Marianne Collins
Reconstruction of expansion helmetia
After all, this curious species had legs, and it grew differently than we thought. What was Helmetia expansion?
Discovered in 1918 by paleontologist Charles Dooltle Walcott, the Cambrian Arthropod Helmetia Expansa remained a mystery for almost 100 years. Until now.
A team of scientists published one in Journal of Systematic Palaeontology Where it describes this bizarre species, which after all had a different behavior from expected.
Helmetia expansa is part of a rare group of primitive arthropods known as congiliturganswhich are closely related to the trilobites. Unlike trilobites, concilitergans did not have calcified and hard exoskeletons, which means that their fossils could only be formed under exceptional conditionsexplains a.
“We need to study more than one specimen to see the whole range of morphology and preservation of the species,” explains researcher Sarah Losso. The team investigated 36 species.
In the holotype, only the gills of this animal are visible, which leads researchers to believe that Helmetia had no legs, and just swim. After all, this is not true – the researchers discovered wide gills and legs to walk.
“All arthropods change their rigid exoskeletons to grow, but no one had seen this behavior before in a concilitergan because it is necessary to capture a specimen at the act of the seedling, and it is difficult to get the right moment right,” explains Losso.
Researchers also discovered a wide variety of adult body sizes as the Helmetia grew. “These patterns tell us not only how these 508 million years have grown, but also the size they could reach,” explains the author.
