When you think about the large creatures you might see in the ocean, perhaps whales and sharks come to mind. The fossil record suggests that the diversity of large, ocean-dwelling animals in earth’s past included many other groups, such as marine reptiles known as ichthyosaurs.
Ichthyosaurs lived during the Mesozoic era of earth’s history, appearing in the fossil record during the earliest Triassic (~251 million years ago) and disappearing during the late Cretaceous (~94 million years ago). Fossils have been found on every continent except Africa and Antarctica.
Ichthyosaur means “fish-lizard”, though they look even more similar to dolphins due to their overall body shape and elongated snout. However, these were most certainly not dolphins. Some of the diagnostic features include the possession of several bones in their skulls that dolphins lack, different vertebrae, retained hindlimbs and a tail fin that extended in a vertical plane rather than a horizontal plane as in dolphins, not to mention various skeletal features found in reptiles but not mammals.
They also got much larger than the largest of dolphins, as displayed by the massive Shonisaurus and Shastasaurus.
It’s unclear what drove ichthyosaurs to extinction, as they appear to have died out before many of their other Mesozoic contemporaries, such as the dinosaurs. One common hypothesis is that other successful marine reptiles outcompeted ichthyosaurs.
Questions for Creationists
Ichthyosaurs lived in oceans around the world, so shouldn’t they have survived Noah’s flood the way whales and sharks did? If they went extinct after the flood, what would have caused it? Why is there no evidence of ichthyosaurs being caught and eaten by humans? Wouldn’t massive beasts like Shonisaurus or Shastasaurus have been reported by now if they were still alive?