A University of Cambridge-led team analysed 183 fossilised anaconda backbones from at least 32 snakes discovered in Venezuela’s Falcón State. Their findings reveal that anacondas reached their impressive size of four to five meters around 12.4 million years ago, in the Middle Miocene, and have remained giants ever since. This discovery challenges previous assumptions that these snakes were larger during warmer past climates.
Survival Amid Miocene Megafauna Decline
While many giant reptiles from the Miocene era, such as the 12-meter caiman Purussaurus and 3.2-meter giant freshwater turtle Stupendemys, went extinct, anacondas defied this trend. Their resilience is attributed to the persistence of wetland ecosystems and ample food sources like capybaras and fish, enabling their large body size to persist despite global climatic shifts.
Fossil Evidence and Ancestral Reconstruction Confirm Gigantism
Lead researcher Andrés Alfonso-Rojas employed measurements of individual fossil vertebrae. He used a method called ancestral state reconstruction. He compared traits with modern related snakes like tree boas. Both approaches confirmed that anacondas evolved their large size soon after appearing in tropical South America and that their average length, around five meters, has remained stable over millions of years.
Anacondas’ Habitat and Prey Sustain Giant Size Today
Modern anacondas inhabit swamps, marshes, and rivers like the Amazon, similar to the extensive wetlands of Miocene northern South America. Although less widespread today, the availability of suitable habitat and prey continues to support their large size, showing the importance of ecosystem conservation for their survival.
Unexpected Findings Challenge Temperature-Based Size Predictions
Contrary to expectations, the ancient anacondas were not larger than today’s giants despite warmer Miocene temperatures, suggesting that factors beyond climate influenced their gigantism. This insight deepens understanding of the evolutionary ecology of tropical snakes and invites further study on how environmental and ecological pressures shape body size.
Q&A: What the Fossils Tell Us About Anaconda Evolution
Q: How long were ancient anacondas?
A: Approximately four to five meters long, matching modern sizes.
Q: Why is the finding surprising?
A: Scientists expected larger sizes during warmer Miocene periods but found no evidence for bigger snakes.
Q: How did researchers estimate body size?
A: By measuring fossil vertebrae and using ancestral state reconstruction comparing with related living snakes.
Q: What other giant reptiles lived alongside anacondas?
A: The giant caiman Purussaurus and giant freshwater turtle Stupendemys.
Q: Why did anacondas survive while other giants went extinct?
A: Continued availability of wetlands and abundant prey helped sustain them.
Frequently Asked Questions (FAQs)
Q1: When did anacondas reach their maximum size?
A: About 12.4 million years ago during the Middle Miocene.
Q2: Where were the fossils discovered?
A: Falcón State, Venezuela, South America.
Q3: How do modern anacondas compare in size?
A: They typically reach four to five meters, with rare specimens up to seven meters.
Q4: What habitats support large anacondas today?
A: Swamps, marshes, and major rivers like the Amazon.
Q5: What does this study imply for conservation?
A: Preserving wetlands and prey species is critical to maintaining anaconda populations.
This groundbreaking research sheds light on the evolutionary history of one of the world’s most iconic giant snakes. Anacondas have been super-sized survivors for millions of years, surviving climatic shifts that extinguished other giant reptiles. Protecting their habitats ensures these giants continue to thrive
