12. Ichthyosaurs
The pre-historic Ichthyosaurs come off as an innocent-looking dolphin species. In some ways, this is true as they do look nearly like what a dolphin looks like today. Yet they are not early dolphins at all, as the Ichthyosaurs is a marine reptiles. How did this happen? Through a process called convergent evolution. This involves two species that may look alike through evolutionary stages but won’t actually be related.
This creature was quite large for its time and shares traits with a mackerel and tuna. That means that, for its time, this was likely the fastest creature in the ocean. This is held up by their powerful tails and crescent shape. Their look shouldn’t fool you, as Ichthyosaurs were horrifying and as dangerous as they come. If they lived today, they’d make even sharks afraid of them.