Scientists discover chimera fossil fossil "quite bizarre"

Paleontologists at the University of Alberta have discovered a new and strange species of crab fossil with the characteristics of many marine arthropods.

"We started looking at these fossils and we found that they had what looked like larvae eyes, a shrimp mouth, claws of frog crab and the shell of a lobster. "said Javier Luque, a post doctoral student, who thought of a chimera, a monster from Greek mythology with a lion's head, a goat's body and a snake's tail, when he came across the discovery.

"These new fossils violate all these rules."

While the unusual crab has characteristics of many different families, paleontologists have discovered that it actually occupies a new branch on the crustacean's life tree, which looks like a platypus of the crab world, Luque explained. .

The discovery is in the details

The fossilized crabs, found in the Andes in Colombia, lived in a shallow coastal sea of ​​the Cretaceous 90 to 95 million years ago. Researchers have recovered more than 70 specimens in soft clay, as well as hundreds of other crustaceans such as shrimp and lobsters.

Although the fossils are no larger than a quarter, Luque explained that their exceptional conservation allowed the researchers to select details as fine as the paws of a paddle and large eyes, suggesting that the crabs spent their life swimming instead of crawling as most do today.

"We found dozens of animals, ranging from tiny specimens of babies to mature individuals, in which we found reproductive organs – a smoking gun that proves that they are adult organisms and not larvae. We can even see individual facets on big eyes made up of these creatures, "said Luque. "It's an incredible amount of detail and we were able to reconstruct them as if they lived yesterday."

This detail allowed the researchers to create a detailed 3D model of the species.

"It is common to find new body shapes in older rocks, such as those of the Paleozoic when life exploded in many new forms," ​​said Luque. "This discovery, since the Middle Cretaceous, shows that there are still surprising discoveries of newer and more strange organisms waiting to be discovered, especially in the tropics.

"One wonders what else to discover."

The research was conducted with the support of the Natural Sciences and Engineering Research Council of Canada, the Killam Trusts, the Smithsonian Tropical Research Institute, the Colombian Geological Survey, the Colombian Association of Petroleum Geologists and Geophysicists and the Society. geological project ARES.

The study "Outstanding preservation of middle Cretaceous marine arthropods and evolution of new forms via heterochrony" was published in Progress of science.