''Gryphaea'', one of the genera known as devil's toenails, is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce 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 no ...

s, marine

bivalve Bivalvia () or bivalves, in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class (biology), class of aquatic animal, aquatic molluscs (marine and freshwater) that have laterally compressed soft bodies enclosed b ...

mollusk Mollusca is a phylum of protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant species of molluscs are recognized, making it the second-largest animal phylum after Arthropoda. The ...

s in the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

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 ...

. These

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 preserve ...

s range from the

Triassic The Triassic ( ; sometimes symbolized 🝈) is a geologic period and system which spans 50.5 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.4 Mya. The Triassic is t ...

period to the middle

Paleogene The Paleogene Period ( ; also spelled Palaeogene or Palæogene) is a geologic period and system that spans 43 million years from the end of the Cretaceous Period Ma (million years ago) to the beginning of the Neogene Period Ma. It is the fir ...

period, but are mostly restricted to the Triassic and

Jurassic The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately 143.1 Mya. ...

. They are particularly common in many parts of

Britain Britain most often refers to: * Great Britain, a large island comprising the countries of England, Scotland and Wales * The United Kingdom of Great Britain and Northern Ireland, a sovereign state in Europe comprising Great Britain and the north-eas ...

. These oysters lived on the

sea bed The seabed (also known as the seafloor, sea floor, ocean floor, and ocean bottom) is the bottom of the ocean. All floors of the ocean are known as seabeds. The structure of the seabed of the global ocean is governed by plate tectonics. Most of ...

shallow waters Shallow water may refer to: * Waves and shallow water ** Shallow water equations * Shallow water marine environment * Shallow Water (album), ''Shallow Water'' (album) * Shallow Water, Kansas, unincorporated community in the United States * Shallow W ...

, likely in large colonies. The complete

s consist of two articulated valves: a larger gnarly-shaped shell (the "toenail") and a smaller, flattened shell, the "lid". The soft parts of the animal occupied the cavity between the two shells, just like modern

oysters Oyster is the common name for a number of different families of Seawater, salt-water bivalve molluscs that live in Marine (ocean), marine or Brackish water, brackish habitats. In some species, the valves are highly Calcification, calcified, a ...

. The shells also feature prominent growth bands. The larger, curved shell sat within the mud on the sea floor. These shells are sometimes found in fossil plates along with ''

Turritella ''Turritella'' is a genus of medium-sized sea snails with an operculum, marine gastropod mollusks in the family Turritellidae.Vos, C.; Gofas, S. (2013). Turritella Lamarck, 1799. Accessed through: World Register of Marine Species at http://www. ...

'',

clams Clam is a common name for several kinds of bivalve mollusc. The word is often applied only to those that are deemed edible and live as infauna, spending most of their lives halfway buried in the sand of the sea floor or riverbeds. Clams h ...

, and sometimes sharks' teeth and fossilized fish scales. Its distribution is common in areas of Europe. A classic location to find these fossils is

Redcar Redcar is a seaside town on the Yorkshire Coast in the Redcar and Cleveland unitary authority. It is in the ceremonial county of North Yorkshire, England, and is located east of Middlesbrough. The Teesside built-up area's Redcar subdiv ...

, on the northeast coast of England. There used to be a common folk belief that carrying one of these fossils could prevent

rheumatism Rheumatism or rheumatic disorders are conditions causing chronic, often intermittent pain affecting the joints or connective tissue. Rheumatism does not designate any specific disorder, but covers at least 200 different conditions, including a ...

. The name "devil's toenail" is also used for some fossil species of the genus ''

Exogyra ''Exogyra'' is an extinct genus of fossil marine oysters in the family Gryphaeidae, the foam oysters or honeycomb oysters. These bivalves were cemented by the more cupped left valve. The right valve is flatter, and the beak is curved to one sid ...

'', which is in the same family (Gryphaeidae) as ''Gryphaea''. Two genera have been removed from this genus: ''

Pycnodonte ''Pycnodonte'' is a genus of extinct oysters, fossil marine bivalve mollusks in the family Gryphaeidae, the foam oysters or honeycomb oysters. Shells of species in this genus are found around the world in fossil shell beds from the Valanginia ...

'' and ''

Texigryphaea ''Texigryphaea'' is an extinct genus of oyster belonging to the order Ostreida and family Gryphaeidae. It dates to the Albian to Cenomanian Age (geology), Ages of the Cretaceous Period (geology), period and is primarily found in Texas and the ...

''.

Selected species

*'' Gryphaea arcuata'' *'' Gryphaea dilatata''

References

External links

The Bedford Museum: ''Gryphaea''

Gryphaeidae Triassic bivalves Prehistoric bivalve genera Jurassic bivalves Cretaceous bivalves Paleocene bivalves Eocene bivalves Fossils of Great Britain Carnian genus first appearances Eocene genus extinctions Fossils of Serbia Mesozoic molluscs of Europe {{paleo-bivalve-stub