For a long time, the idea of giant animals has mostly been tied to dinosaurs on land. Oceans feel different, quieter, even though they hide their own deep history. Fossils occasionally hint at creatures that once filled warm seas in ways that are hard to picture now. One such animal comes from scattered bones rather than a full skeleton, yet those remains are hard to ignore. They belong to a sea snake that lived millions of years before humans appeared. It did not share space with modern whales or coral reefs. Instead, it moved through shallow ancient waters that no longer exist. Its size alone changes how scientists think about early marine ecosystems and the limits of reptile evolution in the ocean.
Palaeophis colossaeus: World’s largest sea snake that lived 56 million years ago
Palaeophis colossaeus is the name given to the largest sea snake known to science. It lived during the Eocene epoch, roughly between 56 and 34 million years ago. The animal is known only from fossilised vertebrae, but those bones are unusually large. Based on their proportions, researchers estimate the snake may have grown between 8 and just over 12 metres long. That places it far beyond any living sea snake today. A 2018 scientific study named “Large palaeophiid and nigerophiid snakes from Paleogene Trans-Saharan Seaway deposits of Mali” described the vertebrae as larger than those of any known modern snake species, marine or terrestrial. Even without a skull or full body, the scale of the bones suggests an animal built for dominance rather than survival at the margins.
This giant sea snake lived near Africa
Evidence points to a warm, shallow marine environment that once covered parts of North Africa. This region is known as the Trans-Saharan Seaway, which existed when global temperatures were higher than today. Areas that are now desert were once coastal waters rich in life. The presence of such a large sea snake suggests these seas were warmer than modern tropical oceans. Large reptiles depend on heat to regulate their bodies, and sustained size on this scale would not have been possible in cooler conditions. The environment likely supported a wide range of fish, sharks, and other marine reptiles, creating space for a predator of unusual size.
This snake might have eaten sharks for survival
No direct evidence shows what Palaeophis colossaeus preyed on, but size offers some clues. A snake measuring more than 10 metres would have needed large meals. Researchers have suggested that if its skull was highly flexible, like many modern snakes, it could have swallowed very large prey. This may have included sizeable fish, sharks, or crocodile-like reptiles called dyrosaurids. The idea is not dramatic speculation so much as basic biology. Big predators usually target big animals. Even so, scientists remain cautious, since only vertebrae have been found and behaviour is harder to reconstruct than bones.
How does it compare to snakes today?
Modern sea snakes are far smaller and less imposing. The longest-living species, the yellow sea snake, reaches around 3 metres at most. Even the largest snake ever known, Titanoboa, which lived on land, was only slightly longer than Palaeophis colossaeus. That animal is also extinct. What remains today are scaled-down versions adapted to cooler seas and different food chains. The giant sea snake belongs to a time when oceans worked differently. Its disappearance does not come with a neat ending. It simply faded as climates shifted, seas retreated, and the world rearranged itself around smaller forms.
