How long have polychaetes been around?
Polychaete fossils are known from rocks dated as far back as the mid-Cambrian period (500 million years ago), such as from the famous Burgess Shale Formation in British Columbia, Canada. Another famous locality is the Francis Creek Shale Formation in Illinois, with Mazon Creek fossils from the Pennsylvanian period (300 million years ago). What is especially fascinating about Mazon Creek polychaetes, like the one shown above, is that they contain species that can be assigned to families that have members in existence to this day. Clearly, the remarkable longevity of polychaetes has been due to their success at being able to live in every possible type of habitat in the world’s oceans. Photo by J.
