Posts Tagged ‘True Oyster’

In part two of my Henson Creek fossil series on this blog I will be discussing Ostrea compressirosta. This bivalve is a member of the subclass Pteriomorpha like the Cucullaea Gigantea mentioned in my previous post, though this one adhered to the surface of the seafloor as opposed to burrowing into the sediment. Both were filter feeders that strained their nourishment from the water using a siphon.

O. Compressirosta ranges in age from the late Paleocene to the late Pliocene, but is found in Maryland only from 58.7 – 55.8 million years ago. Younger fossils have been found in Virginia, North Carolina, and Florida (I’ve heard a lot of people like to retire there, too).

This guy is also a member of the family Ostreidae, which are known as “true oysters” and the kind that we, as humans, like to dip in cocktail sauce. Unfortunately for us, we will never know what this particular oyster tastes like. Like all oysters, O. Compressirosta is monomyarian, meaning it has only one abductor scar from the muscle used to close the two shells. As you can see from the pictures below it also had irregular shell shape. The shell of this particular fossil would have been composed of calcite that weathered away leaving a sandstone cast like the C. Gigantea found in the same location. Oysters like these reproduce hermaphroditically, possessing both the larva and egg producing abilities sometimes switching between the two based on circumstance.

Try not to think about this post next time you are at Red Lobster. Sorry.


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