Cremnoceramus

{{Automatic taxobox

| fossil_range = Turonian-Maastrichtian
~{{fossil range|94|66}}

| image = Fort Hays Limestone, Cremnoceramus deformis 20180915.jpg

| image_caption = Cremnoceramus deformis in early Turonian Fort Hays limestone, showing characteristic wavy rugae.{{cite web |title= Lower Turonian Euramerican Inoceramidae: A morphologic, taxonomic, and biostratigraphic overview |website= Faculty of Science, Vrije Universiteit Amsterdam |page= see Figure 3 for illustration of rugae |access-date= 2020-12-29 |url= https://www.geo.vu.nl/~smit/inoceramus/ino_inleiding/inoceramids.htm }}

| taxon = Cremnoceramus

| authority = Cox, 1969 (posthumous)

| subdivision_ranks = Species

| subdivision =

C. crassus
C. deformis {{small|Meek 1871}}
C. inconstans
C. rotundatus {{small|Fiege 1930}}
C. waltersdorfensis

| type_species =

}}

File:Ogallala opaline sandstone with Cremnoceramus deformis fragments 20201115 143032.jpg

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.{{cite book |last=Collum |first=Christofer J. |editor= Paul A. Johnston and James W. Haggart |title= Bivalves: An Eon of Evolution; Paleobilogical Studies Honoring Norman D. Newell |publisher= University of Calgary Press |date= 1998 |pages= 119–142 |chapter= Taxonomy Biostratigraphy and Phylogeny of the Upper Cretaceous Bivalve Cremnoceramus (Inoceramidae) in the Western Interior of Canada and the United States |access-date= 2020-12-29 |chapter-url= https://www.researchgate.net/publication/326262525 }}

Description

Cremnoceramus were facultatively mobile, blind, suspension feeding bivalves with low-magnesium calcite shells.{{cite web |title= Cremnoceramus |website = Mindat.org |url= https://www.mindat.org/taxon-7234682.html |access-date= 2020-12-29 }}

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.{{cite book |last1=Ludvigsen |first1=Rolf |last2=Beard |first2=Graham |year=1997 |title=West Coast Fossils: A Guide to the Ancient Life of Vancouver Island |url=https://archive.org/details/westcoastfossils0000ludv |url-access=registration |pages=[https://archive.org/details/westcoastfossils0000ludv/page/102 102–103]|publisher=Harbour Pub. |isbn=978-1-55017-179-2 }} 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:{{cite web |title= Cremnoceramus |website= Open Tree of Life |url=https://tree.opentreeoflife.org/taxonomy/browse?id=5297737 |access-date= 2020-12-29 }}

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:[https://paleobiodb.org/classic/checkTaxonInfo?taxon_no=15175 Cremnoceramus] at Fossilworks.org

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:

File:Fort Hays Limestone, Cremnoceramus deformis 20181124 153914.jpg|Horizontal section of articulated C. deformis (Fort Hays ls.)

File:Fort Hays Limestone, Cremnoceramus deformis (Ft. Hays Blockhouse) 20160619 081653.jpg|Lateral section of articulated C. deformis (Fort Hays ls.)

File:Fort Hays Limestone, Cremnoceramus deformis (FUMC) 20160619 071549.jpg|Lateral section of articulated C. deformis (Fort Hays ls.)

File:Fort Hays Limestone, Cremnoceramus deformis (FUMC) 20160619 071713.jpg|Horizontal section of articulated C. deformis (Fort Hays ls.)