Artistic reconstruction of the Burgess Shale concilitergan Helmetia expansa. Credit: Marianne Collins
SciTechDaily has an article about the strange arthropod Helmetia expansa. H. expansa was discovered by Charles Doolittle Walcott in 1918 in the Burgess Shale. It was initially identifed as a crustacean, however, it was never described. A new paper, in the Journal of Systematic Palaeontology, describes Helmetia expansa as a concilitergans, a group closely related to trilobites.
In a new study published in the Journal of Systematic Palaeontology, a team of Harvard researchers led by Sarah Losso, a postdoctoral fellow in the Department of Organismic and Evolutionary Biology, has now provided a formal description of Helmetia expansa. Their findings offer new details about the animal’s anatomy, behavior, and evolutionary connections.
Helmetia expansa is part of a rare group of early arthropods known as concilitergans, which are closely related to trilobites. Unlike trilobites, concilitergans lacked hard, calcified exoskeletons, meaning their fossils could only form under exceptional conditions—such as those found in the 508-million-year-old Burgess Shale in Canada, where even delicate features like guts, legs, and gills were preserved.
Although more specimens were collected, only one individual of Helmetia expansa had been figured and no study examined additional material in detail to formally describe the species or clarify concilitergan evolution. “We need to study more than one specimen to see the species’ full range of morphology and preservation,” said Losso.
