Steindachnerina hypostoma (Boulenger 1887)

Steindachnerina hypostoma (Boulenger, 1887)

Curimatus hypostoma Boulenger, 1887a:172 [type locality: Ucayali River].—Vari, 1989a, tables 2, 3 [phylogenetic relationships].

Curimatus hypostomus.—Eigenmann and Eigenmann, 1889:426 [reference].—Eigenmann and Eigenmann, 1891:47 [reference].—Eigenmann, 1910:422 [reference].

Curimata hypostoma.—Fowler, 1942b:208 [reference].—Eigenmann and Allen, 1942:296 [Peru: Río Huallaga, Yurimaguas; Río Morona; Río Paranapura. Yurimaguas (in part)].—Fowler, 1945:116 [reference].—Géry, 1977:235 [reference].—Ortega and Vari, 1986:11 [Peru, Amazon basin; common name].

Curimata hypostoma hypostoma.—Fowler, 1950:285 [literature compilation].

Steindachnerina hypostomus.—Fernández-Yépez, 1948:58 [assignment to Steindachnerina].

Steindachnerina hypostoma.—Fowler, 1975:375 [reference].—Vari and Vari, 1989:470, figs. 2, 3 [redescription, Amazonian Peru, Brazilian Amazon upstream of Manaus].

DIAGNOSIS.—The 6 or 7 scales between the anus and the anal fin, the 5 or 6 scale rows across the distinctly transversely flattened prepelvic region of the body, and the reduced dorsomedian cranial fontanel distinguishes Steindachnerina hypostoma from its congeners with the exception of S. gracilis, S. planiventris, and S. quasimodoi. The absence of a discrete patch of dark pigmentation on the basal portion of the middle rays of the dorsal fin distinguishes S. hypostoma from those species, all of which have such pigmentation developed to some degree. The 46 to 50 lateral-line scales of S. hypostoma further differentiate the species from S. gracilis, which has 50 to 54 scales in that series and from S. quasimodoi and S. planiventris, which have 40 to 46. Differences in other meristic and morphometric features also discriminate S. hypostoma from S. gracilis, S. planiventris, and S. quasimodoi to varying degrees.

DESCRRIPTION.—Body elongate, relatively wide transversely, particularly in ripe females. Dorsal profile of head straight or very slightly convex. Dorsal profile of body smoothly curved, slightly convex from rear of head to origin of dorsal fin; straighter and slightly posteroventrally slanted at base of dorsal fin, straight or very gently convex from base of last dorsal-fin ray to caudal peduncle. Dorsal surface of body with distinct median keel anterior to dorsal fin, keel more pronounced proximate to fin; surface of body smoothly rounded transversely posterior to fin. Ventral profile of body very gently curved from tip of lower jaw to caudal peduncle. Prepelvic region wide, distinctly flattened, with 5 series of scales in a transverse series across flattened surface. Pelvic fins distinctly separated medially. Postpelvic region somewhat flattened proximate to pelvic fin, gradually becoming transversely rounded posteriorly. Anus distinctly anterior of origin of first anal-fin ray, with 6 or 7 scales in intervening space.

Greatest depth of body 0.24–0.27 [0.25]; snout tip to origin of dorsal fin 0.44–0.48 [0.45]; snout tip to origin of anal fin 0.80–0.85 [0.82]; snout tip to origin of pelvic fin 0.48–0.53 [0.48]; snout tip to anus 0.70–0.75 [0.72]; origin of dorsal fin to hypural joint 0.56–0.60 [0.59]. Dorsal-fin profile acute; anteriormost rays 2.8–3.5 times length of ultimate ray. Pectoral-fin profile acute; length of pectoral fin 0.17–0.20 [0.18], extends slightly over three-quarters of distance to vertical line through origin of pelvic fin. Pelvic-fin profile obtusely acute, length of pelvic fin 0.19–0.22 [0.20], reaches about three-fifths of distance to origin of anal fin. Caudal fin distinctly forked. Adipose fin well developed. Anal fin emarginate, anteriormost branched rays approximately two and one-half times length of ultimate ray. Caudal peduncle depth 0.11–0.12 [0.11].

Head distinctly pointed in profile, more so in larger specimens, head length 0.24–0.28 [0.27]; upper jaw distinctly longer, mouth inferior, portion of buccopharyngeal complex on roof of oral cavity in adults consisting of multiple lobulate fleshy bodies; snout length 0.28–0.31 [0.28]; nostrils very close, anterior circular, posterior crescent-shaped, with aperture closed by thin flap of skin separating nares; orbital diameter 0.28–0.34 [0.29]; adipose eyelid present, poorly developed, with a rotund opening over center of eye; length of postorbital portion of head 0.39–0.45 [0.43]; gape width 0.28–0.34; interorbital width 0.38–0.42 [0.39].

Pored lateral-line scales to hypural joint 46 to 50 [49]; all scales of lateral line pored, canals in scales of lateral line straight; 4 to 6 series of scales extend beyond hypural joint onto caudal-fin base; 8½ to 9½ [8½] scales in transverse series from origin of dorsal fin to lateral une; 6½ to 7½ [7] scales in transverse series from the lateral line to origin of anal fin.

Dorsal-fin rays ii,9 or iii,9 (iii,9 rare; when three unbranched rays present, first very short) [ii,9]; anal-fin rays ii,7 or iii,7 (when three unbranched rays present, first very short) [ii,7]; pectoral-fin rays 14 to 16 [14]; pelvic-fin rays i,8 [i,8].

Total vertebrae 35 (8), 36 (86), 37 (2).

COLOR IN ALCOHOL.—Overall coloration of specimens retaining guanine on scales silvery to silvery golden, darker on dorsal portions of head and body. Specimens fixed in formalin and lacking guanine on scales with overall ground coloration tan to light brown, darker on dorsal portions of head and body. Pores of lateral-line scales outlined by dark pigmentation in some specimens. Lateral-line pigmentation more intense, when present, in smaller individuals, sometimes forming a distinct midlateral stripe (Figure 28). Deeper-lying, dusky, midlateral band extends from supracleithrum to caudal peduncle; typically more obvious in smaller individuals; masked in specimens retaining guanine on scales. Caudal-fin rays outlined by series of small chromatophores, lower lobe of caudal fin dusky. Anterior margin of dorsal fin sometimes dusky, but without spot of dark pigmentation at base of middle rays; other fins hyaline.

DISTRIBUTION.—Amazon basin upstream of Manaus, Brazil (Figure 30).

COMMON NAME.—Chio-chio (Ortega and Vari, 1986:11, Peru).

DISTRIBUTION.—Rio Tocantins system (Figure 30).

MATERIAL EXAMINED.—17 specimens (17, 56.7–73.4).

BRAZIL. Goiás: Rio Araguaia, Aruan, MZUSP 4847, 1 (63.5, holotype of Steindachnerina gracilis); MZUSP 38591, 2 (56.7–63.5, paratypes of Steindachnerina gracilis); USNM 293035, 1 (67.2, paratype of Steindachnerina gracilis); USNM 191632, 1 (−73.4, paratype of Steindachnerina gracilis). Pará: Rio Tocantins, lagoons along margin of river near Tucuruí (−3°42′S, 49°27′W), MZUSP 38592, 6 (61.5–64.9, paratypes of Steindachnerina gracilis); USNM 293034, 6 (57.4–65.4, paratypes of Steindachnerina gracilis, 2 specimens cleared and counterstained for cartilage and bone).

Steindachnerina quasimodoi Vari and Vari, 1989

Steindachnerina quasimodoi Vari and Vari, 1989:476, figs. 6, 7 [type-locality: Pent, Loreto, Río Javari, near Petropolis].

DIAGNOSIS.—The 5 to 7 scales between the anus and the anal fin, the 5 scale rows across the distinctly transversely flattened prepelvic region of the body, and the reduced dorsomedian cranial fontanel distinguishes Steindachnerina quasimodoi from its congeners with the exception of S. gracilis, S. planiventris, and S. hypostoma. The 40 to 46 lateral-line scales to the hypural joint distinguish S. quasimodoi from S. gracilis, which has 50 to 54 scales in that series, and S. hypostoma, which has 46 to 50. The presence of a discrete spot of dark pigmentation in the basal portions of the middle rays of the dorsal fin further separates S. quasimodoi from S. hypostoma, which lacks such pigmentation. Other differences in meristic and morphometric features further differentiate S. quasimodoi from S. hypostoma and S. gracilis. Specimens of S. quasimodoi of greater than 50 mm SL are distinguished from comparably sized individuals of S. planiventris in their greater body depth (0.30–0.34 of SL versus 0.27–0.30), by differences in the degree of convexity of the dorsal surface of the body (compare Figures 32 and 33 with 35), length of the pelvic fins (0.23–0.26 of SL versus 0.19–0.23), and degree of contact of frontals anterior to cranial fontanel (Figure 10).

DESCRIPTION.—Body elongate, deeper bodied in larger specimens, somewhat compressed. Dorsal profile of head slightly convex anterior to vertical line through nostrils, straight from that line to rear of head. Dorsal profile of body slightly convex from rear of head to origin of dorsal fin, angle more pronounced with increasing size; straight and slightly posteroventrally slanted at base of dorsal fin in juveniles, adults with angle more pronounced, straight from base of last dorsal-fin ray to caudal peduncle. Dorsal surface of body transversely rounded anteriorly, with indistinct median keel immediately anterior to dorsal fin, smoothly rounded transversely posterior to fin. Ventral profile of body very gently curved from tip of lower jaw to origin of anal fin, sigmoid from that point to caudal peduncle. Prepelvic region broadly flattened, with about 5 irregular series of scales across flattened ventral surface. Scale series of prepelvic region flanked on each side by series of scales slightly bent to conform to shape to lateral angles of body. Obtuse median keel posterior to pelvic fin origin. Secondary obtuse keel on each side of postpelvic portion of body two scales dorsal of ventral midline. Anus distinctly anterior of origin of first anal fin-ray, with 5 or 6 scales in intervening space.

Greatest depth of body 0.27–0.34 (0.30–0.34 in specimens above 50 mm SL) [0.33]; snout tip to origin of dorsal fin 0.47–0.50 [0.49]; snout tip to origin of anal fin 0.84–0.86 [0.86]; snout tip to origin of pelvic fin 0.50–0.54 [0.50]; snout tip to anus 0.75–0.78 [0.76]; origin of dorsal fin to hypural joint 0.54–0.59 [0.59]. Dorsal-fin profile acute, less so with increasing age; anteriormost rays about three to three and one-half times length of ultimate ray. Pectoral-fin profile acute; length of pectoral fin 0.19–0.21 [0.21], extends posteriorly to a point about two scales anterior of vertical through origin of pelvic fin. Pelvic-fin profile acute, length of pelvic fin 0.23–0.26 [0.26], reaches two-thirds distance to origin of anal fin. Caudal fin forked. Adipose fin well developed. Anal fin emarginate, anteriormost branched rays about three to three and one-half times length of ultimate ray. Caudal peduncle depth 0.11–0.13 [0.13].

Head distinctly pointed, head length 0.27–0.33 [0.28]; upper jaw much longer, mouth inferior; anterior portion of buccopharyngeal complex on roof of oral cavity in adults consisting of multiple lobulate fleshy bodies; snout length 0.31–0.34 [0.33]; nostrils very close, anterior circular, posterior crescent-shaped, with aperture closed by thin flap of skin separating nares; orbital diameter 0.31–0.37 [0.32]; adipose eyelid present, more developed in larger specimens, particularly anteriorly, with broad vertically ovoid opening over center of eye; length of postorbital portion of head 0.36–0.40 [0.36]; gape width 0.30–0.35 [0.33]; interorbital width 0.36–0.43 [0.42].

Pored lateral-line scales to hypural joint 40 to 46 [44]; all scales of lateral line pored, canals in scales of lateral line straight; 4 to 6 series of scales extend beyond hypural joint onto caudal-fin base; 7½ to 9½ [8½] scales in a transverse series from origin of dorsal fin to lateral line; 5½ to 6½ [6½] scales in a transverse series from lateral line to origin of anal fin.

Dorsal-fin rays ii,9 or iii,9 (when three unbranched rays present, first very short) [iii,9]; anal-fin rays ii,7 or iii,7 (when three unbranched rays present, first very short) [iii,7]; pectoral-fin rays 15 to 17 [16]; pelvic-fin rays i,8 or rarely i,7,i [i,8].

Total vertebrae 35 (11), 36 (20).

COLOR IN LIFE.—(The following description is based on a color transparency of a specimen captured in the Rio Javari by S.O. Kullander). Overall coloration bright silver, somewhat darker on dorsal portions of head and body. Iris silver. Fins yellowish with light margins. Dorsal fin with a small dark patch on basal portion of middle rays.

COLOR IN ALCOHOL.—Ground coloration of specimens lacking guanine on scales tan, darker on dorsal portion of body. Dorsal portion of head dusky. Margins of scales on lateral and dorsal portions of body outlined by series of small chromatophores in juveniles. Pigmentation field expanded in larger specimens to cover exposed surface of scales, particularly dorsally. Mid-dorsal line somewhat darker, particularly immediately anterior of dorsal fin. Pores in lateral-line scales outlined dorsally and ventrally by chromatophores. Dorsal fin with diffuse patch of dark pigmentation on basal portion of membranes between third and fifth ray. Dorsal and caudal fins dusky. Adipose dorsal-fin margin dusky. Anal fin hyaline or with scattered chromatophores. Paired fins hyaline.

DISTRIBUTION.—Río Yavari (= Rio Javarí) system of Peru and Brazil, and proximate portions of Peruvian Amazon (Figure 34).

MATERIAL EXAMINED.—41 specimens (41, 33.3–122.6).

PERU. Loreto: Río Yavari, near Petropolis, USNM 293041, 1 (88.9, holotype of Steindachnerina quasimodoi); USNM 293042, 7 (49.7–122.6, paratypes of Steindachnerina quasimodoi; two specimens cleared and counterstained for cartilage and bone); MHN-USM 1698, 4 (50.7–100.6, paratypes of Steindachnerina quasimodoi); MZUSP 38593, 2 (58.4–59.6, paratypes of Steindachnerina quasimodoi). Río Ampiyacu, near the mouth, USNM 175868, 1 (48.4). Pebas (Pevas), CAS-SU 36888, 1 (81.7).

BRAZIL. Amazonas: Rio Javarí system, immediately downstream of confluence of Rio Jaquirana and Rio Gálvez, NRM SOK/1984312.4093, 9 (33.3–121.8, paratypes of Steindachnerina quasimodoi); MZUSP 38594, 3 (50.1–53.6, paratypes of Steindachnerina quasimodoi). Rio Javarí system, opposite Colonia Angamos, Peru, NRM SOK/1984317.4091, 7 (40.0– 69.2, paratypes of Steindachnerina quasimodoi); MHN-USM 1699, 3 (49.8–57.0, paratypes of Steindachnerina quasimodoi); USNM 293040, 3 (34.3–61.5, paratypes of Steindachnerina quasimodoi).

Steindachnerina planiventris Vari and Vari, 1989

Curimalus bimaculatus.—Eigenmann and Eigenmann, 1889:422 [in put, specimens from Içá, Brazil].

Steindachnerina planiventris Vari and Vari, 1989:479, fig. 11 [type-locality: Brazil, Rondonia, Rio Machado, near mouth].

DIAGNOSIS.—The 6 or 7 scales between the anus and the anal fin, the 5 or 6 scale rows across the distinctly transversely flattened pre-pelvic region of the body, and the reduced dorsomedian cranial fontanel distinguish Steindachnerina planiventris from its congeners with the exception of S. gracilis, S. quasimodoi, and S. hypostoma. The 40 to 46 scales along the lateral line to the hypural joint distinguish S. planiventris from S. gracilis, which has 50 to 54 scales in that series, and from S. hypostoma, which has 46 to 50 scales. The presence of a discrete spot of dark pigmentation in the basal portions of the middle rays of the dorsal fin further separates S. planiventris from S. hypostoma, which lacks such pigmentation. Other differences in meristic and morphometric features further differentiate S. planiventris from S. hypostoma and S. gracilis. Specimens of S. planiventris of greater than 50 mm SL are distinguished from comparably sized individuals of S. quasimodoi in their greater body depth (0.27–0.30 of SL versus 0.30–0.34), differences in the degree of convexity of the dorsal surface of the body (compare Figures 32 and 33 with 35), pelvic-fin length (0.19–0.23 of SL versus 0.23–0.26), and degree of contact of the frontals anterior of the cranial fontanel (Figure 10).

DESCRIPTION.—Body elongate, slightly compressed. Dorsal profile of head distinctly convex anteriorly to vertical through nostrils, slightly convex or straight from that point to rear of head. Dorsal profile of body slightly convex from rear of head to origin of dorsal fin; straight and slightly posteroventrally slanted at base of dorsal fin, straight from base of last dorsal-fin ray to caudal peduncle. Dorsal surface of body transversely rounded anteriorly, with distinct median keel immediately anterior to dorsal fin, smoothly rounded transversely posterior to fin. Ventral profile of body gently curved from tip of lower jaw to caudal peduncle. Prepelvic region distinctly flattened, with 5 longitudinal series of scales on ventral flattened surface. Ventral scale series flanked on each side by a series of scales slightly bent to conform to shape to lateral angles of body. Barely discernable median keel posterior to pelvic-fin origin. Secondary obtuse keel on each side of postpelvic portion of body about two scales dorsal of ventral midline. Anus distinctly anterior of origin of first anal-fin ray, with 5 or 6 scales in intervening space.

Greatest depth of body 0.27–0.30 [0.29]; snout tip to origin of dorsal fin 0.46–0.50 [0.49]; snout tip to origin of anal fin 0.83–0.87 [0.87]; snout tip to origin of pelvic fin 0.52–0.56 [0.54]; snout tip to anus 0.72–0.76 [0.75]; origin of dorsal tin to hypural joint 0.54–0.59 [0.57]. Dorsal fin pointed, less so with increasing age; anteriormost rays three to three and one-half times length of ultimate ray. Pectoral fin pointed; length of pectoral fin 0.18–0.23 [0.20], extends about three-quarters distance to vertical line through origin of pelvic fin. Pelvic fin pointed, length of pelvic fin 0.19–0.23 [0.21], reaches about two-thirds distance to origin of anal fin. Caudal fin forked. Adipose dorsal fin well developed. Anal fin barely emarginate, anteriormost branched rays three to three and one-half times length of ultimate ray. Caudal peduncle depth 0.11–0.12 [0.12].

Head distinctly pointed in profile, head length 0.26–0.31 [0.30]; upper jaw distinctly longer, mouth inferior; portion of buccopharyngeal complex on roof of oral cavity in adults consisting of multiple tabulate fleshy bodies; snout length 0.33–0.36 [0.33]; nostrils very close, anterior circular, posterior crescent-shaped, with aperture closed by thin flap of skin separating nares; orbital diameter 0.29–0.33 [0.30]; adipose eyelid present, moderately developed, more so anteriorly, with broad vertically ovoid opening over center of eye; length of postorbital portion of head 0.36–0.41 [0.38]; gape width 0.28–0.34 [0.32]; interorbital width 0.38–0.44 [0.40].

Pored lateral-line scales to hypural joint 40 to 46 [41]; all scales of lateral line pored, canals in lateral-line scales straight; 4 to 6 series of scales extend beyond hypural joint onto caudal-fin base; 6½ to 8½ [7½] scales in transverse series from origin of dorsal fin to lateral line; 5½ to 6½ [5½] scales in transverse series from lateral line to origin of anal fin.

Dorsal-fin rays ii,9 or iii,9 (when three unbranched rays present, first very short) [iii,9]; anal-fin rays ii,7 or iii,7 (when three unbranched rays present, first very short) [iii,7]; pectoral-fin rays 15 to 17 [15]; pelvic-fin rays i,8 [i,8].

Total vertebrae 34 (19), 35 (109), 36 (7).

COLOR IN ALCOHOL.—Specimens retaining guanine on scales golden, somewhat purplish dorsally. Ground pigmentation in specimens lacking guanine on scales tan to light brown, darker on dorsal portions of head and body. Scales on lateral and dorsal surfaces of body with margins outlined by series of small, dark chromatophores; chromatophore series most developed dorsally, increasingly less so ventrally. Dorsal fin with patch of dark chromatophores on basal portion of membranes between third and fifth rays. Median fins, particularly lower lobe of caudal fin in some individuals, dusky. Paired fins hyaline.

DISTRIBUTION.—Rio Madeira and Rio Negro basins, main channel and tributaries of middle Rio Solimões (Figure 34).

MATERIAL EXAMINED.—163 specimens (119, 46.2–87.0).

BRAZIL. Rondonia: Rio Machado, near mouth, MZUSP 38587, 1 (65.7, holotype of Steindachnerina planiventris); MZUSP 38588, 17 (55.5–74.1, paratypes of Steindachnerina planiventris); USNM 267986, 18 (56.3–78.8, paratypes of Steindachnerina planiventris). Rio Machado, Jauarí, River Channel Beach, USNM 267989, 18 (46.2–67.8, paratypes of Steindachnerina planiventris), MZUSP 38590, 18 (53.5–65.2, paratypes of Steindachnerina planiventris). Rio Machado, Santo Antonio, USNM 267987, 6 (56.5–65.1, paratypes of Steindachnerina planiventris), MZUSP 38589, 5 (59.0–67.9, paratypes of Steindachnerina planiventris). Rio Machado, Cururu, USNM 267988, 8. Roraima: Rio Branco, 20 km below Boiaçu, MZUSP 21164, 4 (49.3–53.7). Rio Branco, Serra Grande, NMW 68885, 6 (53.1–87.0). Amazonas: Rio Negro, just below mouth of Rio Branco, USNM 293097, 22 (11, 52.5–80.6). Rio Negro, Anavilhanas, Munícipio de Ayrão, USNM 293098, 7. Rio Solimões, Una Sorubim, above Coarí, MZUSP uncat., 10 (62.3–71.3). Rio Solimões, Coarí, USNM 293099, 12. Rio Solimões, near Ilha Baruruá, above mouth of Rio Jutaí, MZUSP 20987, 3 (2, 63.2–71.7). Rio Solimões, Ilha Xibeco, above mouth of Rio Jutaí, MZUSP uncat., 1 (73.8). Ica (= Rio Içá), USNM 120250, 5 (formerly MCZ 19571).

BOLIVIA. Beni: Río Mamoré, Puerto Siles, AMNH uncat., 2 (65.7–73.5).

Curimatus hypostoma Boulenger, 1887

Curimatus bimaculatus sialis Eigenmann and Eigenmann, 1889b

Curimatus elegans bahiensis Eigenmann and Eigenmann, 1889b

Curimatus gilberti brevipinnis Eigenmann and Eigenmann, 1889b

Curimatus guntheri Eigenmann and Eigenmann, 1889b