Yakamys sirindhornae Discovered in Thailand
A giant rodent weighing roughly 30 kilograms, or 66 pounds, roamed what is now southern Thailand between 33 and 35 million years ago, scientists announced after identifying a previously unknown species from two fossilized teeth. CBS News reported that the ancient animal ranks among the largest known rodents from the Paleogene period, offering new insights into how early rodents evolved to enormous sizes.
The findings, published in the journal Scientific Reports, stem from a molar and an incisor unearthed in 2004 at the Bang Mark coal mine in southern Krabi province. Thailand’s Department of Mineral Resources, in collaboration with researchers from France and Canada, analyzed the specimens to classify the prehistoric creature as Yakamys sirindhornae.
Excavation and Identification in the Krabi Basin
Pannipa Tian, a geologist with Thailand’s Department of Mineral Resources, initially discovered the cream-colored incisor in the dark coal deposits during a 2004 expedition. She recounted to AFP that she initially misidentified the fossil because of its unusual size, thinking it was a bone before her supervisor identified it as a giant rat’s tooth. Another expedition member found the dark-colored molar on the same day.
At the time of the discovery, the research team lacked sufficient evidence and advanced technology to formally identify the species. More than two decades later, a team led by fossil mammal specialist Dr. Yaowalak Chaimanee of the French National Centre for Scientific Research applied detailed morphological and size comparisons to classify the remains. Natural Resources and Environment Minister Suchart Chomklin announced the formal identification on November 4, noting that the species belongs to the now-extinct Ischyromyidae family, one of the earliest major groups of rodents.
Researchers name new fossil species after Thai princess
Researchers named the new species in honor of Her Royal Highness Princess Maha Chakri Sirindhorn to recognize her longstanding support for science, geology, and paleontology in Thailand. It marks the fifth fossil species to receive a royally granted name. The Krabi basin has previously yielded fossils of ancient primates, carnivores, and hoofed mammals, highlighting the region’s rich paleontological significance.
While Yakamys sirindhornae was massive for its era, weighing about half as much as a modern South American capybara, it is far from the largest rodent in the fossil record. Previous discoveries include a 1-ton creature in Uruguay in 2008 that lived 4 million years ago, a 1,545-pound “Rat-zilla” found in South America in 2003, and a human-sized rat discovered in the Amazon rainforest in 2020 that lived 10 million years ago, as detailed by CBS News. With only two teeth recovered for the Thai specimen, the animal’s exact appearance, diet, and behavior remain unknown.
Frequently Asked Questions About Yakamys sirindhornae
When and where were the fossils found?
The molar and incisor were discovered in 2004 at the Bang Mark coal mine in the Krabi basin of southern Thailand, and researchers published the formal identification in November in the journal Scientific Reports.
How big was the ancient rodent compared to modern animals?
The animal weighed an estimated 30 kilograms, or 66 pounds, making it about half the weight of a large modern capybara, which holds the title of the world’s largest living rodent.
What family did Yakamys sirindhornae belong to?
Unlike South American capybaras, the prehistoric species belonged to the extinct Ischyromyidae family, which represents one of the earliest major groups of rodents.
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