SMALL SHELLIES IN THE LATE CAMBRIAN?—ENIGMATIC SILICIFIED SHELLY FOSSILS FROM THE ST. CHARLES FORMATION, LATE CAMBRIAN (FURONGIAN) OF SOUTHEASTERN IDAHO, USA

The St. Charles Formation (Cambrian, Furongian) in Franklin Basin, Idaho, contains a diverse silicified shelly fauna that includes diverse trilobites, brachiopods, echinoderm fragments, gastropod steinkerns, and sponges. Included in this fauna are some relatively common tuberculate plates of an unknown affinity. They are generally a few millimeters in diameter, slightly domed to flat, and subcircular in shape. The individual plates lack symmetry and there are no symmetrical pairs. In fact, there seem to be no two truly identical plates in the fauna. The size and organization of the plates is suggestive of a metazoan, but no metazoan group is a good fit for these fossils. In this way, they are reminiscent of the diverse Small Shelly Fauna of the early Cambrian.