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| Here are two fossil turritella gastropods from the Middle Eocene Avenal Sandstone, collected in the vicinity of the Kettleman Hills, California. At left is Turritella buwaldana; at right is Turritella uvasana. The famous Avenal Sandstone yields over 140 species of mollusks--it is one of the more fossiliferous marine Eocene geologic rock units on the west coast of North America; the formation is noted for its "pygmy" invertebrate fauna, a molluscan assemblage whose fossil specimens are rather diminutive in size--a rather unique occurrence in the marine Eocene of North America; for example, these specimens are, from left to right, 15mm and 10mm long. |