Today’s Thunder Lizard Thursday takes us to the seas,where once lurked the 50-ton Basilosaurus. It was one of the largest animals of the Eocene era, rivaling earlier, landbound sauropod dinosaurs like Seismosaurus and Argentinosaurus in size. Basilosaurus was not a reptile at all, but a prehistoric whale. However, when its bones were first discovered in 1843, it was incorrectly identified as a marine reptile–hence its name, Greek for “king lizard.”
Basilosaurus had tiny flippers, relative to its massive bulk; it is believed that it swam by undulating its long, snake-like body and that it stayed close to the surface–its spinal structure and weaker musculature suggest that it could not dive deep and could catch prey only in short bursts of speed. Prehistoric whales like Basilosaurus actually descended from terrestrial mammals, and evidence for this can be seen in the flippers. The front flippers still have an elbow joint, something that today is only seen in seals.