Two new trans-Andean species of Imparfinis Eigenmann & Norris , 1900 ( Siluriformes : Heptapteridae ) from Colombia

Two new species of Imparfinis are described from the trans-Andean region of Colombia. Imparfinis timana is diagnosed by having longer anal fin base (12.4-15.5% in SL), in combination with long adipose fin (24.6-31.3% in SL), 5-6 gill rakers on the first ceratobranchial, 42-43 vertebrae and additional measurements. Imparfinis usmai is distinguished by the combination of first ray of dorsal fin longest, but not projected as a long filament, long adipose fin (21.1-27.0% in SL), maxillary barbel exceeding pelvic-fin base, 39-40 vertebrae, upper caudal-fin lobe pointed and longer than lower lobe, lower lobe rounded, 78 gill rakers on the first ceratobranchial, as well as additional measurements. Imparfinis timana is only known from río Guarapas, a small tributary of the upper course of the río Magdalena. Imparfinis usmai is broadly distributed in the upper basin of ríos Cauca and Magdalena, and in the lower Patía river basin. The restricted distribution of I. nemacheir to transAndean drainages (Atrato, Magdalena, and Lago de Maracaibo) is also discussed.


Introduction
The genus Imparfinis was described by Eigenmann & Norris (1900), based on the species I. piperatus Eigenmann & Norris, 1900 from southeastern Brazil (São Paulo State).As many of the heptapterid genera lacking a free orbital margin (e.g.Cetopsorhamdia Eigenmann & Fisher, 1916, Heptapterus Bleeker, 1858), Imparfinis is a poorly diagnosed genus.Since its description, no exclusive character has been offered for generic recognition.Only a questionable combination of characters, many of them widely present in separate heptapterid genera, has been used in its diagnosis.This has resulted in several different interpretations by authors dealing with the taxonomy and systematics of Heptapteridae, and a continuously changing species composition.To date, the only attempt to phylogenetically diagnose Imparfinis is that of Bockmann (1998), as part of a comprehensive study of Heptapteridae.Currently the genus includes 19 species (Almirón et al., 2007;Bockmann & Guazelli, 2003;Ferraris, 2007), and is one of the most broadly distributed within the family Heptapteridae, from streams in Costa Rica [Imparfinis lineatus (Bussing, 1970)] to the Paraná and Uruguay river basins in Argentina (I.mishky Almirón, Casciotta, Bechara, Ruíz Díaz, Bruno, D'Ambrosio, Solimano & Soneira, 2007), and to both sides of the Andean cordillera.Most of the species have cis-Andean distributions while three are known to be trans-Andean: I. lineatus, I. nemacheir (Eigenmann & Fischer, 1916), originally described from the río Magdalena basin, in Colombia, and I. spurrellii (Regan, 1913), from the río San Juan basin, also in Colombia.
Recently, explorations conducted in the Cauca and Magdalena drainages in Colombia have resulted in the collection of two species, which fit the most recent diagnoses for Imparfinis offered by Mees (1974) and Mees & Cala (1989), and exhibit all the apomorphic conditions provided by Bockmann (1998) in his phylogenetic diagnosis of Imparfinis.The two species show consistent morphological differences with all described species of Imparfinis, and consequently they are described as new in this paper.SL), IMCN 2003, 2, 51.6-60.7 mm SL, Municipio Pitalito, río Guarapas, Tasajera, 01º51'25"N 76º02'34.2"W,1320 m asl, same date and collectors as the holotype.
Description.Morphometric data given in Table 1.Small heptapterid catfish (largest specimen 76.7 mm SL), with elongated body, triangular in cross-section at dorsal-fin origin, progressively more laterally compressed to tail region.Dorsal profile slightly convex from snout tip to dorsal-fin origin, slightly concave just posterior to dorsal-fin base to adipose-fin origin, straight and descending along adiposefin base, then ascending along caudal peduncle.Ventral profile of head straight, slightly convex along abdomen, then straight to anal-fin origin and slightly descending along caudal peduncle.Head conical and depressed, dorsally covered by thin skin.Snout short and broadly rounded.Mouth subterminal.Premaxillary teeth conical and pointed arranged in rectangular band with 4-5 irregular rows.Dentary with four irregular rows of teeth.Barbels dorsoventrally flattened.Maxillary barbels generally extending to pelvic-fin base, but reaching anal fin in some juvenile specimens.Anterior portion of maxillary barbel in shallow groove.Bases of outer and inner mental barbels aligned.Outer mental barbels surpass pectoral-fin base.Inner mental barbels reach pectoral-fin origin.Eye dorsolateral in position.Orbital margin not free, but delimited by shallow groove, more conspicuous along dorsal rim.Anterior naris tubular.Posterior naris rounded, slightly closer to anterior ocular margin than to anterior naris, bordered by low fleshy margin, with notch in posterior border.Nares disposed in trapezoidal arrangement.Anterior internarial width slightly shorter (mean % in HL: 15.2) than posterior internarial width (mean % in HL: 19.4).Branchiostegal membrane free, supported by 7-8 rays and joined to isthmus only at anteriormost point.Gill rakers on first gill arch eight, 5-6 arranged on anterior margin of ceratobranchial, one on cartilage between ceratobranchial and epibranchial, and 1-2 on epibranchial.
Lateral line canal complete, extending to basal portion of interradial membrane of middle caudal-fin rays.Supraorbital pore S1 medially adjacent to anterior naris.S2+I2 midway between anterior and posterior nares, at end of posteriorly directed membranous tubule originating from commissure connecting supraorbital and infraorbital canals, closer to supraorbital canal.S3 posteriorly adjacent to posterior naris and S4 located approximately at mid-distance between posterior naris and eye margin and at level of medial border of posterior naris.Both S3 and S4 originating from anterior and posterior ends of bifurcated lateral membranous branch with T-shape.S7 located dorsomedial and posterior to eye, originating from short membranous tubule running posteriorly.S8 (corresponding to parietal branch), posteromedial to eye.Parietal branch running posteriorly on frontal bone, and ending close to articular suture with parietosupraoccipital bone.Infraorbital pore I1 laterally adjacent to anterior naris, just between naris and maxillary barbel base.I3 posterior to maxillary barbel base.I4 at vertical through anterior eye margin.I5 at vertical through posterior eye margin.I6 posterior to eye at end of short ventroposterior membranous tubule.Preoperculomandibular canal with 11 pores.Dentary with seven pores.Submental pores (PM1) paired and last mandibular pore (PM7) at level of articulation between anguloarticular and quadrate bones.Preopercle with three pores.Anterior pore (PM8) originating between subpreopercle and preopercle.Middle pore (PM9) originating from membranous tubule passing above interopercle and posterior pore (PM10) from membranous tubule passing above ventral portion of opercle.Last preopercular pore (PO1+PM11) at end of membranous branch dorsal to dorsal edge of opercle, close to articulation between opercle and hyomandibula.PO2 corresponding to pterotic branch, located dorsal to dorsoposterior corner of opercular margin.Axillary branch (LL1) ventral, running posterior to extrascapular.Accessory branch (PO3) dorsal to lateral line canal, ending approximately at axilar pore level.
Precaudal vertebrae 12 and caudal vertebrae 30-31, totaling 42-43 vertebrae.First hemal spine on vertebra 16-17.Pleural ribs nine.Anus approximately at mid-length of pelvic fin, closer to pelvic-fin base than anal-fin origin.Urogenital papilla separated from anus by distance approximately equivalent to length of papilla.
Pectoral fin i,8-9.Basal portion of simple ray ossified, distal portion soft and segmented.First and second branched rays longest.Distal margin of pectoral fin straight.Pelvic fin i,5.First pelvic-fin ray thick and shortest, second and third branched rays longest.Pelvic-fin origin at or slightly posterior to mid-distance of dorsal-fin base.Dorsal fin lacking spinelet (i.e.first lepidotrichium), with one simple (second lepidotrichium), and six branched rays.Dorsal fin triangular, second ray longest.Supporting fin elements represented by seven proximal and six distal radials.Last two branched rays articulating separately with last two pterygiophores.First proximal radial inserted posterior to neural spine of vertebra 7 and last proximal radial inserted anterior to neural spine of vertebra 13.Adipose fin low, its maximum height at mid-length, and longer than anal fin, with free posterior lobe.Adipose-fin origin at vertical through anal-fin origin.Anal fin with 2-3 procurrent rays, associated with first proximal radial, two simple rays and 7-8 branched rays.Anal-fin distal margin rounded.Anal fin supported by 10 proximal and nine distal radials.First proximal radial posterior to hemal spine of vertebra 23-24 and last proximal radial anterior to hemal spine of vertebra 30-31.Caudal fin deeply forked with i,7+8,i principal rays.Upper caudal-fin lobe pointed and longer than lower lobe.Lower caudal-fin lobe rounded.Dorsal procurrent caudal-fin rays 13-16, located posterior to vertebrae PU 5 -PU 6 .Last 2-3 rays segmented.Ventral procurrent caudal-fin rays 13-15, located posterior to vertebrae PU 6 -PU 7 .Last 2-3 rays segmented.Caudal skeleton PH, 1+2, 3+4 partially fused at base with 5. Long epural present.

Coloration in alcohol.
Body brownish on dorsal and lateral surfaces, and ventral region cream.Conspicuous, dark midlateral stripe, extending from posterior margin of opercle to caudal-fin origin.Dorsal surface of maxillary barbel pigmented.Outer mental barbel scarcely pigmented at basal portion.Inner mental barbel light-colored.Parieto-supraoccipital region densely pigmented.Dark blotch on opercle.Four dark saddles in dorsum, first saddle crossing predorsal region, second saddle just in front of dorsal-fin origin, third saddle on posterior half of dorsal-fin base, and last saddle between dorsal and adipose fins.Rays of pectoral, dorsal and caudal fins darkly pigmented.Interradial membranes hyaline.Distal portion of pectoral fin light-colored.First pelvic-fin rays with chromatophores scattered.Anal and adipose fins light-colored.
Distribution.This species is only known from the type locality at the río Guarapas, a small tributary of the upper río Magdalena basin (Fig. 2).
Etymology.Timana is used as a noun in apposition and refers to the indigenous people inhabiting the west flank of the eastern cordillera, in the Colombian Andes, from San Agustin to Pitalito (Departamento del Huila).Diagnosis.Description.Morphometric data given in Table 1.Small heptapterid catfish (largest specimen 100.8 mm SL), with elongated body, triangular in cross-section at dorsal-fin origin, progressively more laterally compressed to tail region.Dorsal profile slightly convex from snout tip to dorsal-fin origin, slightly concave just posterior to dorsal-fin base to adiposefin origin, straight and descending along adipose-fin base, then ascending along caudal peduncle.Ventral profile of head straight, slightly convex along abdomen, then straight to analfin origin and slightly descending along caudal peduncle.Head conical and depressed, dorsally covered by thin skin.Snout short and broadly rounded.Mouth subterminal.Premaxillary teeth conical and pointed arranged in rectangular band with 4-5 irregular rows.Dentary with 4-5 irregular rows of teeth.Barbels dorsoventrally flattened.Maxillary barbels surpassing pelvic-fin base.Anterior portion of maxillary barbel in shallow groove, extending below eye.Bases of outer and inner mental barbels aligned.Outer mental barbels surpass pectoral-fin base.Inner mental barbels reach pectoral-fin origin.Eye dorsolateral in position.Orbital margin not free, but delimited by shallow groove, more conspicuous along dorsal rim.Anterior naris tubular.Posterior naris triangular, slightly closer to anterior ocular margin than to anterior naris, bordered by low fleshy margin, restricted to anterolateral rim.Nares disposed in trapezoidal arrangement.Anterior internarial width slightly shorter (mean % in HL 17.5) than posterior internarial width (mean % in HL 21.6).Branchiostegal membrane free, supported by 6-7 rays and joined to isthmus only at anteriormost point.Gill rakers on first gill arch 8-10, 7-8 arranged on anterior margin of ceratobranchial, one on cartilage between ceratobranchial and epibranchial and 0-1 on epibranchial.

Imparfinis usmai, new species
Lateral line canal complete, extending to basal portion of interradial membrane of middle caudal-fin rays.Supraorbital pore S1 medially adjacent to anterior naris.S2+I2 between anterior and posterior nares, slightly closer to posterior naris, at end of posteriorly directed membranous tubule originating from commissure connecting supraorbital and infraorbital canals, closer to supraorbital canal.S3 just at posterior rim of posterior naris and S4 located posterior to posterior naris and at level of anterior eye margin.Both S3 and S4 originating from anterior and posterior ends of bifurcated lateral membranous branch with T-shape.S8 (corresponding to parietal branch), posteromedial to eye.Parietal branch running posteriorly on frontal bone, and ending close to articular suture with parieto-supraoccipital bone.Infraorbital pore I1 laterally adjacent to anterior naris, just between naris and maxillary barbel base.I3 posterior to maxillary barbel base.I4 at vertical through anterior eye margin.I5 at vertical through posterior eye margin.I6 posterior to eye at end of short ventroposterior membranous tubule.Preoperculomandibular canal with 11 pores.Dentary with seven pores.Submental pores (PM1) paired and last mandibular pore (PM7) at level of articulation between anguloarticular and quadrate bones.Preopercle with three pores.Anterior pore (PM8) originating between subpreopercle and preopercle.Middle pore (PM9) originating from membranous tubule passing above interopercle and posterior pore (PM10) from membranous tubule passing above ventral portion of opercle.Last preopercular pore (PO1+PM11) at end of membranous branch, at level of posterior process of hyomandibula.PO2 corresponding to pterotic branch, located dorsal to dorsoposterior corner of opercular margin.Axillary branch (LL1) ventral, running posterior to extrascapular.Accessory branch (PO3) dorsal to lateral line canal, ending approximately at axilar pore level.
Precaudal vertebrae 11-13 and caudal vertebrae 27-29, totaling 39-40 vertebrae.First hemal spine on vertebra 15-16.Pleural ribs eight or nine.Anus approximately at mid-length of pelvic fin, closer to pelvic-fin base than anal-fin origin.Urogenital papilla separated from anus by distance approximately equivalent to length of papilla.
Pectoral fin i,9.Basal portion of simple ray ossified, distal portion soft and segmented.Pectoral fin triangular, first ray sometimes slightly projected beyond fin margin.Distal margin of pectoral fin slightly convex.Pelvic fin i,5.First pelvic-fin ray thick and shortest, first and second branched rays longest.Pelvic-fin origin at or slightly posterior to middistance of dorsal-fin base.Dorsal fin lacking spinelet (i.e.first lepidotrichium), with one simple (second lepidotrichium), and six branched rays.Dorsal fin triangular, first ray longest, sometimes slightly projected beyond fin margin to less than 10% length of second ray.Supporting fin elements represented by seven proximal and six distal radials.Last two branched rays articulating separately with last two pterygiophores.First proximal radial inserted posterior to neural spine of vertebra 7 and last proximal radial inserted anterior to neural spine of vertebra 13-14.Adipose fin low, its maximum height at anterior third, and longer than anal fin, with free posterior lobe.Adipose-fin origin anterior to anal-fin origin.Anal fin with 2-3 procurrent rays, associated with first proximal radial, 2-3 simple rays and 7-8 branched rays (total of ten principal rays).Anal-fin distal margin rounded.Anal fin supported by 9-10 proximal and 8-9 distal radials.First proximal radial posterior to hemal spine of vertebra 23 and last proximal radial anterior to hemal spine of vertebra 28-29.Caudal fin deeply forked with i,7+8,i principal rays.Upper caudal-fin lobe pointed and longer than lower lobe in adult specimens and juveniles longer than 30 mm SL; both lobes pointed but not prolonged as filaments, and about same size, in juvenile specimens shorter than 30 mm SL.Lower caudal-fin lobe rounded in specimens exceeding 30 mm SL, with both branches of lowermost branched ray approximately equal in length.Dorsal procurrent caudal-fin rays 14-17, located posterior to vertebrae PU 5 -PU 6 .Last two rays segmented.Ventral procurrent caudal-fin rays 13-14, located posterior to vertebrae PU 6 -PU 7 .Last three rays segmented.Caudal skeleton PH, 1+2, 3+4, 5 (MBUCV-V-30943 CS specimen with hypurals 3+4 partially fused with 5 at base).Long epural present.
Coloration.Live specimens as shown in Fig. 4, dorsal and lateral surface of body purplish brown, abdominal surface cream.Dorsal and lateral surface of head and dorsal surface of predorsal region greenish yellow.Dorsal surface of barbels brown, and ventral surface of mental barbels white.Gold iridescent blotch on opercular region.Four dark brown saddles on dorsum, first saddle crossing predorsal region, second saddle just in front of dorsal-fin origin, third saddle on posterior half of dorsal-fin base, and last saddle between dorsal and adipose fins.Humeral region with black diffuse blotch continuous posteriorly with midlateral diffuse band.Fin rays of dorsal, pectoral, pelvic, and caudal fins yellowish brown.Interradial membrane of dorsal fin hyaline and membrane of pectoral fin light yellow.Adipose fin light yellow, with dark chromatophores disperse on fin base.In alcohol, body brownish on dorsal and lateral surfaces and cream on ventral surface.Conspicuous dark mid-lateral stripe, extending from posterior margin of opercle to caudal-fin origin.Dorsal surface of maxillary barbels pigmented.Dorsal surface of mental barbels with sparse chromatophores.Parieto-supraoccipital region densely pigmented.Opercle with dark blotch, some chromatophores grouped below eye, along region corresponding to preopercle.Rays of pectoral, dorsal, anal, and caudal fins darkly pigmented.Interradial membranes hyaline.Mid-portion of pectoral and pelvic-fin rays with chromatophores scattered and distal margin hyaline.Adipose fin with chromatophores at basal portion and distal margin hyaline.
Distribution.This species is broadly distributed along the upper basin of río Cauca and río Magdalena, and in the lower río Patía basin on the Pacific slope of western cordillera of Colombia (Fig. 2).Imparfinis usmai is sympatric with I. nemacheir in the río Magdalena.
Etymology.Dedicated to Saulo Usma for his contributions to the ichthyological collection building in the Cauca valley, and for promoting an active interchange between Colombian and Venezuelan ichthyologists, since his MSc studies in 2000 at Universidad Nacional Experimental de los Llanos Ezequiel Zamora (Guanare, Venezuela).
Remarks.Proper taxonomic recognition of Imparfinis usmai has an especially confusing record in the ichthyological literature, even in strictly taxonomic works.Eigenmann (1922), while redescribed Imparfinis nemacheir, listed a series of specimens coming from the ríos Patía and Cauca, as reference material for this species.Some of these specimens (FMNH 58129,, formerly catalogued at the Carnegie Museum, were reexamined, and we found that these population samples are assignable to I. usmai.This species has also been misidentified as I. nemacheir in Ortega-Lara et al. (2000) (photograph on p. 41, where the scarcely projected first dorsal-fin ray beyond fin membrane and shorter maxillary barbel are evident when compared to the actual I. nemacheir), and in Maldonado-Ocampo et al. (2005) (illustration of Fig. 154, p. 289, showing the characteristic configuration of the caudal fin of I. usmai, with upper lobe longer and pointed and lower lobe rounded; along with most of the reference material therein listed and reidentified in the present work: see CZUT-IC and IMCN lots of paratypes and non-type material of I. usmai).Even more surprising are the identifications of pictured specimens of I. usmai as Rhamdia sebae (Cuvier, 1829) (photograph in p. 70) in Galvis et al. (1997), and as Cetopsorhamdia nasus Eigenmann & Fisher, 1916 (Fig. 2, p. 128) in Ruiz-C. & Román-Valencia (2006).From our revision we can assume that some of the distribution records attributed to Imparfinis nemacheir in ríos Magdalena and Cauca basins, in fact correspond to Imparfinis usmai.This last species (Fig. 5a) being easily differentiated from the sympatric I. nemacheir (Fig. 5b-d) by a series of apparent external features briefly mentioned above, as well as those provided in the identification key, which are exhaustively compared in I. usmai diagnosis.
Those lots listed as non-type material correspond to very old specimens (collection dates: 1912-1913), that do not exhibit all diagnostic characters for the species in every single individual, perfectly understandable given the long history of preservation and manipulation (e.g.broken fins); or more recently collected specimens that are not ideally preserved, with distorted body, broken barbels or fins.

Discussion
Imparfinis nemacheir was described from the upper río Magdalena basin, and a single type was designated (Fig. 5b), although several specimens were available to the authors, as inferred from ranges of variation in some meristic and morphometric characters and differences in color pattern, indicated in the original description (Eigenmann, 1916).Later, Eigenmann (1922) redescribed the species in more detail, offering illustrations of the holotype (Fig. 5c), and designated three paratypes (CM 7126a; IUM 13547 a-b).In addition, he listed a series of specimens from other than the type locality of the río Magdalena (Girardot): Patía (río Telembí), Atrato (Certeguí) and Cauca (Cali), hence expanding the known distribution of the species.As we commented before (see I. usmai remarks), those Patía and Cauca records belong to I. usmai, whereas the Atrato specimens (FMNH 58130) were in effect identified as I. nemacheir, corroborating the presence of the species in that basin.Schultz (1944) reported I. nemacheir from the Lago de Maracaibo basin in Venezuela, and pointed out some disagreement between Maracaibo specimens (Fig. 5d) and Eigenmann's descriptions of Nannorhamdia nemacheir (=I.nemacheir), suggesting that a new subspecific name could be applied.However, he did not mention which characters were different, and our own direct comparisons with the holotype and one paratype (FMNH 58128) of I. nemacheir, did not reveal any difference in the characters evaluated (general appearance, body proportions, meristics, pigmentation pattern, and osteological features discernible from standard xray images), being Maracaibo specimens perfectly referable to I. nemacheir.A major insight on the distribution of I. nemacheir in Colombia was provided by Dahl (1971), in his study of the fishes of northern Colombia, assigning a wide distribution in most of the Magdalena system (including upper Cauca), except río San Jorge (a lower basin tributary), and a significant expansion to the known distribution of the species is accounted by incorporating the río Manso, a tributary of the Sinú system, which drains directly into the Caribbean Sea.Despite of not presenting a list of examined specimens, this work has become a main reference on the geographic distribution of I. nemacheir in Colombia, and has been followed by subsequent authors, as Galvis et al. (1997), who first reported the species for a Colombian side tributary of Lago de Maracaibo basin (río Catatumbo), including also the río San Juan basin and río Cesar (Magdalena basin).Galvis et al. (1997) neither provided a list of examined material deposited in museums, so a confident verification of these distribution records, based on a taxonomic reevaluation of the same material is impossible.Nonetheless an exhaustive examination of available specimens of Imparfinis in the studied ichthyological collections, and specially IAvH-P and ICN-MHN, which are the only institutions in Colombia that still keep the extant collections made by George Dahl, open a question on the presence of I. nemacheir in the río Cauca basin, because efforts to locate specimens of this species from that river were unsuccessful.In fact, except for five specimens from the Atrato basin (IAvH-P 6604, 10697), we failed to obtain any additional material of the species from other Colombian drainages, even thought field work oriented to capture topotype specimens was recently conducted by AOL (ACSI funded project in 2006).On the other hand, according to the ICN-MHN database, there is a single record of I. nemacheir from the río Sinú (ICN-MHN 6913), but this lot is apparently missing, and corroboration of its identification, and so its presence in the Sinú is pending until this or other samples become available.Regarding its supposed presence in the río San Juan basin and río Cesar, all examined samples from the San Juan exclusively correspond to I. spurrellii (Fig. 5e) and no Imparfinis records were found from the last river.This paucity of Colombian material of I. nemacheir highly contrasts with the fairly abundant records from the Lago de Maracaibo basin in Venezuela.Ortega Lara et al. (2000) provided a detailed list of rivers where the species is found in the Cauca valley: Cauca, Jamundí, Mediacanoa, Desbaratado, Bugalagrande, Timba, Catarina, Chanco, and Pijao; however as was indicated in the section remarks of I. usmai, most of these records (e.g.río Chanco) correspond to I. usmai.A more recent study, centered on the fishes of Colombian Andes by Maldonado-Ocampo et al. (2005), listed all main basins and rivers of Colombia, already mentioned above, for the distribution of I. nemacheir, differing from the previous authors by offering a list of lots deposited in Colombian collections, and a distribution map (map 156, p. 339), based on plotted localities of a list of bibliographic references.However, examination of available lots there listed confirmed that these records belong to I. usmai, so a conservative approach would be that the only certain plotted locality for I. nemacheir is that representing its type locality.Posterior works having a more restricted geographic coverage in Colombia, many of them just consisting in regional lists by drainage, and providing several voucher lots, have been consistent in placing I. nemacheir in trans-Andean drainages: Atrato basin (Maldonado-Ocampo et al., 2006b), upper Cauca basin (Ortega-Lara et al., 2006), upper Magdalena basin (Villa-Navarro et al., 2006), and middle Magdalena basin (Mojica et al., 2006), being the presence of I. nemacheir corroborated by us only for Atrato and upper Magdalena basins.Also, in taxonomic works where specimens of I. nemacheir have been examined and included in the revised material (Bussing, 1970;Mees & Cala, 1989), those originate from the trans-Andean systems of the Atrato and Lago de Maracaibo, also in agreement with our findings.
Contrary to what is indicated in the pertinent literature, Bockmann & Guazelli (2003) omitted from the distribution of Imparfinis nemacheir, all trans-Andean drainages of Colombia, including the Magdalena basin (type locality), and added the upper rios Amazon, and Orinoco basins.The occurrence of I. nemacheir in any of these cis-Andean drainages is doubtful as shown in the most recent ichthyological surveys conducted in the Orinoco basin (Mojica, 1999;Lasso et al., 2004Lasso et al., , 2005;;Maldonado-Ocampo et al., 2006a;Galvis et al., 2007a), and Colombian Amazon (Mojica, 1999;Mojica et al., 2005;Bogotá-Gregory & Maldonado-Ocampo, 2006;Galvis et al., 2006;Ortega et al., 2006;Galvis et al., 2007b), where this species has not been reported.Lasso et al. (2004) listed I. nemacheir only from the Lago de Maracaibo basin in Venezuela, and Milani (2005), in a taxonomic revision of Imparfinis from Venezuela, determined this species to be restricted to the Lago de Maracaibo basin, whereas seven other species were reported from the Orinoco basin: I. pristos, I. pseudonemacheir, and at least five other species presumably undescribed.Imparfinis pseudonemacheir (Fig. 5f) is the only species in the Orinoco that could be confused with I. nemacheir, although they are easily differentiated by the conspicuous blotched coloration pattern, smaller size, longer maxillary barbels and symmetrical caudal-fin lobes of I. pseudonemacheir.Our own examination of Colombian ichthyological collections corroborates the absence of I. nemacheir records in the Colombian Amazon and Orinoco, and consequently, we restrict the distribution of this species to the trans-Andean drainages of Atrato, Magdalena and Lago de Maracaibo.Similarly, other widespread heptapterid species, Rhamdia quelen (Quoy & Gaimard, 1824), with a putative cis/trans-Andean presence (Silfvergrip, 1996), has shown to be restricted to cis-Andean South America (Perdices et al., 2002), and other pimelodoid species of the río Magdalena basin, considered to be previously described species of cis-Andean drainages, were recently recognized as different species, restricted to trans-Andean drainages: Sorubim cuspicaudus Littmann, Burr & Nass, 2000; Pseudoplatystoma magdaleniatum Buitrago-Suárez & Burr, 2007.Thus, the geographic distribution verified for I. nemacheir, along with that found for I. timana and I. usmai, further corroborates the endemic nature of the trans-Andean fauna, and add to the growing evidence (e.g.Vari et al., 2005) for this biogeographic pattern of the primary freshwater fishes in South America.