Krabi Giant Rat Fossil: 30kg Rodent Found in Coal Basin

A Krabi giant rat fossil has been identified as a new species of rodent that weighed about 30 kilogrammes and lived 33 to 35 million years ago. Thailand's Ministry of Natural Resources and Environment announced the find on Wednesday, November 4, saying it is the largest rodent known from the Paleogene period, the Bangkok Post and Thai PBS World reported.

Sirindhorn's Giant Rat

The animal has been named Yakamys sirindhornae, or "Sirindhorn's Giant Rat". Minister Suchart Chomklin said the name was granted with royal permission to honour Her Royal Highness Princess Maha Chakri Sirindhorn for her long support of science, geology and paleontology in Thailand. According to Thai PBS World, it is the fifth fossil to carry her name.

The remains were found in sediment layers of the Bang Mak coal basin in Krabi province, Phuket's neighbour across Phang Nga Bay. The research was published this week in the international journal Scientific Reports.

What the scientists found

The team studied fossil molars and incisors from the Bang Mak coal mine. Their analysis places the animal in the late Eocene epoch. Key points from the ministry's announcement:

Age: roughly 33 to 35 million years old.
Size: an estimated 30kg, the biggest rodent yet known from the Paleogene.
Why it matters: it suggests rodents grew to large body sizes 15 to 20 million years earlier than scientists had believed.
Where it is kept: the specimens are held by the Department of Mineral Resources.

"This discovery is significant for the study of mammalian evolution and offers new insights into the historical changes in body size among rodents," Mr Suchart said, as quoted by the Bangkok Post.

A Thai-led international team

The study was a joint project between Thailand's Department of Mineral Resources and researchers from France and Canada. It was led by Dr Yaowalak Chaimanee, a specialist in fossil mammals at the French National Centre for Scientific Research (CNRS).

The minister said the find shows what Thai researchers can achieve with international partners. He added that it highlights Krabi's fossil sites as natural heritage of world-class scientific value, and said the ministry would keep supporting geological research, conservation and public education about Thailand's geo-heritage.

Krabi's growing fossil record

Krabi is best known to visitors for its limestone cliffs, islands and beaches, but the province also has a rich fossil history. The best-known public site is the Shell Cemetery (Su San Hoi), where layers of ancient fossil shells form slabs along the shore. The new discovery adds a very different chapter: a land mammal far larger than any rodent living in Thailand today.

Thailand has produced several important fossil finds in recent years. Read about the country's first pterosaur fossil and the dinosaur fossil tracks you can visit in Thailand. If you are planning a day trip from Phuket, see our Krabi travel guide.

Photo: the Shell Cemetery fossil site in Krabi, by Stefan Fussan / Wikimedia Commons, CC BY-SA 4.0. File photo; not the site of the new find.