The strange crab that hunts at night forces scientists to reconsider the evolution of modern species



Scientists have huge eyes, large claws, paddle-shaped legs and lobster-like shells. He described a newly discovered species as "the strangest crab that ever lived".

FOssiles found in Colombia have revealed the new evolutionary branch of the swimming crabs, Who lived about 95 million years ago.

The little creatures According to reports, paleontologists remembered the carillon.ras: monsters of Greek mythology with lion's head, goat's body and snake's tail, due to their mixed features that look a lot like those of other marine arthropods.


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Called Callichimaera perplexed, which means "beautiful and perplexed chimera", after its unusual combination of characteristics, is the first example of a swimmer arthropod with paddle-like legs since the extinction of marine scorpions more than 250 million years ago.

It was discovered by an international team of researchers led by paleontologist Javier Luque of the prestigious Yale University in the United States.

"Callichimaera perplexed "It is so unique and strange that it can be considered the platypus of the crab world," said Dr. Luque. "It indicates how novel forms evolve and become so disparate over time."

He added: "Generally, we think of crabs as large animals with broad shells, strong claws, small eyes in long eyes and a small tail tucked under the body. All right, Callichimaera It defies all these "cranky" characteristics and forces us to rethink our definition of what makes a crab a crab. "

The fossilized creatures, recovered from the Andes mountain range in Colombia, once lived in a shallow coastal sea during the Cretaceous period.

The researchers recovered more than 70 of the specimens in soft clay, along with hundreds of other crustaceans such as shrimp and lobsters.

The only Callichimaera perplexed the crab had fin-shaped legs that allow it to swim, and large eyes, which are believed to allow it to hunt at night (Oksana Vernygora, University of Alberta)

While the fossils are no larger than a coin, Dr. Luque explained that their exceptional degree of conservation allowed researchers to choose fine details, such as their large legs and eyes, suggesting that crabs spent their lives swimming, instead to crawl like most modern crabs. to do today.

Dr. Luque said From the callichimaera The "unusual and cute" aspect, which includes its small size, its large compound eyes without basins, bent claws, parts of the mouth in the shape of legs, exposed tail and long body are typical characteristics of pelagic crab larvae.

He said that this suggests that several of the larval features seen in the species could have been conserved and amplified in miniaturized adults through changes in time and rates of development.

This process is called "heterochrony" and is thought to lead to the evolution of new parts of the body.

"It is very exciting that today we continue to find completely new branches in the tree of life from a distant past, especially from regions such as the tropics, which despite being access points of diversity today, are places we know least about in terms of its past, diversity, "said Dr. Luque. "It's an incredible amount of detail, and we have been able to reconstruct them as if they were living yesterday."

The high quality of the fossils has even allowed researchers to create a detailed 3D model of the crab.

"It is common to find novel bodily forms in older rocks, for example from the Paleozoic when life exploded in many new ways," said Dr. Luque. "This discovery, from the middle Cretaceous, illustrates that there are still surprising discoveries of more recent strange organisms waiting to be found, especially in the tropics. It makes you wonder "what else is there for us to discover?"

The study appears in the magazine. Scientific advances.


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