View from an old world crab’s eye – unusually large visual features on a 95-million-year-old crab fossil

Fossil crab Callichimaera perplexa. Credit: Daniel Ocampo R. / Vincigo Films

Their legs may get more attention, but a new study says the crab’s eyes have a lot to offer, too—at least scientifically speaking.

In the journal iScience, paleontologists from Yale and Harvard have discovered new and unusually large visual features from a 95-million-year-old crab fossil, Callichimaera perplexa – One of the species first described in 2019 in a study led by former Yale paleontologist Javier Luc — which suggests that Kalyshimaira He was predatory.

Kalyshimaira, which was found in Boyaca, Columbia, and Wyoming, in the United States, was about a quarter size, characterized by large compound eyes without hollows, curved claws, leg-like mouthparts, a bare tail, and a long body. Previous research indicated that it was the first example of arthropods swimming with paddle-like legs since the extinction of sea scorpions more than 250 million years ago.

“The samples we have are extraordinary Kelsey Jenkins

Lead author Kelsey Jenkins studies the crabs found in the Yale Peabody Museum. Credit: Yale University

The study’s co-author is Luque, now a research associate at Harvard University. The study’s co-author is Derek Briggs, G. Evelyn Hutchinson Professor of Earth and Planetary Sciences in the Yale University School of Arts and Sciences. Briggs is also Curator of Invertebrate Paleontology at the Yale Peabody Museum of Natural History.

For the study, the researchers analyzed nearly 1,000 live crabs and fossils, including crabs at various stages of development, which represent 15 types of crabs. The researchers compared the size of the crabs’ eyes and how quickly they grew.

Kalyshimaira It topped the list in both categories. His eyes were about 16% of his body size.

“I’m 5’2”. “If my eyes were that big, they would be a little more than 9 inches in diameter,” Jenkins said. “If something has eyes this size, they are certainly very visible. This is in stark contrast to crabs with small, relict eyes where they may only be 1 to 3% of the animal’s body size.”

Along the same lines, Kalyshimaira The visual growth rate was faster than that of any other crab the researchers studied. “Crabs that grow very quickly with their eyes tend to be more visually inclined – they’re probably very good predators who use their eyes when hunting – while slow-growing eyes tend to be found in scavenger crabs that are less sight-dependent,” Briggs said.

Honestly, it was a new set of eyes that made the latest Kalyshimaira find possible. Jenkins, whose main research experience was with reptiles, wanted to learn more about another type of animal – hence the crabs.

“Javier and Derek guided me, and I was able to provide an outside perspective on a group of animals I was not originally familiar with,” Jenkins said.

Reference: “The Remarkable Optical System of Cretaceous Crabs” Kelsey M. Jenkins, Derek E. J. Briggs, and Javier Luke, Dec 7, 2021 Available here. iScience.
DOI: 10.1016 / j.isci.2021.103579

The research was funded in part by the Paleontological Society, the Yale Institute for Biosphere Studies, the National Science and Engineering Research Council of Canada, and the National Science Foundation.

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