Triportheus Cope, 1872

Chalcinus Valenciennes in Cuvier & Valenciennes, 1850:258 [Published as 1849].

Type species: Chalcinus brachipomus Valenciennes, 1850, by subsequent designation of Eigenmann, 1910:440.

Preoccupied by Chalcinus Rafinesque, 1815, in Hymenoptera .

Triportheus Cope, 1872:263 . Type species: Triportheus albus Cope, 1872 by subsequent designation of Jordan, 1919:363.

Coscinoxyron Fowler, 1907:450 . Type species: Chalcinus culter Cope, 1872:265 by original designation and monotypy.

Diagnosis. Triportheus is diagnosed from other genera of the Characidae by the derived presence of: (1) a very short dorsal process of cleithrum terminating just above the dorsal limit of the mesocoracoid (versus process of cleithrum distinctly extending beyond the upper margin of the mesocoracoid); (2) the expansion of the upper end of the cleithrum which meets the upper portion of the mesocoracoid as a small median blade-like projection (versus expansion of cleithrum absent); (3) the expansion of anterior margin of the cleithrum anteroventrally to lie just lateral to the anterior margin of the coracoid and forming a bifurcated anterior process (versus anterior process of the cleithrum not bifurcated); and (4) the branching of lateral-line scales one to three times (versus canal tubes single and unbranched). An additional character distinguishing Triportheus is the low number of scales (1-2) in the transverse series from the pelvic-fin insertion to the lateral line.

Distribution. Río Magdalena, río Orinoco, Essequibo River, rio Amazonas, rio Tocantins, rio São Francisco, rio Parnaíba, río Paraguay, and lower rio Paraná basins.

Remarks. Myers (1940:170) proposed the suppression of Chalcinus Valenciennes (1850) which was preoccupied by Chalcinus Rafinesque (1815) in Hymenoptera . Eschmeyer (1998:1886) suggested Chalcinus Valenciennes was not preoccupied by Chalcinus Rafinesque (1815), since it was “apparently an unjustified emendation of Chalcis Fabricius (1787) in Hymenoptera ”. However, according to the ICZN (1999:9, article 10.6), a name once available remains so, irrespective of its lack of validity as an unjustified emendation, and (p. 42, article 33.2.3), it remains available with its own author and date and is a junior objective synonym of the name in its original spelling. Thus, Chalcinus Valenciennes is a junior homonym of Chalcinus Rafinesque, regardless of whether it was a justified emendation for Chalcis Fabricius.

Keys to the species of Triportheus

The genus Triportheus is readily distinguished from other characids by its body shape, midventral keel and large pectoral fins. However, it demonstrates a limited degree of intrageneric morphological variation. This fact associated to high species endemism (most of species are confined to one of the major South American drainage basins) would limit the usefulness of an all-inclusive species key. In order to facilitate identification of the species, regional keys, each of which includes a drainage system or a set of drainages, are presented. Only three species, T. auritus, T. brachipomus, and T. albus, are present in more than one drainage. Triportheus magdalenae (Steindachner, 1878) is the only Triportheus species in the río Magdalenae basin, and the only known occurrence of the genus to the west of the Andean Cordilleras. Table 2 displays the known distribution of the Triportheus species in the major river basins and drainages in South America. As some species distributions are based on very old and/or too limited samples, they will probably change by reporting new occurrences or species provided by further collecting efforts.

Key to the species of Triportheus in the Amazon basin

1. Body deep; depth at dorsal-fin origin usually more than 30% of SL; 2 scale rows between pectoral-fin insertion and ventral keel .............................................................. 2

1’. Body elongated; depth at dorsal-fin origin usually less than 30% of SL; 1 large scale row between pectoral-fin insertion and ventral keel ............................................... 5

2. Branched anal-fin rays, 20-21 ............................. T. pictus

2'. Branched anal-fin rays, 24-31 ......................................... 3

3. Lateral line scales, 28-37; at least 6 scale rows between lateral line and dorsal fin origin; branched anal fin rays, 24-28; gill rakers on lower limb of first gill arch, 24-37 ...................................................................................... 4

3'. Lateral line scales, 30-33; less than 6 scale rows between lateral line and dorsal fin origin; branched anal fin rays, 25-31; gill rakers on lower limb of first gill arch, 23-28 .......................................................................... T. curtus

4. Lateral line scales, 28-34; gill rakers on lower limb of first gill arch, 24-30 ............................................ T. rotundatus

4'. Lateral line scales, 34-37; gill rakers on lower limb of first gill arch, 29-37 ............................................. T. angulatus

5. Lateral line scales, 32-35 ..................................... T. albus

5'. Lateral line scales equal or more than 40 ....................... 6

6. Gill rakers on lower limb of first gill arch, 22-28; lateral line scales, 40-46; branched anal-fin rays, 24-28 ......................................................................... T. auritus

6'. Gill rakers on lower limb of first gill arch, 53-83; lateral line scales, 43-47; branched anal-fin rays, 28-30 ........................................................................... T. culter

Key to the species of Triportheus in the Paraná-Paraguay basins

1. Gill rakers on lower limb of first gill arch, 38-48; lateral line scales, 33-37; branched anal-fin rays, 26-31; predorsal distance, 56.1%-61.6% of SL (mean 58.8%); depth at dorsal fin origin, 31.9%-36.9% of SL (mean 33.6%) ................................................................... T. nematurus

1’. Gill rakers on lower limb of first gill arch, 26-33; lateral line scales, 28-37; branched anal-fin rays, 25-30; predorsal distance, 59.3%-64.6% of SL (mean 61.8%); depth at dorsal fin origin, 34.6%-42.5% of SL (mean 38.6%) ................................................................. T. pantanensis

Key to the species of Triportheus in the rio Araguaia - Tocantins basins

1. Body elongated; 1 scale row between pectoral-fin insertion and ventral keel; depth at dorsal-fin origin usually less than 30% SL ................................................................... 2

1'. Body deep; 2 scale rows between pectoral-fin insertion and ventral keel; depth at dorsal fin origin, 27.0%-36.2% of SL (mean 31.2%); lateral line scales, 32-35; gill rakers on lower limb of first gill arch, 40- 47; scale rows between lateral line and dorsal-fin origin, 5-6 ................................................ T. trifurcatus

2. Lateral line scales, 40-46; gill rakers on lower limb of first gill arch, 22-28 .................................................. T. auritus

2'. Lateral line scales, 32-35; gill rakers on lower limb of first gill arch, 30-39 ..................................................... T. albus

Key to the species of Triportheus in the rio São Francisco and Parnaíba basins and northeastern Brazilian coastal drainages

1. Lateral line scales, 34-37; gill rakers on lower limb of first gill arch, 35-44; scale rows between lateral line and dorsal-fin origin, 6; depth at dorsal-fin origin, 27.6%-35.0% of SL (mean 30.7%) .................................................. T. signatus

1'. Lateral line scales, 30-33; gill rakers on lower limb of first gill arch, 52-57; scale rows between lateral line and dorsal fin origin, 5; depth at dorsal fin origin, 28.2%-37.0% of SL (mean 33.4%) ................................................ T. guentheri

Key to the species of Triportheus in the río Orinoco and coastal rivers from the Essequibo river in Guyana to rio Araguari in Brazil

1. Body elongate; 1 scale row between pectoral-fin insertion and ventral keel; depth at dorsal-fin origin usually less than 30% SL ................................................................... 2

1'. Body deep; 2 scale rows between pectoral-fin insertion and ventral keel; depth at dorsal-fin origin usually more than 30% SL ................................................................... 3

2. Lateral line scales, 40-46; gill rakers on lower limb of first gill arch, 22-28; branched anal-fin rays, 24-28; scale rows between lateral line and dorsal-fin origin, 6 ......................................................................... T. auritus

2'. Lateral line scales, 32-38; gill rakers on lower limb of first gill arch, 30-40; branched anal-fin rays, 22-27 ............................................................... T. brachipomus

3. Branched anal fin rays, 28-32; lateral-lines scales, 34-39; gill rakers on lower limb of first gill arch, 24-28; depth at dorsal-fin origin, 28.7.6%-37.1% of SL (mean 33.4%); scale rows between lateral line and dorsal-fin origin, 7 ................................................................. T. orinocensis

3'. Branched anal fin rays, 24-27; lateral-lines scales, 33-36; gill rakers on lower limb of first gill arch, 27-33; depth at dorsal-fin origin, 26.7%-37.6% of SL (mean 32.9%); scale rows between lateral line and dorsal-fin origin 5-6 .............................................................. T. venezuelensis