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Burgess Shale fossil reveals 508-million-year-old eggs

A small 508-million-year-old shrimp-like creature discovered in the Burgess Shale of Yoho National Park a century ago has earned itself a huge reputation.

A small 508-million-year-old shrimp-like creature discovered in the Burgess Shale of Yoho National Park a century ago has earned itself a huge reputation.

Waptia fieldensis is today recognized as the oldest example of a fossilized creature demonstrating brood care in the fossil record. A recent study revealed clusters of eggs with preserved embryos tucked under the carapace of what are most likely females.

This extraordinary find, shared in the Dec. 17 issue of the scientific journal Current Biology by its authors, Jean-Bernard Caron, Curator of Invertebrate Palaeontology at the Royal Ontario Museum and Jean Vannier, who is with the Université Claude Bernard Lyon 1, France, is just one of many new discoveries linked in recent years to the Burgess Shale deposit of the Canadian Rockies.

The Burgess Shale and its Cambrian Period fossils have recently offered up new species, such as one of the oldest ancestors of humans, a 505-million-year-old acorn worm, and new fossil sites in the Canadian Rockies.

Researchers have also made surprising discoveries by taking another look at fossils excavated a century ago, with Waptia and its stash of eggs being the most recent.

The 7.5-centimetre-long Waptia, meanwhile, is an arthropod, placing it in the same family as crayfish and lobsters. Like its relatives, Waptia has a segmented tail that ends in a fan, antennae and appendages used for swimming and feeding. It also has a bivalve, or a two-part, carapace.

The carapace, according to the authors, appears to play an important role in brood care, allowing Waptia to protect and nurture its eggs.

“As the oldest direct evidence of a creature caring for its offspring, the discovery adds another piece to our understanding of brood care practices during the Cambrian Explosion, a period of rapid evolutionary development when most major animal groups appear in the fossil record,” Caron, also associate professor in the Departments of Earth Sciences and Ecology and Evolutionary Biology at the University of Toronto, stated in a recent press release from the ROM.

Two other fossilized species, 450-million-year-old Ostracods, or seed shrimp, and 515-million-year-old bivalve bradoriid arthropods, neither of which were found in the Canadian Rockies, also exhibit brood care.

During their study, Caron and Vannier examined 1,845 Waptia specimens stored at the ROM and the Smithsonian Institute in Washington, D.C. They found clusters of seven to 12 eggs hidden beneath the carapace on each side of the body in five of the specimens, which the researchers believe are female.

Waptia, which is one of the more common finds in the Burgess Shale deposits, was first described by American palaeontologist Charles D. Walcott in 1912.

Finding parental strategies, such as Waptia’s, so early in the fossil record “suggests a rapid evolution of a variety of modern-type life-history traits, including extended investment in offspring survivorship, soon after the Cambrian emergence of animals.

“These new findings suggest that the presence of a bivalve carapace played a key role in the early evolution of parental care in arthropods,” the authors wrote in their Current Biology article.


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