> From the coelacanth to the cockroach, these "living fossil" creatures haven't changed much in millions or even hundreds of millions of years. Despite looking

> From the coelacanth to the cockroach, these "living fossil" creatures haven't changed much in millions or even hundreds of millions of years. Despite looking the same, I wonder if it's possible to class them as the same species through all the timespan. For example, if it were possible to put a modern-day coelacanth in a time machine, and bring it back 400 Myr to the Devonian period, could it mate with another coelacanth from that period, and produce viable offspring? Or perhaps they changed a lot, not on physical form, but on a biochemical level, comprising separate species that just look the same?