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| Fossils from the late middle Ordovician Johnson Spring Formation, as exposed in the vicinity of Mazourka Canyon, Inyo County, California. Left to right: Two articulate brachiopods, called scientifically Ptychopleurella arthuri; exterior and interior views of the pedicle valves, left to right respectively. At right: Four solitary Streptelasma rugose horn corals. Photographs taken from a specific public domain document. |