Greenwood et al. (1966) gave equal rank to the Atherinomorpha and their Acanthopterygii (= present Percomorpha). In 1969 D. E. Rosen and C. Patterson combined them under the category Acanthopterygii, and Rosen (1973a) defined the group. As described in Lauder and Liem (1983), acanthopterygians have a more mobile upper jaw than the teleosts below this level (except for the Lampriformes). This is due largely to the presence of a well-developed ascending process on the premaxilla. There is a secondary loss of the forward movement of the jaw (protrusibility) in several acanthopterygian lines. In addition, in most members of this taxon Baudelot's ligament, the ligamentous support of the pectoral skeleton (via attaching to the supracleithrum), originates on the basioc-cipital; in most lower teleosts, the Stephanoberyciformes, and—where it may be considered a secondary modification—some other acanthopterygian taxa,
Baudelot's ligament originates on the first vertebra (Johnson and Patterson, 1993).
Johnson and Patterson (1993) recognized a new sequence and different interrelationships of some of the following major taxa. They regarded the Stephanoberyciformes as the most primitive acanthopterygian, followed by the Zeiformes and Beryciformes. In addition, they recognized the first two series given here—the Mugilomorpha and Atherinomorpha—the orders Gasterosteiformes and Synbranchiformes, and the family Elassomatidae in an unresolved polychotomy. The resulting taxon, thought to be monophyletic, is termed by them the Smegmamorpha, a term derived from the first letters of the six components (recognizing the Mastacembeloidei as one component) and meaning "cleansing agent" in Greek and Latin. The smegmamorphs are diagnosed primarily by the first epineural originating at the tip of a transverse process on the first vertebra. The Smegmamorpha and Scorpaeniformes and higher taxa compose the Percomorpha of Johnson and Patterson (1993), a considerably different use of the term than recognized herein (for further comment, see under Percomorpha). However, it is important to note that the taxon Acanthopterygii as used here has the same composition as Johnson and Patterson's (1993) Acanthopterygii. Are Smegmamorpha as defined by Johnson and Patterson (1993) monophyletic? Some components probably are, but the molecular studies of Wiley et al. (2000), Roe et al. (2002), Miya et al. (2003), and Chen et al. (2003) failed to support it. The detailed work of Springer and Johnson (2004) should be studied for more information on this group. On page 117 of that publication, V. G. Springer did not believe the group to be monophyletic and broke it into three groups, Gasterosteomorpha, Atherinomorpha, and Mugilomorpha (with the last two groups being closely related but not closely related to the Gasterosteomorpha). Coauthor Johnson disagrees with this conclusion and with Springer's feeling that the name Smegmamorpha is marginally offensive (G. D. Johnson, pers. comm., 2005).
There can be little doubt that, with all the work done since 1994, changes are required in our classification. We know a lot more now. Some of the new, exciting molecular work is being done in the laboratories of Guillaume Lecointre in Paris, France; Masaki Miya in Chiba, Japan; and Mutsumi Nishida in Tokyo, Japan. These workers and their colleagues as well as many others are finding support for new clades that must be taken seriously, especially in those areas where agreement is found when different approaches are taken. However, I faced a dilemma in how to deal with so much conflicting information, and no comprehensive synthesis seemed possible. I therefore have decided to simply refer to some of the areas where we face exciting new understandings while making very few changes from Nelson (1994).There are so many such studies now available that a review here would be impossible. However, it is my hope that within a few years an attempt at a comprehensive classification can be undertaken.
Thirteen orders, 267 families, 2,422 genera, and 14,797 species (24% limited to freshwater).
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