Cremnoceramus

Cremnoceramus ("cremno-" = "kremnos" [Greek]: precipice or over hanging wall or bank; "ceramus" = "keramos" [Greek]: clay pot) is an extinct genus of fossil marine pteriomorphian bivalves that superficially resembled the related winged pearly oysters of the extant genus "Pteria". They lived from the Turonian to the Maastrichtian of the Late Cretaceous.
Description.
"Cremnoceramus" were facultatively mobile, blind, suspension feeding bivalves with low-magnesium calcite shells.
"Inoceramids", like the "Cremnoceramus" in particular, had thick shells composed of particular "prisms" of calcite deposited perpendicular to the surface, and unweathered fossils commonly preserve the mother-of-pearl luster the shells had in life. Compared to the many examples of broad and flattened "Inoceramidae", "Cremnoceramus" shells are rather "high-walled", deep bowl-shaped. The top shell is commonly encrusted with oysters.
Species.
The following species are recognized:
Biostratigraphic significance.
The first appearance of the species "Cremnoceramus rotundatus" marks the beginning of the Coniacian stage.
Distribution.
Fossils of the genus have been found in:
Gallery.
Note the oyster encrustation of the top shells:
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<!-- File:Fort Hays Limestone, Cremnoceramus deformis 20180915.jpg|"Cremnoceramus deformis" in early Turonian Fort Hays limestone, showing characteristic wavy rugae.<ref name = Vrije >