HomeScienceAnacondas became massive 12 million years ago and their size never changed

Anacondas became massive 12 million years ago and their size never changed

Scientists from Cambridge led the detailed fossil work. They measured 183 fossil vertebrae from old anacondas in Venezuela. These bones came from at least 32 different anaconda individuals.

December 10, 2025 / 12:58 IST
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Anacondas Became Massive 12 Million Years Ago and Their Size Never Changed (Representational Image: Canva)
Anacondas Became Massive 12 Million Years Ago and Their Size Never Changed (Representational Image: Canva)

A quiet river at dusk can feel ancient. It carries hints of creatures that lived long before us. A new study now shows one such survivor, the anaconda, has stayed giant for millions of years.

Why Have Anacondas Stayed So Large?
Anacondas have kept massive sizes for ages, researchers say. The new findings appear in the Journal of Vertebrate Paleontology on 1 Dec. The study shows ancient anacondas lived during warm Miocene wetlands. They grew large in lush habitats across ancient South America. Researchers say these huge snakes lived around 12.4 million years ago. Fossils suggest their size hardly changed across long periods.

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Scientists from Cambridge led the detailed fossil work. They measured 183 fossil vertebrae from old anacondas in Venezuela. These bones came from at least 32 different anaconda individuals. The team used ancestral state tools to check old body sizes. They compared ancient traits with close modern snake relatives. Their model placed early anacondas at around 17 feet long. This length appears close to modern anaconda sizes today.

Did Ancient Anacondas Grow Bigger Than Today?
The team hoped to find even bigger ancient snakes. Warm Miocene climates made many animals very large. Giant crocodiles and huge turtles lived widely during that time. Many of these species later vanished as the world cooled. Study co-author Andrés Alfonso-Rojas said these giants died out as wetlands shrank. But anacondas stayed large despite these massive habitat shifts. He called them “super-resilient” in a released statement.