ABSTRACT
No definition is available for the Percomorpha as they do not appear to have any unique autapomorphies not already present in their presumed common ances try with the atherinomorphs and related groups. This difficulty in definition of the Percomorpha is not surprising in view of their evident polyphyly, as seen also in the order Perciformes, from molecular analysis (Fig. 15.1; see also Orti and Li, Chapter 1, Fig. 1.5). Constituent orders of the Percomorpha are the Lampriformes*, Beryciformes, Zeiformes, Gasterosteiformes, Indostomiformes*, Pegasiformes*, Syngnathiformes, Dactylopteriformes, Synbranchiformes, Scorpaeiniformes, Perciformes, Pleuronectiformes, and Tetraodontiformes (*sperm ultrastructure unknown). The various groups will be treated here chiefly in the sequence adopted by Nelson (2006) in which definitions are given.
