The Mystery of Mass Extinctions Is No Longer Murky (IMAGE)
Caption
Crinoids, commonly known as "sea lilies," from the approximately 460-million-year-old Ordovician Bobcaygeon Formation in Ontario, Canada. These marine animals, which are echinoderms related to starfish and sand dollars, attached themselves to the sea floor and filtered food from the water with their feathery appendages. Crinoids are still alive today, but they are part of the Paleozoic evolutionary fauna, which was more abundant and diverse in the shallow seas that covered much of the present-day land area. The delicate specimens on this slab of rock were preserved when a strong storm toppled them to the sea floor and then buried them with a thin layer of mud.
Credit
Shanan Peters, University of Wisconsin-Madison.
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