Notopteridae, Bleeker, 1851

Hilton, Eric J. & Lavoué, Sébastien, 2018, A review of the systematic biology of fossil and living bony-tongue fishes, Osteoglossomorpha (Actinopterygii: Teleostei), Neotropical Ichthyology 16 (3), pp. 1-35 : 4-5

Notopteridae .

The featherbacks, or Old World knifefishes, of the family Notopteridae comprise ten species in four genera distributed in the freshwaters of south and southeast Asia ( Chitala , six species; Notopterus , one species; Fig. 4 ) and Africa ( Papyrocranus , two species; Xenomystus , one species; Fig. 5 ) ( Kottelat, 2013). The taxonomy of this family was revised by Roberts (1992), who noted that more material is needed to be examined from across the ranges of Notopterus and Xenomystus to better investigate the monospecific nature of these two genera. A single whole body fossil taxon († Notopterus primaevus , from the Tertiary of Sumatra; Sanders, 1934) is known, but is in need of preparation and redescription. † Palaeonotopterus greenwoodi , from the Early Cretaceous of Morocco, was initially described based on isolated braincase and fragmentary skull bones ( Forey, 1997, Taverne, Maisey, 1999) as a member of Notopteridae based on the presence of a supraorbital branch of the otic sensory canal, although this character was since identified in mormyroids ( Cavin, Forey, 2001). Cavin, Forey (2001) considered † Palaeonotopterus greenwoodi to be either a stem notopterid or a stem mormyroid, and in subsequent phylogenetic analysis, it has been recovered as a stem group mormyroid ( Hilton, 2003; Wilson, Murray, 2008). As noted by Cavin, Forey (2001), however, its anatomy is largely unknown and prevents confident phylogenetic interpretations.

All notopterids are extremely laterally compressed with an elongate anal fin that is confluent with the rounded caudal fin. The dorsal fin (absent in Xenomystus ) has a short base but is tall and rounded. The body profile particularly that of Chitala , undergoes a dramatic ontogenetic change, in which there is a substantial dorsal concavity above the head in adult fishes (not evident in Notopterus or Xenomystus , and only slightly developed in Papyrocranus ). All species have a series of small abdominal scutes formed by paired elements ( Hilton, 2003: fig. 34). The species of Xenomystus and Papyrocranus are electroreceptive, whereas those of Notopterus and Chitala are not ( Bradford, 1982).

Notopteridae is widely regarded as the sister group of Mormyroidea (= Mormyridae + Gymnarchidae ) based on both morphological ( Ridewood, 1904, 1905; Taverne, 1979; Lauder, Liem, 1983; Li, Wilson, 1996a) and molecular data ( Lavoué, Sullivan, 2004). Hilton’s (2003) analysis resulted in a Notopteridae + Osteoglossidae clade, but he allowed that there were several characters that were not included in that analysis that supported the conventional grouping, as found in more recent phylogenetic analyses ( Bonde, 2008; Wilson, Murray, 2008; Murray et al., 2010, 2018).

Figures

Fig. 4. Notopterinae. a. Notopterus notopterus (UF 237410; 167 mm SL). b. Chitala ornata (UF 237959; 498 mm SL). Photos by Z. Randall.

Fig. 5. Xenomystinae. a. Xenomystus nigri (CU 91453). b. Papyrocranus afer (CU 97661). Scale bars = 2 cm.