The Rio Nhamundá is a poorly-known clearwater river draining the southern Guiana Shield of Brazil. In this study we report the findings of a preliminary ichthyological survey of the river, focusing here on catfishes (Siluriformes). We identify a total of 32 species (seven families) from the river, and include four species already known from museum collections. Overall, our survey results show that even rapid surveys can provide important information on Amazon fish biodiversity, providing a new species description, range extensions for many species, and additionally highlighting taxa in need of taxonomic revision and genetic study. As well as the traditional forms of data collected on biodiversity surveys (i.e. preserved specimen vouchers), our study also provides "new" types of data in the form of DNA barcodes and images of live colour pattern, information which will be invaluable in future studies addressing those difficult groups.

The Rio Nhamundá is one of the south-draining Guiana Shield tributaries of the Rio Amazonas, Brazil. The river is located between the Uatumã-Jatapú and Trombetas rivers (Figure 1), and comprises the administrative border between Amazonas State and Pará State. Chemically, the Rio Nhamundá is of the clearwater type (Carvalho de Lima & Araujo-Lima, 2004), being poor in sediments, dissolved minerals, and humic compounds (Crampton, 2011).

The ichthyofauna of the southern Guiana Shield rivers is poorly known in comparison to the northern Brazilian Shield rivers (Lujan and Armbruster, 2011), and few scientific collections appear to have been made in the area. One exception is the Trombetas river, which has seen extensive surveys over several years (Ferreira, 1993). Aquarium hobbyists have, however, explored parts of the Rio Nhamundá in search of new discus (Symphysodon spp.) variants (Bleher, 2006/7), and ornamental fishermen currently operate on the river, and specialise mainly in the catching of these discus (pers. obs.).

The aim of this study is to assess our current knowledge of Siluriformes (catfishes) of the Rio Nhamundá, and to report the results of a preliminary survey of the lower reaches of the river. We also provide the description of a new suckermouth catfish species which was collected on the trip.

Figure 1. Map of the Nhamundá.

In order to assess the current knowledge of the catfishes of the Rio Nhamundá we carried out a survey of Web databases as well as published checklists and literature. The Web databases searched were FishBase (Froese & Pauly, 2014), Catalog of Fishes (Eschmeyer, 2014), and the Global Biodiversity Information Facility (GBIF; http://www.gbif.org). The FishBase and GBIF searches were conducted using the rfishbase 0.2-2 (Boettiger et al., 2012) and rgbif 0.5.0 (Chamberlain et al., 2014) packages in the R programming language (R Core Team, 2014); scripts to repeat these searches are presented in SUPPLEMENTARY. The Catalog of Fishes was searched manually using their Web interface (date 05-03-14) using the terms "Nhamundá" and "Nhamunda" to avoid potential discrepancies due to the accent on the last letter. Local searches were performed on PDF copies of the Checklist of Catfishes (Ferraris, 2006), the Check List of the Freshwater Fishes of South and Central America (Reis et al., 2003), and on over 3,500 locally stored articles on Neotropical ichthyology in PDF format (search script is available in SUPPLEMENTARY). We additionally checked records for the neighbouring Trombetas and Uatumã rivers using rfishbase, rgbif, Catalog of Fishes, and Checklist of Catfishes.

We also checked the collection records at the Instituto Nacional de Pesquisas da Amazônia (INPA) for records of collections made from the Nhamundá.

Fishes were collected during the November 2013 dry season using a combination of methods mostly targeting larger species: gill netting, rod and line fishing, spear fishing, hand netting, and hand catching using snorkelling equipment. Fishes were photographed alive where possible, and then euthanised using a eugenol (clove oil) solution. Tissue samples—usually from muscle and fin membranes on the right-side pectoral-fin base—were taken from a subset of specimens and stored in absolute ethanol. Fishes to be retained as vouchers were then fixed in 10% formalin for several days before being transferred to 70% alcohol for long-term storage.

Measurements of preserved material were taken with dial callipers to a precision of 0.1 mm. All measurements and counts for symmetrical features were taken from the left side of the specimen. For loricariids, morphometric measurements and meristic counts follow Armbruster (2003), and terminology for lateral plate rows follows Schaefer (1997). Counts of cheek plate odontodes included only the long, highly hypertrophied odontodes on the posterior part of the plate. The dorsal-fin spinelet is included as a spine, and the nuchal plate is not included in the predorsal plate row count. Terminology of colour pattern follows Kottelat and Freyhof (2007).

For the checklist, we used published literature to identify our specimens, and we also provide the characters found in those references that we used to make each identification. When required, we examined photographs of type material on the All Species Catfish Inventory Web page (http://acsi.acnatsci.org). We tried to keep terminology consistent across the species, but also tried to maintain a degree of agreement with original authors' work to aid in referring back to their characters. For example, when reporting the Farlowella spp., we refer to the "scutes" of Retzer & Page (2006) as "plates", following Schaefer (1997), but maintain reference to the "plates of second lateral row" of Retzer & Page (2006) instead of "mid-dorsal lateral plates" of Schaefer (1997).

The symbolic codes for institutional resource collections follows Sabaj Pérez (2013).

DNA barcodes were generated for one to three individuals per species. DNA was extracted using a ... TBC

We also searched the Barcode of Life Data Systems (BOLD; http://www.boldsystems.org/) and GenBank (http://www.ncbi.nlm.nih.gov/nucleotide) for deposited COI sequences, in order the evaluate the coverage

Our survey of online databases and published checklists (SUPPLEMENTARY) revealed a single record of a doradid collected in the Rio Nhamundá, which was an unidentified Ossancora sp. On further investigation these fish were found to be paratypes of Ossancora asterophysa Birindelli & Sabaj Pérez, 2011 (ROM 88244, MZUSP 7838). The literature survey revealed three further species from the river: Hassar orestis (Steindachner, 1875) (MZUSP 9547); Pygidianops amphioxus de Pinna & Kirovsky, 2011 (MZUSP 104675); and Centromochlus sp. (INPA 35087). The survey of the INPA collections revealed ...

By contrast, the survey of the Web databases and checklists for the Trombetas river listed 44 siluriform species (SUPPLEMENTARY), while the study of Ferreira (1993) listed 95 siluriform species from the Trombetas. From the Uatumã river, the desk survey of Web databases and checklists provided five species (SUPPLEMENTARY).

Identification to species level follows Ferraris et al. (2005) based on the following characters: coracoid not exposed ventrally; pelvic fin with branched rays; anterior teeth on premaxilla not visible when mouth closed; caudal fin emarginate; and body uniform dark colouration without dark spots.

Three individuals were caught by hand from their lodgements in woody substrates at the margin of the main river stem. Water temperature was 28.9°C. An example of a live specimen is pictured in Figure YYY.

Auchenipterichthys longimanus INPA CTGA_14501. 130.0 mm SL .

Identification to species level follows Britski and Akama (2011) based on the following characters: prognathous lower jaw; skull roof covered by thin integument; inner mental barbel reaching base of outer mental barbel; dorsal-fin spine serrated only along anterior margin; and caudal fin emarginate (our specimens had suffered damage to the lobes of the caudal fin, presumably due to piranhas).

Two individuals were caught at night using gill nets [Val, where were these set?]. An example of a live specimen is pictured in Figure YYY.

Trachycorystes trachycorystes INPA CTGA_14429. 305.0 mm SL.

Identification to species level follows Royero (1993), Sarmento-Soares & Martins-Pinheiro (2008) and Vari & Ferraris (2013) based on the following characters: irregular, mosaic-like black and white colour pattern; bifid third nuchal plate; and long post-cleithral process reaching past the nuchal plates. Our specimens, however, differ from those described/pictured by Royero (1993) in a number of aspects: unpigmented area dorso-posteriorly to the orbit (slightly elongated and smaller than orbit diameter); third nuchal plate larger than that figured by Royero (1993); third nuchal plate unpigmented (including some of the surrounding skin); caudal fin hyaline with oblique dark stripes reaching to tips of upper and lower lobes.

Twelve individuals were caught either by hand from their lodgements in woody substrates, or more effectively using a hand net at the surface after attracting insects—on which they were feeding—with a light; under such conditions they appeared abundant on the lower Nhamundá.

INPA CTGA_14508. 47.8 mm SL.

Identification to species level follows Sarmento-Soares & Martins-Pinheiro (2008) based on the following characters: dark brown body colour; and short post-cleithral process (about 60% of head length) not reaching vertical through origin of dorsal fin.

Four individuals were caught by hand from their lodgements in woody substrates at the margin of the main river stem (they were also observed in rocky habitats, but were more difficult to catch in this situation). Water temperature was 28.9°C. An example of a live specimen is pictured in Figure YYY.

INPA CTGA_14503. 101.0 mm SL .

Identification to species level follows Sousa (2010) based on the following characters: flattened body shape; upper limit of pre-opercular canal not reaching lateral border of the cranium; seven branched rays in the dorsal lobe of the caudal fin; dorsal margin of the orbit high; procurrent rays of the caudal fin expanded into bony shields; and diverticula of the swim bladder simple, with tapered rear end.

Two individuals were caught by hand-net at night over a sandy/silty substrate in the lake-like lower reaches of the river. Water current was minimal. An example of a live specimen is pictured in Figure YYY.

INPA CTGA_14540. 69.7 mm SL .

####Goeldiella eques (Müller & Troschel, 1849)

Identification to species level follows Eigenmann & Norris (1900) and Eigenmann (1912) based on the following characters: rounded caudal fin with larger lower lobe; distinct cranial fontanelle; maxillary barbels long, extending to caudal (extended only to caudal peduncle in our specimen); dorsal spine notched anteriorly; dark stripe along lateral line (in our specimen this comprised just a elongated blotch under the dorsal fin); base of caudal with dark bar; and obliquely angled dark saddle behind head (from dorsal insertion to base of opercle); body and fins irregularly mottled.

One individual was caught by hand-net on the Rio Paratucu (Rio Nhamundá tributary), and delivered a painful sting, confirming that many heptapterids are venomous (Wright, 2009). This specimen is pictured in Figure YYY.

INPA CTGA_14537. 134.0 mm SL.

Identification to genus level follows Eigenmann & Eigenmann (1890) and Eigenmann (1917)based on the following characters: occipital process narrow, reaching dorsal plate; fontanel continued to base of occipital process, with bridge above the posterior margin of the eye; dorsal-fin and pectoral-fin spines strong; humeral process spine-like; dorsal fin with six branched rays.

We are currently unable to identify this fish to species level given the large diversity and paucity of modern treatments of the genus. Important characters include the caudal fin lobes of approximately equal length, short barbels, the complete lack of dark longitudinal stripe, the wedge-shaped mark on the dorsal-fin, and the dark saddle anterior to the dorsal fin.

One individual was caught by hand-net on a sandy beach habitat. This specimen is pictured in Figure YYY.

INPA CTGA_14290. 48.9 mm SL.

Identification to species level follows Armbruster (2004), and Kner (1854) based on the following characters: three rows of lateral plates on the caudal peduncle; snout naked with fleshy tentacles lacking odontodes; 8-9 branched dorsal-fin rays (three individuals with nine rays and eight individuals with eight rays); and black colour with small white dots (apparent in life, but only apparent on abdomen in preserved material). We also note that Ancistrus (and particularly the Amazonian species) are a group in dire need of taxonomic revision.

Eleven individuals were caught by hand on both woody and rocky substrates. The species appeared abundant throughout the river. NNN examples of live specimens are pictured in Figure YYY, also illustrating the dorsal-fin rays.

INPA CTGA_14490. 87.8 mm SL.

Identification to species level follows Armbruster (2004), Kner (1854), Muller et al. (1994), Günther (1864), Pellegrin (1912), and Eigenmann (1912) based on the following characters: three rows of lateral plates on the caudal peduncle; snout naked with fleshy tentacles lacking odontodes; body and head wide and extremely flattened; snout long and pointed; seven branched dorsal rays; three branched anal fin rays; six branched pectoral fin rays; eyes large (orbit diameter approximately 20% of HL) and situated high on the head; narrow gill openings; and colouration black, with small tiny yellow-white dots in life.

Among the several similar described Ancistrus—e.g. A. dolichopterus Kner, 1854, A. hoplogenys (Günther, 1864), A. leucostictus (Günther, 1864), A. ranunculus Muller, Rapp Py-Daniel & Zuanon, 1994—this fish is most similar in shape of head and eyes to A. macrophthalmus (Pellegrin, 1912) and A. lithurgicus Eigenmann, 1912; however, the fish from the lower Nhamundá has just three branched anal-fin rays, compared to four for both of these species. More individuals will need to be collected, and further investigation of available names in Ancistrus carried out in order to be sure that this represents an undescribed species.

Two individuals were caught by hand at night from rocky substrates near the mouth of the river. Water current was minimal, and the temperature was 32.0°C. An example of a live specimen is pictured in Figure YYY.

INPA CTGA_14547. 93.1 mm SL.

Identification to species level follows Armbruster (2004), Rapp-Py Daniel (1985) and La Monte (1929) based on the following characters: lateral plates with well-developed keels; hypertrophied odontodes present along snout margin; three rows of lateral plates on the caudal peduncle; large interorbital distance; pronounced medial ridge on snout; head plates with sinuous rows of odontodes; interopercular plate with between 15 and 20 strong and distally hooked odontodes; pectoral spine roughly same length as head, with long odontodes; and spots on body roughly same size as those on head.

Nine individuals were caught by hand from woody substrates in a variety of habitats (main river, lake, igarapé). The species was abundant. An example of a live specimen is pictured in Figure YYY.

INPA CTGA_14311. 178.3 mm SL.

Identification to species level follows Retzer & Page (1997) and Retzer (2006) based on the following characters: seven predorsal plates; dorsal fin located opposite anal fin; three rows of abdominal plates; five rows of anterior lateral plates, with middle row incomplete; plates of second lateral row diamond-shaped; fourth row of anterior lateral plates sharply keeled; odontodes on lateral plates small; snout-mouth-length / head-length > 0.5; body-depth / pelvic-fin-length < 0.86; pectoral-fin-length / snout-mouth-length > 0.65; snout-mouth-length / pectoral-fin-length > 1.0; fin spines and rays with dark spots.

The above characters are consistent with F. nattereri, but some key differences in colour pattern are noted. Retzer & Page (1997) report that: for most specimens of F. nattereri, the first anal and dorsal fin rays are entirely darkly pigmented (our specimen has spotted rays); a distinct dorso-lateral dark-stripe is present from base of snout to dorsal fin (this stripe was not apparent in the preserved specimen, but was observed in life); upper and lower caudal fin lobes pigmented with dark stripes of equal size, with stripes often not reaching caudal fin base (the stripes in our specimen reached the caudal base). Retzer & Page (1997) recognise that F. nattereri probably comprises a complex of species.

One individual was caught by hand from shallow, fast flowing water over a rocky substrate on main river stem. Water temperature was 28.3°C. The live specimen is pictured in Figure YYY.

INPA CTGA_14331. 199.8 mm SL.

Identification to species level follows Armbruster et al. (2007) and Armbruster (2008) based on the following characters: five rows of lateral plates on the caudal peduncle; lateral plates not keeled; dentaries forming angle of < 90°; dentary teeth almost twice as long as premaxillary teeth; dentary teeth widely spaced with medial gap between tooth cups as wide as the tooth cups themselves; supraorbital crests very distinct; dark E-shaped pattern on snout (irregular in some individuals); pattern on body of oblique dark bands (almost horizontal wavy stripes in some individuals), with dark bands generally wider than pale bands (i.e. body more dark coloured than pale coloured); dorsal fin with complete bands; and caudal fin with dark vertical bands.

The Hypancistrus from the Nhamundá is similar to H. furunculus Armbruster, Lujan & Taphorn (2007), but we hypothesise that this species represents a distinct species due to the pronounced supraorbital crests, wide gap between the dentary tooth cups, and colour pattern of wide dark bands and thin pale bands. Comparison to the type material of H. furunculus is necessary to confirm or refute these hypotheses.

Twelve individuals were caught by hand at night from rocky substrates near the mouth of the river. Water current was minimal, and the temperature was 32.0°C. Four examples of live specimens are pictured in Figure YYY to illustrate variation in colour pattern.

INPA. (A) 68.6 mm SL; (B) 73.1 mm SL; (C) 64.3 mm SL; (D) 60.8 mm SL.

Identification to species level follows Aquino & Schaefer (2010) based on the following characters: flattened head with eyes placed ventrolaterally and visible from below; laterally expanded nuchal plate; six pairs of lateral abdominal plates posterior to coracoids; thoracic plates present; three midventral plates between cleithral posterior process and first plate of ventral series; anal shield composed of single plate; second infraorbital laterally contacting to two ventral dermal plates; patch of odontodes present on anterolateral aspect of cleithrum at opening to branchial chamber; and caudal fin with series of around three dark bands (irregular in our specimens).

Thirteen individuals were caught by hand from submerged terrestrial vegetation. Water current was minimal. An example of a live specimen is pictured in Figure YYY.

INPA catalogued specimen.

Identification to species level follows Zawadzki et al. (2013) and Rapp Py-Daniel (1988) based on the following characters: greater than three (around eight to ten) predorsal plates limiting the posterior border of the supraoccipital; elongated caudal peduncle; caudal fin strongly emarginated; dark spots on lighter background; and lower lobe of caudal fin darker than upper lobe.

Five individuals were caught by hand from woody substrates at the margin of the main river stem. Water temperature was 28.9°C. An example of a live specimen is pictured in Figure YYY.

INPA CTGA_14317. 196.4 mm SL.

Identification to species level follows Armbruster (2005) based on the following characters: three rows of lateral plates on the caudal peduncle; bar-shaped opercle; snout plates present; lateral plates not keeled; > 30 teeth per jaw ramus; body and fins (except dorsal and caudal) dark with small pale dots; plates not outlined with dark pigment; and caudal fin with darker lower lobe. We note that the whisker-like odontodes characteristic of the genus were not apparent in our single, juvenile specimen of 45.2 mm, but we did observe bifurcating tentacules on the interopercular plate, and combined with the other characters, are confident that the specimen belongs to Lasiancistrus schomburgkii as proposed by Armbruster (2005).

Two individuals were caught by hand from woody substrates at the margin of the main river stem. An example of a live specimen is pictured in Figure YYY.

INPA CTGA_14329. 45.2 mm SL.

Identification to species level follows Armbruster (2004), Armbruster (2008) and Isbrücker & Nijssen (1989) based on the following characters: premaxilla with three teeth, the inner being very long; lips oval, lacking fimbriae on the upper lip; more than four predorsal plates; tall and narrow supraoccipital crest; and dark body with numerous white dots.

Three individuals were caught by hand from woody substrates at the margin of the main river stem. Water temperature was 28.9°C. An example of a live specimen is pictured in Figure YYY.

INPA CTGA_14488. 207.0 mm SL.

Identification to species level follows Isbrücker (1981), Thomas & Rapp Py-Daniel (2008) and Thomas & Sabaj Pérez (2010) based on the following characters: elongate lip filaments; three premaxillary teeth per ramus; premaxillary teeth approximately twice as long as dentary teeth; developed odontode crests on head and dorsal trunk plates; 34 lateral plates; 19 coalesced lateral plates; dorsal fin spine not elongated (24% of SL); post-orbital notch relatively well developed; abdomen mostly plated (with the exception of an anterior v-shaped naked area over the pectoral girdle); all fins except anal fin with dark sub-distal bands (most prominent on caudal and dorsal fins).

Identification of this species is tentative, as there appears to be considerable variation in the L. cataphracta group; we await the forthcoming systematic revision of the genus (Thomas & Sabaj Pérez, 2010).

One individual was caught by hand from shallow, fast flowing water over a rocky substrate on main river stem. Water temperature was 28.3°C. The live specimen is pictured in Figure YYY.

INPA CTGA_14332. 144.3 mm SL.

Identification to species level follows Armbruster (2008) based on the following characters: evertible cheek plates with > 10 hypertrophied odontodes; dentaries forming angle of < 90°; deep body, not dorso-ventrally flattened; lips lacking fimbriae; villiform teeth of equal size in premaxilla and dentary; colour pattern of four irregular dorsal saddles (first and second are usually combined in small specimens); dorsal and caudal fins without orange margin (in life); head plates not outlined in black; dark bar between eyes, and e-shaped dark blotch on the snout (broken in some specimens); and fins with dark and light bands of approximately equal width (irregular in some specimens).

An interesting observation is that our specimens exhibited variation in terms of the degree of abdomen plating and markings: adult specimens from rocky collection points near the mouth of the river showed complete abdomen plating and a vermiculated pattern (Fig YYY); those from further up the river lacked abdomen plating and associated colouration (with the exception of one individual that was partially plated with discrete spots).

Twenty-eight individuals were caught by hand from both woody substrates and rocky substrates. NNN examples of live specimens are pictured in Figure YYY to illustrate variation in abdomen plating and colour pattern.

INPA CTGA_14316. 115.6 mm SL.

Identification to species level follows Isbrücker & Nijssen (1976) and Covain & Fisch-Muller (2007) based on the following characters: lower lip bilobate with median furrow; whip on upper caudal spine absent; abdomen covered with small plates lacking organisation; elliptical area of abdominal plates at level of pelvic girdle absent; rostrum not strongly pronounced; pelvic-fin spine longer than last pelvic-fin branched ray; colouration comprising dark dots (except ventral surface and anal fin); lower lobe of caudal darker than upper; and basicaudal spot present in juveniles;

Three individuals were caught by hand-net at night over a sandy/silty substrate in the lake-like lower reaches of the river. Water current was minimal. An example of a live specimen is pictured in Figure YYY.

INPA CTGA_14542. 216.4 mm SL.

Identification to species level follows Vera-Alcaraz et al. (2012) and Fichberg & Chamon (2008) based on the following characters: postorbital notch present; inferior lip with short, round papillae; teeth on dentary larger than premaxilla; four rows of lateral plates; all fins with a broad longitudinal dark band parallel to the first rays (fins almost entirely dark in our specimen); lower lip margin with long fringes; dorsal surface of head and predorsal region with two longitudinal dark bands. Note that the characteristic dorsal breeding odontodes of R. lanceolata were not visible in this single specimen (probably female).

One individual was caught by hand from shallow, fast flowing water over a rocky substrate on main river stem. Water temperature was 28.3°C. The live specimen is pictured in Figure YYY.

INPA CTGA14330. 86.8 mm SL.

Identification to species level follows Eigenmann & Eigenmann (1890) based on the following characters: two rows of maxillary teeth (posterior row very small and hidden within the skin folds) and one row of dentary teeth; first dorsal and pectoral rays not spinous; adipose fin long; barbels flattened; upper jaw slightly prognathous; and dark spots on flanks and adipose fin.

Five individuals were caught after being attracted to the boat by suspending a dead-fish bait in the water. An example of a live specimen is pictured in Figure YYY.

INPA CTGA_14531. 254.0 mm SL.

Identification to species level follows Lundberg & Aguilera (2003) and Mol (2012) based on the following characters: dermal bones of the skull coarsely sculpted with reticulated ridges surrounding rounded pits; supraoccipital process greatly expanded laterally; anterior nuchal plate enlarged; colour pattern comprises dark upper and white/yellow lower parts of flank; and caudal fin bright red/orange.

One individual was caught by baited hand-line in a deep pool of the main river stem. The live specimen is pictured in Figure YYY.

CTGA_14459. ??? mm SL.

Identification to species level follows Buitrago-Suárez & Burr (2007) and based on the following characters: head strongly depressed with extended cranial fontanelle; loop-like dark bars forming reticulated pattern which extends far below lateral line and connects dorsally; no clear demarcation between dark dorsal and pale ventral regions; and caudal fin with fewer than 45 spots.

While we follow the taxonomy of Buitrago-Suárez & Burr (2007), we also consider the possibility that P. reticulatum Eigenmann & Eigenmann, 1889 is a junior subjective synonym of P. fasciatum (Linnaeus), in light of the study of Carvalho-Costa et al. (2011), who reported minimal genetic differentiation among the taxa considered conspecific with P. fasciatum previous to the study of Buitrago-Suárez & Burr (2007).

Four individuals were caught at night using gill nets [Val, where were these set?]. The Pseudoplatystoma specimens were not retained as vouchers. An example of two live specimens is pictured in Figure YYY.

CTGA. ??? mm SL.

Identification to species level follows Shibatta & Pavanelli (2005), Mees (1974) and Eigenmann (1912) based on the following characters: lower jaw not projecting beyond upper jaw; head large and rounded in dorsal view; head and body with numerous small papillae; insertion of pelvic fin though vertical of posterior base of dorsal; short caudal peduncle; rounded caudal fin; post-cleithral process short, not reaching vertical through dorsal-fin origin; axillary pore absent; lateral-line canal terminating on caudal peduncle; premaxillary dentigerous plates with lateral margins posteriorly prolonged; colour brown, with dark mottled appearance; and caudal fin with dark dots irregularly distributed.

An important inconsistency should be noted regarding the caudal fin shape. Eigenmann (1912) described the caudal fin of B. villosus as being "notched", but figured a specimen with a rounded caudal fin (Mees, 1974). The photograph of the holotype (FMNH 53219) on the All Species Catfish Inventory Web page (http://acsi.acnatsci.org/base/image_list.html?mode=genus&genus=Pseudopimelodus) shows a fish lacking most of the caudal fin. The specimens we collected had a rounded caudal fin.

Four individuals were caught by hand from their lodgements in woody substrates at the margin of the main river stem. Water temperature was 28.9°C. An example of a live specimen is pictured in Figure YYY.

INPA CTGA_14497. 176.0 mm SL .

Our desk survey shows that few ichthyological surveys of the Rio Nhamundá have taken place, and that our collection is one of the first to be made on the river. The checklist is far from complete however, missing entirely the callichthyids and aspredinids, for example (we sampled habitats more likely to yield these families, such as igarapés, only superficially). Despite this, we feel that rapid publication of even modest datasets and small-scale surveys can make valuable additions to biodiversity science in the Amazon, by both presenting the early discovery of new species and the extension of ranges for known species. The study also highlights the paucity of neotropical ichthyological data in GBIF/GenBank, and makes a small contribution.

We applied a conservative approach to applying names to the species we collected, and where individuals differed from published literature we avoided identifying these simply as "sp." (unless the species was truly undetermined, as was the case for the Pimelodella). For example, the revision by Armbruster (2008) proposed Peckoltia vittata to be a wide ranging species of the Orinoco and Lower Amazon, whereas the aquarium industry refer to approximately ten populations of Peckoltia—which could be considered P. vittata by Armbruster (2008)—as separate species each designated its own L (Loricariidae) number for putatively undescribed taxa in the trade (Seidel & Evers, 2005). While future molecular and morphological analysis may show that some of these populations are in fact supported as distinct species, referring to them as such at this stage would hamper such efforts by atomising biodiversity data associated with related species/populations. Therefore, where a species was thought to be distinct, we preferred the aff. and cf. terminology to link the records to other collection events/species.

The biogeographic composition of the collection is interesting. While many of the species recorded were cosmopolitan species of the lowland Amazon—e.g. Auchenipterichthys longimanus, Trachycorystes trachycorystes, Goeldiella eques, Hypoptopoma incognitum, Lasiancistrus schomburgkii, Loricaria cataphracta, Pseudoloricaria laeviuscula, Rineloricaria lanceolata, Calophysus macropterus, and Phractocephalus hemioliopterus—there are suggestions of connections to more specialised faunas. For example: the presence of Ancistrus dolichopterus, Dekeyseria scaphirhyncha and Hypostomus carinatus, suggest links to the Rio Negro fauna; Tatia nigra, however, is only known from the neighbouring Uatumã and Trombetas rivers, both south draining rivers of the Guiana Shield; three species—Tatia aff. musaica, Ancistrus aff. macrophthalmus and Pseudolithoxus XXX (see discussion above)—appear to have connections with the Orinoco river; while the presence of Leporacanthicus galaxias in particular is strange, because although possibly similar forms are reported from the Orinoco and Madeira drainages (Seidel & Evers, 2005), this is a species known from the Rio Tocantins, a north draining Brazilian Shield river far to the east.

Thus, the ichthyofauna of the Rio Nhamundá appears to have some interesting affiliations to several faunal areas. This is perhaps exemplified by the best known fish from the river, the discus cichlid Symphysodon. Specimens exported from this locality are famous in the aquarium trade for their phenotypic variation (Bleher, 2006). Genetic groups of both the Heckel (S. discus) and brown (S. aequifasciatus) discus species are found in sympatry in the Nhamundá, which may in fact comprise an area of natural hybridisation between the two species (Villar Amado et al., 2011).

In summary, the Nhamundá may therefore be an important location the Detecting presence of restricted range fishes is important in setting conservation priorities (Nogueira et al., 2010). Further surveys are required in the upper section of the river above the rapids, and these may well show possibly endemic species (Alofs et al., 2014).