''Cucullaea gigantea'' is an extinct species of

false ark shell The false ark shells (''Cucullaea'') are a small genus of Marine (ocean), marine bivalve molluscs related to the ark clams. The genus is the only member of the Family (biology), family Cucullaeidae. Species The World Register of Marine Species l ...

found in the United States, in the

Aquia Formation The Aquia Formation is a geologic sandstone formation that extends from the upper Chesapeake Bay to the James River near Hopewell, Virginia. It consists of clayey, silty, very shelly, glauconitic sand. Fossil records indicate that this stratig ...

in Maryland and Virginia along the Potomac River and its tributaries, and in Alabama. They flourished in marine environments during the

Paleocene The Paleocene ( ), or Palaeocene, is a geological epoch (geology), epoch that lasted from about 66 to 56 mya (unit), million years ago (mya). It is the first epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), ...

, ranging from 58.7 to 55.8 million years ago. ''Cucullaea gigantea'' average about 8–14 cm in length, about twice the size of its relative ''Cucullaea'' ''recendens'' which average 5–8 cm. ''Cucullaea'' were infaunal suspension feeders, meaning they burrowed into the seafloor and strained their food from the water.

References

Cucullaeidae Prehistoric bivalves of North America {{Paleo-bivalve-stub