Fishes of the Cusiana River (Meta River basin, Colombia), with an identification key to its species.

The Cusiana River sub-basin has been identified as a priority conservation area in the Orinoco region in Colombia due to its high species diversity. This study presents an updated checklist and identification key for fishes of the Cusiana River sub-basin. The checklist was assembled through direct examination of specimens deposited in the main Colombian ichthyological collections. A total of 2020 lots from 167 different localities from the Cusiana River sub-basin were examined and ranged from 153 to 2970 m in elevation. The highest number of records were from the piedmont region (1091, 54.0 %), followed by the Llanos (878, 43.5 %) and Andean (51, 2.5 %). 241 species distributed in 9 orders, 40 families, and 158 genera were found. The fish species richness observed (241), represents 77.7 % of the 314 estimated species (95 % CI=276.1-394.8). The use of databases to develop lists of fish species is not entirely reliable; therefore taxonomic verification of specimens in collections is essential. The results will facilitate comparisons with other sub-basins of the Orinoquia, which are not categorized as areas of importance for conservation in Colombia.

Introduction

The Orinoco River, with an estimated richness of 1002 species of freshwater fishes, is the second most diverse drainage in the Neotropical region (Reis et al. 2016). Nonetheless, the basin has been exposed to increasing threats due to human activities that place the enormous fish diversity at risk (Barletta et al. 2010, Rybicki and Hanski 2013, Lasso et al. 2016). The systems draining the Andean region (western tributaries of the Orinoco) are considered the most threatened at basin scale (Rodríguez et al. 2007, Machado-Allison et al. 2010, Lasso et al. 2016). The rivers originating in the Andes are heavily exposed to threats like habitat fragmentation, contamination, deforestation, the introduction of non-native species and mining (Machado-Allison et al. 2010, Anderson and Maldonado-Ocampo 2011, Lasso et al. 2016). Additionally, large gaps regarding the basic knowledge of fish diversity of the Andean sub-basins are persistent, especially in Colombia (Maldonado-Ocampo et al. 2008, Machado-Allison et al. 2010, Lasso et al. 2016). Filling those gaps are essential to guide adequate conservation efforts for the freshwater ecosystems and therefore face the threats above mentioned.

The Meta River basin, with headwaters on the Eastern Cordillera of Colombia, is one of the major tributaries of the Orinoco River (Usma-Oviedo et al. 2016). Studies on its fish diversity (e.g., Urbano-Bonilla et al. 2009, 2014, Villa-Navarro et al. 2011, Maldonado-Ocampo et al. 2013, Urbano-Bonilla and Maldonado-Ocampo 2013), and recent efforts (Zamudio et al. 2008, Urbano-Bonilla et al. 2016) have advanced our understanding of the ecology of some species. The Cusiana River sub-basin is one of the best-known Andean tributaries of the Meta River basin; the first inventories of its fish diversity dated back to the 90’s with the establishment of oil companies in the area. The Cusiana River sub-basin has been considered as a conservation priority area for the Orinoco biodiversity due to its high diversity in several groups (Lasso et al. 2010, Trujillo et al. 2011), including fishes (Villa-Navarro et al. 2011).

Here an updated checklist and an identification key are presented for the fishes of the Cusiana River sub-basin. We hope our results may establish a guideline that can be replicated in other basins of the Orinoco drainage.

Materials and methods

The Cusiana River sub-basin has an extension of 7324 km² and 271 km in length, originating at 3800 m asl on the eastern slope of the Eastern Cordillera in the Quebradas La Iglesia, Melgarejo, and Las Cañas, Boyacá Department (), and empties at 150 m asl in the Meta river, Casanare Department () (IGAC 1999) (Fig. 1). The Cusiana River sub-basin was divided by altitudinal limits in three distinctive regions based on Abell et al. (2008): Llanos (139–300 m asl), Piedmont (300–1235 m asl) and High Andes (1235–3000 m asl).

Figure 1.

Collection localities in the Cusiana River sub-basin.

The checklist was assembled by examining specimens deposited in Colombian ichthyological collections. Acronyms used in the text follow Sabaj-Pérez (2016) except uncatalogued material housed at Fundación Universitaria del Trópico Americano (UNITROPICO). The taxonomic list follows the classification system proposed by Reis et al. (2003) with recent modifications proposed by Oliveira et al. (2011) for characiform families, Betancur-R et al. (2016) at high-level groups for osteichthyans in general, and Thomaz et al. (2015) for genera of the . Valid species names were confirmed through queries on the Catalog of Fishes of the California Academy of Sciences (Eschmeyer et al. 2017). Species were categorized as endemic (DoNascimiento et al. 2017), threatened (Mojica et al. 2012), migratory (Usma-Oviedo et al. 2013), and species subject of conservation (González et al. 2015).

Species richness interpolation and extrapolation was calculated following Chao et al. (2014) and using the package iNEXT 2.0.12 (Hsieh et al. 2016) for R v.3.4.0 (R Core Development Team 2017). The number of localities were obtained per Orinoco basin from the data set of the “Catalogue of the Freshwater Fishes of Colombia” (DoNascimiento et al. 2017).

To construct the key (for order, families and species), original descriptions of species, taxonomic revisions, and direct examination of specimens were used. Finally, in order to share the information produced herein, the dataset was uploaded to SiB Colombia’s data portal (GBIF Colombia Node) in accordance with their protocols for species lists. For the latter, the complete dataset was structured and standardized to comply with the international biodiversity standard: Darwin Core standard (Wieczorek et al. 2012). After mounting the dataset on a Darwin Core spreadsheet template, it was uploaded to SiB Colombia’s Integrated Publishing Tool for international visualization in their data portal. A DOI was provided by SiB Colombia for the shared dataset available at http://doi.org/10.15472/er3svl, all the results, discussion and quantities herein cited follow the version 1.8 of the published dataset.

Results

In total, 2020 lots from 167 different localities from the Cusiana River sub-basin ranging from 152 to 2970 m asl were examined. Most of the records were found in the piedmont (1091, 54.0%), followed by the llanos (878, 43.5%) and Andean Orinoquia (51, 2.5%), suggesting sampling bias in elevation for this drainage, being inversely-proportional to elevation (Fig. 2). The number of localities in Cusiana River sub-basin represents the quantile 0.83 among the tributaries of the Orinoco drainage in Colombia (Table 1). 241 species were found distributed in nine orders, 40 families, and 158 genera. The order showed the highest richness with 106 species, followed by (89), (20), and (15). The remaining orders were represented by one to three species. The most speciose families were the (54), (30), (15), (15), (11), and (9), while the 34 remaining families were represented by 1 - 8 species. Extrapolation suggests that the expected richness for the Cusiana River sub-basin is roughly 314 species (95% CI = 276.1–394.8) (Fig. 3); with the observed richness corresponding to around 77.7% the expected richness.

Figure 2.

Distribution of sampling records along the Elevational gradient in the Cusiana River sub-basin. Asterisks indicate categories with the lowest sampling along the elevational gradient.

Table 1.

Number of sampling sites per basin.

Basin	Number of sampling locations
Guamal-Humadea	213
Guacavía-Guatiquía-Humea	174
Cusiana	167
Ariari	74
Upía	61
Guayuriba	57
Cravo-Norte	56
Pauto	56
Cravo-Sur	53
Arauca	43
Guayabero	35
Tua	29

Figure 3.

Species accumulation curve in the Cusiana River sub-basin. Abbreviations: S.obs = observed richness, S.est = estimated richness. Continuous line represents interpolation, and dashed line represents extrapolation.

Concerning threatened species, five are currently categorized as Vulnerable (, , , , PageBreakand ), and two as Nearly Threatened ( and ). There are 34 species endemic to the Orinoco drainage, 20 are migratory, and 8 are subjects of conservation. A total of 50 species are new records for the Cusiana River sub-basin, while and are also new records for Colombia. Some species from the genera , , , , , , , , , , , , , , , , , and , require further revision by specialists.

Discussion

Regional checklists of freshwaters fishes become dynamic over time as studies in freshwater fish taxonomy and distribution advance for the Neotropical region (Reis et al. 2016). The most recent checklist for the Meta River basin reported 258 species for the Cusiana River sub-basin (Usma-Oviedo et al. 2016); it is a higher number of species than reported herein because re-identification and taxonomic updating processes of specimens excluded 59 of the 258 nominal species reported by Usma-Oviedo et al. (2016). For example, most of the undetermined (e.g., sp., sp, sp., and sp.) and erroneous records (e.g., , , , and ) originally counted as independent species were merged with other recorded species after our verification of the data. This is not surprising, taxonomy proceeds at a faster pace than the institutional ability to maintain updated records. For this reason, there is a need to account for validation of species identification when regional checklists are assembled from multiple secondary sources in order to avoid errors due to outdated or unverified data.

Extrapolation suggests that the drainage could have a richness of roughly 314 species, indicating that the number of species found in the present study represents 77.7% of the expected richness in the area (Table 1). However, this estimate represents a rough estimate because sampling efforts have not been uniform across the drainage. A historical sampling-specific bias is not expected in the Cusiana River sub-basin, with the possible exception of an elevational bias (as is true for the whole Orinoco drainage in Colombia). Given the non-uniform nature of sampling in comparable river systems, we suggest that our extrapolations of species richness may be useful for comparisons among drainages using collection records as the input for rough estimation. This is particularly important since most checklist studies compare observed and not estimated richness, with the latter a more appropriate measure because it incorporates (and even overestimates) uncertainty from the samples into the estimation, and it also serves accounts for sampling effort among drainages.

Among similar Orinoco Andean tributaries, the Cusiana is one of the best-sampled sub-basins, exceeding in species richness other recently well-sampled sub-basins such as Orotoy (113 spp.; Ramírez-Gil et al. 2011) and Pauto (182 spp.; Maldonado-Ocampo et al. 2013). In fact, the Cusiana River sub-basin represents the quantile 0.83 among Orinocoan drainages, indicating that 83 % of the other drainages had fewer than 74 localities represented in the collections. The importance of the Cusiana River sub-basin is not only determined by its fish richness, but also because of its diverse and extensive aquatic ecosystem richness (rivers, streams, lagoons, estuaries, palm swamps, riparian forests, and flooded savannas) that provide important areas for fish reproduction, shelter and food. Because aquatic ecosystems have dynamic ecological and environmental processes (Teresa et al. 2015, Ribeiro et al. 2016, Toussaint et al. 2016), management and conservation projects of sub-basins should be addressed at regional (sub-basin) scales.

The documentation of the ichthyofauna in cis-Andean Colombian sub-basins has been increasing during the last decade, but new records and species can likely still be found in areas previously thought to be well-sampled (e.g., Ballen 2011, Vanegas-Ríos et al. 2015, Ballen et al. 2016a, 2016b, Burns et al. 2017, García-Alzate et al. 2017). Most of the sampling effort has been carried out in the piedmont and lowland areas PageBreakin the Cusiana as well as in other sub-basins, and exploration of High Andean areas could lead to the discovery of local endemic species at the basin scale that usually are underestimated (Carvajal-Quintero et al. 2015).

Sub-basins adjacent to the Cusiana draining along the eastern slope of the Eastern Cordillera in the Orinoco region of Colombia (e.g., Guachiría, Casanare, Upía, Túa, and Cravo Sur) have not been well sampled and their richness is surely underestimated (Urbano-Bonilla et al. 2014). Continuous efforts are still to be carried out in order to document the fish fauna present along this region; this information is crucial to better understand how different anthropogenic activities (mining, oil extraction, agricultural, and livestock practices) are affecting the environmental conditions of these areas and as a consequence, the fish that live therein. Combination of this kind of information and further environmental data is a necessary step in order to generate freshwater conservation strategies using different approaches and therefore go further toward effective protection initiatives for species subject of conservation in the region.

1	Five pairs of gills in ventral position	MYLIOBATIFORMES: Potamotrygonidae (2 species)
–	Two lateral gill openings, or just one gill opening under head	2
2	Eyes located on the same side of body	PLEURONECTIFORMES: Achiridae (2 species)
–	Eyes located on opposite sides of body	3
3	Dorsal fin absent	4
–	Dorsal fin present	5
4	Anal fin absent; one ventral gill opening	SYNBRANCHIFORMES: Synbranchidae: Synbranchus marmoratus
–	Anal fin present, always long, two lateral gill openings	GYMNOTIFORMES (20 species)
5	Body naked or covered with bony plates; barbels present near the mouth	SILURIFORMES (90 species)
–	Body totally or partially covered with scales; barbels absent	6
6	Dorsal and anal fins with two or more spines; scales ctenoid	7
–	Dorsal and anal fins without spines; scales cycloid (ctenoid in some groups)	8
7	Lateral line interrupted	CICHLIFORMES (15 species)
–	Lateral line continuous	ACANTHURIFORMES: Sciaenidae (2 species)
8	Mouth superior and somewhat protractile; adipose fin absent	CYPRINODONTIFORMES (3 species)
–	Mouth usually in terminal position, never protractile; adipose fin usually present	CHARACIFORMES (106 species)
MYLIOBATIFORMES
Potamotrygonidae
1	Dorsum brown with yellow or orange regularly distributed ocelli, ocelli rarely fused; teeth of both jaws in adult males with cusps on the central axis, teeth in females flattened in all rows	Potamotrygon motoro
–	Dorsum light brown with black or dark brown spots forming reticulate hexagonal lattices, mainly on the interorbital region; teeth small with triangular slightly monocuspid crowns in males and trapezoid tricuspids in females	Potamotrygon orbignyi
PLEURONECTIFORMES
Achiridae
1	Pectoral fins present; gill openings wide and extending ventrally on both sides of head	Hypoclinemus mentalis
–	Pectoral fins absent; gill openings limited to a narrow slit and never connected ventrally to both sides of head	Apionichthys sauli
GYMNOTIFORMES
1	Caudal fin and dorsal filament present	Apteronotidae
–	Caudal fin and dorsal filament absent	2
2	Mouth in upper position, body cylindrical	Gymnotidae
–	Mouth terminal or subterminal, body compressed	3
3	Teeth present; nares tubular	Sternopygidae
–	Teeth absent; anterior nares not tubular	4
4	Absence of mental accessory electric organ	Hypopomidae: Brachyhypopomus brevirostris
–	Presence of mental accessory electric organ	Rhamphichthyidae
Apteronotidae
1	Lower jaw with a distinct V-shaped median groove accommodating the pointed decurved upper jaw	Adontosternarchus devenanzii
–	Lower jaw without a V-shaped median groove	2
2	Snout tubular	3
–	Snout obtuse or elongate but not tubular	5
3	Absence of teeth on upper jaw	Platyurosternarchus macrostoma
–	Presence of teeth on upper jaw	4
4	Total anal-fin rays 212–242	Sternarchorhynchus oxyrhynchus
–	Total anal-fin rays 193–210	Sternarchorhynchus roseni
5	Mid-dorsal pale stripe absent	Compsaraia compsa
–	Mid-dorsal pale stripe present	6
6	Presence of two clear bands surrounding caudal peduncle	Apteronotus albifrons
–	Presence of a single clear band surrounding base of caudal peduncle	7
7	More than 10 scales above lateral line	Apteronotus galvisi
–	10 or fewer scales above lateral line	Apteronotus bonapartii
Gymnotidae
1	Without a particular color pattern on body; anal fin confluent with tail	Electrophorus electricus
–	Body color pattern formed by dark oblique bands alternating with pale bands; anal fin not confluent with tail	2
2	Obliquely-oriented dark bands or band pairs with straight or high-contrast margins, 23 dark bands (usually more than 30)	Gymnotus cataniapo
–	Obliquely-oriented dark bands or band pairs with irregular and wavy margins 23	Gymnotus carapo septentrionalis
Sternopygidae
1	Orbital margin free; all anal-fin rays simple; background color variable from uniformly gray to black; humeral black blotch present, rarely diffused; white narrow band under the lateral line, from the midbody to end of anal fin	Sternopygus macrurus
–	Orbital margin continuous; background color variable from translucent to white; humeral blotch absent	2
2	Anal fin either completely black or with a black margin; no horizontal dark stripes on body; scales above lateral line 15–18	Eigenmannia limbata
–	Anal fin hyaline; 2 or 3 horizontal dark stripes on body; scales above lateral line 8–11	Eigenmannia sp.
Rhamphichthyidae
1	Anterior nares inside upper lip	2
–	Anterior nares outside upper lip	3
2	Absence of sixth infraorbital bone	Hypopygus lepturus
–	Presence of sixth infraorbital bone, as a narrow tube, positioned vertically, parallel to posterior border of eye	Hypopygus neblinae
3	Number of pectoral-fin rays fewer than 16	Gymnorhamphichthys hypostomus
–	Number of pectoral-fin rays more than 16	4
4	Anal fin usually clear or hyaline	Rhamphichthys apurensis
–	Anal fin usually dark with a terminal dark band	Rhamphichthys rostratus
CYPRINODONTIFORMES
1	Pectoral fin with 1–2 unbranched rays	Poeciliidae: Poecilia sp.
–	Pectoral fin with all rays branched	Cynolebiidae
Cynolebiidae
1	Scales on the ventral surface of the head	Anablepsoides sp.
–	Scales absent on the ventral surface of the head	Rachovia maculipinnis
SILURIFORMES
1	Mental barbels absent; ventral mouth in the form of a sucking disk with wide lower lip	2
–	Mental barbels present; terminal mouth	3
2	Body naked	Astroblepidae
–	Body covered with bony plates	Loricariidae
3	Body depressed; skin covered with tubercles and completely keratinized	Aspredinidae
–	Body not depressed; skin without tubercles	4
4	Body covered with bony plates	5
–	Body not covered with bony plates	6
5	Sides of body covered with two rows of bony plates	Callichthyidae
–	Sides of body with a mid-lateral row of dermal plates armed with a lateral thorn	Doradidae
6	Opercle and interopercle with odontodes	Trichomycteridae
–	Opercle and interopercle without odontodes	7
7	Lateral-line system branched on head	Pimelodidae
–	Lateral-line system simple, not branched on head	8
8	Suborbital sulcus present	Auchenipteridae
–	Suborbital sulcus absent	9
9	Adipose fin absent	Cetopsidae
–	Adipose fin present	10
10	Eyes set on anteriormost half of head, thick skin	Pseudopimelodidae
–	Eyes set on posteriormost half of head, thin skin	Heptapteridae
Astroblepidae
1	Adipose fin present	Astroblepus sp.
–	Adipose fin absent	Astroblepus mariae
Loricariidae
1	Tail strongly depressed	2
–	Tail oval in cross-section	12
2	Dorsal-fin insertion in front of the anal-fin insertion	3
–	Dorsal-fin insertion anterior to the anal-fin insertion	5
3	Three rows of abdominal plates	Farlowella mariaelenae
–	Two rows of abdominal plates	4
4	Breeding odontodes on preorbital ridge present	Farlowella acus
–	Breeding odontodes on preorbital ridge absent	Farlowella vittata
5	Teeth villiform	6
–	Teeth spoon-shaped, elongate, comb-shaped or even absent but never villiform	7
6	Pectoral-fin rays i,7	Lamontichthys llanero
–	Pectoral-fin rays i,6	Sturisoma tenuirostre
7	Premaxillary teeth larger than dentary teeth	Loricaria cataphracta
–	Premaxillary teeth equal to or smaller than dentary teeth	8
8	Snout round in outline; upper lip with long filaments covering mouth opening	Dentectus barbarmatus
–	Snout acute to ovoid in outline; filaments covering mouth opening absent	9
9	Dentary teeth larger than premaxillary teeth	Rineloricaria eigenmanni
–	Dentary teeth smaller than or equal to premaxillary teeth	10
10	A pair of digitiform papillae on rictal region of mouth and an additional pair on mouth roof	Spatuloricaria sp.
–	Digitiform papillae on rictal region of mouth but absent on its mouth roof	11
11	Anterior margin of abdominal plate cover oval in outline; fringes on upper lip darkly pigmented	Loricariichthys brunneus
–	Anterior margin of abdominal plate cover irregular in outline; fringes on upper lip unpigmented	Limatulichthys griseus
12	Snout naked, not covered with plates	13
–	Snout covered with plates	17
13	Fleshy tentacles on snout present; three series of lateral plate series on caudal peduncle	Ancistrus triradiatus
–	Fleshy tentacles on snout absent; five series of lateral plate series on caudal peduncle	14
14	Cheek odontodes straight; fleshy excrescence on parieto-supraoccipital absent	Chaetostoma dorsale
–	Cheek odontodes curved; fleshy excrescence on parieto-supraoccipital present	15
15	No dark spots on any fin but dark stripes present along rays in all fins; enlarged second unbranched ray in anal fin bearing two fleshy ridges in mature males	Chaetostoma formosae
–	Dark spots on fins; anal fin never bearing paired fleshy ridges in mature males	16
16	Ventral portion of body posterior to pelvic-fin insertion light, never covered with abundant dark spots; pectoral-fin spine with dark spots	Chaetostoma sp.
–	Body uniformly spotted; pectoral-fin spine without spots	Chaetostoma joropo
17	Posterior serrae on pectoral-fin spine present	Hypoptopoma machadoi
–	Posterior serrae on pectoral-fin spine absent	18
18	Spoon-shaped teeth	19
–	Villiform teeth	21
19	Cheek odontodes absent	Hypostomus plecostomoides
–	Cheek odontodes present and erectile	20
20	Dark background with yellow or white vertical and irregular bands; small adult size	Panaqolus maccus
–	Color pattern consisting of horizontal stripes; large adult size	Panaque nigrolineatus
21	Eyes visible in ventral view; adipose fin absent	22
–	Eyes not visible in ventral view; adipose fin present	23
22	Twenty-six or more premaxillary teeth, 21 or more mandibular teeth; teeth slender, tightly spaced along the jaw rami, spacing between teeth equal to or greater than the tooth shaft width, tooth cusps small	Otocinclus huaorani
–	Fewer than 25 premaxillary teeth, 20 mandibular teeth; teeth robust, spacing between teeth equal to or greater than tooth shaft width, tooth cusps robust	Otocinclus vittatus
23	Coracoid bearing odontodes in ventral surface	Parotocinclus sp.
–	Coracoid covered with skin and not bearing odontodes	24
24	Setiform odontodes on sides of head; three series of lateral plates on caudal peduncle	Lasiancistrus tentaculatus
–	No setiform odontodes on sides of head; five series of lateral plates on caudal peduncle	25
25	Hypertrophied cheek odontodes surpassing base of pectoral fin; pectoral-fin spine reaching or surpassing tip of pelvic-fin leading ray	Dolichancistrus fuesslii
–	No hypertrophied cheek odontodes; pectoral-fin spine not reaching tip of pelvic-fin leading ray	26
26	Multiple buccal papillae	Aphanotorulus ammophilus
–	Single medial buccal papilla	27
27	More than 11 branched dorsal-fin rays	Pterygoplichthys multiradiatus
–	Less than 11 branched dorsal-fin rays	28
28	Lower caudal-fin lobe dark and upper lobe light, no spots on caudal-fin; caudal peduncle elongated	Aphanotorulus emarginatus
–	Spots on caudal fin, no distinct dark background on lower caudal-fin lobe; caudal peduncle not elongated	29
29	Dark blotches closely-set on dorsal fin	Hypostomus niceforoi
–	Dark spots arranged in two longitudinal series on interradial membranes, no blotches on dorsal fin	Hypostomus argus (please note that these differences in coloration are preliminary observations based on limited samples along with type specimens, further and more extensive sampling will be required in order to test such differences between Hypostomus argus and H. niceforoi in the Orinoco basin of Colombia; G.A. Ballen & S. Reinales, in prep.)
Aspredinidae
1	Dorsal, ventral and lateral series of bony plates present on body; mouth inferior; hard pectoral spine, without serrae on the anterior margin	Hoplomyzon sexpapilostoma
–	No obvious bony plates on body; mouth terminal; hard pectoral spine serrate on anterior and posterior margins	Bunocephalus aloikae
Callichthyidae
1	Snout depressed; maxillary barbel long, usually extending beyond gill opening	2
–	Snout compressed; maxillary barbel short, usually not extending beyond eye	3
2	Caudal fin forked, without conspicuous dark bands; dorsal fin spine about half the length of the first branched rays; six branched anal-fin rays	Hoplosternum littorale
–	Caudal fin truncated, with dark transverse band and dark distal margin; dorsal-fin spine long (52–64% dorsal-fin base length); four or five branched anal-fin rays	Megalechis picta
3	Dorsal fin with a dark blotch	Corydoras sp.
–	Dorsal fin without dark blotches	4
4	A dark oblique stripe on body runs across dorsolateral body scutes to caudal-fin base. No vertical bars on caudal peduncle or on caudal fin	Corydoras axelrodi
–	A large dark blotch on the sides extending from slightly in front of dorsal fin to nearly adipose fin, tapering off posteriorly. A vertical bar in the caudal peduncle. Five to seven vertical bars on the caudal fin	Corydoras septentrionalis
Doradidae
1	Maxillary barbel branched	Leptodoras nelsoni
–	Maxillary barbel simple, not ramified	2
2	Anterior and posterior dorsal-fin serrae absent	Amblydoras affinis
–	Anterior, posterior, or both dorsal-fin serrae present	3
3	Procurrent caudal-fin rays modified in fulcra; dark background with clear longitudinal stripe	Platydoras armatulus
–	Procurrent caudal-fin rays not modified in fulcra; color pattern without a clear longitudinal stripe	4
4	Thick lips, premaxillary and dentary teeth absent	Oxydoras sifontesi
–	Thin lips, premaxillary and dentary teeth present	5
5	Small body, caudal truncate	Amblydoras bolivarensis
–	Large body, caudal emarginate with two distinct lobes	Pterodoras rivasi
Trichomycteridae
1	Nasal barbel present (associated with anterior nostril), mouth subterminal	2
–	Nasal barbel absent, mouth ventral	4
2	Sides of body with a dark band or row of spots from just above the gill-opening to the base of the upper caudal-fin rays	Trichomycterus dorsostriatus
–	Sides of body uniformly pigmented	3
3	Eight branched pectoral-fin rays (rarely nine rays); a single median epiphyseal pore (rarely two asymmetrical pores)	Trichomycterus sp.
–	Seven branched pectoral-fin rays (rarely six rays); a pair of symmetrical epiphyseal pores	Trichomycterus migrans
4	Lower jaw rami not articulated medially, only joined by soft tissue	Vandellia beccarii
–	Lower jaw rami medially articulated	4
4	Caudal peduncle with numerous procurrent caudal-fin rays, embedded in wide dorsal and ventral membranes continuous with the caudal fin, caudal fin rounded or truncated	Ochmacanthus alternus
–	Caudal peduncle with few procurrent caudal-fin rays, restricted to the origin of the caudal fin, and lacking wide dorsal and ventral membranes continuous with the caudal fin, caudal fin emarginated	Schultzichthys bondi
Cetopsidae
1	First ray of pectoral and dorsal fins spinous, lateral line extending to over the posterior portion of the base of the anal fin but falling short of the caudal peduncle	Cetopsidium pemon
–	First ray of pectoral and dorsal fins not spinous, lateral line either shorter or extending posteriorly at least onto the posterior portion of the caudal peduncle	Cetopsis orinoco
Heptapteridae
1	Eye margin free, first dorsal and pectoral-fin rays with a pungent spine	2
–	Eye margin not free, first dorsal and pectoral-fin rays soft and segmented (at least their distal part)	6
2	Occipital process in contact with the nuchal plate, posterior cranial fontanelle open	3
–	Occipital process not reaching posteriorly the nuchal plate, posterior cranial fontanelle closed or reduced	5
3	Adipose-fin equals to one third of SL or shorter	Pimelodella metae
–	Adipose-fin longer than one third of SL	4
4	Upper caudal-fin lobe narrower and shorter than the lower caudal-fin lobe	Pimelodella cristata
–	Upper caudal-fin lobe about same width than lower lobe and distinctively longer	Pimelodella gracilis
5	Upper caudal-fin lobe distinctively shorter than the upper lobe; if undamaged, maxillary barbel surpassing the caudal peduncle	Rhamdia muelleri
–	Caudal-fin lobes subequal, maxillary barbel not surpassing the caudal peduncle	Rhamdia quelen
6	Lower caudal-fin lobe longer than upper lobe	Phenacorhamdia taphorni
–	Lower caudal-fin lobe equal or shorter than upper lobe	7
7	Lateral-line canal incomplete, extending only to dorsal-fin base	Nemuroglanis mariai
–	Lateral-line canal complete, extending to caudal-fin base	8
8	Lateral-line canal posteriorly interrupted as a series of short canal segments	Imparfinis microps
8	Lateral line continuous	9
9	Adipose-fin rectangular	10
–	Adipose-fin triangular	11
10	Anal-fin origin at vertical through adipose-fin origin, adipose-fin longer than one fourth of SL, six pale bars across dorsum and sides of body	Chasmocranus rosae
–	Anal-fin origin anterior to adipose-fin origin, adipose-fin shorter than one fourth of SL, four pale bars across dorsum and sides of body	Cetopsorhamdia orinoco
11	First dorsal and pectoral-fin ray extended as a long filament, maxillary barbel surpassing anal-fin base	Imparfinis pseudonemacheir
–	First dorsal and pectoral-fin ray not extended as a long filament, maxillary barbel not reaching anal-fin origin	12
12	Blotched pattern of body pigmentation	13
–	Uniform dark pattern of pigmentation	14
13	Pelvic-fin origin approximately at vertical through dorsal-fin origin, adipose-fin base extending far posteriorly beyond distal end of anal-fin	Undescribed genus and species
–	Pelvic-fin origin slightly behind mid-length of dorsal-fin base, adipose-fin base ending around same level of distal end of anal fin	Cetopsorhamdia shermani
14	Snout conical and conspicuously projected beyond mouth opening, maxillary barbel not surpassing distal end of pectoral fin, dorsal and ventral margins of end of caudal peduncle with a conspicuous white area, caudal fin clear contrasting with dark caudal fin base	Cetopsorhamdia aff. picklei
14	Snout depressed, not projected conspicuously beyond mouth opening, maxillary barbel surpassing distal end of pectoral fin, dorsal and ventral margins of end of caudal peduncle dark, pigmented as remaining of body, caudal fin dusky, not contrasting with caudal fin base	Imparfinis sp.
Pseudopimelodidae
1	Lateral line incomplete; premaxillary tooth patch without posterolateral projection; small size	2
–	Lateral line complete; premaxillary tooth patch with posterolateral projection; large size	3
2	Bar-shaped blotch on caudal-fin base; lateral line reaching a vertical through adipose-fin origin	Microglanis iheringi
–	Triangle-shaped blotch on caudal-fin base; lateral line reaching middle of dorsal-fin base	Microglanis poecilus
3	Caudal fin lanceolate; pectoral-fin spine covered with thin skin; anterior nares on the margin of the mouth	Cephalosilurus apurensis
–	Caudal fin forked; pectoral-fin spine covered with thick skin; anterior nares behind the maxillar barbel insertion	Pseudopimelodus bufonius
Pimelodidae
1	Upper jaw projected well beyond lower jaw with premaxillary tooth patch exposed	Sorubim lima
–	Lower jaw just slightly or not projected at all, premaxillary tooth plate not completely exposed	2
2	Upper portion of caudal-fin base with well-defined dark blotch	3
–	Caudal-fin base without well-defined dark blotch	4
3	Leading pectoral-fin ray soft and not pungent or spinous	Megalonema platycephalum
–	Leading pectoral-fin ray strong, pungent, with anterior and posterior serrae	Platysilurus mucosus
4	Eye visible in ventral view, set below midline of head in lateral view; barbels flat and wide	Hypophthalmus edentatus
–	Eye not visible in ventral view, set above midline in lateral view; barbels round in cross-section	5
5	Body color pattern consisting of dark vertical bars	6
–	Body color pattern consisting of dark spots or plain coloration, never with vertical bars	7
6	Abundant (more than 50) spots on caudal-fin	Pseudoplatystoma metaense
–	Few (less than 50) spots on caudal-fin	Pseudoplatystoma orinocoense
7	Body color pattern consisting of numerous spots or blotches, sometimes fussing so that a vermicular pattern appears; interorbital region flat	8
–	Body color plain or striped, never with spots or blotches; interorbital region convex	9
8	Blotches on body; round vomerine tooth patches separated medially as two independent units	Leiarius marmoratus
–	Spots on body; laterally-elongated vomerine tooth patches fused medially as a single wide band, sometimes the medial contact between patches visible	Zungaro zungaro
9	Each caudal-fin lobe with dark longitudinal dark stripe from base to tip of caudal fin; distinct blotch on dorsal fin	Pimelodus ornatus
–	No dark marks on caudal fin	10
10	Giant in adult size; eye small, its diameter much more than three times in dorsal-fin base length; presence of a patch of teeth on roof of mouth	Brachyplatystoma vaillantii
–	Small in adult size; eye large, its diameter about three times in dorsal-fin base length, absence of a patch of teeth on roof of mouth	Pimelodus blochii
Auchenipteridae
1	Mental barbels absent	2
–	Mental barbels present	3
2	Caudal fin deeply forked	Ageneoisus ucayalensis
–	Caudal fin truncate	Ageneiosus magoi
3	7–9 anal-fin rays	Centromochlus romani
–	>18 anal-fin rays	4
4	Dorsal-fin spine shorter than pectoral-fin spine	Pseudepapterus hasemani
–	Dorsal-fin spine longer than or equal to pectoral-fin spine	5
5	Caudal fin obliquely truncated	Trachelyopterus galeatus
–	Caudal fin forked	Entomocorus gameroi
CHARACIFORMES
1	Mouth without teeth	Curimatidae
–	Mouth with teeth	2
2	Canine teeth present	3
–	Canine teeth absent	6
3	Adipose fin absent; caudal fin rounded	Erythrinidae
–	Adipose fin present; caudal fin not rounded	4
4	Dentary canine teeth hypertrophied; caudal fin truncated; rostrum short	Ctenoluciidae
–	Dentary without hypertrophied canine teeth; caudal fin bifurcated; rostrum large	5
5	Scales ctenoid	Ctenolucidae
–	Scales cicloid	Acestrorhynchidae
6	Upper jaw without teeth; upper lip with teeth	7
–	Upper jaw with teeth; upper lip without teeth	8
7	Predorsal process present; mouth evertible	Prochilodontidae: Prochilodus mariae
–	Predorsal process absent; mouth non-evertible	Chilodontidae
8	Abdominal serrated keel present	Serrasalmidae
–	Abdominal serrated keel absent	9
9	Branchial membrane fused to isthmus	Anostomidae
–	Branchial membrane free from isthmus	10
10	Pectoral fins strongly developed and horizontally oriented	11
–	Pectoral fins vertically oriented	12
11	Fewer than three unbranched rays in pectoral fin	Parodontidae
–	Three unbranched rays in pectoral fin	Crenuchidae
12	Chest extremely compressed and expanded, forming a ventral keel	13
–	Chest not expanded to form ventral keel	14
13	Anal-fin origin anterior to dorsal-fin origin; ventral keel well developed	Gasteropelecidae: Thoracocharax stellatus
–	Anal-fin origin posterior to dorsal-fin origin; ventral keel moderately developed	Triportheidae
14	Upper lobe of caudal fin longer than lower lobe	Lebiasinidae
–	Both lobes of caudal fin of equal size	15
15	Two rows of teeth in the dentary	Bryconidae
–	One row of teeth in dentary	16
16	Anterior margin of maxilla greatly arched above and meeting premaxilla border at right angle	Iguanodectidae: Bryconops giacopinni
–	Anterior margin of maxilla not greatly arched above and not meeting premaxilla border at right angle	Characidae
Curimatidae
1	Lateral line incomplete, with only few pored scales	Curimatopsis sp.
–	Lateral line complete with all or almost all lateral scales with pores	2
2	Caudal fin with scales reaching two thirds in length in both lobes	Curimatella immaculata
–	Caudal fin with scales only on the base of caudal-fin rays	3
3	Lateral line with 42 or more scales	4
–	Lateral line with 39 or fewer scales	8
4	Lateral-line scales more than 90	Potamorhina altamazonica
–	Lateral-line scales 42–60	5
5	Mouth terminal; dorsal fin without dark spot	6
–	Mouth inferior; dorsal fin with or without dark spot	7
6	Interorbital width 53–58% of HL; anal-fin rays iii,10-iii,12.; abdominal region, pectoral, pelvic and anal fins with red coloration in live specimens	Curimata cerasina
–	Interorbital width less than 52% of HL. Anal-fin rays iii,8-iii,9; abdominal region, pectoral, pelvic and anal fins without red coloration in live specimens	Psectrogaster ciliata
7	Dark spot on the dorsal fin; prepelvic region of body not flattened or only obtusely flattened; 1 to 3 scales between posterior border of anus and anal-fin origin	Steindachnerina pupula
–	No dark spot on the dorsal fin; prepelvic region of body distinctly flattened; 5 to 7 scales between posterior border of anus and anal-fin origin	Steindachnerina hypostoma
8	Without a dark spot on the basal portion of the middle rays of the dorsal fin	Cyphocharax spilurus
–	With a dark spot on the basal portion of the middle rays of the dorsal fin	Steindachnerina argentea
Erythrinidae
1	Maxilla with 2–3 canine teeth; caudal fin usually spotted; dark lateral stripe absent or diffuse	Hoplias malabaricus
–	Maxilla without canine teeth; caudal fin not spotted; dark lateral stripe very well marked	Hoplerythrinus unitaeniatus
Cynodontidae
1	Dorsal-fin origin anterior to anal-fin origin	Hydrolycus armatus
–	Dorsal-fin origin in line with anal-fin origin	Raphiodon vulpinus
Ctenoluciidae
1	In adults, all lateral-line scales perforated (82 or more); body without round spots, except one at the base of caudal fin	Boulengerella cuvieri
–	In adults, only up to 25 lateral-line scales perforated; body with black spots	Boulengerella maculata
Acestrorhynchidae
1	Lateral line complete with 99–131 scales; dorsal-fin origin anterior to the anal-fin origin	Acestrorhynchus microlepis
–	Lateral line incomplete with 33–37 lateral-line scales; dorsal-fin origin posterior to the anal-fin origin	Gnathocharax steindachneri
Chilodontidae
1	10 or 11 branched anal-fin rays; anal-fin margin convex or straight; mouth terminal or slightly superior, dorsal fin with a series of dark spots on posterior rays; posterior margin of scales smooth	Chilodus punctatus
–	6 to 8 branched anal-fin rays; anal-fin margin somewhat concave in vast majority of specimens; mouth subterminal; dorsal fin with dark pigmentation across distal portions of anterior rays but lacking dark spots on remaining portions of fin; posterior margin of scales somewhat serrate	Caenotropus labyrinthicus
Serrasalmidae
1	Adipose-fin base long, its length longer than the distance between posterior margin of dorsal-fin base to the adipose-fin origin	Metynnis argenteus
–	Adipose-fin base short, its length shorter than the distance between posterior margin of dorsal-fin base to the adipose-fin origin	2
2	Two rows of teeth on the premaxilla	Mylossoma duriventre
–	One row of teeth on the premaxilla	3
3	Base of dentary teeth circular and separated from adjacent ones; lower jaw prominent and projecting greatly forward from upper jaw	Catoprion mento
–	Base of dentary teeth flattened, in contact or very close to adjacent ones; lower jaw equal or slightly anterior to upper jaw	4
4	29 or fewer anal-fin rays; snout, head, jaws, and body short and robust; dorsal profile of head to posterior margin of eyes convex; prepelvic and abdominal region red in life; black and conspicuous humeral blotch posterior to opercle	Pygocentrus cariba
–	30 or more anal-fin rays; snout, head, jaws, and body long and slender; dorsal profile of head to posterior margin of eyes concave; prepelvic and abdominal region red only during breeding season	5
5	Base of posterior premaxillary tooth (6th) approximately equal to adjacent one (5th); ectopterygoid teeth unicuspid, generally 5 or fewer	Pristobrycon striolatus
–	Base of posterior premaxillary tooth (6th) wider than adjacent one (5th); ectopterygoid teeth bicuspid or tricuspid, generally 7 or more	6
6	Posterior margin of caudal fin hyaline, with black vertical bar at base of caudal fin	Serrasalmus irritans
–	Caudal fin completely black or with its posterior margin black	7
7	Body width 1.7 or less in SL; lateral spots vertically elongated	Serrasalmus altuvei
–	Body width 1.7–2.0 in SL; lateral spots rounded	Serrasalmus rhombeus
Anostomidae
1	Caudal fin with scales only on its base and without dark bars	2
–	Caudal fin with scales at least over two-thirds of both lobes. Caudal-fin with oblique dark bars	Leporellus vittatus
2	Dentary teeth tricuspid to pentacuspid; 7 branched anal-fin rays	Schizodon scotorhabdotus
–	Dentary teeth incisiform or bicuspid; 8 or more branched anal-fin rays	3
3	Body with seven dark vertical bars, the second with a “Y” shape	Leporinus y-ophorus
–	Body with rounded spots or longitudinal stripes	4
4	Body with 4–5 longitudinal stripes separated by white or yellow stripes	Leporinus striatus
–	Body with two rounded black spots at midline	Leporinus gr. friderici
Parodontidae
1	Dark vertical bars present; dark lateral stripe absent	Parodon apolinari
–	Dark vertical bars absent; dark lateral stripe present	Parodon aff. suborbitalis
Crenuchidae
1	Chest naked without scales between pectoral fins	Characidium gr. boavistae
–	Chest covered with scales between pectoral fins	2
2	Body pigmentation composed by irregular lines and dots	Characidium pteroides
–	Body pigmentation composed by well-defined vertical bars	3
3	9 or fewer branched pectoral-fin rays	4
–	10 or more branched pectoral-fin rays	5
4	All vertical bars always originating on dorsum; body depth 23% of HL or less	Characidium gr. zebra
–	Not all vertical bars originating on dorsum, thin vertical bars not reaching the dorsum between vertical bars originating on dorsum; body depth 24% of HL or more	Characidium sp.
5	Mid-lateral stripe diffuse or absent; vertical bars fragmented in rhomboidal shape	Characidium cf. steindachneri
–	Mid-lateral stripe very well developed; vertical bars continuous and with dots appearance at junction with mid-lateral line	Characidium chupa
Triportheidae
1	Pectoral fin not surpassing ventral-fin origin	Engraulisoma taeniatum
–	Pectoral fin surpassing ventral-fin origin	2
2	24–27 branched anal-fin rays; 5–6 scale rows between lateral line and dorsal-fin origin	Triportheus venezuelensis
2	28–32 branched anal-fin rays; 7 scale rows between lateral line and dorsal-fin origin	Triportheus orinocensis
Lebiasinidae
1	Adipose fin present	Lebiasina erythrinoides
–	Adipose fin absent	2
2	One row of teeth in the premaxilla; maxilla S curved; dark lateral stripe complete and well-marked (from mouth to caudal fin)	Copella arnoldi
–	Two rows of teeth on the premaxilla; maxilla not S curved; dark lateral stripe incomplete and thin (from mouth to few scales after head)	Pyrrhulina lugubris
Bryconidae
1	Two rows of teeth in the premaxilla	Salminus sp.
–	Three rows of teeth in the premaxilla	2
2	Dark lateral stripe present, from opercle to tip of middle caudal-fin rays; upper caudal-fin lobe unpigmented	Brycon whitei
–	Dark lateral stripe absent; upper caudal-fin lobe pigmented	Brycon falcatus
Characidae
1	Lateral line incomplete	2
–	Lateral line complete	16
2	Dorsal fin with a black blotch	3
–	Dorsal fin without blotches	4
3	Body height 26.6 to 29.3% of SL	Hyphessobrycon dorsalis
–	Body height is 34.5 to 36.9% of SL	Hyphessobrycon sweglesi
4	One row of premaxillary teeth	5
–	Two rows of premaxillary teeth	7
5	Dorsal-fin origin posterior to the anal-fin origin	Paragoniates alburnus
–	Dorsal-fin origin anterior to the anal-fin origin	6
6	A dark embedded crescent-shaped mark on base of each caudal lobe; no red color on caudal fin	Microschemobrycon casiquiare
–	Without such dark pigmentation on the base of caudal fin; caudal fin red in life	Aphyocharax alburnus
7	Caudal fin with black pigmentation in both lobes	Hyphessobrycon otrynus
–	Caudal fin without black pigmentation	8
8	Anal-fin base with a conspicuous dark band	Hemigrammus barrigonae
–	Anal-fin base without dark pigmentation	9
9	25–27 branched anal-fin rays; caudal peduncle red or rose in life	Hemigrammus stictus
–	14–22 branched anal-fin rays; no red or pink color on caudal peduncle	10
10	A small dark line of black chromatophores along the anal- and caudal-fin bases	Cyanogaster noctivaga
–	Caudal fin without dark coloration or with a well-developed spot at its base or on caudal-fin lobes	11
11	With a conspicuous caudal spot	12
–	Without a caudal spot or with a lateral stripe continuing along middle caudal-fin rays, but not forming a caudal spot	14
12	Dark melanophores present on sides of body and between anal fin and lateral line	Hyphessobrycon metae
–	No dark melanophores present on sides of body and between anal fin and lateral line	13
13	Caudal spot triangle-shaped covering the central portion of caudal-fin base, continuing along middle caudal-fin rays and usually not in contact with the lateral stripe	Hemigrammus micropterus
–	A large caudal spot covering entire caudal-fin base, continuing along middle caudal-fin rays and in contact with lateral stripe	Hemigrammus newboldi
14	Body depth 27% or less of SL; 14–16 branched anal-fin rays; maxillary teeth absent; black blotch on upper caudal-fin lobe	Hyphessobrycon diancistrus
–	Body depth 28% or more of SL; 18–20 branched anal-fin rays; maxillary teeth present; without dark blotch on upper caudal-fin lobe	15
15	12 dentary teeth; 6–7 perforated lateral-line scales. Without a dark blotch at caudal peduncle	Hyphessobrycon taguae
–	14 dentary teeth; 9–10 perforated lateral-line scales. With a dark blotch at caudal peduncle	Hyphessobrycon acaciae
16	Dorsal-fin origin at or posterior to vertical through anal-fin origin	17
–	Dorsal-fin origin anterior to the anal-fin origin	22
17	61–68 anal-fin rays	Xenagoniates bondi
–	25–55 anal-fin rays	18
18	Length of maxilla equal or shorter than vertical diameter of eye; adult males with hypertrophied caudal-fin squamation on lower caudal-fin lobe	Gephyrocharax valencia
–	Length of maxilla longer than vertical diameter of eye; adult males without hypertrophied caudal-fin squamation	19
19	No external mammiliform teeth	Charax sp.
–	External mammiliform teeth present in the maxilla and premaxilla	20
20	50–65 lateral-line scales	Roeboides dientonito
–	66 or more lateral-line scales	21
21	66–70 perforated lateral-line scales; 12–14 gill rakers on lower arm of the first gill arch	Roeboides sp.
21	70–88 perforated lateral-line scales; 7–11 gill rakers on lower arm of the first gill arch	Roeboides affinis
22	16 or less total anal-fin rays	23
–	17 or more total anal-fin rays	27
23	Premaxillary teeth arranged in 2 rows; Anterior triad of larger teeth with rounded base absent	Ceratobranchia sp.
–	Premaxillary teeth arranged in 3 rows; Anterior triad of larger teeth with rounded base present	24
24	Dorsal-fin origin anterior to pelvic-fin insertion	Creagrutus sp.
–	Dorsal-fin origin posterior or aligned with pelvic-fin origin	25
25	Third infraorbital poorly developed, leaving a broad gap between its posterior margin and the horizontal limb of preopercle	Creagrutus bolivari
–	Third infraorbital well-developed contacting or with a small gap from horizontal limb of preopercle	26
26	38–42 lateral-line scales; interorbital distance 34.0–37.9% of HL	Creagrutus atratus
–	36–38 lateral-line scales; interorbital distance 28.6–35.4% of HL	Creagrutus cf. taphorni
27	40 or more total anal-fin rays	28
–	39 or less total anal-fin rays	33
28	Cycloid scales on body sides	29
–	Ctenoid scales on body sides, or at least in preventral area	30
29	Maxilla shorter than vertical diameter of eye; cleithrum without a notch on posteroventral portion; body sides with dark sinuous lines	Markiana geayi
–	Maxilla longer than vertical diameter of eye; cleithrum with notch on posteroventral portion, near base of posteriorly directed spiniform projection; body sides with dark sinuous lines	Charax metae
30	58 or fewer lateral-line scales; premaxillary and dentary teeth multicuspid; ctenoid scales only on preventral area	Ctenobrycon spilurus
–	59 or more lateral-line scales; one or more conical or canine teeth; ctenoid scales on entire body	31
31	100–110 lateral-line scales	Cynopotamus bipunctatus
–	70–84 lateral-line scales	32
32	35–38 branched anal-fin rays; 73–76 lateral-line scales	Acestrocephalus sardina
–	39–45 branched anal-fin rays; 79–84 lateral-lines scales	Galeocharax gulo
33	A pair of cuspidate teeth on premaxilla pointing forward on labial sides of upper jaw; two large black blotches on body sides, one anterior to dorsal-fin origin and another on caudal peduncle	Exodon paradoxus
–	No cuspidate teeth on premaxilla; different color pattern than that described above	34
34	One row of premaxillary teeth	35
–	Two rows of premaxillary teeth	38
35	Premaxillary teeth with five cusps, the outer cusps very small; dentary teeth with five cusps, the three central cusps flat and approximately equal in size and the outer cusps very small	Cheirodontops geayi
–	Premaxillary teeth with nine cusps; dentary teeth heptacuspid, with central cusp longer than others	36
36	A remarkable elongation of the second unbranched dorsal-fin ray in males; maxilla somewhat triangular, short, with mid-length portion deeper and gradually narrowing to the posterior tip	Odontostilbe pao
–	No elongation of the second unbranched dorsal-fin ray in males; maxilla somewhat spatula-like shaped, short or elongate, with a deep mid-length region, narrowing abruptly at posterior tip	37
37	Adipose-fin origin at vertical through second or third last anal-fin ray insertion; mature males with hooks on first to sixth-seventh branched anal-fin rays	Odontostilbe splendida
–	Adipose-fin origin at vertical through last anal-fin ray insertion; mature males with hooks on first to twenty second branched anal-fin rays	Odontostilbe pulchra
38	Presence of a predorsal spine; anterior three anal-fin rays black	Poptella compressa
–	No predorsal spine; three anterior anal-fin rays unpigmented	39
39	33–38 total anal-fin rays	40
–	32 or less total anal-fin rays	42
40	Body depth 28.0–37.0% of SL; maxilla with 20–30 conical teeth; 6 scale rows between lateral line and dorsal-fin origin; one humeral spot	Phenacogaster maculoblonga
–	Body depth 38.0% or more of SL; maxilla with 1–3 multicuspidate teeth; 7–9 scale rows between lateral line and dorsal-fin origin; two humeral spots	41
41	Caudal peduncle with a large dark spot	Tetragonopterus argenteus
–	Caudal peduncle without spot	Gymnocorymbus bondi
42	16–20 total anal-fin rays	43
–	23–32 total anal-fin rays	44
43	17–18 anal-fin rays	Knodus deuterodonoides
–	16 anal-fin rays	Bryconamericus cf. cismontanus
44	Spine-like pelvic bones projecting anteriorly from pelvic-fin base, with distal tip free from musculature	Jupiaba polylepis
–	No spine-like pelvic bones	45
45	4 teeth on the inner row of premaxilla	46
–	5 teeth on the inner row of premaxilla	48
46	3 or fewer teeth on maxilla	Knodus alpha
–	More than three teeth on maxilla	47
47	5 or fewer maxillary teeth in adult individuals (>5 cm SL); second premaxillary tooth of inner row pentacuspid; 12–13 predorsal scales; fins of live specimens reddish	Hemibrycon loisae
–	6 or more maxillary teeth in adult individuals (>5 cm SL); second premaxillary tooth of inner row heptacuspid; 14–16 predorsal scales; fins of live specimens not reddish	Hemibrycon metae
48	One or both caudal-fin lobes with dark coloration	49
–	Both caudal-fin lobes without distinct pigmentation	50
49	Only upper caudal-fin lobe with dark pigmentation	Moenkhausia lepidura
–	Both caudal-fin lobes with black pigmentation	Moenkhausia dichoura
50	Middle caudal-fin rays without dark coloration	Moenkahusia copei
–	Middle caudal-fin rays with dark coloration	51
51	Predorsal line naked	Astyanax bimaculatus
–	Predorsal line with scales	52
52	Base of anal fin with an oblique dark stripe extending across caudal peduncle and onto middle and upper caudal-fin rays	Astyanax metae
–	Base of anal fin without oblique dark stripe	53
53	45 or more lateral-line scales	Astyanax integer
–	Fewer than 45 lateral-line-scales	Astyanax venezuelae
Cichlidae
1	African lips (posterior portion of the lower lip not covering part of the upper lip); three roundish ocellar blotches in adults (large and oval blotches in juveniles)	Cichla orinocensis
–	American lips (posterior portion of the lower lip covering part of the upper lip); different color pattern than above	2
2	Bone expansion in the upper region of the first gill arch forming a well-developed fleshy lobe	3
–	First gill arch without such a lobe	6
3	Lower pharyngeal bone without teeth along its margin	Mikrogeophagus ramirezi
–	Lower pharyngeal bone with teeth along its margin	4
4	Lateral spots on body present; two pectoral spots	Apistogramma macmasteri
–	No lateral spots on body; with or without a single pectoral spot	5
5	Pectoral fin base with spot; with distinct abdominal stripes	Apistogramma hongsloi
–	Without spot on pectoral fin base; without abdominal stripes	Apistogramma hoignei
6	Irregular predorsal scale pattern	7
–	Uniserial or triserial predorsal scale pattern	11
7	Six or seven anal-fin spines; 24–30 scales in upper lateral line series; vertical bars 6 and 7 parallel; body deep (50.7–55.6%of SL)	Mesonauta egregius
–	Three anal-fin spines; 40 or more scales in upper lateral line series; elongate and somewhat cylindrical body (less than 50.0% of SL)	8
8	Humeral blotch present	9
–	Humeral blotch absent	11
9	Lateral line crossing middle portion of humeral blotch	Crenicichla alta
–	Lateral line crossing upper portion of humeral blotch	10
10	Chain of blotches along lateral lines; length of posterior dorsal-fin spine 9.6–10.6% of SL; caudal peduncle length at ventral part 10.0–11.5% of SL; length of ventral fin 19.4–20.4% of SL	Crenicichla sveni
–	No chain of blotches along lateral lines; length of posterior dorsal-fin spine 10.8–11.2% of SL; caudal peduncle length at ventral part 11.8–12.2% of SL; length of ventral fin 17.3–18.2% of SL	Crenicichla sp.
11	Maxilla extending posterior to the anterior margin of eye; caudal-fin length (from caudal-fin base to tips of middle caudal-fin rays) 16.2–24.6% of SL; head depth at orbit level 16.7–21.6% SL; caudal peduncle depth where least 10.7–14.2% of SL	Crenicichla geayi
–	Maxilla only reaching anterior margin of eye; caudal-fin length (from caudal-fin base to tips of middle caudal-fin rays) 22.7–24.7% of SL; head depth at orbit level 15.1–15.6% SL; caudal peduncle depth where least 9.34–9.83% of SL	Crenicichla gr. wallacii
12	Uniserial predorsal scale pattern	13
–	Triserial predorsal scale pattern	14
13	8 branched anal-fin rays; caudal fin rounded; less than 8 scales in the lower lateral line	Andinoacara sp.
–	7 branched anal-fin rays; caudal fin subtruncate-truncate; more than 8 scales in the lower lateral line	Bujurquina mariae
14	Dark stripe extending from posterodorsal margin of eye to lower angle of preopercle	Aequidens metae
–	Dark stripe restricted to a suborbital blotch only	14
15	Head sides with bluish or greenish iridescent stripes (in live specimens)	Aequidens diadema
–	Head sides without bluish or greenish iridescent stripes (in live specimens)	Aequidens tetramerus
Sciaenidae
1	Lateral-line scales not covered by smaller scales; body depth 3.8–4.3% of SL; predorsal distance 3.0–3.1% of SL; anal-fin base 5.9–9.3% of SL; caudal peduncle length 3.4–3.7% of SL; postorbital length 2.0–2.4% of SL; length of second anal-fin spine 1.8–2.3 % of HL	Pachyurus gabrielensis
–	Lateral-line scales covered by smaller scales; body depth 3.0–3.8% of SL; predorsal distance 2.7–3.0% of SL; anal-fin base 11.2–17.1% of SL; caudal peduncle length 3.8–4.7% of SL; postorbital length 1.6–2.0% of SL; length of second anal-fin spine 2.6–6.0% of HL	Plagioscion squamosissimus