Mark Wilson April 17th, 2011 The technical term is ostreolith,
but “oyster ball” is much more descriptive. These fossils are
found by the thousands in the Carmel Formation (Middle Jurassic)
in southwestern Utah. As far as I know, this is the only place
they’ve ever been found. Colin Ozanne (’96) worked on these
ostreoliths as part of his Independent Study project, and the
results of our work were published in a 1998 issue of Palaios.
Colin now, by the way, is an Engineer Trial Attorney for the US
Army Corps of Engineers in Buffalo, New York. Ostreoliths are
“circumrotatory accumulations” of the little oyster Liostrea
strigilecula. The most common form began with a clam shell
fragment as a nucleus. Oyster larvae recruited on the top shell
surface and grew in the normal way. A current, though, flipped
the shell over, exposing the underside that was in turn
encrusted by more oyster larvae. These grew into larger oysters
until, again, the shell flipped back over. A new generation of
oysters then encrusted the old