Salminus franciscanus, a new species from the rio São Francisco basin, Brazil (Ostariophysi: Characiformes: Characidae)

Salminus franciscanus, the large-sized dourado from the rio São Francisco basin, Brazil, is described. The new species was actually known ichthyologically since at least Valenciennes (in Cuvier & Valenciennes, 1850) but it was never properly identified. Salminus franciscanus can be diagnosed from its congeners by the combination of the presence of an enlarged second tooth in the outer series of the dentary considerably larger than the remaining teeth, the absence of a dark post-orbital stripe, scale counts (68-82 lateral line scales, 11-14 horizontal series of scales between dorsal-fin origin and lateral line, and 68 horizontal series of scales between the lateral line and the pelvic-fin insertion), and a developed extension of the middle rays of the caudal fin. The historical taxonomy of the species is discussed.


Introduction
Salminus is a genus of mid-to large sized characid fishes (ranging from 15 to at least 75 cm SL), occurring in the Amazon, Orinoco, La Plata and São Francisco river basins in cisandean South America and in the río Magdalena and a few other river drainages in transandean portions of the continent.Species of the genus are vernacularly called as "dourado" or "tabarana" in Brazil, and as "dorado", "dorada" or "pirayú" in Spanish-speaking South American countries.Salminus are well-known as one of the main targets of both commercial and amateur fisheries in the La Plata and São Francisco river basins.Salminus species are predatory, mainly piscivorous fishes, which inhabit large rivers and undertake spawning migrations during the rainy season (cf., e.g., Moraes Filho & Schubart, 1955;Godoy, 1975;Sverlij & Espinach Ros, 1986;Esteves & Pinto Lôbo, 2001;Rodríguez-Olarte & Taphorn, 2006).The phylogenetic relationships of Salminus are still unclear.The genus is usually considered, on morphological grounds, a basal characid (e.g., Géry, 1977;Malabarba & Weitzman, 2003).Phylogenetic analysis using molecular data has suggested Salminus to be the sistertaxon of Brycon (Ortí & Meyer, 1997;Calcagnotto et al., 2005), another purported basal characid, a view contradicted by mor-phology (Roberts, 1969;Lima, 2006).
In spite of the great popularity and economical importance of Salminus, our knowledge of the taxonomy of the genus is still unsatisfactory.This is a common situation among many South American freshwater fishes groups, even among large-sized, economically important fishes (Böhlke et al., 1978;Vari & Malabarba, 1998).Eigenmann's (1916) brief revision of the genus, actually solely a key for the species based on the examination of less than 20 specimens, was, for a long time, the main taxonomic work for the genus.Eigenmann (1916) recognized four valid Salminus species: S. maxillosus, from the La Plata basin, S. brevidens, endemic to the rio São Francisco basin, S. hilarii, occurring in the Paraná, São Francisco, Amazon, and Orinoco river basins, and S. affinis, of the río Magdalena in Colombia.Virtually no changes to this taxonomy of the genus were proposed until Géry & Lauzanne (1990).That study, which was focused on the type specimens of almost all nominal species of the genus, in the MNHN and NMW collections, challenged the nomenclature for Salminus adopted by Eigenmann (1916) and followed by subsequent authors.Their main finding was that Hydrocynus brasiliensis Cuvier, the oldest name available for a species in the genus and usually applied to for the large-sized Salminus species from the rio São Francisco basin (e.g., Britski et al., 1984), was actually based on a specimen probably collected at the upper rio Paraguay basin, as evidenced by the fewer scales in that species than occur in the large-sized Salminus species occurring at the rio São Francisco basin.They concluded that Hydrocynus brasiliensis is rather applicable to the large-sized Salminus occurring at the La Plata basin, with Hydrocyon brevidens, S. cuvieri, S. maxillosus and S. orbygnianus all synonyms of H. brasiliensis.The first two of these are objective synonyms, since they were both based on the holotype of Hydrocynus brasiliensis.As a consequence of this shift in the usage of the name Hydrocynus brasiliensis, the large-sized Salminus from the rio São Francisco, identified as S. cuvieri by Steindachner (1880), S. brevidens by Eigenmann (1916), and S. brasiliensis by Géry (1977) and Britski et al. (1984), was left nameless.Due to the lack of adequate material, Géry & Lauzanne (1990) refrained from formally naming the species.
During a revisionary study of Salminus conducted by the senior author (Lima, 2006), we confirmed the conclusions reached by Géry & Lauzanne (1990) on the identity of Hydrocynus brasiliensis and on the absence of an available name for the Salminus species from the rio São Francisco basin.Considering that this is a large-sized fish, important as a fishery resource and recognized since a long time as distinct by ichthyologists, we consider it unwise to postpone further its description.We, therefore, take this opportunity to finally baptize this long-known, yet still unnamed dourado species.

Material and Methods
Counts and measurements were taken according to Fink & Weitzman (1974) and Menezes & Weitzman (1990), with the addition of head height, measured at the vertical that passes through the basis of the supraoccipital process.Most measurements were taken with a caliper, to the nearest 0.1 mm.Standard length and a few other measurements of large-sized specimens (> 400 mm SL) were taken with a divider and a rule, to the nearest 1 mm.Lateral line scale counts includes all pored scales, including those posterior to the hypural joint.

Diagnosis. Salminus franciscanus can be diagnosed from all
Salminus species, except S. brasiliensis, by the presence of a second dentary tooth in the outer tooth series that is considerably larger than the remaining teeth (vs.second dentary teeth only slightly larger than remaining teeth in S. affinis and S. hilarii).Salminus franciscanus can be additionally diagnosed from S. affinis by the absence of the dark post-orbital stripe that is characteristic from the latter species.Salminus franciscanus can be diagnosed from S. brasiliensis in possessing much lower scale counts, i.e., lateral line (68-82, modally 77 scales, vs. vs.79-102, modally 96), horizontal between dorsal-fin origin and lateral line (11-14, modally 12, vs. 14-18, modally 16) and horizontal between lateral line and pelvic-fin insertion (6-8, modally 6, vs. 6-9, modally 8).In spite of the great overlap, Salminus franciscanus has generally more lateral line (68-82, modally 77 scales, vs. 54-72, modally 65-66), horizontal between dorsal-fin origin and lateral line (11-14, modally 12, vs. 9-12, modally 10), and horizontal between lateral line and pelvic-fin insertion (6-8, modally 6, vs. 4-7, modally 5), scales, when compared to the sympatric S. hilarii.In life, Salminus franciscanus can also be distinguished from S. hilarii by the presence of golden coloration mainly over the facial bones and pectoral girdle (vs.facial bones and pectoral girdle silvery).See under "Remarks", below, for more details on the diagnosis of Salminus franciscanus regarding its congeners.straigth along dorsal-fin base and slightly convex to straight from posterior of dorsal-fin base to adipose-fin origin.Dorsal profile of caudal peduncle slightly concave.Ventral profile of head and body slightly convex from lower lip to pelvic-fin insertion, straight to slightly convex from latter point to analfin origin, and approximatelly straight along anal-fin base.Ventral profile of caudal peduncle slightly concave.Head profile acute anteriorly.Mouth terminal.Maxilla extending posteriorly little beyond vertical through posterior margin of eye in specimens greater than 165 mm SL, not reaching latter point in smaller specimens.Adipose eyelid relatively well developed, covering anterior portion of eye.Premaxilla with two series of teeth.Teeth of outer series considerably larger that those of inner series other than for second tooth of inner series.Outer series with 4-8 teeth approximatelly equal in size; teeth with distinct, elongate basal portion (shaft), and apical portion (crown).Crown triangular, with angles possibly constituting poorly differentiated cusps.Inner tooth series with 7-15 teeth.Symphyseal tooth relatively large, second tooth slightly smaller, third and subsequent teeth considerably smaller.Teeth of inner series of form comparable to those from outer series, except for proportionally shorter shafts and being more massive overall.Middle portion of ventral margin of maxilla slightly concave.Maxilla with 23-37 teeth of form similar to those of outer series in premaxilla, but slightly smaller and decreasing very gradually in size posteriormost with less developed crowns.Last teeth conical.Dentary with 16 to 29 teeth on primary series; teeth similar in form to those of outer series in premaxilla outer series, and other than first through third teeth slightly smaller than those on premaxilla.Second teeth on primary series of dentary considerably larger than other teeth in that series in specimens of all sizes.Third through last teeth progressively decreasing in size with less developed crowns.Teeth of outer series of dentary, outer series on premaxilla, and teeth on maxilla with crowns slightly recurved lingually.Inner tooth series on dentary with 53-58 conical teeth arranged in continuous series from symphysis to terminus of inner rim of replacement teeth trench.Teeth in inner series oriented at right angle to teeth of primary series with apices directed lingually.

Coloration in alcohol.
Overall coloration from specimens still retaining guanine plumbeous-gray, with brownish hue dorsally.Top of head (including supraorbital, infraorbitals 4 and 5, and dorsal portion of opercle), snout and anterior portion of maxilla brown.Remaining infraorbitals and ventral portion of opercle silvery.Lateral portions of body lightly colored, with silvery hue and dark-grey dorsally.Dark humeral spot present, but relatively inconspicuous.Spot horizontally ovoid, formed by pigmentation subjacent to scales, and situated above second and third lateral line scales.Dark, straight longitudinal stripes formed by dark chromatophores concentrated on mid to distal portions of each scale extending along trunk.Stripes more discernible dorsally.Caudal peduncle with broad median stripe, originating 3-5 scales from hypural joint and continuing posteriorly over 3-4 central principal caudalfin rays.Dorsal and anal fins with few chromatophores forming ill-defined dark stripes across interradials membranes.Pectoral, pelvic, and adipose fins clear, with few, scattered dark chromatophores.Specimens lacking guanine as result of long storage in formalin brown overall, without silvery hue on lateral portions of body, infraorbitals or opercle.
Life coloration.Description based on photographs of two freshly collected specimens from rio Paraopeba (not preserved; Fig. 3), one specimen from rio Urucuia (not preserved), and one specimen from rio São Francisco (MZUSP 89512).Dorsal portion of body and head dark gray; lateral portions of body lightly pigmented with silvery hue.Infraorbitals, opercular series, and pectoral girdle golden.Fins, including adipose fin, yellow-orangish but with reddish margin on caudal fin.
Sexual dimorphism.The presence of hooks on pelvic and anal fins (less often other fins) is considered to be a dimorphic sexual character, present in mature males of most Characidae (Malabarba & Weitzman, 2003).Anal and pelvic fin hooks were found in several examined specimens of Salminus franciscanus (MZUSP 39727, 7, 235.0-283.0 mm SL, and MZUSP 20443, 297.0 mm SL).Two of these specimens (MZUSP 39727, 260 and 283 mm SL) were found to be males on dissection.Salminus franciscanus females are reported to grow larger than males of the species (Sato & Godinho, 2003).

Biology, ecology, and fisheries.
There is little published information about the general biology and ecology of Salminus franciscanus, when compared to its much better known congener S. brasiliensis, an unfortunate fact since the species has been recognized as distinct (even if under misapplied names) since late XIX century.Salminus franciscanus is reported to reach one meter in total length and to weigh up to 30 kg (Sato & Godinho, 1999, 2003;as S. brasiliensis;C.B.M. Alves, pers. comm.), being, consequently, one of the largest known Characiformes.It is a piscivore, which undertake reproductive migrations during the rainy season (Sato & Godinho, 1999, 2003;as S. brasiliensis).Juveniles (< 600 g) were collected in marginal lagoons of the rio São Francisco, which indicates that those are recruiting habitats for the species (Sato & Godinho, 2003;as S. brasiliensis).Salminus franciscanus is one of the main targets of the commercial and amateur fisheries in the middle rio São Francisco basin (Petrere, 1989;Sato & Godinho, 2003;as S. brasiliensis).The early larval development of the species was described by Santos & Godinho (2002;as S. brasiliensis).

Discussion
The incorrect identification of a specimen of Salminus franciscanus by Valenciennes (in Cuvier & Valenciennes, 1850) to S. cuvieri was the reason for the application of that name (Lütken, 1875a;Steindachner, 1880), and its senior synonyms S. brevidens (Günther, 1864;Eigenmann, 1916;Moraes & Schubart, 1955) and S. brasiliensis (e.g., Britski et al., 1984) to the species.As noted by Géry & Lauzanne (1990), none of those names is appropriatelly applied to the large-sized species of Salminus occurring in the rio São Francisco basin, which was, consequently, left unnamed up to now.
Given the pronounced similarity among the species of Salminus, the distinctness of S. franciscanus and its congeners was repeatedly discussed in the sparse literature dealing with the taxonomy of the genus.Lütken (1875bLütken ( , 2001) ) was the first author to propose a possible diagnosis between what is herein described as Salminus franciscanus (his S. cuvieri) and the sympatric S. hilarii.Lütken (1875bLütken ( , 2001)), after presenting a thorough morphological comparison between both species, concluded that only scales counts (higher in Salminus franciscanus) and a "difference in teeth size", presumably a reference to the great development of the second dentary tooth in S. franciscanus, distinguished the two species.Lütken (1875bLütken ( , 2001) ) warned that these differential characters should be considered as tentative since he examined only three specimens of Salminus franciscanus (one of which a skin) and a single individual of S. hilarii, that he considered a juvenile.That individual measured 8 1/4 Danish inches ( = 21.6 cm) which would make it rather an adult of this relatively small-sized species of Salminus.Interestingly, Lütken (1875bLütken ( , 2001) ) was the first author to notice the discrepancy between the descriptions of Hydrocyon brevidens by Cuvier (1819) and Salminus cuvieri by Valenciennes (in Cuvier & Valenciennes, 1850).He noted that "Salminus cuvieri Val.cannot be the Hydrocyon brevidens from Cuvier, who, according to the original description, possess more than 100 lateral line scales... being, consequently, more probably identical to the species that inhabits the La Plata River" (Lütken, 2001: 121; our translation).Obviously, Lütken (1875bLütken ( , 2001) ) was unaware of the fact that the same specimen was used in the description of both species and that the difference in lateral line counts was due to a mistake by Valenciennes.Steindachner (1880: 80), when describing Salminus affinis, considered this species very similar to S. franciscanus (his S. cuvieri; hence the epithet "affinis"), from which it was said to be diagnosable only by the presence, in the latter species, of a more robust and developed "canine" tooth ("Hundszahne") ( = second dentary tooth) and by the development, in S. franciscanus, of the central caudal-fin rays into a distal projection.As noted under "Diagnosis" and below, both are in fact valid characters to diagnose these species.Steindachner (1880: 82-83) compared Salminus franciscanus with S. hilarii, but considered them probably synonymous, believing that specimens of S. hilarii were juveniles (thus, ignoring Lütken´s observations, who has compared specimens from both species of the same size).Curiously, Steindachner (1880) used Salminus cuvieri for S. franciscanus, and, in the same paper, S. brevidens for the species from the La Plata basin (= S. brasiliensis).Günther (1864) was the first author to employ Salminus brevidens for S. franciscanus, a practice that prevailed in the literature from Eigenmann (1916) up to Britski et al. (1984).Finally, Géry & Lauzanne (1990) noted that Hydrocynus brasiliensis is the older name and consequently has priority over its objective synonyms Hydrocyon brevidens and Salminus cuvieri, and more pertinently that the name should be applied to the Salminus species from the La Plata basin, rather than to one of the species from the rio São Francisco basin.
The more striking diagnostic feature of Salminus franciscanus when compared to its congeners is the great development of the second dentary tooth, which is considerably larger than the remaining dentary teeth.This feature, already reported for the species by previous authors (Lütken, 1875b(Lütken, , 2001;;Steindachner, 1880;Géry & Lauzanne, 1990), is not, however, exclusive to Salminus franciscanus, since S. brasiliensis and, to a lesser extent, some examined specimens of S. affinis also possess a second dentary tooth distinctly larger than the remaing teeth.However, unlike Salminus franciscanus, which retain a second dentary tooth considerably larger than the re-Table 1. Morphometric data of Salminus franciscanus.A: MNHN A. 8556 (stuffed specimen, its data not included in the range or mean).maining teeth throughout its development, in S. brasiliensis the disparity in size between this tooth and the remaining dentary teeth present a ontogenetic change.Individuals larger than 350 mm SL of the latter species possess this tooth similar in size to the remaining dentary teeth.The great development of the second dentary tooth is the better clue to diagnose Salminus franciscanus from the sympatric S. hilarii, which, inasmuch as possessing a second dentary tooth slightly larger than the remaining teeth in small specimens (< 150 mm SL), never possess it as developed as S. franciscanus.Another interesting feature present in Salminus franciscanus is the great development of the extension of the central caudal-fin extension, throughout of which extends the laterosensory tube.Salminus franciscanus has a well-developed central caudalfin extension, which extends 1/3 or even ½ beyond primary margin of fin.Salminus brasiliensis is the only congener to possess an well-developed central caudal-fin extension, which, however, is not as well developed as the one observed in S. franciscanus.In Salminus hilarii, the central caudal-fin extension is very short, being apparent only as a small convexity on the distal portion of the caudal fin, while S. affinis apparently does not possess any development of the median caudal-fin rays beyond the primary margin of the fin.
Comparative material examined Lehmann (MHNUC) has lent a valuable specimen of the now rare S. affinis.Carlos B.M. Alves (Bio-Ambiental Consultoria, Belo Horizonte) provided color pictures of living S. franciscanus, including the one used here as Fig. 3, and was instrumental in claryfing several minor problems related to localities.Maraísa Ribeiro also provided photographs of a living specimen of S. franciscanus.Eduardo G. Baena radiographed specimens and prepared Fig. 4. Alberto Akama collected and prepared the skeletonized specimen used in this study.Yoshimi Sato (CODEVASF, Estação de Hidrobiologia e Piscicultura de Três Marias, Três Marias) provided various information about the species.Two anonymous reviewers greatly contributed for the improvement of the present paper.This paper is a portion of a Ph.D. Thesis (Lima, 2006), and we are grateful to FAPESP (Grant # 01/14449-2) for the financial support to the senior author.This paper is dedicated to the memory of Jacques Géry (1917Géry ( -2007)).

Fig. 4 .
Fig. 4. Map of eastern and northeastern Brazil showing the distribution of Salminus franciscanus.A square indicates the type locality.
Body relatively slender, moderately deeper in specimens larger than 360 mm SL.Greatest body depth at dorsal-fin origin.Dorsal profile of head and body slightly convex from margin of upper lip to vertical through anterior nostril, straight to slightly concave from latter point to supraoccipital spine, moderately convex from latter point to dorsal-fin origin, then