Textbooks aren’t known for their originality. They build on the basics, and often include the same standard examples from one generation of students to the next. (I haven’t checked, but I wouldn’t be surprised if the fox terrier clone is still creeping somewhere.) That’s why ichthyosaurs are a textbook staple.

Mesozoic “fish lizards”, ichthyosaurs were marine reptiles that independently became adapted to a life at sea around 200 million years before dolphins. Despite their distance from the oceanic mammals in both time and evolutionary history, though, ichthyosaurs look enough like dolphins for the two to be practically inseparable in textbooks. They’re a striking example of convergent evolution – two lineages independently evolving