See this little guy? He's a trilobite. His family of marine arthropods first appeared in the early Cambrian era (520 My). They formed the class Trilobita and flourished in all the worlds oceans. They flourished for millions and millions of years in all the worlds oceans. There were a dizzying variety of trilobites- numerous species and sub-species that adapted and specialized in their local environments.

Suddenly at the Permian extinctions, they were gone. One of the most successful marine arthropods in fossil record was gone almost over night.

Perhaps there's a lesson for us to learn from the humble trilobite. Things can go bad enough to press you to extinction if you can not improvise, adapt and survive.