Gephyrocharax major Myers, 1929

Vanegas-Ríos, James A., 2016, Taxonomic review of the Neotropical genus Gephyrocharax Eigenmann, 1912 (Characiformes, Characidae, Stevardiinae), Zootaxa 4100 (1) : 38-45

Gephyrocharax major Myers, 1929

( Figs. 17–19 )

Gephyrocharax chocoënsis [not of Eigenmann, 1912]. Pearson, 1924: 46 [in part, misidentified, name misspelled].

Gephyrocharax major Myers in Eigenmann & Myers, 1929: 477, 479–480 [key, original description, nine syntypes (“cotypes”), CAS 44286 (IU 17290), type locality: “Popoi R., Upper Beni” (= Bolivia: La Paz, upper Beni River basin, Popoi or Popoy River)]. Schultz, 1944: 323 [key]. Böhlke, 1958: 51 [comments on similarities with G. chaparae ]. Weitzman & Fink, 1985: 103 [examined material]. Weitzman, 2003: 224 [catalogue]. Carvalho, Flores, Espino, Trevejo, Ortega, Jerep, Reis & Albert, 2012: 975, 993, table 2, unnumbered fig. on page 684 [ Peru: Madre de Dios River basin, Las Piedras River]. Ortega, Hidalgo, Trevejo, Correa, Cortijo, Meza & Espino, 2012: 36 [listed from Peru]. Bonilla-Rivero & López-Rojas, 2013: 489, fig. 1 [distribution map]. Vanegas-Ríos, Azpelicueta, Mirande & Gonzales, 2013: 282 [examined material]. Thomaz, Arcila, Ortí & Malabarba, 2015: Add. File 5 [tentative classification].

Gephyrocharax chaparae Fowler, 1940: 70 –72, figs. 25–27 [original description, holotype ANSP 68967, type locality: “Todos Santos, Rio Chapare , Bolivia ” (= Bolivia, Cochabamba, Todos Santos, Chapare River)]. Weitzman, 2003: 224 [catalogue]. Bonilla-Rivero & López-Rojas, 2013: 489, fig. 1 [distribution map]. Vanegas-Ríos, Azpelicueta, Mirande, Gonzales, 2013: 282 [examined material]. Thomaz, Arcila, Ortí & Malabarba, 2015: Add. File 5 [tentative classification]. [new synonym].

Corynopomops opisthopterus Fowler, 1943: 6 –7, fig. 4 [original description based on single specimen, holotype ANSP 69195, type locality: “Todos Santos, Bolivia ” (= Bolivia, Cochabamba, Todos Santos, Chapare River]. Böhlke, 1958: 40, 42–43, 50–51, table 1 [revision, proposed as synonym of G. chaparae ]. Weitzman & Fink, 1985: 2 [same conclusion and synonym by Böhlke, 1958]. Weitzman, 2003: 224 [listed in synonyms of G. chaparae , catalogue]. Vanegas-Ríos, Azpelicueta, Mirande & Gonzales, 2013: 282 [listed as synonym of G. chaparae , examined material]. [new synonym].

Gephyrocharax chaporae . Schultz, 1944: 322 [key, name misspelled].

Gephyrocharax chapare . Chernoff, Machado-Allison, Willink, Sarmiento, Barrera, Menezes & Ortega, 2000: 274, 279, table 1 [listed from Amazon drainages of Bolivia, name misspelled].

Diagnosis. Gephyrocharax major differs from its congeners by having the caudal-fin rays 11 and 12 strongly curved ventrally in adult males (vs. these caudal-fin rays straight), the lateral border of nasal bone concave in dorsal view, arched at an angle equal to or less than 135° (vs. lateral border straight along its length or arched at an angle higher than 135°), the pouch-scale radii in adult males distributed along the dorsal and posterior borders (vs. pouch-scale radii confined to the posterior border), the caudal-fin rays 12 and 13 in adult males slightly separated from each other, maintaining nearly the same distance along the rays lengths, with the respective interradialis bundle not pronouncedly developed posteroventrally (vs. these caudal-fin rays strongly separated or diverging posteriorly due to a interradialis bundle markedly developed posteroventrally, except in G. chocoensis ). Gephyrocharax major is also distinguished from its congeners by the base of caudal-fin ray 12 extending on the posterior portion of hypural bone 2 (vs. base of this ray extending on the posterior portion of hypural 1 or on a narrow space between hypurals 1 and 2, except in G. intermedius and G. m a r t a e). The snout to pectoral-fin length (24.3–29.9 % SL vs. 20.7 % SL) also differentiates G. major from G. m a r t a e. The possession of a terminal lateral line tube between caudal-fin rays 10 and 11 (vs. absence of this tube) distinguishes G. major from G. melanocheir , G. t o r re s i, and G. v a l e n ci a. Additionally, the species differs from G. atracaudatus , G. caucanus , G. chocoensis , G. intermedius , and G. va l en c i a by having two tendinous fibers posteriorly inserted from flexor dorsalis superior to caudal-fin rays (vs. one tendinous fiber).

Description. Morphometric data in Table 5 . Largest male 60.0 mm SL, largest female 64.4 mm SL. Body laterally compressed, with maximum depth at vertical through midpoint between pelvic- and anal-fin origins. Dorsal profile of head somewhat convex from margin of upper lip to distal tip of ascendant process of premaxilla, and straight from that point to tip of supraoccipital spine. Dorsal profile of body slightly convex from posterior end of supraoccipital spine to dorsal-fin origin, slanting posteroventrally along dorsal-fin base, and straight from posteriormost dorsal-fin ray to caudal peduncle ( Fig. 17 ). Ventral profile of body convex from tip of dentary to pelvic-fin origin, slightly concave from this point to anal-fin origin, and slanting posterodorsally and straight from this point to caudal peduncle origin. Anterior fontanel absent (frequently adult specimens with frontals contacting posterior to epiphyseal bar) or reduced to narrow opening anterior to epiphyseal bar. Anterior nostril rounded and separated by skin fold from larger posterior nostril. Groove with at least three rows of neuromasts extending from half-length between posterior pore of nasal bone and nostrils to posterior portion of frontals. Small groove with few neuromasts between nostrils and nasal bones.

Mouth superior, lower jaw projecting slightly anterior to tip of upper jaw. Premaxilla with two rows of teeth. Outer row with 2 (1), 3*** (49), 4*/** (135), or 5 (21) teeth; usually tricuspid, rarely conical or bicuspid teeth. Inner row with 4* (194) or 5 (15) teeth; symphyseal tooth tetracuspid, remaining teeth pentacuspid (rarely tetracuspid). Maxilla rarely toothless (1), usually with 1* (85), 2 (111), or 3 (10) teeth; tri- to pentacuspid ( Fig. 18 A), larger specimens usually with greater number of cusps and broader anteriormost tooth. Maxilla posteriorly reaching vertical through anterior one-third of eye. Dentary with 9 (1), 10 (11), 11*** (32), 12 (28), 13*/** (37), 14 (14), 15 (9), 16 (3), or 17 (1) teeth; three anteriormost teeth larger, pentacuspid, followed by one median-sized tooth usually tri- to pentacuspid, and 5 (1), 6 (11), 7*** (32), 8 (28), 9*/** (37), 10 (14), 11 (9), 12 (3), or 13 (1) smaller conical to tricuspid teeth ( Fig. 18 B).

Dorsal-fin rays ii,7 (6), 8* (199), or 9 (3). Eight* or 9**/*** proximal pterygiophores on dorsal fin (17 rad, 14 c&s). Dorsal-fin origin located at vertical through anal-fin rays 5–11. Adipose-fin origin located at vertical between bases of two posteriormost anal-fin rays. Anal-fin rays iv (12), v*/** (160), or vi (35), 26 (1), 27 (1), 28 (2), 29 (31), 30** (46), 31 (50), 32* (43), 33 (23), 34 (6), or 35 (4) (holotype ANSP 69195 abnormally with iv,12 rays, not included in comparisons). Twenty-nine to 34 proximal pterygiophores on anal fin (17 rad, 14 c&s). Anal-fin origin closer to origin of hypural joint than to snout tip. Pectoral-fin rays i,9 (12), 10*/*** (97), 11** (86), or 12 (10). Pectoral-fin distal tip posteriorly reaching one-quarter to one-half of pelvic-fin length. Pelvic-fin rays i,6 (205) in all specimens ( Fig. 6 ). Pelvic-fin origin located at vertical between pored lateral-line scales 8–11 and anterior to body midlength. Caudal fin forked with 10/9 principal rays in all specimens.

Scales cycloid, with numerous radii along posterior margin. Lateral line complete, pored scales 40 (3), 41 (17), 42** (33), 43* (55), 44 (65), 45 (21), 46 (9), 47 (2), 48 (1) (some scales lost in holotype ANSP 69195, possibly 38). Terminal lateral-line tube present. Predorsal scales 17 (23), 18** (54), 19 (64), 20* (40), 21*** (19), or 22 (3). Scale rows between dorsal fin and lateral line 6 (102) or 7* (104). Scale rows between lateral line and anal fin 5**/ *** (111) or 6* (96). Scale rows between lateral line and pelvic fin 4 (18), 5*** (164), or 6*/** (62). Circumpeduncular scales 14 (10), 15 (35), 16*/** (83), 17*** (45), or 18 (9). One or two rows of scales forming sheath along three-quarters or almost entire length of anal-fin base (scales missing in lectotype CAS 42286 and holotypes ANSP 68967 and 69195); main ventral row with 14 (1), 15 (2), 17 (2), 18 (1), 20 (3), 21 (2), 23 (60), 24 (9), 25 (5), 26 (15), 27 (19), 28 (12), 29 (11), 30 (6), 31 (5), or 32 (5) scales. Total number of vertebrae 39 (7), 40*/ ** (13), 41 (7), or 42 (1); 16 (7), 17*/** (21), or 18 (1) precaudal and 22 (4), 23** (13), 24 (8), or 25 (2) caudal (17 rad, 14 c&s); holotype ANSP 69195 abnormal, with 34, 23 and 17 vertebrae respectively. Gill-rakers on dorsal limb of first branchial arch 6 (11), 7* (98), or 8 (18); ventral limb with 11 (2), 12 (55), 13* (63), or 14 (6).

Color in alcohol. Ground color pale yellowish or light brown, darker along mid-dorsal line, slightly lighter ventrally. Minute dark chromatophores scattered over body, absent or reduced on lateral and ventral regions of abdomen and caudal peduncle. Dark midlateral stripe diffuse (silvery in specimens retaining guanine), extending from posterior region of humeral blotch or at vertical through pelvic-fin origin to caudal peduncle. Dark chromatophores present along myosepta between lateral line and upper portion of anal fin. Dark humeral blotch vertically elongate (irregularly shaped in some specimens). Dark blotch on caudal peduncle, somewhat ovoid, horizontally elongate, and extending from posterior region of peduncle across interradialis muscles to base of middle caudal-fin rays. Dorsal fin light gray or faint yellow, with scattered dark chromatophores on borders of rays and membranes. Anal fin light gray, with dark chromatophores concentrated on interradial membranes. Caudal fin light gray, slightly darkened by presence of dark chromatophores mostly concentrated on middle rays. Pectoral and pelvic fins light gray, chromatophores absent or reduced on rays. Head darker dorsally than ventrally. Few scattered dark chromatophores on opercle and infraorbitals. Premaxilla, anterior portion of maxilla, dentary, and lips with faintly concentrated dark chromatophores. Variations in color pattern between males and females described under sexual dimorphism.

Sexual dimorphism. Males with bony hooks on anal-, caudal-, and pelvic-fin rays. Caudal fin with short, slender, anterodorsally oriented hooks, especially on dorsal branched portions of rays 13–16 ( Fig. 18 C). Pelvic-fin rays, except innermost ray, with short, slender anteroventrally oriented hooks, more numerous on bases of rays; usually one or two per segment, rarely paired. Anal fin with slender, anterodorsally or anterolaterally placed hooks with broad bases; from 3 to 17 pairs per ray located from posteriormost unbranched ray and up to eight anterior branched rays, larger hooks on middle and posterior rays of this range. Occasionally, middle anal-fin rays slightly longer than remaining rays on adult males, resulting in convex-shaped anal-fin margin from posteriormost unbranched anal-fin ray across anterior branched rays to branched rays 15 or 17. Females with anal-fin rays gradually decreasing in length from anteriormost branched ray to posteriormost branched ray; anal-fin margin somewhat concave or straight. Anal-fin base of adult males often slightly concave along its midlength, this base straight in females. Adult females without externally developed urogenital papillae.

Some adult males with numerous chromatophores more concentrated on interradial membranes of anal and caudal fins, medially placed to pouch scale. Mature males with caudal-fin rays 11 and 12 curved, these rays straight in females. Mature males with hypertrophied scale forming pouch on lower caudal-fin lobe and with ventral procurrent rays 2 and 3 forming spur-shaped structure. Scarce small aggregations of apparent glandular tissue located on caudal-fin rays and medially to pouch scale. Second and third procurrent rays straight or slightly convex, adpressed, usually fused distally in large adult males; these rays more developed sagittally than laterally in comparison with remaining procurrent rays. First ventral procurrent ray straight or somewhat convex on its ventral margin ( Fig. 18 C). Second ventral procurrent ray somewhat longer than third ray, reaching distally midlength of first ventral procurrent ray, and more expanded sagittally than third ventral procurrent ray. Pouch scale with 15–38 radii distributed along dorsal and posteroventral margins and usually located between caudal-fin rays 10 or 11 and midpoint between first and second ventral procurrent rays. Posteroventral pouch-scale lobe absent ( Figs. 18 C–D). Dorsal surface of pouch scale attached via soft tissue (apparently connective) to caudal-fin rays 10 or 11 to 13. Posterior margin of pouch scale located between caudal-fin rays 10 or 11 and third ventral procurrent ray (rarely on dorsal margin of fourth procurrent ray). Five or six scales (rarely three) in vertical series situated ventral to terminal lateral-line scale, overlaying posterior portion of pouch scale. Dorsal margin of pouch scale usually with large notch (well developed in mature males) in which part of soft tissue attached from caudal-fin rays. Ventral portion of pouch scale with two accessory scales (one small and other of large size and horizontally elongate), juxtaposed, forming part of opening pocket. Larger accessory scale posterior to smaller accessory scale, forming posteroventral region of pocket and extending onto second and third ventral procurrent rays. Females with large scale with 18 (1), 19 (1), 20 (2), 22 (2), 23 (1), 25 (3), 26 (1), 29 (1), 35 (1), or 37 (1) radii on lower caudal-fin lobe.

below including holotype of Corynopomops opisthopterus (C) and holotype (D) plus paratypes of G. chaparae (several lots in same jar mixed with topotypes, see details in text). Ranges of males

including lectotype values, while ranges of females including these holotype values. M = mean; SD = standard deviation.

Characters CAS 44286 CAS 236011 ANSP 69195 ANSP 68967 Males Females and unsexed juveniles Mature males with gill gland, formed by fusion of 3 (1), 4 (2), 5 (2), 6 (5), 7 (6), 8 (8), 9 (23), 10 (6), 11 (11), 12 (6), 13 (1), or 14 (1) anterior gill filaments of ventral limb of first gill arch. Total number of ventral limb gill filaments 21 (3), 24 (1), 25 (7), 26 (2), 27 (9), 28 (9), 29 (18), 30 (13), 31 (7), or 32 (7). Gill-gland length 1.7–4.6 % SL (mean = 3.0 % SL). Regression comparisons of morphometric data by sex with major differences in pectoral fin to pelvic fin length (higher values in females than in males), but larger specimens not completely separating on SL axis.

Distribution. Gephyrocharax major is a widespread species, distributed in numerous drainages flowing into the Yuruá, Nanay, Madre Dios, Beni, and Mamoré rivers basins in the Amazon River system of Bolivia and Peru ( Fig. 2 ).

Remarks. The eleven paratypes (ANSP 68968–68978) designated by Fowler (1940) for G. chaparae were found mixed with 14 topotypes in the same jar (ANSP 69161) that were not cited in the original description but were collected in the same collecting event (August 8th, 1937). These paratypes and topotypes could not be discriminated from each other due to the scarce information provided in Fowler (1940). However, they were confirmed as the same species. Fowler (1940) described G. chaparae mainly based on, in his own words, the incomplete description of G. m a j o r by Myers (in Eigenmann & Myers 1929), which apparently did not allow him to identify the specimens with safety. Fowler (1940) emphasized on some differences between G. chaparae and G.

major : the proportion of the head length (3.8–4.0 in SL vs. 4.2–4.4 in SL), number of lateral-line scales (36–38 vs. 40–41 plus 3 lateral), and dorsal-fin origin to hypural complex length (2.6–2.8 in SL vs. 2.5 in SL). However, after the comparison made among the type specimens of both species ( G. chaparae : ANSP 68967, ANSP 68969–68978, and 69161; G. m a j o r: CAS 44286 and 236011), none of these differences were found to be consistent ( G. chaparae and G. major , respectively, head length: 3.9–4.5 in SL vs. 4.1–4.6 in SL; lateral-line scales: 41–45 vs. 41–45; dorsal-fin origin to hypural complex length: 2.4–2.8 in SL vs. 2.4–2.7 in SL). Furthermore, the type specimens of G. chaparae and G. major were not grouped separately along the components in the SPCA of the morphometric data ( Figs. 19 A–B). A similar finding was found in the meristic, osteological, and myological data that did not reveal any differences distinguishing both nominal species. These results support the hypothesis of G. chaparae as a junior synonym of G. major .

Böhlke (1958) was the first author proposing Corynopomops opisthopterus Fowler as junior synonym of G. chaparae . This supposition was followed by Weitzman & Fink (1985) and Vanegas-Ríos et al. (2013). Although the holotype of C. opisthopterus was not included in the SPCA of the type series of G. chaparae and G. major due to its abnormal, apparently malformed body, the species is considered to be a synonym of G. major based on their morphological similarities.

The SPCA of the morphometric data comparing the examined specimens of G. m a j o r grouped by basins (Acre, Beni, Madre de Dios, Mamore, Nanay, Tahuamanu, Ucayali, and Yuruá rivers basins) did not differentiate the groups ( Figs. 19 C–D). This result agreed with the great overlap found in the meristic data, pigmentation of body, and skeleton and muscle anatomy comparisons (Beni River: UMSS 10015; Chapare River: UF 38194 and UMSS 2833; Orton River: MUSM 8518 and 21519; Ucayali River: MUSM 18906 and 26100). Thus, G. m a j o r is recognized as a widespread species across the western portions of the Amazon basin in Bolivia and Peru and its occurrence at the Yurúa and Nanay rivers basins are confirmed for the first time. The specimens of the Nanay River basin are consequently considered the northernmost record of the species.

Herein a lectotype is designated from the respective syntypes of G. m a j o r (previously CAS 44286, now CAS 236011), turning them paralectotypes. In Myers’s description of G. m a j o r (in Eigenmann & Myers 1929), the specimens IU 17291 (now CAS 44286) were cited as cotypes, leaving the remaining cited specimens as non-types. Following the recommendation 16E by the ICZN (1999), a type is more appropriated than a series of syntypes (or cotypes) even more when in Myers’s description neither a figure (photo) nor a particular datum was associated to a possible type ( Fig. 17 A).

Material examined. Bolivia: ANSP 68967, holotype of Gephyrocharax chaparae , 32.8 mm SL (rad), female, [Cochabamba], Todos Santos, Chapare River,, approximately 16°47'59.99"S 65°7'59.99"W 215 m a. s. l. ANSP 68968–68978, and 69161, 25 paratypes (11 paratypes mixed with 14 topotypes), 24.5–44.7 mm SL (3 rad 30.2– 44.7 mm SL), [Cochabamba], Todos Santos, Chapare River, approximately 16°47'59.99"S 65°7'59.99"W 215 m a. s. l. ANSP 69195, holotype of Corynopomops opisthopterus , 30.9 mm SL (rad), [Cochabamba], Todos Santos, Chapare River, approximately 16°47'59.99"S 65°7'59.99"W 215 m a. s. l. AUM 23725, 1, 25.3 mm SL, Beni, Amazon River basin, Madeira River basin, tributary of Beni River about 15 km S of Rurrenabaque, approximately 14°33'38.14"S 67°29'43.28"W 232 m a. s. l. CAS 44286 (previously syntypes), lectotype of Gephyrocharax major by present designation, 40.6 mm SL (rad), male, [La Paz, close to Popoy], upper Beni River basin, Popoi River [or Popoy River], approximately 15°37'0.12"S 67°17'60.00"W 532 m a. s. l. CAS 78813, 23, 40.3–48.1 mm SL, Beni, Amazon River basin, Beni River, Rurrenabaque, approximately 14°26'29.65"S 67°31'54.64"W 333 m a. s. l. CAS 236011, 8 paralectotypes of Gephyrocharax major by present designation, 35.4–55.8 mm SL (8 rad), same data of the lectotype. UF 30697, 54, 23.1–28.4 mm SL, Sara, Santa Cruz, small streams and pools 3 km S of Santa Rosa, approximately 17°6'51.42"S 63°35'52.76"W 262 m a. s. l. UF 38194, 7, 41.4–46.8 mm SL (2 c&s 45.4–46.5 mm SL), Cochabamba, Chapare , creek 7 km NW of Villa Tunari, approximately 16°56'51.34"S 65°22'19.07"W 268 m a. s. l. UF 82024, 6, 25.1–40.1 mm SL, Beni, Yacuma, Seco creek, tributary of Matos River 29 km E, 12 km S San Borja, 14°58'60.00"S 66°26'0.00"W 202 m a. s. l. UF 82333, 29, 18.5–31.6 mm SL, Santa Cruz, Andrés Ibáñez, Piray River basin, Jorge River 12 km W of Warnes, 17°27'27.73"S 63°13'13.79"W 327 m a. s. l. UMSS 1163, 1, 22.8 mm SL, Cochabamba, Mamoré River basin, Isiboro, Chipiriri, Colonia Santa Rosa River, 16°50'42.85"S 65°23'44.33"W approximately 243 m a. s. l. UMSS 1894, 1, 35.1 mm SL, Mamoré River basin, Isiboro, Chipiriri, Santa Fé River, 16°48'10.81"S 18'30.46"W 225 m a. s. l. UMSS 2833, 25, 33.2–50.9 mm SL (2 c&s 43.7–50.2 mm SL), Cochabamba, Mamoré River basin, Isiboro, Chipiriri, Senda Bayer River, 16°53'5.15"S 65°23'3.53"W approximately 254 m a. s. l. UMSS 2868, 6, 40.2–45.3 mm SL, Mamoré River basin, Isiboro, Chipiriri, Villa Samual San Juan River, 16°52'56.51"S 65°20'44.03"W approximately 249 m a. s. l. UMSS 3468, 15, 34.8–50.5 mm SL, Isiboro, Mamoré River basin, Chipiriri River basin, Senda Bayer River, 16°52'0.04"S 65°23'26.46"W 245 m a. s. l. UMSS 3818, 10, 31.0– 50.8 mm SL, Mamoré River basin, Isiboro, Chipiriri, Colonia Senda Bayer River, 16°51'4.95"S 65°21'40.63"W approximately 240 m a. s. l. UMSS 3997, 1, 38.1 mm SL, Mamoré River basin, Isiboro, Chipiriri, Villa General Barrientos River, 16°49'38.90"S 65°22'2.73"W approximately 232 m a. s. l. UMSS 4386, 4, 27.5–32.3 mm SL, Madeira, Mamoré River basin, Ichilo, 15 de Junio creek, Puerto Cochabamba, 16°51'57.30"S 65°8'55.21"W approximately 229 m a. s. l. UMSS 4449, 5, 30.6–35.7 mm SL, Madeira, Mamoré River basin, Ichilo, unknown creek, 16°52'44.45"S 65°27'50.89"W approximately 271 m a. s. l. UMSS 4673, 5, 35.1–51.0 mm SL, Mamoré River basin, Isiboro, Chipiriri, Villa 14 de Septiembre River, 16°50'26.33"S 65°20'41.77"W approximately 234 m a. s. l. UMSS 4765, 6, 21.2–26.3 mm SL, Mamoré River basin, Isiboro, Chipiriri, Chipiriri River, 16°53'40.61"S 65°23'4.45"W approximately 263 m a. s. l. UMSS 4787, 1, 41.8 mm SL, Mamoré River basin, Isiboro, Chipiriri, Colonia Santa Fé River, 16°52'12.89"S 65°19'59.31"W approximately 243 m a. s. l. UMSS 5260, 5, 39.7–49.0 mm SL, Mamoré River basin, Isiboro, Chipiriri, Villa 14 de Septiembre River, 16°50'25.52"S 65°16'32.95"W approximately 226 m a. s. l. UMSS 5289, 12, 34.9–47.1 mm SL (2 ds 43.6–44.9 mm SL), Mamoré River basin, Isiboro, Chipiriri, Colonia San Carlos River, 16°50'40.21"S 65°18'58.54"W approximately 232 m a. s. l. UMSS 5428, 3, 39.1–53.3 mm SL, Mamoré River basin, Isiboro, Chipiriri, Porvenir River, 16°49'58.04"S 65°18'37.67"W 234 m a. s. l. UMSS 6685, 2, 45.1–45.7 mm SL, Madeira, Mamoré River basin, Ichilo, Fabopal River, 16°58'39.06"S 65°13'40.03"W approximately 248 m a. s. l. UMSS 9708, 3, 35.5–39.5 mm SL, La Paz-Beni, Amazonas, Madeira, Beni, upper Beni, Mapuri Chuqui, 15°32'0.42"S 67°23'10.53"W approximately 406 m a. s. l. UMSS 10015, 5, 31.8–42.0 mm SL (2 c&s 32.7–41.2 mm SL), La Paz-Beni, Amazonas, Madeira, Beni, upper Beni, Tacuaral creek, Tohomonoco, 15°27'16.68"S 67°26'54.48"W approximately 396 m a. s. l. Peru: ANSP 142379, 3, 26.3–27.5 mm SL, Madre de Dios, Manu National Park, Manu River close to Cosha Cashu, 11°59’30”S 71°14’W approximately 392 m a. s. l. ANSP 142385, 5, 32.3–41.7 mm SL, Cuzco/Madre de Dios, mouth of Carbón River, below of Atalaya on north-south highway and up and down of Ford, 12°53’S 71°20’W approximately 634 m a. s. l. MUSM 171, 3, 47.0– 64.4 mm SL, Ucayali, Coronel Portillo, Pucallpa, Ivita, Ucayali River basin, Neshuya, Lechería creek, approximately 8°23'50.68"S 75°0'45.08"W 176 m a. s. l. MUSM 1929, 4, 37.5–54.7 mm SL, Madre de Dios, Manu National Park, Manu, Pakitza, Picaflor creek, approximately 12°16'S 70°51'W 299 m a. s. l. MUSM 3774, 1, 58.2 mm SL, Madre de Dios, Manu National Park, Manu, Pakitza, Picaflor creek, approximately 12°16'S 70°51'W 299 m a. s. l. MUSM 3829, 1, 55.3 mm SL, Manu National Park, Manu, Pakitza, Picaflor creek, approximately 12°16'S 70°51'W 299 m a. s. l. MUSM 3840, 3, 44.7– 50.9 mm SL, Madre de Dios, upper Madre de Dios River, Manu, Salvación creek, approximately 12°52'36.04"S 71°21'30.28"W 497 m a. s. l. MUSM 4557, 4, 31.4–62.7 mm SL, Madre de Dios, Manu, Manu National Park, Pakitza, Paucar creek, approximately 11°56'40.00"S 71°16'59.00"W 351 m a. s. l. MUSM 4975, 3, 39.7–47.3 mm SL, Madre de Dios, Manu, Manu National Park, Pakitza, Martin Pescador creek, approximately 11°56'40.00"S 71°16'59.00"W 351 m a. s. l. MUSM 8518, 7, 35.5–49.4 mm SL (1 c&s 49.4 mm SL), Madre de Dios, Manu, Manu National Park, Pakitza, Martin Pescador creek, 11°56'40.00"S 71°16'59.00"W 351 m a. s. l. MUSM 9078, 1, 53.4 mm SL, Madre de Dios, Tambopata, SNPH, Pv. Enahuipe, Palma Real River, 12°32'3.21"S 68°51'34.29"W 206 m a. s. l. MUSM 12946, 2, 59.8–60.0 mm SL, Puno, Sandia, ZRTC, Candamo River, headwaters, Agua Negra creek, approximately 13°23'34.25"S 69°59'6.64"W 433 m a. s. l. MUSM 13354, 6, 27.8–39.1 mm SL, Loreto, Maynas, Santa María de Nanay, Nanay River, approximately 3°48'54.83"S 73°23'26.70"W 92 m a. s. l. MUSM 13390, 2, 49.4–53.7 mm SL, Cuzco, La Convención, Echarate, Sejakiato, Camisea River, Sejakiato creek, approximately 11°42'52.58"S 72°55'42.66"W 409 m a. s. l. MUSM 14913, 38, 26.4–3.0 mm SL, Madre de Dios, Tahuamanu, Tahuamanu River, Nohage (Nohaya) creek, approximately 11°24'29.55"S 69°31'28.27"W 271 m a. s. l. MUSM 15744, 10, 32.0– 49.3 mm SL, Madre de Dios, Manu National Park, Pakitza, Manu River, approximately 12°15'53.48"S 70°51'9.89"W 307 m a. s. l. MUSM 15884, 3, 43.6–51.1 mm SL, Loreto, Ucayali, Pisqui River basin, Rashaya A, Caño Vibora, approximately 7°41'56.85"S 75°7'49.33"W 148 m a. s. l. MUSM 17729, 2, 55.3– 57.0 mm SL, Ucayali, Coronel Portillo, Shesha River basin, Paujil creek, 8°03'52"S 73°53'33.6"W 231 m a. s. l. MUSM 17860, 1, 51.0 mm SL, Ucayali, Coronel Portillo, Shesha River, 8°05'46.4"S 73°51'36.4"W 230 m a. s. l. MUSM 18906, 15, 35.9–47.2 mm SL (38.0– 47.2 mm SL), Pasco, Oxapampa, Puerto Bermúdez, Atas creek, 10°21'5.4''S 74°58'50.1''W 268 m a. s. l. MUSM 18969, 6, 29.9–33.1 mm SL, Pasco, Oxapampa, Puerto Bermúdez, Chivis River, approximately 10°17'46.68"S 74°56'2.44"W 243 m a. s. l. MUSM 19304, 20, 31.2–49.7 mm SL, Pasco, Oxapampa, Puerto Bermúdez, creek about km 18, 10°20'12.6''S 74°59'16.5''W 258 m a. s. l. MUSM 19380, 21, 28.0– 37.6 mm SL, Huánuco, Pachitea, Puerto Inca, Pintoyacu River, approximately 9°22'0.17"S 74°59'8.69"W 210 m a. s. l. MUSM 19782, 8, 14.8–33.9 mm SL, Pasco, Oxapampa, Puerto Bermúdez, Anacayali River, approximately 10°11'33.08"S 74°52'26.59"W 246 m a. s. l. MUSM 20919, 9, 33.0– 42.3 mm SL, Madre de Dios, Tahuamanu, Iberia, María Cristina creek, 11°24’ 37.10S 69°28’24.97”W 167 m a. s. l. MUSM 20960, 6, 42.1–50.0 mm SL, Cuzco, La Convención, lower Urubamba River River basin, Miaria, Charapa creek, 11°17’49.75”S 72°59’44.61”W 365 m a. s. l. MUSM 21338, 4, 43.6–47.1 mm SL, Madre de Dios, Tahuamanu, Yaverija River basin, Primavera creek, 11°0’34.87''S 69°33’25.67”W 273 m a. s. l. MUSM 21519, 45, 29.5–46.9 mm SL (3 c&s 39.8–46.1 mm SL), Madre de Dios, Tahuamanu, Tahuamanu River basin, Acre River system, Noaya River, 11°7’40.11''S 69°34’27.33”W 289 m a. s. l. MUSM 22391, 6, 21.4–50.8 mm SL, Cuzco, La Convención, Miaria, lower Urubamba River basin, approximately 11°18'17.36"S 72°59'34.03"W 288 m a. s. l. MUSM 23977, 7, 43.7– 60.5 mm SL, Madre de Dios, Manu, Los Amigos River basin, Los Amiguillos River, unnamed creek, 12°25'12.55"S 70°17'40.56"W 267 m a. s. l. MUSM 23978, 1, 39.0 mm SL, Madre de Dios, Manu, Los Amigos River basin, Los Amiguillos River, unnamed creek, 12°25'12.55"S 70°17'40.56"W 267 m a. s. l. MUSM 24397, 1, 55.1 mm SL, Madre de Dios, Manu, Los Amigos River basin, Los Amiguillos River, 12°25'23.90"S 70°17'30.02"W 261 m a. s. l. MUSM 25423, 3, 47.6–56.5 mm SL, Madre de Dios, Tambopata, Mazuko, Inambari River basin, Isarael creek to left of Inambari River, 13°7'40.01"S 70°24'37.17"W 330 m a. s. l. MUSM 25497, 2, 48.8–50.6 mm SL, Madre de Dios, Tambopata, Mazuko, Coricancha, Inambari River basin, Sachabacay creek, 13°6’22.90”S 70°24’45.27”W 331 m a. s. l. MUSM 26100, 10, 37.4–42.5 mm SL (2 c&s 41.1–41.5 mm SL), Cuzco, La Convención, Echarate, lower Urubamba River basin, CCNN Miaria, Shimbillo creek, 11°21'47.36"S 73°0'3.99"W 308 m a. s. l. MUSM 26763, 3, 51.0– 61.5 mm SL, Cuzco, Quispicanchi, Camanti, Araza River basin, San Lorenzo, Araza River, 13°12'51.44"S 70°32'57.12"W 405 m a. s. l. MUSM 27505, 7, 24.0– 63.3 mm SL, Ucayali, Atalaya, Raimondi, Yuruá River basin, Breu River, creek about 30 minutes downstream of CCNN Paucar, 9°30'5.73"S 72°21'16.73"W 405 m a. s. l. MUSM 27641, 2, 28.2–32.9 mm SL, Ucayali, Atalaya, Raimondi, Yuruá River basin, Breu River, Cocha 2 in front of CCNN Yacobina, 9°31'6.02"S 72°20'70.28"W 400 m a. s. l. MUSM 28073, 2, 12.6–33.6, Huánuco, Pachitea River basin, Honorio, Caño Inturuya 8°45'54.06"S 74°31'38.38"W 166 m a. s. l. MUSM 28278, 5, 37.4–47.6 mm SL, Huánuco, Puerto Inca, Pachitea River basin, Zungaruyacu River, Huacana creek, 9°28'31.43"S 75°14'41.94"W 258 m a. s. l. MUSM 28286, 23, 26.1–35.1 mm SL, Huánuco, Puerto Inca, Pachitea River basin, Zungaruyacu River, Huacana creek, 9°28'31.43"S 75°14'41.94"W 258 m a. s. l. MUSM 28471, 11, 32.4–43.1 mm SL, Cuzco, La Convención, Echarate, Urubamba River basin, CCNN Miaria, Shimbillo creek, 11°21'4.42"S 73°0'25.99"W 307 m a. s. l. MUSM 29663, 11, 20.6–28.3 mm SL, Pasco, Oxapampa, Puerto Bermúdez, Ciudad Constitución, Palcazu River basin, creek about 4 m of Palcazu River, 9°52'13.85"S 75°03'53.9"W 252 m a. s. l. MUSM 31414, 127, 17.5–31.3 mm SL, Ucayali, Atalaya, Sepahua, lower Urubamba River basin, Mishahua River, 11°12'56.79"S 72°58'2.06"W 285 m a. s. l. MUSM 33566, 1, 53.4 mm SL, Ucayali, Coronel Portillo, Abujao, Ucayali River basin, unnamed creek, 8°39'13.99"S 73°21'16.63"W approximately 273 m a. s. l. MUSM 33567, 11, 32.0– 53.5 mm SL, Ucayali, Coronel Portillo, Abujao, Ucayali River basin, unnamed creek, 8°39'14.34"S 73°21'16.40"W approximately 273 m a. s. l. MUSM 33593, 10, 34.8–46.3 mm SL, Ucayali, Coronel Portillo, Abujao, Ucayali River basin, Shansho creek, 8°34'16.99"S 73°31'2.13"W 238 m a. s. l. MUSM 35517, 82, 20.9–36.6 mm SL, Ucayali, Atalaya, Sepahua, Ocote creek, tributary of Mishahua River, close to mouth of Mishahua River, 11°13'8.48"S 72°58'3.79"W 279 m a. s. l. MUSM 35620, 49, 24.5–40.1 mm SL, Cuzco, La Convención, Urubamba River, Chimbillo creek, between Sepahua and Pakiria River, 11°21'44.65"S 73°0'7.54"W 264 m a. s. l. MUSM 42090, 1, Madre de Dios. Manu National Park, Manu, Pakitza, Picaflor creek, approximately 12°16'S 70°51'W 299 m a. s. l. ROM 83457, 1, 41.1 mm SL, Madre de Dios, Manu, Salvación creek, at its confluence with upper Madre de Dios River, 12°52'60.00"S 71°12'0.00"W ° approximately 712 m a. s. l. ROM 83577, 2, 29.6–35.3 mm SL, Madre de Dios, Pakitza, Manu National Park, Manu, Aquajal creek, 11°49'60.00"S 71°21'0.00"W approximately 394 m a. s. l.

Figures

FIGURE 2. Geographic distribution of Gephyrocharax major, a Cis-Andean species, from Amazon River basin in Bolivia and Peru.

FIGURE 6. Tukey box plots of (A) number of maxillary teeth, (B) number of branched anal-fin rays, (C) number of branched pelvic-rays, and (D) number of lateral-line scales comparing among Gephyrocharax species. Number of specimens between brackets.

FIGURE 17. Gephyrocharax major, (A) male, lectotype by present designation, 40.6 mm SL, CAS 44286; (B) male, 45.7 mm SL, CAS 78813; (C) female, 48.1 mm SL, CAS 78813; (D) male, 60.0 mm SL, MUSM 12946; (E) female, holotype of Corynopomops opisthopterus, 30.9 mm SL, ANSP 69195; (F) female, holotype of G. chaparae, 32.8 mm SL, ANSP 68967. Photographs represent some geographic groups analyzed using SPCA in text.

FIGURE 18. Gephyrocharax major, (A – B) upper and lower jaws, female, 46.5 mm SL, UF 38194; (C – D) detail of lower caudal skeleton and associated pouch scale, male, 49.4 mm SL, MUSM 8518. Anguloarticular: aa, dentary: dt, maxilla: mx, premaxilla: pm, pouch scale: ps, principal caudal-fin ray: pcr, retroarticular: ra, spur-shaped structure: sss, ventral procurrent ray: vpr. Lateral view, left side. Scale = 1 mm.

FIGURE 19. Sheared principal component analysis of morphometric data of Gephyrocharax major: (A – B) comparison among type specimens of G. major and G. chaparae (its junior synonym); (C – D) comparison among specimens organized by geographic groups. Left plots (A and C) showing first and second principal components (PC 1 vs. PC 2), right plots (B and D) showing second and third principal components (PC 2 vs. PC 3). Sheared principal component: H, principal component centered by groups: S. Percentage of explained variance beside each component.

Tables

TABLE 5. Morphometric data of lectotype (A), nine paralectotypes (B) by present designation (CAS 44286 and 236011, respectively), and other examined specimens of Gephyrocharax major. Ranges

	A	n	B	M SD	C	D	n Range M SD n	Range	M SD
Standard length (mm)	40.6	9	35.4–55.8	41.0 6.3	30.9	32.8	116 31.0–60.0 43.4 5.8 153	22.8–64.4	40.2 9.6
Percentages of standard length: Depth at dorsal-fin origin Snout to dorsal-fin origin	31.3 61.4	9 9	29.6–35.6 61.1–65.1	32.0 1.8 63.0 1.2	30.3 70.0	26.7 64.3	100 26.6–36.1 30.7 1.6 113 99 59.0–67.8 62.6 1.8 109	25.9–36.8 59.0–67.0	30.8 2.3 63.6 1.6
Snout to pectoral-fin origin Snout to pelvic-fin origin Snout to anal-fin origin Dorsal fin to pectoral fin length Dorsal fin to adipose fin length Dorsal fin to hypural complex length Eye to dorsal-fin origin Pectoral fin to pelvic fin length Pelvic fin to anal fin length Dorsal-fin length Dorsal-fin base length Pectoral-fin length	26.1 46.5 60.0 46.7 26.1 39.4 50.3 20.9 16.4 19.1 9.4 24.2	9 9 9 9 9 9 9 9 9 9 9 9	25.3–28.4 45.5–48.2 60.0–64.4 45.0–50.6 25.7–27.6 37.2–41.2 49.9–53.9 19.8–23.5 16.3–18.3 19.5–22.7 10.4–11.3 24.2–28.6	27.3 1.0 47.1 1.1 62.7 1.3 47.4 1.8 26.9 0.7 39.3 1.2 51.7 1.3 20.8 1.2 17.6 0.6 21.4 1.0 10.9 0.3 26.6 1.6	30.3 50.0 69.0 49.6 19.3 31.2 57.8 21.2 19.0 20.9 10.8 28.1	26.8 43.3 59.5 43.8 24.8 36.0 51.6 17.1 15.7 19.3 9.2 25.2	99 24.3–28.9 26.5 1.0 108 99 41.9–48.0 44.7 1.4 106 99 55.1–64.4 59.2 1.9 108 99 42.6–51.5 46.9 1.6 108 99 23.7–29.6 26.4 1.2 107 99 35.1–43.7 39.9 1.8 108 100 47.7–55.9 51.6 1.6 110 99 17.2–21.0 19.2 0.8 106 99 14.4–19.4 16.0 1.0 106 99 15.5–22.4 18.9 1.4 107 99 8.4–11.9 9.8 0.7 108 99 22.3–30.3 26.4 1.6 107	24.5–29.9 43.0–49.3 56.0–64.2 42.2–52.6 23.2–29.7 34.7–43.1 46.4–55.6 17.0–23.8 13.5–20.2 14.0–22.7 7.8–11.5 22.3–29.7	27.0 1.1 46.0 1.4 60.9 1.9 46.9 2.4 26.4 1.4 38.6 1.8 52.0 2.2 20.1 1.5 16.7 1.5 19.1 1.5 9.9 0.8 26.2 1.5
Pelvic-fin length Anal-fin length Anal-fin base length Caudal peduncle depth Caudal peduncle length Bony head length	13.8 18.9 34.6 11.3 11.6 23.2	9 8 9 9 9 9	13.5–15.7 17.8–21.1 33.5–37.5 10.6–11.7 8.3–11.6 21.7–24.7	14.7 0.8 19.8 1.3 35.4 1.5 11.0 0.5 10.0 1.0 24.0 1.0	14.0 – – 10.7 – 27.0	13.7 20.2 34.4 10.7 10.8 24.0	99 11.8–18.8 15.1 1.2 106 99 14.5–21.1 17.6 1.3 104 99 32.2–39.0 36.0 1.3 108 99 8.9–12.7 11.2 0.8 108 99 8.0–13.9 11.3 1.4 108 100 21.1–26.5 23.2 1.0 112	12.7–16.7 15.4–21.4 32.0–38.2 8.3–11.7 7.9–13.6 21.1–26.1	14.7 1.0 18.3 1.3 35.1 1.3 10.3 0.6 10.1 1.4 23.7 1.1
Percentages of head length: Snout length Horizontal eye length	27.7 35.6	9 9	26.7–29.9 30.3–35.6	28.2 0.9 32.3 1.1	26.8 31.9	28.2 36.3	99 21.1–31.6 27.5 2.0 112 99 29.8–37.9 33.5 1.7 112	21.1–31.7 29.6–39.9	26.9 2.5 34.5 2.5
Postorbital head length Least interorbital width Upper jaw length	44.2 38.9 42.0	9 9 9	42.2–46.5 35.6–39.3 42.0–46.3	43.8 1.6 37.9 1.2 43.9 1.0	44.2 34.2 40.2	41.3 37.4 41.9	99 37.0–47.9 42.6 1.9 108 98 34.2–40.5 37.1 1.4 108 98 40.2–47.4 43.6 1.5 108	37.6–46.6 31.0–40.0 40.4–47.9	42.0 2.0 36.9 1.8 43.7 1.5