Metynnis melanogrammus, Ota & Py-Daniel & Jégu, 2016

Ota, Rafaela Priscila, Py-Daniel, Lúcia Helena Rapp & Jégu, Michel, 2016, A new Silver Dollar species of Metynnis Cope, 1878 (Characiformes: Serrasalmidae) from Northwestern Brazil and Southern Venezuela, Neotropical Ichthyology (Neotrop. Ichthyol.) 14 (4), No. e 160023, pp. 1-12: 2-9

publication ID

http://doi.org/ 10.1590/1982-0224-20160023

persistent identifier

http://treatment.plazi.org/id/03867A1C-C761-2203-D6EF-2353F74FFA33

treatment provided by

Carolina

scientific name

Metynnis melanogrammus
status

new species

Metynnis melanogrammus   , new species

urn:lsid:zoobank.org:act:9E6F426E-95B9-4938-B827-4D222D1BF348

( Figs. 1-8 View Fig View Fig View Fig View Fig View Fig View Fig View Fig View Fig )

Metynnis hypsauchen Zarske & Géry, 2008: 179   [ Guyana: comparison to Metynnis longipinnis   : photo].

Metynnis cf. hypsauchen Zeinad & Prado, 2012: 153   [ Brazil, rio Sucunduri, rio Madeira basin: photo].

Holotype. INPA 52216 View Materials , male, 141.3 mm SL, rio Parauari , Monte Sinai community, Maués, Amazonas, Brazil, 4º21’28”S 57º35’54”W, 31 May 2010, R. R. de Oliveira & W. Pedroza. GoogleMaps  

Paratypes. Brazil: Amazonas: ANSP 200146 View Materials , 2 View Materials , 142.6 View Materials - 144.3 mm SL, rio Cucuí, tributary of rio Negro, São Gabriel da Cachoeira   , 1º10’46”S 66º50’26”W, 20 Feb 2014, V. Machado & T. Hrbek. INPA 11804 View Materials , 1, 176.3 mm SL, igarapé Paunini, tributary of rio Jaú , Parque Nacional do Jaú , rio Negro basin, Barcelos GoogleMaps   , 2º12’44”S 62º23’47”W, 12 Jun 1995, M. Garcia & E. Ferreira. INPA 18657 View Materials , 4 View Materials , 1 View Materials skel., 144.8-172.4 mm SL, lago Curirarra, 4 hours upstream rio Caurés, Barcelos GoogleMaps   , 1º20’04”S 62º21’40”W, 25 Dec 1976, Expedition Negro-Caurés. NUP 17869 View Materials , 1, 155.8 mm SL, same data as INPA GoogleMaps   18657. INPA 34811 View Materials , 2 View Materials , 136.0- 149.4 mm SL, collected with the   holotype. INPA 37249 View Materials , 2 View Materials , 107.2 View Materials - 113.8 mm SL, shore of rio Jatapu, São Sebastião do Uatumã   , 2º01’03”S 58º10’26”W, 1 Oct 2011, L. Rapp Py- Daniel, G. Torrente-Vilara, R. P. Ota & W. Pedroza. INPA 42313 View Materials , 1 View Materials , 95.3 mm SL, rio Padauari, Parque Estadual do rio Negro , Novo Airão GoogleMaps   , 2º09’26”S 60º17’32”W, 13 Apr 2005, F. Medonça, A. Pires & M. Picanso. INPA 46289 View Materials , 3 View Materials , 160.9 View Materials - 165.9 mm SL, rio Negro, Barcelos GoogleMaps   , 0 o 36’19”S 63 o 21’25”W, 19 Feb 2014, V. Machado & T. Hrbek. INPA 46469 View Materials , 2 View Materials , 142.5 View Materials - 153.7 mm SL, rio Negro in front of Castanheira community, São Gabriel da Cachoeira GoogleMaps   , 0 o 20’04”S 65 o 38’18”W, 10 Feb 2014, V. Machado & T. Hrbek. INPA 46472 View Materials , 1, 153.1 mm SL, same data as ANSP GoogleMaps   200146. INPA 52432 View Materials , 5 View Materials , 2 View Materials skel., 117.8-134.7 mm SL, lago do Acaricuara, rio Negro basin, Manaus   , 3 o 04’55”S 59 o 57’38”W, 18 Feb 2011, N. Penhalosa-Duarte, A. A. Peneira, A. L. A. Mesquita, D. M. M. Mendes & M. F. Catarino. MZUEL 15328, 1, 135.0 mm SL, lago do Prato, rio Negro basin, Parque Nacional de Anavilhanas , Novo Airão GoogleMaps   , 2°43’02”S 60°44’41”W, 5 May 2016, J. L. O. Birindelli, F. Jerep, L. H. Rapp Py-Daniel, D. A. Bastos, R. P. Ota & S. Hashimoto GoogleMaps   . Pará: INPA 39507 View Materials , 3 View Materials , 125.0- 179.5 mm SL, lago Jacaré, rio Trombetas, Oriximiná   , 1º20’48”S 56º51’17”W, 30 Nov 2007, D. A. Bastos. MZUSP 119008 View Materials , 2 View Materials , 129,2 View Materials - 130,7 View Materials mm SL, same data as INPA GoogleMaps   39507. Roraima: INPA 19994 View Materials , 3 View Materials , 140.9 View Materials - 166.8 mm SL, lago do Uruaí, rio Branco , Caracaraí, c. 1°50’S 61°10’W, 27 Nov 1976, E. Ferreira GoogleMaps   . Venezuela, Amazonas: MCNG 12414 View Materials , 1, 160.9 mm SL, Río Pasimoni, approximately 20 km above confluence with Río Casiquiare , 1°49’59”N 66°34’59”W, 19 Apr 1985, L. N. P. Cardozo & E. Casdon GoogleMaps   .

Diagnosis. Metynnis melanogrammus   differs from all congeners by having highly concentrated dark chromatophores on the lateral-line scales, resulting in markedly dark pigmentation along the lateral line. Additionally, M. melanogrammus   can be diagnosed from M. altidorsalis   , M. anisurus, M. argenteus   , M. cuiaba   , M. guaporensis   , M. lippincottianus   , M. luna   , M. maculatus   , M. mola   , M. otuquensis   and M. polystictus   by the possession of 13-18 gill-rakers on the upper limb and 16-24 on the lower limb (vs. 8-12, 11- 14 in M. altidorsalis   and M. argenteus   ; 8-10, 12- 14 in M. cuiaba   ; 22-36, 25- 38 in M. guaporensis   and M. luna   , 8-12, 10- 14 in M. lippincottianus   and M. maculatus   ; 7-10, 12- 15 in M. mola   ; 8-11, 12- 13 in M. otuquensis   and 7-11, 11- 15 in M. anisurus and M. polystictus   ). Metynnis melanogrammus   differs from M. fasciatus   by having a shorter head length, 24.3-27.5% SL (vs. 28.0-33.7%) and by a color pattern with dark blotches concentrated at the level of the lateral line and ventral to that region (vs. wide dark bars reaching the ventral portion of body). Finally, it can be distinguished from M. hypsauchen   and M. longipinnis   by having more predorsal and lateralline scales: 56-65, 90-107, respectively (vs. 36-54, 65- 82 in M. hypsauchen   ; and 40-58, 74- 94 in M. longipinnis   ).

Description. Morphometric data summarized in Table 1. Body extremely compressed, overall aspect of body elliptical, body deepest at vertical through dorsal-fin origin. Predorsal and postdorsal origin equal in length. Dorsal profile of head convex from mouth to vertical through anterior portion of eye, slightly concave from latter point to base of supraoccipital process, and convex from that point to dorsal-fin origin. Dorsal body profile very steep from snout to dorsal-fin origin and with strong posteroventral slope after this point. Dorsal-fin base straight. Body profile almost straight from dorsal-fin insertion to adipose-fin origin. Adipose-fin base gently convex. Head short and oval with ventral half of opercle approximately twice as large as dorsal half, with posterior margin surrounded by broad opercular membrane, covering up to four scales horizontally at point of greatest head length.

Ventral body profile convex with series of 19 to 24 (23*) simple prepelvic spines, followed by 6 to 9 (8*) broader, simple, well developed postpelvic spines, some with both anterior and posterior points. Additional 1 to 3 (1*) pairs of spines, composing ventral keel; total spines 28 to 34 (32*), never surpassing anus ( Fig. 2 View Fig ). Caudal peduncle relatively short; profile of lower caudal peduncle slightly concave.

Snout slightly rounded. Mouth terminal with molariform teeth; jaws isognathous. Premaxillary teeth in labial row contacting teeth in lingual row. Five teeth in labial row and two in lingual row ( Figs. 3a, b View Fig ). Premaxillary teeth 1-3 in labial row with slightly sharp edges; teeth 1 and 2 separated laterally ( Fig. 3a View Fig ). Dentary with four teeth decreasing in size posteriorly ( Fig. 3c View Fig ); pair of symphyseal dentary teeth always present behind main series of teeth ( Fig. 3d View Fig ). Maxillary edentulous.

Scales cycloid, numerous, diminute, irregular in size. Lateral line complete with 90 to 107 (97*) perforated scales; first six or eight scales larger than remaining. Scales rows above lateral line 52 to 66 (63*). Scales rows below lateral line 53 to 69 (60*). Scales rows between adipose-fin origin and lateral line 30 to 35 (34*). Circumpeduncular scales 30 to 37 (34*). Predorsal scales 56 to 65 (60*).

reaching vertical through anal-fin origin when adpressed. Anal-fin rays iii, 33 to 41 (39*); with sexually dimorphic distal margin (see Sexual dimorphism, below); unbranched rays well-developed and joined into spine-like structure. Caudal fin forked, with lobes of similar size.

Dorsal-fin rays ii, 16 to 19 (18*); not reaching adiposefin origin when adpressed; dorsal fin preceded by strong and forward-oriented spine. Dorsal-fin origin at mid-body or slightly posterior of vertical through pelvic-fin origin; dorsal-fin margin truncate. Adipose fin well-developed and extremely long with base longer than distance between dorsal-fin origin and adipose-fin origin. Adipose margin straight and truncate. Pectoral-fin rays i, 12(5) to 17 (14*) with distal margin convex, with anterior rays longer than remaining, forming rounded edge. Pelvic-fin rays i, 5 or 6 (6*) with distal margin convex, anterior rays slightly more elongate than remaining, forming rounded edge not

First branchial arch with short gill rakers, 13 to 18 (15*) gill rakers on upper limb; 16 to 25 (20*) gill rakers on lower limb; lower gill rakers slightly longer than upper. Total vertebrae 37(3); abdominal vertebrae 12(3); caudal vertebrae 21(3). One vertebra (3) between verticals through last dorsal-fin pterygiophore and first anal-fin pterygiophore. Supraneurals 5(2), or 6(1).

Ostelogical description. Neurocranium high and triangular. - Olfactory region: Mesethmoid narrow, pointed and triangular anteriorly in dorsal view, dorsal profile convex in lateral view ( Figs. 4a, b View Fig ). Mesethmoid with narrow ventral process articulated to anterior region of vomer ( Fig. 4a View Fig ). Lateral wings of mesethmoid elongate, positioned on anterior half of bone. Lateral ethmoid elongate, dorsal portion reaching anteroventral surface of frontal, and lateral wing thin, pointed distally, and ventrally directed. Vomer excluded from limits of olfactory fossa, marked by longitudinal granulation on distal portion in ventral view ( Fig. 4c View Fig ). Nasal narrow, elongated, with well-defined canal ( Fig. 4b View Fig ). - Orbital region: Parasphenoid long and strongly curved ventrally ( Fig. 4a View Fig ), with ventral aperture forming two thin projections nearly parallel to each other ( Fig. 4c View Fig ) across ventral margins of prootic and basioccipital. Frontal subrectangular, relatively short, approximately 32% of neurocranium length ( Figs. 4a, b View Fig ). Fontanel elongate. Epiphyseal bar dividing cranial fontanel; anterior fontanel oval to somewhat rounded, and posterior fontanel elongate ( Fig. 4b View Fig ). Neurocranium with slightly concavity at frontal bone ( Fig. 4a View Fig ). Pterosphenoid laminar, laterally articulated to sphenotic ( Figs. 4a, c View Fig ). Orbitosphenoid possessing two laterally compressed bony lamellae, anterior lamella upturned with anterior portion contacting frontal, and posterior lamella anteroventrally projected and almost reaching parasphenoid. - Otic region: Prootic trapezoidal, with anterodorsal circular aperture ( Fig. 4a View Fig ). Ventral margin of sphenotic concave, with pointed lateral spine for insertion of dilatator opercula. Parietal with dorsal surface sculptured by grooves, and posterior plate gradually becoming narrower. Intercalar diminute, laminar, very thin, and posteriorly located, covering articulation between exoccipital and pterotic. Pterotic quadrangular and possessing two-pointed posteroventrally directed processes covering lateral opening of posttemporal fossa. Epiotic solid with lateral arm extending towards posterior margins of parietal and pterotic, dividing posttemporal fossa into dorsal and ventral portions ( Figs. 4a, b View Fig ). - Occipital region: Basioccipital forming entire ventral surface of saccular capsule. Exoccipital surrounding lateral occipital foramen, lagenar capsule large. Supraoccipital spine long, well-developed, dorsal profile convex, and with distal portion curved down ( Fig. 4a View Fig ). Infraorbital series: Antorbital narrow and anteriorly curved. Five weakly developed infraorbitals forming semi-circle and leaving naked area on cheeks, not covering lateral surface of vertical arm of preopercle. Lateral branches of sensory channel of infraorbital 4 absent. Infraorbital 5 with “I” shaped sensory channel ( Fig. 5a View Fig ). Supraorbital oval and narrow with slightly convex anteroventral margin, not contacting infraorbital 5. Orbital region overall wide ( Fig. 4a View Fig ). Jaws: Premaxilla strongly attached to mesethmoid. Ascending premaxillary process elongate with distal tip gently pointed and slightly inclined in relation to lateral premaxillary process. Lateral premaxillary process subrectangular and well-developed, possessing dorso-lateral process with concavity for maxillary insertion. Four joined crypts of replacement teeth forming unique long replacement teethtrench on premaxillary ( Fig. 3a View Fig ). Descending arm of maxillary expanded and large, forming nearly right angle with ascending arm. Dentary rectangular and slightly arched with two to four rounded or oval replacement tooth-trenches, posterior trenches more elongate than anterior ones. Four bony lamellae at dentary symphysis. Symphyseal dentary teeth welldeveloped and surpassing dorsal edge of first tooth from main row. Retroarticular trapezoidal and contacting posteroventral portion of dentary. Anguloarticular elongate and articulated with quadrate by thin cartilage ( Fig. 3b View Fig ). Coronomeckelian approximately round. Hyopalatine or Pterygoid arch: Ascending process of quadrate perpendicular to longitudinal axis, shorter and wider than ventral process and with rectangular margin. Posterior margin of ventral process of quadrate not reaching vertical through symplectic’s posterior tip. Hyomandibular narrow and elongate, with ventrally directed triangular projection along anterior margin. Endopterygoid trapezoidal. Symplectic small, located at metapterygoid-quadrate fenestra. Ectopterygoid toothless, narrow and oblique. Ecto-endopterygoid articulation delimiting insertion of posterior margin of autopalatine. Metapterygoid laminar, anteroventrally articulated with quadrate and posteroventrally with hyomandibular. Metapterygoid possessing diminute circular foramina bordered posteriorly by hyomandibular. Autopalatine subquadrangular with regular contour ( Fig. 5b View Fig ). Opercular series: Opercle narrow, laminar, and semicircular. Preopercle laminar and situated along ventral margins of quadrate and hyomandibular, with many grooves on ventral region, and entirely divided by ventrolaterally oriented median laterosensory canal. Interopercle laminar, narrow and somewhat triangular. Subopercle laminar, narrow and elongated, situated along ventral margin of opercle ( Fig. 5b View Fig ). Hyoid arch: Four branchiostegal rays, fourth longest.Anterior ceratohyal narrow and rectangular. Urohyal “T” shaped in lateral view bearing thin dorsal flange. Dorsal hypohyal more developed than ventral hypohyal. Urohyal attached to anterior margin of ventral hypohyal. Interhyal small, narrow and articulated to hyomandibular and posteroventral portion of posterior certatohyal. Dorsal and ventral hypoyal almost equal in size. Basihyal narrow with dorsal portion larger than ventral portion ( Fig. 5c View Fig ). Branchial skeleton: Ceratobranchials 1-5 with 17-19 thin gill-rakers. Epibranchials 1-4 ossified with 13-16 thin gill-rakers, shorter than those from ceratobranchial; 5th epibranchial cartilaginous even in adults. Pharyngobranchials 1-4 ossified. Basibranchials 1-3 thin and ossified. Hypobranchials 1-3 with 2-3 thin gill-rakers. Weberian apparatus and associated centra: Compound centra 1 and 2 approximately equal in size, lateral process of centrum 2 well-developed, axially directed and elongate, ventrolateraly articulated with centrum 3. Centrum 4 largest. Neural arches 3 and 4 separated by suture, neural arch 3 small, and neural arch 4 bearing elongated neural spine of fourth vertebra, fused with supraneural 1. Intercalarium thin, and scaphium short. Inner arm of os suspensorium with robust posteriorlyoriented process. Outer arm of os suspensorium short and dorsoventrally flattened. Tripus aligned with intercalarium and lateral process of third centrum, with straight ventral margin. Claustrum with short ascending arm, and bearing triangular flange along dorsal margin. Neural complex with narrow posterior lamellar portion. Axial skeleton: All vertebrae with neural arches, neural spines and conical neural zygapophyses. Posteriorly directed triangular processes on first two ribs, second smaller. Precaudal vertebrae lack haemal spines and bear parapophyses articulating with ribs. Caudal vertebrae with haemal arches and ventral haemal spines, except vertebra 16, which lacks haemal spine. Pectoral girdle: Cleithrum well-developed with pointed dorsal distal tip extending to middle portion of supracleithrum.Supracleithrum elongate and bearing two small spine-like processes on middle portion of bone. Posttemporal thin, oblique and slightly curved with pointed dorsal distal tip, and elongated median transversal process. Extrascapular lamellar, small, and positioned anteroventral to posttemporal. Postcleithrum 1 oval and vertically elongate. Postcleithrum 2 vertically elongate with narrow lamellar posterior portion, and anterior portion overlapped by cleithrum. Postcleithrum 3 very elongate and pointed, extending beyond ventral margin of pectoral fin. Scapula with wide anterior process, and welldeveloped scapular foramen. Coracoid contacting cleithrum anterior- and posteriorly, with ventral margin curved. Mesocoracoid vertically oriented with dorsal portion articulated with middle region of horizontal process of cleithrum and ventral portion contacting coracoid ( Fig. 5c, d View Fig ). Pelvic girdle: Basipterigyum elongate with ischiac process long and pointed reaching first third of pelvic-fin rays; located above ventral margin of abdomen on dorsal margin of ventral spines ( Figs. 2a, b View Fig ). Dorsal fin: Twenty proximal-middle dorsal-fin radials, each with lateral lamellar process. Anterior proximal-middle dorsal-fin radial modified, reduced in size, and bearing anteriorly directed predorsal spine. Spine rounded with serrate dorsal surfasse. Anteroventral cavity of spine reduced or absent ( Fig. 6a View Fig ). Anal fin: Forty-one proximalmiddle anal fin radials, anterior three each with lateral lamellar process. Males with anterior lobe on anterior rays ( Fig. 6b View Fig , see more details under Sexual dimorphism). Caudal fin and supporting skeleton: Epural 1 anteriorly situated, and epurals 1-2 filling all space between neural arch and spine of preural centrum 3, pleurostyle and uroneural 2. Haemal arches and spines of preural centra 2 and 3 well developed, narrow and fused. Hypural 1 well-developed, hypural 2 narrow, hypural 3 horizontally directed, hypural 4 proximate to hypural 5 and smaller. Hypural 2 not in contact with compound ural centrum. Neural arches and spines of preural centrum 2 and narrow and elongate. Parhypural proximate to hypural 1. Uroneural 2 narrow and proximate to pleurostyle. Principal caudal-fin rays 9+8 ( Fig. 6c View Fig ).

the vertical through the pectoral-fin’s distal margin ( Figs. 1a, b View Fig ). Eye with broad dark transversal bar crossing pupil (not discernible in specimens retained for a long period in formalin). Dorsal, anal and caudal fins proximally hyaline and darker towards fin margins, with pigmentation along distal margin forming narrow dark stripe. Dorsal fin of mature specimens with vertically elongate dark spots or small dark stripes along interradial membranes. Pectoral and pelvic fins hyaline. Caudal fin with distally dark and diffuse band.

Color in alcohol. Overall body coloration light-brown to yellow, head and body darker dorsally. Scales of lateral line with dark chromatophores, forming thin dark stripe along lateral line. Flanks with inconspicuous rounded or vertically elongate dark blotches on middle portion of body and ventral to lateral line. Males with small dark spots scattered irregularly over the body, but most concentrated above the lateral line and below the lateral line on the anterior body ( Fig. 1a View Fig ). Chromatophores can form a large irregular blotch over the supracleithrum, not surpassing posteriorly Color in life. Based on observations of freshly collected specimens, overall body color silvery. Except for pectoral fin, all fins light yellow in base coloration. Anterior rays of anal- and pelvic-fins orange to an intense red. During breeding period, males with intense vertically elongate and irregularly-shaped blood-red blotch near supracleithrum, situated between lateral line and the region just dorsal to prepelvic spines. Conspicuous red dots occasionally present over anterodorsal region of body, extending posteriorly to vertical through dorsal-fin insertion ( Fig. 7 View Fig ).

Sexual dimorphism. Metynnis melanogrammus   presents the same sexual dimorphism illustrated by Zarske & Géry (1999: 173) for M. hypsauchen   and also recorded for M. guaporensis Eigenmann, 1915   by Ota et al. (2013). This dimorphism involves the presence in mature males of an anteriorly rounded lobe formed by an extention of the tenth to thirteenth branched rays of the anal-fin. This lobe has a concavity in the fin margin after the first two branched rays. With the exception of M. fasciatus   , M. guaporensis   , M. hypsauchen   , M. longipinnis   , M. luna   , and M. melanogrammus   , the males of remaining congeners possesses a continuous anterior lobe lacking the concavity ( Ota, 2015). The anal fins of females and juveniles have only the anterior unbranched rays elongate, conferring a characteristic falcate feature to this fin.

Mature males also have more intense body coloration than females, marked by a blood-red, vertically elongated blotch on the supracleithrum region, and dark spots scattered across the body (see Color in alcohol and Color in life). Females only possess notable coloration on the anterior anal-fin rays, which are orange to light red. Prolongation of anterior dorsal-fin rays, which is very common in other Metynnis species   (e.g., Metynnis cuiaba Pavanelli et al., 2009   ) was not observed either in males or females of M. melanogrammus   .

Distribution. Metynnis melanogrammus   is known from the rio Negro basin in Brazil and Venezuela, the Uatumã and Trombetas rivers, both of which are left-bank tributaries of the rio Amazonas, and from the rio Parauari, a right-bank tributary of the rio Amazonas. Zeinad & Prado (2012) recorded the new species (as Metynnis cf. hypsauchen   ) at lago Aracu, rio Sucunduri (c. 5°35’59.83”S 59°33’41.80”W, November 2009), a right-bank tributary of rio Madeira basin in Amazonas State, Brazil ( Fig. 8 View Fig ). Despite a recent thorough survey of Serrasalmidae in the rio Madeira basin in Brazil ( Ota et al., 2013), no preserved specimens of the new species from that basin are known.

Ecological notes. Specimens of Metynnis melanogrammus   are primarily found in lakes and rivers with dark-stained waters, such as the rio Negro in Brazil and Venezuela, and the rio Uatumã in Brazil. The new species has also been collected in clear water lakes in the Parauari (type locality), Trombetas and Sucunduri rivers, but is not known from white-water systems   .

Examination of a dissected female (INPA 18657, 169.2 mm SL) collected in December revealed the possession of small, numerous, yellowish oocytes, typical of mature female during reproduction. An image of a freshly collected Metynnis melanogrammus   ( Fig. 7 View Fig ) taken in November, shows the typical breeding coloration of the species.

Etymology. From the Greak melas (black or dark) and gramma (letter), referring to the well-marked dark lateral line present in the new species. An adjective in the nominative singular.

Conservation status. Metynnis melanogrammus   is relatively common in the rio Negro basin, and is widely distributed along rivers from Northwestern South America in Brazil and Venezuela, with an Extent of Ocurrence (EOO) of approximately 522.458 km 2. No specific threats were detected. Accordingly, we suggest that the new species be categorized as Least Concern (LC) according to IUCN criteria ( IUCN, 2014).

Remarks. The new species described herein is similar to Metynnis hypsauchen   in body shape, sexual dimorphism of the anal fin, and color pattern. Not surprisingly, analyzed material deposited at INPA and MCNG was misidentified as M. hypsauchen   , and the species was recorded in the literature ( Zeinad & Prado, 2012) as Metynnis   cf. hysauchen. The first obvious feature used to recognize specimens described herein as M. melanogrammus   as a potentially new species similar to M. hypsauchen   , is the presence of a markedly dark lateral line, a feature that is absent in M. hypsauchen   . In addition, Metynnis melanogrammus   possesses distinctly smaller scales than M. hypsauchen   which is reflected by higher scale counts, i.e., predorsal (56-65 vs. 36-54), rows above and below lateral line (52-66, vs. 35-55), between adipose-fin origin and lateral line (30-35 vs. 19-25), and total perforated scales of the lateral line (90-107 vs. 65-82).

Ahl (1923) and Gosline (1951) regarded M. hypsauchen   as the most common and widespread species of the genus. Indeed, Metynnis hypsauchen   is widespread throughout the Amazon River system, in the Río Orinoco basin, and in some Guyanese rivers (e.g., Machado-Allison & Fink, 1995; Jégu, 2003; Ota et al., 2013). This species occcurs in sympatry with Metynnis melanogrammus   in the rio Negro basin of Brazil and Venezuela, and also in the rio Uatumã and rio Trombetas basins in Brazil. The new species is known from the rio Madeira basin solely by a photograph of a single specimen from the rio Surunduri ( Fig. 7 View Fig ). There are no confirmed specimen records of M. hypsauchen   in rio Madeira tributaries ( Ota et al., 2013). The record of M. hypsauchen   at the Aripuanã and Madeira rivers by Rapp Py-Daniel et al. (2007) was based on misidentifications of specimens of M. guaporensis   and M. luna   (R. P. Ota, pers. obs.).

R

Departamento de Geologia, Universidad de Chile

V

Royal British Columbia Museum - Herbarium

T

Tavera, Department of Geology and Geophysics

Kingdom

Animalia

Phylum

Chordata

Class

Actinopterygii

Order

Characiformes

Family

Serrasalmidae

Genus

Metynnis

Loc

Metynnis melanogrammus

Ota, Rafaela Priscila, Py-Daniel, Lúcia Helena Rapp & Jégu, Michel 2016
2016
Loc

Metynnis cf. hypsauchen

Zeinad & Prado & Peixes fluviais do Brasil & Campinas 2012: 153
2012