''Pycnodonte'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

oyster Oyster is the common name for a number of different families of salt-water bivalve molluscs that live in marine or brackish habitats. In some species, the valves are highly calcified, and many are somewhat irregular in shape. Many, but not al ...

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

marine Marine is an adjective meaning of or pertaining to the sea or ocean. Marine or marines may refer to: Ocean * Maritime (disambiguation) * Marine art * Marine biology * Marine debris * Marine habitats * Marine life * Marine pollution Military * ...

bivalve Bivalvia (), in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of marine and freshwater molluscs that have laterally compressed bodies enclosed by a shell consisting of two hinged parts. As a group, bival ...

mollusk Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is e ...

s in the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Gryphaeidae The Gryphaeidae, common name the foam oysters or honeycomb oysters, are a family of marine bivalve mollusks. This family of bivalves is very well represented in the fossil record, however the number of living species is very few. All species ...

, the foam oysters or honeycomb oysters. Shells of species in this genus are found around the world in

shell beds from the

Valanginian In the geologic timescale, the Valanginian is an age or stage of the Early or Lower Cretaceous. It spans between 139.8 ± 3.0 Ma and 132.9 ± 2.0 Ma (million years ago). The Valanginian Stage succeeds the Berriasian Stage of the Lower Cretaceou ...

(140.2 Ma) to the

Early Pleistocene The Early Pleistocene is an unofficial sub-epoch in the international geologic timescale in chronostratigraphy, being the earliest division of the Pleistocene Epoch within the ongoing Quaternary Period. It is currently estimated to span the time ...

(0.781 Ma). They are a commonly found fossil in

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...

shellbeds of the

Navesink Formation The Navesink Formation is a 66 to 70 mya greensand glauconitic marl and sand geological formation in New Jersey. It is known for its Cretaceous period fossil shell beds and dinosaur bones. Description The Navesink Formation, named after Navesin ...

New Jersey New Jersey is a state in the Mid-Atlantic and Northeastern regions of the United States. It is bordered on the north and east by the state of New York; on the east, southeast, and south by the Atlantic Ocean; on the west by the Delaware ...

Species

Species within the genus ''Pycnodonte'' include: *''Pycnodonte amakusensis'' Tashiro 1978 † *''Pycnodonte aucella'' (Roemer, 1849) † *''Pycnodonte belli'' (Stephenson, 1941) † *''Pycnodonte brongniarti'' (Bronn 1831) † *''Pycnodonte callifera'' (Lamarck, 1819) † *''Pycnodonte convexa'' (Say 1820) † *''Pycnodonte costei'' Coquand 1869 † *''Pycnodonte heermanni'' Conrad 1855 † *''Pycnodonte kansasense Bottjer † *''Pycnodonte mutabilis'' (Morton, 1828) † *''Pycnodonte newberryi'' (Stanton) † *''Pycnodonte panda'' Morton 1833 † *''Pycnodonte percrassa'' Conrad 1840 † *''Pycnodonte roanokensis'' (Cragin, 1893) † *''Pycnodonte squarrosa'' de Serres 1843 † *''Pycnodonte taniguchii'' † *''Pycnodonte trigonalis''† *''Pycnodonte vesicularis'' (Lamarck 1806) † *''Pycnodonte vesiculosa'' Sowerby 1822 † *''Pycnodonte wardi'' (Hill and Vaughan, 1898) † Fossils of species within this genus have been found all over the world in sediments from

Quaternary The Quaternary ( ) is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS). It follows the Neogene Period and spans from 2.58 million years ...

(age range: 140.2 to 0.0781 million years ago). The fossils generally exist in large layers or beds. In

Utah Utah ( , ) is a state in the Mountain West subregion of the Western United States. Utah is a landlocked U.S. state bordered to its east by Colorado, to its northeast by Wyoming, to its north by Idaho, to its south by Arizona, and to it ...

, in the

Capital Reef National Park Capitol Reef National Park is an American national park in south-central Utah. The park is approximately long on its northsouth axis and just wide on average. The park was established in 1971 to preserve of desert landscape and is open all ye ...

area, this layer of fossils is up to ten feet thick, and is present in the lower Tununk section of the

Mancos Shale The Mancos Shale or Mancos Group is a Late Cretaceous (Upper Cretaceous) geologic formation of the Western United States. The Mancos Shale was first described by Cross and Purington in 1899 and was named for exposures near the town of Mancos, ...

Fraction, just above the

Dakota Sandstone The Dakota is a sedimentary rock, sedimentary geologic unit name of Formation (stratigraphy), formation and Group (stratigraphy), group rank in Midwestern North America. The Dakota units are generally composed of sandstones, mudstones, clays, and ...

and below the Blue Gate Shale layer. In the

Hanksville, Utah Hanksville is a small town in Wayne County, Utah, United States, at the junction of State Routes 24 and 95. The population was 219 at the 2010 census. Situated in the Colorado Plateau's cold desert ecological region, the town is just south ...

area, the ''Pycnodonte newberryi'' oyster bed is exposed over a large area. Studies are currently being conducted to determine whether there is more than one species in these beds.

Gallery

File:Pycnodonte vesicularis left valve interior.jpg, ''Pycnodonte vesicularis'' left valve interior; Aubeterre Formation, Campanian, SW France. File:Pycnodonte vesicularis right valve interior.jpg, ''Pycnodonte vesicularis'' right valve interior; Aubeterre Formation, Campanian, SW France File:Gryphaeidae - Pycnodonte brongniarti.JPG, ''Pycnodonte brongniarti'' File:Pycnodonte vesicularis MHNT.PAL.LAM.2001 Global.jpg, ''Pycnodonte vesicularis'' MHNT File:Pycnodonte convexa.jpg, ''Pycnodonte convexa''

References

Gryphaeidae Prehistoric bivalve genera Jurassic bivalves Cretaceous bivalves Jurassic animals of North America Extant Triassic first appearances {{paleo-bivalve-stub