An example of the use of the term in paleontology is to describe hollow calcium carbonate, calcium sulfate or calcium phosphate plates grown as body armor by a number of Early Cambrian animals. Unlike sponge spicules, Early Cambrian sclerites appear to be external armor rather than internal structural elements. Sclerites are found on a curious collection of early animals including a common spongelike animal called "Chancelloria"; an armored slug-like form "Wiwaxia"; an armored worm with a pair of brachiopod-like shells "Halkieria"; and another armored worm "Microdictyon" that is generally considered to be a lobopod/onychophore.