Scientists have discovered new evidence of a previously unknown species of giant that once roamed southern Thailand.
The discovery, revealed from the discovery of a pair of ancient fossil teeth, has now helped identify an unknown species of colossal rodent, which once weighed close to 30 kilograms.
Likened to a “giant rat” by paleontologists, this ancient mammal now represents one of the largest creatures of its kind from the Paleogene period, providing insights—and raising new questions—over how the ancestors of modern rodents grew to such sizes.
The discovery was revealed after the retrieval of a curious pair of fossil teeth—a molar and an incisor—unearthed in a coal mine in Thailand’s southern Krabi province more than two decades ago.
“At first, I thought it was a bone,” said Pannipa Tian, a geologist with Thailand’s Department of Mineral Resources and one of the discoverers of the fossils.
“I showed it to my supervisor, who told me it was a giant rat’s tooth,” she added in a recent statement to AFP.
Later the same day, a molar was uncovered along with the incisor found by Tian. The location had previously been the discovery site of ancient fossils belonging to other mammal species, including ancient primates.
After more than twenty years, the fossils Tian uncovered were finally identified as belonging to a rodent, and one comparable in size to the world’s largest living variety today: South America’s capybara.
While similar in size to some of today’s largest capybaras, this ancient fossil rodent hails from an entirely different family of rodents known as Ischyromyidae.
Much remains to be determined about the ancient species, including how it looked and what it ate, although the two fossils may offer some clues about the creature’s diet and other behaviors.
Following the discovery, the new species was given the formal name Yakamys sirindhornae, a name given in tribute to the country’s Princess Sirindhorn, a notable advocate for paleontological research.
The discovery was detailed in the recent study, “A giant Eocene ischyromyid from Southeast Asia reveals the early evolution of rodent gigantism,” which appeared in Scientific Reports.
Micah Hanks is the Editor-in-Chief and Co-Founder of The Debrief. A longtime reporter on science, defense, and technology with a focus on space and astronomy, he can be reached at micah@thedebrief.org. Follow him on X @MicahHanks, and at micahhanks.com.