Mysterious ichthyosaur graveyard may have been a breeding ground

Why giant marine reptiles congregated at a site in what’s now Nevada has been unknown

An illustration of Shonisaurus popularis, ancient dolphinlike reptiles, swimming in water

For generations, ancient dolphinlike reptiles called Shonisaurus popularis (shown in this artist’s rendition) returned to their favorite safe water haven to breed, researchers say.

Gabriel Ugueto/Smithsonian

Some 230 million years ago, massive dolphinlike reptiles called ichthyosaurs gathered to breed in safe waters — just like many modern whales do.