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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 ]
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.
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]
Some crab-shaped species have evolved away from the crab form in a process called decarcinisation. Decarcinisation, or the loss of the crab-like body, has occurred multiple times in both Brachyura and Anomura. [25] [26] However, there are varying degrees of carcinisation and decarcinisation. Thus, not all species can necessarily be distinctly ...
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.
For the study, scientists analyzed what could have triggered the disappearance of the snow crabs beginning in 2020 and boiled it down to two categories: the snow crabs either moved or died.
Some of these areas always teem with crabs. Scientists count thousands. But in 2021, thousands dwindled to hundreds. "The survey last year was a huge red flag for me," she told Mashable.The ...
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 ...