Exemples: all arthropods (insects chelicerata crustaceans and myriapods) and nematoda.
It’s a philogenetic group composed by animals that have a three-layed-cuticle. This cuticle can be shifted as the animal grows in a processes called ecdysis.
References:
Telford MJ Bourlat SJ Economou A Papillon D Rota-Stabelli O (April 2008). The evolution of the Ecdysozoa. Philos. Trans. R. Soc. Lond. B Biol. Sci. 363 (1496): 152937. doi:10.1098/rstb.2007.2243. PMC 2614232. PMID 18192181.
Barnes Robert D. (1982). Invertebrate Zoology. Philadelphia PA: Holt-Saunders International. pp. 877880. ISBN 0-03-056747-5.
