A researcher in Canada has discovered the oldest non-marine crab ever which also happens to be the most complete fossil of a crab ever discovered because it was trapped in amber for over a 100 million years.
The University of Alberta said in a statement that the discovery was made by one of their PhD graduates "whose work adds to growing evidence that the crab form is an evolutionary darling".
The crab in question was found encased in a piece of amber jewellery at a market in the city of Tengchong, which is located in Yunnan Province, in south-western China, in 2015, according to the university.
Javier Luque, who is a research associate at Harvard University and a former post-doctoral researcher at Yale University, and who began studying the fossilised crab trap in amber as a University of Alberta PhD student, said: "This crab is telling us a very interesting story about the tree of life of crabs."
He added: "There is a lot of excitement about crab evolution, because evolution has produced crab-like forms, known as carcinization, many times independently."
The University statement said: "Luque explained that evidence provided by the molecular record, which is built by comparing similarities and differences in DNA and RNA, predicts that non-marine crabs — such as the Christmas Island red crabs that live in mountains or the freshwater crabs in rivers all over the world — split from their marine counterparts more than 125 million years ago.
"However, the fossil record on non-marine crabs, which consists of only tiny bits and pieces of claws, indicated that marine crabs conquered land and freshwater much later, somewhere between 75 and 50 million years ago."
Luque said: "So we’ve had this gap between the predicted molecular time of split of non-marine crabs and the known fossil record of about 50 million years."
The University explained that Luque was approached about the crab trapped in amber by an expert in vertebrate snake biology called Professor Michael Caldwell.
Luque said: "When I saw it for the first time I could not believe my eyes. This spectacular crab looks so modern, like something you may find in British Columbia flipping rocks, but it is actually quite old and different from anything seen before, fossil or alive."
The university said that Luque was solicited for his expertise "stemming from his work on crab evolution and the discovery of the 95- to 90-million-year-old Callichimaera perplexa, a swimming arthropod known as the platypus of crabs because of its unusual mixture of body features, such as its cartoonish anatomy that included googly eyes, a long body and long paddle-like legs."
The University statement also said that Luque believes this new branch in the "crab tree of life — named Cretapsara athanata" ("the immortal Cretaceous spirit of the clouds and waters”), was most likely "trapped in brackish or freshwater near a coastal environment during the Cretaceous period 100 million years ago."
The University added that the fossilised crab trapped in amber for over 100 million years "not only represents the oldest non-marine crab yet described, but it is also the most complete fossil crab ever discovered."
