crab
Crabs are decapod crustaceans of the infraorder Brachyura (meaning "short tailed" in Greek language, Greek), which typically have a very short projecting tail-like abdomen#Arthropoda, abdomen, usually hidden entirely under the Thorax (arthropo ...
s belonging to the family
Geryonidae
Geryonidae is a family of crabs, including the following subfamilies and genera:
* Benthochasconinae
**'' Benthochascon''
**'' Raymanninus''
*† '' Coeloma''
*'' Coenophthalmus''
*'' Echonilatus''
* Geryoninae
**† '' Archaeoplax''
**' ...
or
Mathildellidae
Mathildellidae is family of crabs belonging to the superfamily Goneplacoidea
Goneplacoidea is a superfamily of crabs containing 11 extant families, and two families known only from fossil
A fossil (from Classical Latin , ) is any pre ...
. The genus includes 17 species, formerly distributed among several subgenera. The
fossil record
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 ...
of the genus extends from the
Thanetian
The Thanetian is, in the International Commission on Stratigraphy, ICS Geologic timescale, the latest age (geology), age or uppermost stage (stratigraphy), stratigraphic stage of the Paleocene epoch (geology), Epoch or series (stratigraphy), Serie ...