Archelon ischyros, chief or lead turtle, swam the shallowseas of the late Cretaceous, a contemporary of dinosaurs. The bone platesof the carapace are reduced to struts possibly covered with thick skinsimilar to a modern leather-back turtle. Large front flippers and strongvertical strokes were possibly used to propel itself through the waterin a similar manner to the aqua-flight of penguins. This turtle would havebeen twice as long as the leather-back, about the size of a Volkswagenbus, reaching 4 meters in some individuals.

This is a cast of the discovery made by the Watson family in thePierre Shale near Buffalo Gap, South Dakota. July 2000.