrecognized, nonlinear relationship between certain skeletal measurements (skull size) and body mass.”

And to be fair, a 1000-pound rodent is still by far the heaviest ever known. Capybaras, which are the largest still living, only weigh up to 91 kilograms (201 pounds).

In addition to being very large, this rodent also likely had a very powerful bite. In simulations, it was estimated that at its most powerful point, the rodent would have been able to generate 4165 Newtons of pressure, which is more than enough to break a human femur.

So, while it would be interesting to be able to study this massive animal up close, it is likely best that it has long since gone extinct.

If you enjoyed this story, you might enjoy this post about 4 ancient animals that are older than trees.