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The Cretaceous crab revolution was a major diversification event of brachyuran crabs (also known as true crabs) that took place during the Cretaceous Period, from 145 to 66 million years ago. [ 1 ] [ 2 ] Nearly 80% of modern groups of crabs originated during this event. [ 3 ]
Crabs vary in size from the pea crab, a few millimeters wide, to the Japanese spider crab, with a leg span up to 4 m (13 ft). [6] Several other groups of crustaceans with similar appearances – such as king crabs and porcelain crabs – are not true crabs, but have evolved features similar to true crabs through a process known as carcinisation .
More than 99 percent of all species that ever lived (over five billion) [1] are estimated to be extinct. [2] [3] Estimates on the number of Earth's current species range from 10 million to 14 million, [4] with about 1.2 million or 14% documented, the rest not yet described. [5]
The crabs can travel up to 1.46 km (0.91 mi) in a day, and up to 4 km (2.5 mi) in total. [4] Only a few land crabs, including certain Geosesarma species, have direct development (the mother carries the eggs until they have become tiny, fully developed crabs), and these do not need access to water to breed.
In the family Hippidae, the body is almost ovoid, the first pereiopods have no claws, and the telson is long, none of which are seen in related groups. [5] Unlike most other decapods, sand crabs cannot walk; instead, they use their legs to dig into the sand. [6] Members of the family Hippidae beat their uropods to swim. [6]
While counting snow crabs at sea in 2021, fisheries biologist Erin Fedewa saw that something was deeply amiss.Fedewa, a National Oceanic and Atmospheric Administration (NOAA) scientist, spends ...
Billions of snow crabs have disappeared from the ocean around Alaska in recent years, and scientists now say they know why: Warmer ocean temperatures likely caused them to starve to death.
Hermit crab species range in size and shape, from species only a few millimeters long to Coenobita brevimanus (Indos Crab), which can approach the size of a coconut and live 12–70 years. The shell-less hermit crab Birgus latro (coconut crab) is the world's largest terrestrial invertebrate .