Superorder Protacanthopterygii

As stated in Nelson (1994) and still regarded as true, the classification of the protacanthopterygians has been and continues to be unstable, largely because the many characters exhibit a mosaic distribution, show reduction, are otherwise highly modified, or are primitive for the euteleosts. The composition of this assemblage over the past many decades has undergone much reduction, largely as a result of Rosen (1973a). In Nelson (1984) I recognized it with the one order, Salmoniformes, containing four suborders, and in Nelson (1994) with a differing arrangement but with the same content placed in three orders. Much of the work immediately prior to Johnson and Patterson (1996), and employed in Nelson (1994), was by W. L. Fink, D. E. Rosen, and C. P. J. Sanford. Herein, I follow many of the conclusions in the detailed work of Johnson and Patterson (1996) for relationships within the orders. However, because of much continuing disagreement about higher relations, I choose to not change the overall composition followed in Nelson (1994), but the ordinal recognition and sequence are changed. It will be important for all future researchers to carefully study Johnson and Patterson (1996) and the more recent works, mostly molecular, that arrive at differing conclusions. I also encourage careful study of Williams (1987), who indeed may have been correct in certain conclusions not commonly acknowledged (it is unfortunate that his work was not fully published). Nelson (1994) reviewed some of the history of the classification of this group, summarizing some of the conclusions of those with differing views of its classification, such as Williams (1987).

The most major deviation here from Johnson and Patterson (1996) is that they regarded the Esociformes as sister to the Neoteleostei (i.e., not as prota-canthopterygians). Although not conclusive, Williams (1987), Arratia (1997,

1999), Zaragueta-Bagils et al. (2002), and López et al. (2004) found esociforms and salmoniforms to be sister taxa; while such a relationship is not formally expressed here, the arrangement is not incompatible with it either. A comparison of the arrangement ofJohnson and Patterson (1996) and that given here is as follows:

Four orders with 12 families, 94 genera, and about 366 species.

Johnson and Patterson (1996) Herein

Euteleostei

Euteleostei

Protacanthopterygii

Protacanthopterygii

Argentiniformes

Argentiniformes

Salmoniformes

Osmeriformes

Salmonoidei

Salmoniformes

Osmeroidei

Esociformes

Neognathi

Neoteleostei—for remaining euteleosts

Esociformes

Neoteleostei

Order ARGENTINIFORMES (33)—marine smelts. Complex posterior branchial structure ("epibranchial" organ), termed the "crumenal organ" (Johnson and Patterson, 1996, discussed this and other characters).

Greenwood and Rosen (1971) recognized the two suborders given here as each other's closest relatives; they were included in their suborder Argentinoidei, as two superfamilies, Argentinoidea and Alepocephaloidea, as given in Nelson (1994). The recognition of this taxon at the ordinal level with two suborders follows Johnson and Patterson (1996). Possible fossil groups include the family Pattersonellidae described by L. Taverne in 1982.

Six families, 57 genera, and about 202 species.

Suborder Argentinoidei. Adipose fin usually present; caudal fin forked; dorsal fin near body center; maxillae and premaxillae (when present) toothless; supramaxilla absent; mouth usually small; branchiostegal rays 2-7; lateral line scales 40-70; swim bladder, when present, physoclistous; mesocoracoid present or absent. Many are bathypelagic. Color usually silvery. Hatch from small eggs (about 1-3 mm diameter) with larval development gradual and transformation to demersal juvenile.

The classification of this taxon is based on Johnson and Patterson (1996:308-309); other references include Kobyliansky (1990, 1998), Mecklenburg et al. (2002), and Carter and Hartel (2003). Johnson and Patterson (1996) and Patterson and Johnson (1997a, b) noted errors involved in an earlier cladistic study of D. P. Begle.

Nineteen genera and about 72 species.

Family ARGENTINIDAE (166)—argentines or herring smelts. Marine; Atlantic, Indian, and Pacific.

Eyes not tubular; adipose fin over anal fin base; postcleithra and mesocoracoid present; dorsal fin origin in front of pelvics; pectoral fin base on ventrolateral surface; dorsal fin rays 10-14; anal fin rays 10-17; pectoral fin rays 11-25; pelvic fin rays 10-15; branchiostegal rays 4-6; vertebrae 43-70 (most with 46-55).

Two genera, Argentina and Glossanodon, with about 23 species.

Family OPISTHOPROCTIDAE (167)—barreleyes or spookfishes. Marine; tropical to temperate, Atlantic, Indian, and Pacific.

Eyes usually tubular; pectoral fin base on side; pelvic fin base on side in some; adipose fin in some; photophores in some; most lack swim bladder; frontals fused; parietals not meeting on midline (true also for bathylagids); branchiostegal rays 2-4.

Six genera, Bathylychnops, Dolichopteryx, Macropinna, Opisthoproctus, Rhynchohyalus, and Winteria,, with about 11 species.

Family MICROSTOMATIDAE (168)—pencilsmelts. Marine; tropical to temperate seas, Atlantic, Indian, and Pacific (extending from the subarctic to the Antarctic).

Eleven genera and about 38 species.

Subfamily Microstomatinae (pencilsmelts). Lateral line and lateral-line scales extending onto tail; postcleithra present; mesocoracoid absent; pectoral fin base on side; dorsal fin rays 9-12; anal fin rays 7-10; pectoral fin rays 7-14;

pelvic fin rays 8-12; branchiostegal rays 3 or 4; vertebrae 41-50. Primarily tropical to temperate latitudes.

Three genera with about 18 species. Nansenia. Adipose fin present; dorsal fin in front of pelvics. Fourteen species found from the subarctic to the subantarctic. Microstoma. No adipose fin; dorsal fin behind pelvics.

One or two species. Xenophthalmichthys. No adipose fin; dorsal fin origin behind pelvic fin insertion; eyes tubular (protruding anteriorly); pectoral fin base well up on side, fin with 7 rays; pelvic fin with 7 or 8 rays.

One or two species.

Subfamily Bathylaginae (deepsea smelts). Adipose fin present or absent; postcleithra and mesocoracoid absent; pectoral fin base near ventral surface; dorsal fin rays 6-13; anal fin rays 10-28; pectoral fin rays 7-16; pelvic fin rays 6-11; branchiostegal rays 2; vertebrae 38-55. Extending from the subarctic to the Antarctic.

Eight genera, Bathylagichthys, Bathylagoides, Bathylagus, Dolicholagus, Leuroglossus, Lipolagus, Melanolagus, and Pseudobathylagus, with about 20 species.

Suborder Alepocephaloidei. Dorsal fin inserted well back on body; no adipose fin; upper jaw with teeth except in Leptochilichthys; one or two supramaxillae; mouth usually large; no swim bladder; mesocoracoid present; dark-colored fishes. Hatch from large eggs with direct development.

The classification of this taxon is based on Johnson and Patterson (1996: 311-312). They and Patterson and Johnson (1997a, b) noted errors involved in an earlier cladistic study of D. P. Begle. Inoue et al. (2003) placed this taxon in the Ostarioclupeomorpha (= Otocephala) based on molecular characters. About 38 genera with 130 species.

Family PLATYTROCTIDAE (Searsiidae) (169)—tubeshoulders. Marine; all oceans (absent from Mediterranean).

Black shoulder sac apparatus located under shoulder girdle produces blue-green luminous fluid, conspicuous opening through tubular papilla just below lateral line; light organs present in many species (directed horizontally in young and ventrally in adults); subcutaneous canal system, usually connected to scale pockets by pores; pectoral fin rays 14-28; pelvic fin rays 6-10, pelvic fins absent in Platytroctes apus; swim bladder absent; branchiostegal rays 4-8; vertebrae 40-52. Maximum length about 30 cm. Most species occur between 300-1,000 m.

Thirteen genera, Barbantus, Holtbyrnia, Maulisia, Mirorictus, Normichthys, Paraholtbyrnia, Pellisolus, Persparsia, Platytroctes, Sagamichthys, Searsia, Searsioides, and Tragularius, with 37 species (Matsui and Rosenblatt, 1987).

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