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The Largest Sea Snake of All Time Grew Up to 40 Feet Long and Hunted Whales—A Herpetologist Explains
By Scott Travers, Forbes Contributor
Mar 13, 2025, 08:30am EDT
Imagine a snake as long as a school bus gliding silently through the ancient seaways, stalking its prey. This extraordinary creature, known as Palaeophis colossaeus, has left scientists stunned and eager to uncover more secrets about its existence. As an herpetologist, I am thrilled to share with you the incredible story of this 40-foot-long behemoth that ruled the seas and possibly even hunted whales.
The discovery of P. colossaeus fossils in deposits from the Trans-Saharan Seaway offers a unique window into a period when marine environments were undergoing dramatic changes. This enormous snake, which thrived during the early to middle Eocene epoch around 56-34 million years ago, challenges our understanding of snake evolution and provides valuable insights into a bygone era.
Unbelievably, fossil evidence suggests that P. colossaeus could have reached lengths between 8.1 and 12.3 meters, which is nothing short of astonishing when compared to the longest modern sea snakes, such as Hydrophis spiralis, which can only grow up to 3 meters in length. This colossal creature’s massive size implies it occupied a top-predator niche, feeding on substantial marine organisms – possibly even early forms of whales or large fish.
The existence of P. colossaeus is crucial for our understanding of Eocene climate conditions and the dynamics of ancient marine ecosystems. Its remains have also shed light on how environmental factors influenced body size among ectotherms. Large ectothermic animals, like this massive snake, typically require higher ambient temperatures to sustain their metabolism. Consequently, its enormous size indirectly supports reconstructions of Eocene climate models that propose significantly warmer tropical seas compared to those we observe today.
What is even more fascinating is the unique physiology and adaptations exhibited by P. colossaeus. Unlike modern sea snakes, which have evolved streamlined bodies with laterally compressed skeletons, this ancient creature’s vertebrae are remarkably robust and broad. This primitive grade morphology suggests that it may not have been optimized for high-speed aquatic locomotion like its contemporary relatives.
Instead, the structure of its vertebrae indicates that P. colossaeus might have relied on sheer bulk and strength to maneuver and ambush prey, rather than relying solely on sleek, sinuous motions observed in modern marine snakes. Furthermore, studies of its bone vascularization hint at a higher growth rate and potentially faster metabolism compared to many extant snakes.
This extraordinary creature’s mix of primitive traits and specialized features serves as a poignant reminder that evolution is a continuous process of experimentation, shaping diverse body plans that can each thrive under similar environmental conditions.
