Evolutionary diversification event during the Cretaceous period
The Cretaceous crab revolution was a major diversification event of
brachyuran crabs (also known as true crabs) that took place during the
CretaceousPeriod, from 145 to 66 million years ago.[1][2] Nearly 80% of modern groups of crabs originated during this event.[3] The Cretaceous crab revolution is a smaller component of the greater
Mesozoic marine revolution.[4]
Early diversification
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] During this time, crabs evolved into many different body plans and lifestyles, including the
carcinized body shape like that of blue crabs that many people are familiar with.[7][8] At the same time, many families of crabs evolved away from the carcinized body plan, termed decarcinization.[1][2] The Cretaceous crab revolution also witnessed the evolution of more unusual body forms in crabs, including the enigmatic Callichimaera perplexa.[1] This rapid diversification allowed true crabs to inhabit many different environments including fresh water environments,
coral reefs, swimming within the water column, and many others.[3] Cretaceous crabs exhibit expert shell-breaking behavior with powerful claws (the left claw is smaller than the right) (Dietl & Vega, 2008).
^Borradaile, L.A. (1916). "Crustacea. Part II. Porcellanopagurus: An instance of carcinization, in British Antarctic ("Terra Nova") Expedition, 1910". Zoology. 3: 111–126.