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After an analysis of new fossil material, the subgenera were elevated to the rank of genus, and three new genera were erected. [3] Most of the family's current diversity is found in temperate waters of the Northern Hemisphere .
The oldest known true crabs are Eoprosopon klugi and Eocarcinus praecursor from the Early to Middle Jurassic. [5] [6] While that fossil crab, and a few other Jurassic species, establish that crabs existed in older time periods, crabs did not truly diversify into numerous species until the beginning of the Cretaceous. [3]
The order is estimated to contain nearly 15,000 extant species in around 2,700 genera, with around 3,300 fossil species. [1] Nearly half of these species are crabs, with the shrimp (about 3,000 species) and Anomura including hermit crabs , king crabs , porcelain crabs , squat lobsters (about 2500 species) making up the bulk of the remainder. [ 1 ]
Since its ancestors were long-tailed decapods, and its successors were short-tailed crabs, Eocarcinus has been described as "the lobster who decided to become a crab". [5] Previously considered to be the oldest known true crab , a 2010 revision concluded that Eocarcinus could not be accommodated among the Brachyura, and was instead transferred ...
Dakoticancroidea is a superfamily of fossil crabs divided into the following two families: [1] [2] [3] † Dakoticancridae Rathbun, 1917 † Avitelmessus Rathbun, 1923 † Dakoticancer Rathbun, 1917 † Tetracarcinus Weller, 1905 † Ibericancridae Artal, Guinot, Van Bakel & Castillo, 2008 † Ibericancer Artal, Guinot, Van Bakel & Castillo, 2008
Potamonautes lirrangensis, the Malawi blue crab, [2] is a species of freshwater crab in the family Potamonautidae. This common and widespread species is found in Lake Malawi , Lake Kivu , the upper Congo River Basin and Malagarasi River in the Democratic Republic of the Congo , Malawi , Rwanda , and Tanzania . [ 1 ]
Fossils are rarely preserved in tropical settings in comparison to other parts of the world, making this fossil an even more unusual discovery. [7] An in-depth study of the crab's eyes indicated that Callichimaera was an active predator living high in the water column .
Coeloma is an extinct genus of crabs belonging to the family Mathildellidae. The genus includes 19 species, [ 2 ] distributed among several subgenera, and is in need of revision. [ 1 ] The fossil record of the genus extends from the Eocene to the Miocene .