Cynodon septenarius, TOLEDO-PIZA, 2000

TOLEDO-PIZA, MÔNICA, 2000, The Neotropical Fish Subfamily Cynodontinae (Teleostei: Ostariophysi: Characiformes): A Phylogenetic Study and a Revision of Cynodon and Rhaphiodon, American Museum Novitates 3286, pp. 1-1 : 1-

Cynodon septenarius , new species

Cynodon gibbus : (misidentification): Eigenmann, 1912: 395 ( British Guiana [= Guyana]; description); 3 of 7 cited specimens examined). c Pellegrin, 1909: 148 ( Brazil, Tonnantins [= Tonantins]).

DIAGNOSIS: Cynodon septenarius lacks the band of dark pigmentation covering the base of the caudal­fin rays that is characteristic of C. gibbus (compare figs. 24 and 21 ). Dark pigmentation is sometimes scattered in the region of the caudal peduncle and caudal­fin base, but in those cases the pigmentation is never very dense and does not form the conspicuous dark band present in C. gibbus . The presence of 7 (versus 8) branched pelvic­fin rays and the relatively larger orbital diameter (30.1­ 34.4 versus 24.9­ 33.8 of HL) also distinguish Cynodon septenarius from C. gibbus (see comments under Remarks of these two species accounts). Cynodon septenarius can be distinguished from Cynodon meionactis by the lack of the band of dark pigmentation covering the base of the caudal­fin rays present in the latter species, and the presence of 7 (versus 8) branched pelvic­fin rays. See also under Comments on C. meionactis , and see Géry et al. (1999).

DESCRIPTION: (Table 1) Body compressed laterally, deep anteriorly, greatest body depth approximately at vertical through pectoral­fin base, depth decreasing progressively posteriorly. Dorsal profile of head concave at interorbital region. Predorsal body profile strongly convex, forming pronounced hump at vertical through middle of orbit; straight and slightly posteroventrally slanted along dorsal­fin base, proportionally less slanted and almost straight in region of body extending from that point to vertical through last base of anal­fin ray; concave between latter point and origin of dorsalmost procurrent caudal­fin ray. Ventral profile of body convex to posterior tip of coracoids; straight and posterodorsally slanted (sometimes slightly convex) from that point to pelvic­fin base; straight from there to anal­fin origin; straight and posterodorsally slanted along anal­fin base, then concave to caudal­fin origin. Ventral surface of body with keel extending from isthmus to pelvic­fin base; keel anteriorly supported by expanded coracoids.

Laterosensory canal system in infraorbitals and opercular bones highly branched; canals more developed in larger individuals. Mouth obliquely aligned relative to horizontal axis of body. Upper jaw very long relative to head length; posterior tip of maxilla extending posteriorly to vertical through posterior tip of second infraorbital; relatively more elongate in smaller individuals. Third infraorbital not in contact with preopercle ventrally. Adipose eyelid with notch in region of orbital margin where second and third infraorbitals meet.

Teeth in both jaws conical, in single row, varying in size. Premaxilla with 3 small canines of similar size, one in anterior and one in posteriormost portion; third canine sometimes slightly smaller, intermediate in position to 2 others and usually separated from posteriormost canine by 2 or 3 small conical teeth. Several small conical teeth located between anterior and middle canines. Maxilla with slightly enlarged conical teeth separated by smaller teeth of similar size; teeth gradually becoming smaller posteriorly.

Dentary with well­developed canine, extending up into snout when mouth is closed, tip of canine reaching nostrils anteriorly. One smaller dentary canine, about half size of largest, followed by another smaller conical tooth anteriorly; canines posterior to largest canine progressively decreasing in size; dentary canines separated by conical teeth of various sizes. Teeth on ectopterygoid and mesopterygoid very small and conical. No teeth on metapterygoid.

Scales without distinct serration. Scales small on dorsal portions of body; scale size increasing towards lateral line with largest scales along lateral line; scales on region dorsal to anal fin small. Scales along pre dorsal midline very small and arranged in somewhat irregular rows. Row of scales forming keel from posterior portion of coracoid to pelvic­fin base less rounded in shape than those covering the rest of the body. Scales below lateral line obliquely arranged. Lateral­line scales with many divergent branches of lateral­line canal. Divergent branches more developed in larger individuals; dorsal and ventral branches of lateral­line canal starting to develop in specimens of 110 mm SL. Lateral­line canal extending to posterior tip of middle caudal­fin ray.

Dorsal­fin rays ii,10. Dorsal­fin origin slightly posterior to vertical through anal­fin origin. First basal dorsal­fin pterygiophore inserting behind neural spine of 19th to 21st vertebrae. Distal margin of dorsal fin straight to somewhat concave. First anal­fin pterygiophore inserting behind hemal spine of 22nd to 24th vertebrae. Distal margin of anal fin straight. Scales covering basal one­third to one­half length of anal­fin rays. Pectoral­fin rays i,15–17; fin pointed distally. Posterior tip of longest pectoral­fin ray extends beyond vertical through anal­fin origin, and reaches vertical through dorsal­fin origin. Pelvic fin short; pelvic­fin rays i,7. Base of pelvic fin inserted at level of ventral profile of abdomen. Caudal fin forked, middle caudal­fin ray elongate, slightly longer than rays immediately dorsal and ventral to it, but its tip not extending to vertical through tip of dorsalmost principal ray. Distal margin of upper caudal­fin lobe somewhat concave, with lower lobe rounded. Scales covering only basal portion of caudal­fin rays, not extending onto their branched portions.

VERTEBRAE: 51(2), 52(6), 53(19), 54(5).

COLOR IN ALCOHOL: Specimens retaining guanine on scales with silver coloration on sides of body and head (including lower jaw, except for tip) as far dorsally as horizontal through dorsal margin of orbit darker dorsally, including tip of lower jaw. In many specimens dark pigmentation of dorsal portion of head extends onto dorsal half of opercle and around infraorbitals. Specimens lacking guanine with yellowish­tan ground coloration (dark tan in some specimens) on sides of body and head, slightly darker dorsally. Specimens show varying degrees of guanine retention. A few specimens from the Rio Negro (MZUSP 32597) have an overall body coloration darker than the usual pattern exhibited by other specimens. Spot of dark pigmentation present on posteriormost portion of supracleithrum. Specimens retaining pigmentation on fins with dorsal fin dusky and distal half of pelvic fins and dorsal portion of pectoral fins (especially unbranched pectoral­fin ray) covered with dark chromatophores. Distal half of anal fin with band of dark chromatophores. Adipose fin hyaline.

GEOGRAPHIC DISTRIBUTION: Cynodon septenarius occurs in the Rio Solimões/Amazonas drainage east of the mouth of Rio Içá (located close to the border of Brazil and Colombia), eastward into the Rios Negro, Branco, Trombetas, and Tapajós ( fig. 25 ). Cynodon septenarius also occurs in the Essequibo and Demerara Rivers in Guyana, and in the upper portions of the Río Orinoco basin in Venezuela. Cynodon septenarius is found in sympatry with C. gibbus in a few localities within the Amazon basin (see geographic distribution of C. gibbus , for details).

ETYMOLOGY: The specific name, septenarius , is a Latin adjective which means ‘‘consisting of seven,’’ in reference to the seven branched pelvic­fin rays that distinguishes this species from its congeners, C. gibbus and C. meionactis .

REMARKS: Three specimens (MZUSP 32597, 2 specimens and MZUSP 32585) of Cynodon septenarius have 8 branched pelvic­fin rays, the former having 7 on the right side, and the latter 8 on both sides, and 1 specimen (MZUSP 32590) has 6 pelvic­fin rays (table 2). Since these atypical specimens belong to lots with other specimens with 7 branched pelvic­fin rays, and, in addition, lack the band of dark pigmentation at the caudal­fin base characteristic of C. gibbus and C. meionactis , and have relatively large orbital diameters, they were herein assigned to C. septenarius .

MATERIAL EXAMINED: 187 (51, 94.5­ 312):

TYPE MATERIAL: Holotype: BRAZIL. Amazonas : MZUSP 32590 (247.0 mm SL) Rio Tefe´, Supiã­Pucu (between 3°40′ and 4°20′S; 65°50′ and 65°10′W), collector: Michael Goulding, 28 July 1979; paratypes: BRAZIL. Amazonas: MZUSP 53306 (9, 204–248.0), CAS 204164 (2, 223.0–230.0), INPA 14531 (2, 237.0–240.0), MCP 21735 (2, 232.0–235.0), MNRJ 18171 (2, 240.0– 243.0), USNM 352434 (2, 240.0–245.0) all taken with holotype.

NONTYPE MATERIAL: BRAZIL Amazonas: INPA 5451 (1, 167.0) Rio Uatuma˜, at Balbina dam; INPA 5512 (1, 165.0) Rio Uatuma˜, Sumaúma (= Samaúma?); INPA 5347 (1, 212.0) Rio Uatuma˜, Igarapé Anaua´; INPA 5509 (1, 159.0) Rio Uatuma˜, Santa Luzia; INPA 5821 (5, 175.0–187.0) Rio Negro; INPA 8493 (3, 106.1–138.2) Rio Negro, between Tarumã and Tarumã­Mirim; MZUSP 31129 (1, 200.0); MZUSP 32605 (2, 177.0– 196.0) Rio Negro, Ilha de Tamaquare´; MZUSP 6145 (4, 174.0–182.0) Rio Negro, above Manaus; MZUSP 6196 (2, 164.0– 189.0) Igarapé Jaraqui, left margin of Rio Negro, above Manaus; MCZ 21409 (1, 191.0) Rio Negro, Lago do Aleixo; MZUSP 32599 (2, 206.0–208.0) Rio Negro, São Pedro; MZUSP 32597 (7, 200.0 –213.0), MZUSP 32598 (1, 168.0) São Gabriel da Cachoeira; MZUSP 32601 (1, 194.0) Rio Negro, Anavilhanas; MZUSP 32603 (2, 187.0–213.0) Rio Negro, Cachoeira do Bicho­Açu; NMW 57111 (1, 171.0), mouth of Rio Negro; MZUSP 21707 (4, 170.0–190.0) Lago Janauacá and surroundings, Rio Solimões; MZUSP 26933 (1, 212.0) Lago Janauacá and around Manaus; MCZ 150891 (1, 191.0), MZUSP 32602 (1, 168.0) Rio Marauia´, near mouth; MZUSP 32604 (3, 213.0– 239.0) Rio Marie´, Lago do Curuá­Muru; MZUSP 32590 (20, 204.0–247.0) Rio Tefe´, Supiã­Pucu; MZUSP 32591 (24, 139.0– 226.0) Rio Tefe´, Mastro; MNHN 1909 0300 (1, 189.0) Rio Tonantins; MZUSP 32600 (1, 199.0) Rio Arirara´, near mouth; Pará: INPA 5325 (1, 161.0) Rio Trombetas, below Cachoeira Porteira; MZUSP 32586 (3, 164.0– 202.0) Rio Trombetas, Cumina´; MZUSP 5415 (11, 174.0 –184.0) Rio Trombetas, Oriximina´; INPA 5367 (1, 203.0) Rio Trombetas, Lago Tapagem; MZUSP 15641–15647 (8, 164.0–202.0) mouth of Lago do Leonardo, Reserva Biológica de Trombetas; INPA 7116 (2, 225.0) Rio Cupari, tributary of Rio Tapajós, near mouth; MZUSP 21389 (1, 183.0) Rio Tapajós, São Luı´s; MZUSP 32585 (55, 164.0–236.0) Rio Tapajós, between Itaituba and São Luís; INPA 7115 (2, 208.0–209.0) Rio Cupari, tributary of Rio Tapajós, near mouth; INPA 5334 (1, 214.0) Rio Tocantins, Itupiranga; Roraima: MZUSP 32596 (2, 202.0–205.0) Rio Branco, Xeriuni. GUYANA. AMNH 223193 (2, 109.6–140.5), AMNH 223192 (1, 229.0), FMNH 53513 (1, 210.0), CAS 79232 (1, 312.0) Malali; FMNH 53514 (2, 94.5–200.0), CAS 79231 (2, 228.0–282.0) Wismar; AMNH 72950 (1, 253.0) confluence of Mazaruni and Cuyuni Rivers, about 100 m off Kartabo Point; AMNH 17634 (1, 147.0) Guyana; VENEZUELA. Amazonas: ANSP 159592 (10, 180.0–235.0) Río Sipapo, mouth of lagoon ca. 3 km above Pendare; ANSP 161553 (4, 181.0–215.0) Río Cunucunuma ca. 40 km from confluence with Río Orinoco; ANSP 161555 (3, 205.0–222.0) Río Cunucunuma ca. 40–50 km above confluence with Río Orinoco; ANSP 161554 (3, 193.0–215.0) Río Orinoco at sand playa just upstream from Quiratare; ANSP 161557 (1, 199.0) rocks on western shore of Río Casiquiare ca. 2 km downstream from mouth of Río Pamoni.

Figures

Fig. 24. Cynodon septenarius, new species, holotype, MZUSP 32590, mm SL, Brazil, Amazonas, Rio Tefe´, Supiã­Pucu.

Fig. 21. Cynodon gibbus, neotype, MZUSP 6539, 146.4 mm SL, Brazil, Amazonas, Lago Manacapuru.

Fig. 25. Map of central and northern portions of South America showing geographic distribution of Cynodon septenarius (arrow indicates type locality). Some symbols represent more than one lot of specimens or locality.