The Earliest Undoubted Gastropods (Snails)

The earliest undoubted gastropods [Phylum Mollusca, Class Gastropoda] known in the fossil record are of Early Ordovician age (about 485 to 480 million years old). They are from shallow-marine Lower Ordovician rocks in Missouri.

Four views of a specimen of Sinuopea regalia (37.3 mm high [tip missing], 40 mm wide): front view (apertural), back (abapertural), bottom, and top. This specimen is from the Gasconade Formation near Sullivan, Missouri.

Four views of a specimen of Rhacopea grandis 32.2 mm high [tip missing], 80 mm wide: front (apertural), bottom, and top. This specimen is from the Gasconde Formation, near Bourbon, Missouri. Warm-water, shallow-marine stromatolites (fossil algal structures) are found also in these rocks.

Both specimens were given to me by Dr. Michael Vendrasco, and I sincerely appreciate his generosity.

Gastropod-like fossils occur throughout Cambrian-age rocks but all, except those of the latest-most Cambrian are questionable and might belong to another extinct molluscan class.