The crab family has just received a bunch of new cousins, including a 95-year-old, who will force scientists to rethink the definition of cancer – and perhaps the different ways animals evolve over time.
An international team of researchers, led by paletologist Yale Javier Lue, has announced the discovery of hundreds of exceptionally well-preserved specimens of rock formations in Colombia and the United States, dating from the Cretaceous Century 90-95 million years ago. The cache includes hundreds of small shrimp fossils with a comma, with their curved curve; a few wafers that are the widespread "real" shrimps; and an entirely new branch of the evolutionary crab tree.
The most intriguing discovery, according to the researchers, is Callichimaera perplexa, the earliest example of floating arthropods with spiked feet after the extinction of marine scorpions more than 250 million years ago. The name derives from the chimera, a mythological creature that has body functions from more than one animal. The full name of Calicimera becomes a "confusing beautiful chimera."
Video Credit: Photos by Daniel Ocampo R., Winshengho and Javier Luke's Movies, Yale University / Animation and 3D Reconstruction by Alex Duke.
Callichimaera is about the size of a quarter. His "unusual and sweet" looks, Luke's notes – big, sophisticated eyes without nests, curved nails, parts like mouths, open tail, and long body – are typical of crab larvae from the open sea. This suggests that some ancient crabs may have retained some of their larval features in adulthood, expanding them and developing a new body architecture. This is an evolutionary process called "heterochronicity."
"Callichimaera perplexa is so unique and strange that it can be considered a cow disease in the crab world," says Luke. "She suggests how the new forms develop and they become so incompatible over time. We usually think of crabs as large animals with wide pancakes, strong nails, small eyes in long eyes and a small tail under the body. Well, Callichimaera opposes all these "obscene" traits and forces us to rethink our definition of what cancer cancer does. "
Luke also noted the importance of discovering the tropical region of the world. Fewer researchers are actively looking for fossils in the tropics, he said, and the amount of soil cover and thick vegetation of tropical forests make access to well-discovered rocks more difficult.
"It is very exciting that today we continue to discover entirely new branches in the tree of life from a distant past, especially from regions like the tropics, which although hot spots of diversity today are the places we know the least about their past – said Luke.
Luke's team included researchers from the University of Alberta, the University of Kent, the University of Montreal, the Smithsonian Institute for Tropical Research in Panama, the Canadian Society of Parks and Wildlife, the National Autonomous University of Mexico, the University of Nevada, and the College of Communication and Design Boca Raton, Florida.
Publication: J. Luque, et al., "Extremely Retarding Mid-Cryid Marine Arthropods and the Evolution of New Forms through Heterochromia," Science Advances, 24 Apr 2019: Vol. 5, no. 4, eaav3875; DOI: 10.1126 / sciadv.aav3875