The Sea Serpent, Pterosphenus

One of the most fantastic animals to have swam the oceans may have been the sea serpent Pterosphenus, from the mid Eocene! Its fossil vertebrae and ribs have been found in Africa, Asia and the Americas, and show that it was a member of the palaeophiid family, a group of estuarine and marine snakes that achieved enormous size just before the rise of whales. Although no full skeleton of Pterosphenus has ever been found, the vertebrae of some individuals are so big that, depending on the vertebra count, they may have been anything from 5 to a whooping 16 m long, according to some estimates! Although this upper estimate may not be the most likely, if it were correct it would make Pterosphenus the longest snake known (tho likely much less massive than the likes of Titanoboa and Palaeophis colossaeus). Again, there is nothing certain about this, tho.

Pterosphenus appears to have been particularly elongated, and the body flattened laterally suggesting it was very specialized for a fully marine lifestyle. It couldn´t slither on land, and likely gave birth to live young. We know young Pterosphenus spent the first part of their lives in shallow water for protection. No skull is known so I imagined it here with long pointed jaws to catch fish, its most likely prey (in this case, flying fish, which were already evolving back then). Another, smaller fossil snake, Archaeophis, is believed to have been a palaeophiid too, and does have slender, pointed jaws. Archaeophis is believed to have lived a bit like a modern sea snake or a moray eel, catching fish in reefs. Pterosphenus may have been more pelagic, swimming long distances across the sea as an adult. Whether it was venomous or not is unknown. What is clear is it must have been an incredible sight! Digital illustration