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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 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 ]
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
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 ...
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]
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 .
Mesolimulus is an extinct genus of horseshoe crab.The best known examples are found in Solnhofen limestone near Solnhofen, Bavaria, Germany.Originally assigned to the living genus Limulus, they are related to and look virtually identical to modern horseshoe crabs.