- Deuterostomes (from Greek: lit. ‘mouth second’) are bilaterian animals of the superphylum Deuterostomia (/ˌdjuːtərəˈstoʊmi.ə/), typically characterized by their anus forming before the mouth during embryonic development. Deuterostomia is further divided into 4 phyla; Chordata, Echinodermata, Hemichordata, the extinct Vetulicolia known from Cambrian fossils. The extinct clade Cambroernida is also thought to be a member of Deuterostomia.