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Fossils Show Anacondas Reached Modern Size 12.4 Million Years Ago and Stayed Giant

Researchers say semi‑aquatic living with broad diets likely buffered the species through past climate shifts.

Overview

  • A Cambridge-led team analyzed 183 fossilized vertebrae from at least 32 snakes found in Falcón State, Venezuela, and dated the size plateau to roughly 12.4 million years ago.
  • Ancient anacondas measured about 4–5 meters (13–16.5 feet), effectively matching modern Eunectes, with rare individuals reaching up to 7 meters.
  • Body-length estimates from vertebrae were validated using ancestral state reconstruction on a snake family tree, strengthening confidence in the results.
  • The findings contrast with other Miocene megafauna such as Purussaurus and Stupendemys, which shrank or vanished as climates cooled and habitats contracted.
  • Authors propose that stable access to wetlands and diverse prey helped sustain anacondas’ large bodies over time, though they caution that deforestation and climate change now threaten those conditions.