World’s largest sea snake was a 12-metre giant that may have eaten sharks

The concept of enormous animals has historically been associated mostly with terrestrial dinosaurs. Oceans conceal their own rich past, but they feel different and quieter. Sometimes, in ways that are difficult to imagine now, fossils provide clues about species that formerly inhabited warm oceans. One such species is made up of scattered bones rather than a whole skeleton, yet those remnants are difficult to overlook. They come from a kind of sea snake that existed for millions of years before people. It did not coexist with coral reefs or whales as they exist today. Rather, it travelled through shallow, extinct old oceans. Scientists' perceptions of early marine ecosystems and the boundaries of reptile evolution in the ocean are altered simply by its vastness.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.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.Size provides some hints about what Palaeophis colossaeus preyed on, but there is no concrete proof. Large meals would have been necessary for a snake larger than ten meters. It may have been able to swallow very huge prey if, like many modern snakes, its cranium was extremely flexible, according to research. This could have featured large fish, sharks, or reptiles called dyrosaurids that resembled crocodiles. The concept is more fundamental biology than dramatic speculation. Large animals are typically the prey of large predators. Because just vertebrae have been discovered and behaviour is more difficult to reconstruct than bones, scientists are still wary.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.