Gryphaea
genus of molluscs (fossil)
Gryphaea (commonly known as devil's toenails) is a genus of marine gryphaeid oysters known from the Mesozoic Era. Its fossils are almost worldwide-known but they are mostly common in Jurassic strata from Europe, North America, and South America. Gryphaea fossils are particularly important in the tectonically deformed Andean basins of Argentina and Chile and serve as index fossils. Gryphaea species appeared during the Late Triassic period and flourished during the Early Jurassic, eventually becoming extinct around the Late Jurassic. The name "devil's toenail" originated because of the curved shells of Gryphaea resembling a toenail. There used to be a common folk belief that carrying one of these fossils could prevent rheumatism.
A complete Gryphaea shell consists of two articulated valves: a larger gnarly-shaped valve and a smaller, flattened valve. The soft parts of the animal occupied the cavity between the two shells, just like modern oysters. The larger, curved valve sat within the soft sediment on the sea floor. In seabeds dominated by soft sediments, Gryphaea shells provided stable surfaces for colonization by benthic organisms.
This brief starts where responsible research should: with the source description of “Gryphaea” as genus of molluscs (fossil). Everything that follows is an evidence route, not borrowed authority.
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The subject matters to the science & nature register because the source frames it as genus of molluscs (fossil). Its deeper value depends on whether names, dates, institutions and citations support that framing.
Stable identifiers, scientific names and standards terminology offer the best bridge between this overview and specialist evidence. The source revision retrieved here is dated Aug 25, 2026. The linked authority identifier is Q129290. None of the 0 selected statements returned an explicit reference.
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This entry incorporates text from “Gryphaea” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.