Eumetazoa (Greek: εὖ [eu], well + μετά [metá], after + ζῷον [zóon], animal) is a clade comprising all major animal groups except sponges, placozoa, and several other obscure or extinct life forms, such as Dickinsonia. Characteristics of eumetazoans include true tissues organized into germ layers, the presence of neurons, and an embryo that goes through a gastrula stage. The clade is usually held to contain at least Ctenophora, Cnidaria, and Bilateria. Whether mesozoans and placozoans belong is in dispute. Ctenophora now appear basal eumetazoa.