Cremnoceramus

Cremnoceramus Temporal range: Turonian-Maastrichtian ~94–66 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Cremnoceramus deformis in early Turonian Fort Hays limestone, showing characteristic wavy rugae.[1]
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Bivalvia
Order:	Pteriida
Family:	†Inoceramidae
Genus:	†Cremnoceramus Cox, 1969 (posthumous)
Species
C. crassus C. deformis Meek 1871 C. inconstans C. rotundatus Fiege 1930 C. waltersdorfensis

Weathered Cremnoceramus deformis shell fragment highlighting the orientation and texture of the calcite prisms definitive of thick-shelled Cremnoceramus and Inocermidae in general

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.[2][3]

Description

Cremnoceramus were facultatively mobile, blind, suspension feeding bivalves with low-magnesium calcite shells.[3] 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.[4] 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:[5]

• C. crassus
• C. deformis
• C. inconstans
• C. rotundatus
• C. waltersdorfensis

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:[6]

• Gosau Formation, Austria
• Cotinguiba Formation, Brazil
• Pointe-Noire, Congo-Brazzaville
• Jicin, the Czech Republic
• Arnager Limestone Formation, Denmark
• Craie de Villedieu Formation, France
• Germany
• Anaipadi Formation, India
• Tongobury, Madagascar
• Austin Group, Mexico
• Sant Corneli and El Zadorra Formation, Spain
• Lewes Nodular Chalk Formation, the United Kingdom
• Niobrara Formation, New Mexico, United States

Gallery

Note the oyster encrustation of the top shells:

• 
  Horizontal section of articulated C. deformis (Fort Hays ls.)
• 
  Lateral section of articulated C. deformis (Fort Hays ls.)
• 
  Lateral section of articulated C. deformis (Fort Hays ls.)
• 
  Horizontal section of articulated C. deformis (Fort Hays ls.)

References

1. "Lower Turonian Euramerican Inoceramidae: A morphologic, taxonomic, and biostratigraphic overview". Faculty of Science, Vrije Universiteit Amsterdam. p. see Figure 3 for illustration of rugae. Retrieved 2020-12-29.
2. Collum, Christofer J. (1998). "Taxonomy Biostratigraphy and Phylogeny of the Upper Cretaceous Bivalve Cremnoceramus (Inoceramidae) in the Western Interior of Canada and the United States". In Paul A. Johnston and James W. Haggart (ed.). Bivalves: An Eon of Evolution; Paleobilogical Studies Honoring Norman D. Newell. University of Calgary Press. pp. 119–142. Retrieved 2020-12-29.
3. "Cremnoceramus". Mindat.org. Retrieved 2020-12-29.
4. Ludvigsen, Rolf; Beard, Graham (1997). West Coast Fossils: A Guide to the Ancient Life of Vancouver Island. Harbour Pub. pp. 102–103. ISBN 978-1-55017-179-2.
5. "Cremnoceramus". Open Tree of Life. Retrieved 2020-12-29.
6. Cremnoceramus at Fossilworks.org