Researchers found a 508-million-year-old creature carrying about twenty-four eggs with preserved embryos in its small body. This is the earliest example of brood care on record.
In 1912, the shrimp-like specimen was discovered in Burgess Shale of the Canadian Rockies. The site is well known for its fossils from the Cambrian period (from 541 to 485.4 million years ago). Multiple fossils of the three-inch long (7.5 centimetres) creature called Waptia fieldensis were found there.
In a new study – published December 17 in the journal Current Biology – the researchers analysed the fossils of 866 Waptia fieldensis from the Smithsonian Institution National Museum of Natural History in Washington, D.C and 979 specimens housed at the Royal Ontario Museum in Canada.
Five of the creatures from the Royal Ontario Museum were carrying eggs – which is an example of brood care, according to the researchers. Brood care can also be seen in kangaroos which carry their offspring in their pouches.
Jean-Bernard Caron, an associate professor in the departments of Earth Sciences and Ecology & Evolutionary Biology at the University of Toronto and a curator of invertebrate palaeontology at the Royal Ontario Museum, said that the new discovery helped scientists better understand the practices of brood-care in the Cambrian explosion (an evolutionary event that started about 542 million years ago).
Waptia fieldensis is the predecessor of arthropods – invertebrate animals that include insects, crustaceans, myriapods, and arachnids. Using microscopic analysis, the researchers were able to look at Waptia fieldensis’ body. The critter has a bivalve carapace – a two-part structure that covers the front segment of its tiny body.
Beneath the carapace, the researchers found the egg-shaped clusters, meaning that the bivalve carapace helped Waptia fieldensis hold its eggs and care for its brood. On each side of its body, the creature had a single layer of egg-shaped clusters. Each of the eggs was about 0.07 inches long (two millimetres).
Jean Vannier, co-author of the study and a senior researcher of geology at the French National Center for Scientific Research, said that Waptia fieldensis shows how diverse brood care was in early arthropods. For instance, Kunmingella douvillei – another ancient arthropod that lived about 515 million years ago – also had eggs inside its body, but they did not contain embryos and were attached to the appendages, according to Vannier.
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