Fossilized teeth from a mine in southern Thailand reveal a newly identified giant rodent, Yakamys sirindhornae, estimated to have weighed about 66 pounds.
Scientists have identified fossils of a giant rodent that lived in Thailand approximately 34 million years ago, during the middle of the Paleogene period. The newly named species, Yakamys sirindhornae, may have weighed around 66 pounds, roughly twice as much as other known rodents of its time.
The remains consist of a lower second molar and a lower incisor recovered from the Bang Mark Pit at the Krabi lignite mine in Thailand's Krabi Province. The fossils were identified through an international collaboration involving scientists from McGill University, Thailand's Department of Mineral Resources, and French research organizations including CNRS and Université de Poitiers.
The genus name Yakamys combines "yak," the Thai word for giant, with "mys," the Greek word for mouse or rat. The species name, sirindhornae, honors Princess Maha Chakri Sirindhorn, in recognition of her longstanding support for science and paleontological research in Thailand.
The research team applied seven established methods that use tooth measurements to calculate body mass. Their results suggest that Yakamys sirindhornae weighed approximately 30 kilograms, making it about twice as heavy as other known rodents from the same period, including Hulgana.
The researchers emphasize that determining an extinct animal's weight from a small number of fossilized teeth involves considerable uncertainty. "This is only a ballpark figure, as there is substantial uncertainty associated with fossil body-mass estimation," said Virginie Millien, a biology professor at McGill University and co-author of the study.
The discovery suggests that Southeast Asia played an important role in the early evolutionary history of large-bodied rodents. "Today, the largest living rodent is the capybara, but very large rodents are not restricted to recent ecosystems," Millien said. "Giant rodents evolved repeatedly during the later history of the group, mostly in South America. This discovery suggests that Southeast Asia also played an important role in the early evolutionary history of large-bodied rodents."
The research was published in Scientific Reports and received support from CNRS, Université de Poitiers, Université de Montpellier, McGill University, and the Department of Mineral Resources of Thailand.
The find expands scientists' understanding of where and when rodent gigantism emerged, showing that unusually large rodents evolved in Southeast Asia much earlier than previously recognized for that region.
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This article was drafted with AI assistance and checked against the sources above. Company claims are reported as claims. Cover image is AI-generated.
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