Earth’s Largest Rodents Were Smaller Than We Once Thought

Stocky capybaras weigh 175 pounds and are less than an ounce in weight. Some prehistoric rodents looked like a cross between a capybara and a hairy Hippopotamus, but the largest capybara is a Pipqueak. Paleontologists think Phoberomys pattersoni could have weighed as much as 1,300 pounds. Josephoartigasia monesi was thought to be as large as a bison.

The size predictions have caused debate. "People have said they're the size of bison, but no one had any methods that could confidently nail down these sizes."

A new method was proposed for accurately describing the dimensions of these rodents. The study was published in the journal Royal Society Open Science.

The wetlands of South America were inhabited by giant rodents between two million and eight million years ago. The Josephoartigasia skull was discovered in 2008 and it was found to have a powerful bite that was three times as strong as a tiger bite.

Our understanding of the rodents is dependent on their size. A zoologist who studies the body sizes of rodents and was not involved in the new study says body size is a key trait in mammals. The size of Phoberomys was estimated by using fossils.

Accurately estimating the size of these rodents has been a challenge. There isn't a lot of fossils. Paleontologists have found leg bones and other parts of Phoberomys's skeleton, but Josephoartigasia is only known from a single skull. Fossil evidence is often not enough for researchers to rely on the anatomies of extinct animals. Josephoartigasia's skull is not found in living rodents. Increasing the size of a capybara can lead to distorted sizes like those seen in a carnival mirror.

The occipital condyle is a joint that connects the skull with the spine. It's a bellwether for comparing different species because the skull and spine stay securely attached if the joint is small. When you look at body size, you want to make sure the parts that have changed the least are the ones that have stayed the same.

The width of the joint was measured in more than 400 species of mammals. The occipital condyle width was an accurate predictor. He was able to compare the size of the prehistoric rodents' joints with those of other large mammals because they were the same width.

Mr. Engelman said that he couldn't make the people bigger than they were. Unreasonable assumptions couldn't get them that large.

Mr. Engelman thinks that the decrease in brawn may boost the brains of the rodents. He said that they may not have the small brains people think they have.

These figures are more realistic than previous estimates of these rodents. He thinks more fossil evidence is needed before it is certain how large rodents grow. We will have significant uncertainties until we have more than a skull.

It's still a really big rat despite the new findings being less eye-catching than before.