Gephyrocharax

Vanegas-Ríos, James A., 2016, Taxonomic review of the Neotropical genus Gephyrocharax Eigenmann, 1912 (Characiformes, Characidae, Stevardiinae), Zootaxa 4100 (1) : 82

Key to the species of Gephyrocharax

1. Distance between snout and pectoral-fin origin 20.7% SL; five maxillary teeth; in adult male posteriormost unbranched analfin ray more sagittally expanded than anteriormost branched anal-fin ray and seven anterior branched anal-fin rays posteriorly projecting beyond midlength of fin; posteroventral pouch-scale lobe of adult male present, with many convergent radii; bony hooks absent on caudal-fin rays of adult male........................................................ G. martae

- Distance between snout and pectoral-fin origin 22.8–31.2 % SL; maxillary teeth absent or, where present, up to four (rarely five, n = 2); in adult males posteriormost unbranched anal-fin ray sagittally as expanded as anteriormost branched anal-fin ray and seven anterior branched anal-fin rays posteriorly not projecting beyond midlength of fin; posteroventral pouch-scale lobe of adult males absent or, when present, with radii not converging to it; bony hooks present on caudal-fin rays of adult males.....................................................................................................(2)

2. Caudal-fin rays 11 and 12 strongly curved ventrally along their lengths in adult males; nasal bone (in dorsal view) with its lateral border greatly concave, arched at an angle equal to or less than 135°; base of caudal-fin ray 12 extending on posterior portion of hypural 2; pouch scale of adult males with radii distributed along dorsal and posterior borders............. G. m aj or

- Caudal-fin rays 11 and 12 straight along their lengths in adult males; nasal bone (in dorsal view) with its lateral border straight along its entire length or slightly concave, arched at an angle greater than 135°; base of caudal-fin ray 12 extending on posterior portion of hypural 1 or on narrow space between hypurals 1 and 2 (variable in G. intermedius ); pouch scale of adult males with radii only distributed along posterior border...........................................................(3)

3. Unbranched pelvic-fin ray hypertrophied, distally curved in adult males.................................. G. sinuensis

- Unbranched pelvic-fin ray not hypertrophied, not distally curved in adult males...................................(4)

4. Terminal lateral-line tube on middle caudal-fin rays present...................................................(5)

- Terminal lateral-line tube on middle caudal-fin rays absent....................................................(6)

5. Posteroventral pouch-scale lobe of adult males absent or reduced; caudal peduncle blotch conspicuous, more developed vertically than longitudinally...............................................................................(8)

- Posteroventral pouch-scale lobe of adult males well developed, oriented toward posteriormost ventral procurrent rays of caudal fin; caudal peduncle blotch absent, diffuse or, when conspicuous, more developed longitudinally than vertically..........(9)

6. Humeral blotch absent; interradialis muscles not surpassing posterodorsal border of pouch scale in adult males; outermost branched pectoral-fin ray of adult males moderately branched, never forming fan-shaped structure, without bony hooks and dark pigmentation distally....................................................................... G. valencia

- Humeral blotch present; interradialis muscles surpassing posterodorsal border of pouch scale in adult males; outermost branched pectoral-fin ray of adult males highly branched distally forming fan-shaped structure with few minute bony hooks and whitish area or dark blotch (sometimes black, orange, or reddish in live specimens of G. m e lanoche ir)..............(7)

7. Vertebrae 38–39; snout length 22.1–28.4 % HL; five anterior dorsal-fin rays with intense dark pigmentation at theirs bases; pouch scale of adult males reaching dorsally to caudal-fin ray 10 or area between rays 9 and 10; adipose fin present; adult specimens with anterior fontanel well developed or, if frontals slightly contacting, forming a medium-sized opening..................................................................................................... G. melanocheir

- Vertebrae 40–41; snout length 28.3–31.8 % HL; five anterior dorsal-fin rays without intense dark pigmentation at theirs bases (rays faintly dusky by scattered chromatophores); pouch scale of adult males reaching dorsally to caudal-fin ray 10 or area between rays 11 and 12; adipose fin usually absent or vestigial (> 80% of examined specimens); adult specimens with anterior fontanel absent or extremely reduced by extensive contact between frontals................................ G. torresi

8. Dorsal and ventral procurrent rays and principal rays 1–6 and 14–19 of caudal fin with intense dark pigmentation; gill gland of adult males present........................................................................ G. atracaudatus

- Caudal-fin rays without intense dark pigmentation, rays usually light gray and with scattered dark chromatophores; gill gland of adult males usually absent (present only in five of 87 examined specimens).......................... G. intermedius

9. Caudal peduncle blotch large and conspicuous, extending beyond midlength of middle caudal-fin rays; denticles absent on gill rakers; teeth of inner premaxillary row with cusps forming an anteriorly concave arch...................... G. venezuelae

- Caudal peduncle blotch absent, weakly demarcated or, when well defined, not exceeding midlength of middle caudal-fin rays; denticles present on gill rakers; teeth of inner premaxillary row with collinear cusps...............................(10)

10. Vertebrae 41–42; adult males with an intense dark pigmentation (often red in life) between pelvic- and anal-fin origins; least interorbital width 27.1–33.7 % HL; caudal peduncle blotch absent or, when present, diffuse, not reaching midlength of middle caudal-fin rays.............................................................................. .. G. caucanus

- Vertebrae 39–40; adult males lacking intense dark pigmentation near pelvic-fin origin; least interorbital width 35.3–43.7 % HL; caudal peduncle blotch conspicuous, more concentrated on middle caudal-fin rays than on caudal peduncle, and reaching midlength of middle caudal-fin rays............................................................. G. chocoensis