Subclass Cladistia

Order POLYPTERIFORMES (Brachiopterygii) (17)—bichirs. This taxon has been thought by some workers to be a member of the Sarcopterygii or at least to be more closely related to them than to the Actinopterygii; they are regarded here as the sister group of all other actinopterygians. This latter view, with some recent support from Britz and Bartsch (2003) and possibly Venkatesh et al. (2001), seems with other comprehensive studies to be better supported than the hypothesis accepted in Nelson (1994) that they represent the earliest chondrostean lineage with surviving members.

Family POLYPTERIDAE (59)—bichirs. Freshwater; Africa.

Rhombic ganoid scales; spiracular opening large but canal lost; dorsal fin consisting of 5-18 finlets, each with a single spine to which is attached one or more soft rays; pectoral fin rays supported by numerous ossified radials which attach to a cartilaginous plate and two rods, thence to the scapula and cora-coid; a pair of gular plates, no branchiostegals; maxilla firmly united to skull; intestine with spiral valve; lungs partially used in respiration; vertebrae with ossified centra and neural canal. Polypterids have many primitive characters that are unknown in other living Actinopterygii and many autapomorphies (Britz and Johnson, 2003). Among the latter, they have only four rather than the usual five gill arches. Of various hypotheses concerning the homology of the posteriormost arch of polypterids, Britz and Johnson (2003) make a convincing argument that it represents the fourth arch of other Actinopterygii and that the fifth arch is absent. Britz and Bartsch (2003) discussed rib homology in gnathostomes and the unique rib type of polypterids. Maximum length about 90 cm, most species less than 30 cm.

Two genera with at least 16 extant species. In addition, there are fossils in Africa back to the middle Cretaceous and, perhaps, from the Late Cretaceous and Early Paleocene in South America (e.g., Dagetella, LLatinopollis, a replacement name for Pollia, Sainthilairia,, and Serenoichthys) (references to studies of fossils and extant forms, other than those already given, include Gayet et al., 1995; Dutheil, 1999; Murray, A. M. 2000; Stewart, 2001; and Gayet et al., 2002).

Erpetoichthys (synonym Calamoichthys) calabaricus (reedfish or ropefish). Body eel-like; pelvics absent. Confined to coastal areas adjacent to the Gulf of Guinea. Although previous editions (Nelson, 1984, 1994), for stability, favored retaining Calamoichthys as the valid generic name over the technically correct Erpetoichthys, I now use Erpetoichthys based on Eschmeyer (1998, Online).

Polypterus (bichirs). Body elongate; pelvics present. At least 15 species (e.g., Gosse, 1988; Hanssens et al., 1995; Daget et al., 2001; Britz, 2004a). There is need for a revision to determine how many of the additional nominal species might be valid.

Was this article helpful?

0 0

Post a comment