Tetranematichthys (de Pinna, 1998)

Peixoto, Luiz Antônio Wanderley & Wosiacki, Wolmar Benjamin, 2010, Description of a new species of Tetranematichthys (Siluriformes: Auchenipteridae) from the lower Amazon basin, Brazil, Neotropical Ichthyology 8 (1), pp. 69-75 : 74

Key to the species of Tetranematichthys

1. Lateral margin of head at anterior portion of orbit, parallel to the posterior limit of operculum, in ventral view ( Fig. 5a ); ventral region light or dark colored; presence or absence of digit-like projections on distal portion of mandibular barbel; length of mandibular barbel 5.2- 24.6% HL; length of main ray of upper caudal-fin lobe 14.5- 20.5% SL; body width at pectoral-fin insertion 82.1- 110.0% HO; head length 24.4- 31.0% SL ................................................. 2

1a. Lateral margin of head at anterior portion of orbit, diverging laterally to posterior limit of operculum, in ventral view ( Fig. 5b ); uniform color pattern with dark patches along the body; presence of digit-like projections on distal portion of mandibular barbel; length of mandibular barbel 6.3-23.5% HL; length of main ray of upper caudal-fin lobe 18.1-19.9% SL; body width at pectoral-fin insertion 117.0- 125.0% HO; head length 28.5-32.3% SL ……. T. quadrifilis (rio Guaporé Basin)

2. Dorsal region without blurred light area; dark patches of pigmentation present along the body; ventral region dark colored; one light colored stripe present on the caudal-fin; pelvic-fin without distinct light colored stripe; anterior margin of mandibular barbel with digit-like projections; length of mandibular barbel 7.4-24.6% HL; snout length 41.2-49.3% HL; body width at pectoral-fin insertion 69.2- 79.3% HL …...…. T. wallacei (rio Tocantins, rio Orinoco and several stretches of the rioAmazon, except rio Guaporé)

2a. Dorsal region with blurred light area; dark patches of pigmentation absent along the body; ventral region light colored; two light colored stripes present on the caudalfin; pelvic-fin with distinct light colored stripe; anterior margin of mandibular barbel serrated on distal portion; length of mandibular barbel 4.5-6.0% HL; snout length 28.8- 34.5% HL; body width at pectoral-fin insertion 82.1-88.7% HL........ T. barthemi (rio Saracá, rioAraticum and rio Urubu).

Figures

Fig. 5. Ventral view of head and anterior portion of (a) Tetranematichthys barthemi, holotype, male, MPEG 11081, 154.2 mm SL; and (b) Tetranematichthys quadrifilis, MPEG 6535, 127.2 mm SL, showing the difference between the alignments of the postorbital portion of head.