Cyclida are an enigmatic, extinct group of crustaceans. They lived in the oceans from the Carboniferous Period till the end of the Cretaceous Period (~360 – 66 million years ago). How they relate to other groups of crustaceans has been debated for more than a century. Cyclids are small (mostly < 2 cm) and thus hard to recognize. As a result, this group remains understudied in terms of diversity (55 species only) and ecology. Smaller individuals may have been parasites, but larger ones could...
