only in taxon functionally related to locomotion Vertebrata <vertebrates> multicellular organism organism subdivision appendage girdle complex It is still called a complex when one of the two parts is missing (?) There are fossil fishes with only an outgrowth (no record of a girdle), including thelodonts (which have a suprabranchial fin) as well as some anaspids which have a distinctive 'paired fin' (with differing published assertions on whether it's homologous to a pec fin or pelvic fin or both or neither). There are many fishes and other vertebrates with only a girdle and no outgrowth.[VSAO] lateral structure