A new species of Corydoras (Siluriformes: Callichthyidae) from the rio Madre de Dios basin, Peruvian Amazon, with comments on Corydoras aeneus identity

Abstract A new species of Corydoras is described from tributaries to the rio Araza, an affluent of the rio Inambari, itself a tributary to the rio Madre de Dios, rio Madeira basin in the Peruvian Amazon. The new species can be distinguished from its congeners by the following features: (I) absence of contact between the posterior process of the parieto-supraoccipital and the nuchal plate, (II) a single, large conspicuous dark brown or black blotch on anterodorsal portion of flank; blotch somewhat rounded to roughly diamond shaped, and (III) absence of dark blotches on fins. General comments on the identity of Corydoras aeneus are also provided.

In spite of Corydoras being widely distributed within cis-Andean South America, more than the half of its representatives occur in the Amazon basin (Britto, 2003;Tencatt, Ohara, 2016b).The rio Madeira basin, one of the most iconic tributary of the rio Amazonas basin, holds the world's richest fish fauna (Torrente-Vilara et al., 2013;Jézéquel et al., 2020), currently harboring 45 species of Corydoras, which represents about one quarter of the total species of the genus (Ohara et al., 2016;Tencatt, Evers, 2016;Tencatt, Ohara, 2016a,b;Tencatt et al., 2021).As widely known, the Corydoradinae are extremely appreciated in the aquarium hobby, which led to the capture and discovery of many putative new species within the trade (see Tencatt, Evers, 2016;Tencatt et al., 2022a).Considering the extensive creation of trade names generated by the high demand of this group, the "C-number" code-system was created in 1993, which was later replaced by the "CW-number" coding in 2006, in order to prevent the creation of nomina nuda through the use of commercial names (Evers, 1993; and see Corydoras World website).
One of the coded species recorded for the rio Madeira basin is CW16, a species with very peculiar general color and morphological patterns, both essentially shared with Corydoras aeneus (Gill, 1858) and its relatives, which compose the Corydoradinae lineage 7 sensu Alexandrou et al. (2011).The analysis of material from the rio Araza basin, a bigger affluent of the rio Inambari, itself a tributary to the rio Madre de Dios, rio
Diagnosis.Corydoras maclurei can be distinguished from its congeners, except for C. difluviatilis Britto & Castro, 2002, C. flaveolus Ihering, 1911, C. gladysae, C. gracilis Nijssen & Isbrücker, 1976, C. hastatus Eigenmann & Eigenmann, 1888, C. hephaestus Ohara, Tencatt & Britto, 2016, C. latus, C. melanotaenia Regan, 1912, C. micracanthus Regan, 1912, C. nanus, C. petracinii, C pygmaeus Knaack, 1966, and C. undulatus Regan, 1912, by the absence of contact between the posterior process of the parieto-supraoccipital and the nuchal plate (vs.bones in contact).The new species can be distinguished from C. difluviatilis, C. flaveolus, C. gladysae, C. gracilis, C. hastatus, C. hephaestus, C. latus, C. melanotaenia, C. micracanthus, C. nanus, C. petracinii, C pygmaeus, and C. undulatus by having just a single, large conspicuous dark brown or black blotch on anterodorsal portion of flank; blotch somewhat rounded to roughly diamond shaped (vs.flank covered by numerous dark markings, variably with a distinct longitudinal series of blotches along flank midline in C. difluviatilis; covered by numerous dark markings, with a distinct longitudinal series of blotches along flank midline in C. flaveolus, C. gladysae, C. micracanthus, and C. petracinii; dorsal portion of flank with a long, arched, continuous dark stripe, which runs parallel to body dorsal profile, extending at least from corner of mouth region to posterior portion of caudal peduncle, dorsally and ventrally bordered by scarcely spotted regions, which often form longitudinal brownish yellow longitudinal bands; ventrolateral body plates with small dark brown or black blotches, variably aligned in longitudinal rows in C. gracilis; midline of flank with a slender dark longitudinal stripe, which may be absent or diffuse in some individuals; ventral margin of flank, just posterior to pelvic fin, with a small spot or dark longitudinal stripe, which generally becomes gradually diffuse posteriorly; stripe/spot variably diffuse; posterior portion of caudal peduncle with large, conspicuous dark blotch; midline longitudinal stripe, when present, variably fused to peduncular blotch in C. hastatus; a single, extremely large dark patch, typically almost entirely covering flank in C. hephaestus; ventral portion of dorsolateral body plates and dorsal portion of ventrolateral body plates with a longitudinal row of brownish yellow small roundish areas, more evident  extending at least from dorsal-fin base anterior portion to caudal peduncle posterior portion; dorsally and ventrally bordered by scarcely spotted regions, which often form longitudinal brownish yellow longitudinal bands; ventral portion of dorsolateral body plates and dorsal portion of ventrolateral body plates with a series of longitudinally aligned dark brown or black spots, which merge at dorsal-fin region and form a stripe, that can range from narrow to broad; ventrolateral body plates with dark brown or black blotches, generally longitudinally aligned in C. nanus; dorsal half of dorsolateral body plates densely covered by dark brown or black chromatophores; midline of flank with a longitudinal dark stripe, extending from corner of mouth region to posterior portion of caudal peduncle, dorsally and ventrally bordered by pale regions; ventral margin of flank, just posterior to pelvic fin, with a dark longitudinal stripe; posterior portion of caudal peduncle with moderate-sized, horizontally ellipsoid to roughly diamond shaped conspicuous dark blotch; midline longitudinal stripe fused to peduncular blotch; anterior portion of flank on region between midline and ventral stripes variably with longitudinally aligned dark spots in C. pygmaeus; with relatively large dark brown or black markings, forming a marbled or somewhat anastomosed pattern at least on anterior portion of flank; blotches variably forming up to three irregular and/or intermittent longitudinal bands; first band, if present, along dorsolateral body plates, second, if present, along midline of flank, and third, if present, along ventrolateral body plates; third band variably more regular and continuous in C. undulatus).Corydoras maclurei can be additionally distinguished from C. difluviatilis, C. flaveolus, C. gladysae, C. gracilis, C. hastatus, C. micracanthus, C. nanus, C. petracinii, and C. pygmaeus by the absence of dark blotches on fins (vs. at least one of the fins with conspicuous dark blotches).
Description.Morphometric data in Tab. 1. Head laterally compressed with convex dorsal profile, roughly triangular in dorsal view.Snout typically moderately developed, rounded; variably short and/or smoothly pointed.Head profile convex from tip of snout to anterior nares, ascending nearly straight or slightly convex from this point to dorsalfin origin; region of anterior portion of parieto-supraoccipital and/or region between posterior process of parieto-supraoccipital and nuchal variably slightly concave.Profile slightly convex along dorsal-fin base.Postdorsal-fin body profile slightly concave to nearly straight to adipose-fin spine, concave from this point to caudal-fin base.Ventral profile of body nearly straight or slightly convex from isthmus to pectoral girdle, and slightly convex from this point until pelvic girdle.Profile nearly straight or slightly convex from pelvic girdle to base of first anal-fin ray, ascending concave until caudalfin base.Body roughly elliptical in cross section at pectoral girdle, gradually becoming more compressed toward caudal fin.
Eye rounded, located dorsolaterally on head.Orbit delimited anteriorly by lateral ethmoid, anterodorsally by frontal, posterodorsally by sphenotic, posteroventrally by infraorbital 2, and anteroventrally by infraorbital 1 (Fig. 2).Anterior and posterior nares close to each other, only separated by flap of skin.Anterior naris tubular.Posterior naris close to anterodorsal margin of orbit, separated from it by distance similar to naris diameter.Mouth small, subterminal, width similar to bony orbit diameter.Maxillary barbel moderate in size, almost reaching or reaching anteroventral limit of gill opening.Outer mental barbel slightly longer than maxillary barbel.Inner mental barbel fleshy, base of each counterpart slightly separated from each other.Small rounded papillae covering entire surface of all barbels, upper and lower lips, snout and isthmus.Mesethmoid short to moderate in size, with anterior tip poorly developed, slightly smaller than 50% of bone length (see Britto, 2003:123, character 1, state 1; fig.1B); posterior portion wide, partially exposed and bearing small odontodes.Nasal capsule delimited posteriorly and dorsally by frontal, anteriorly by mesethmoid, and ventrally and posteriorly by lateral ethmoid.Nasal relatively wide, laterally curved, inner margin with moderately-developed laminar expansion contacting only frontal; close but not directly in contact with mesethmoid; outer margin with poorly-developed laminar expansion (Figs.2A, 3).Lateral ethmoid relatively slender in lateral view, slightly expanded anteriorly, with anterodorsal expansion relatively distant from nasal, and anterior margin contacting posterior portion of mesethmoid (Fig. 2B).Frontal elongated, narrow, width less than half of entire length; anterior projection short, size smaller than nasal length (Fig. 3).Frontal fontanel large, slender, and somewhat ellipsoid; posterior tip extension slightly surpassing anterior margin of parieto-supraoccipital (Fig. 3).Sphenotic somewhat trapezoid, contacting parieto-supraoccipital dorsally, pteroticextrascapular posteriorly, second infraorbital posteroventrally and frontal anteriorly (Fig. 2A).Pterotic-extrascapular roughly pipe-shaped, with posteriormost portion contacting first lateral-line ossicle, posteroventral margin contacting cleithrum, and anteroventral margin contacting opercle and infraorbital 2; posterior expansion almost  entirely covering lateral opening of swimbladder capsule, leaving slender area on its dorsal margin covered only by thick layer of skin.Parieto-supraoccipital wide, posterior process long, not contacting nuchal plate; nearly contacting in some specimens; region between posterior process and nuchal plate covered by thick layer of skin; variably with small-to moderate-sized platelets (Fig. 4).
Four branchiostegal rays decreasing in size posteriorly.Hypobranchial 1 deep; hypobranchial 2 somewhat triangular, tip ossified and directed towards anterior portion, posterior margin cartilaginous; ossified portion well developed, its size about twice cartilaginous portion.Five ceratobranchials with expansions increasing posteriorly; ceratobranchial 1 with strongly reduced to small process on anterior margin of mesial portion; ceratobranchial 3 with continuous laminar expansion on postero-lateral margin; laminar expansion variably notched; ceratobranchial 5 toothed on posterodorsal surface, with 32 to 39 (3) teeth aligned in one row.Four epibranchials with similar size; epibranchial 2 slightly larger than others, with small pointed process on laminar expansion of posterior margin; epibranchial 3 with mesially-curved uncinate process on laminar expansion of posterior margin; uncinate process variably roughly triangular.Two wide pharyngobranchials (3 and 4); pharyngobranchial 3 with relatively large Lateral-line canal reaching cephalic laterosensory system through pteroticextrascapular, branching twice before reaching sphenotic: pterotic branch, with single pore, preoperculomandibular branch conspicuously reduced, with single pore opening at postotic main canal; postotic main canal widens just posterior to pterotic branch.Sensory canal continuing through pterotic-extrascapular, reaching sphenotic as temporal canal, which splits into two branches: one branch giving rise to infraorbital canal, other branch connecting to frontal through supraorbital canal, both with single pore.Supraorbital canal branched, running through nasal bone.Epiphyseal branch conspicuously reduced; pore opening close to supraorbital main canal, directed towards frontal fontanel.Nasal canal with three openings, first on posterior edge, second on posterolateral portion and typically fused with first pore, and third on anterior edge.Infraorbital canal running through entire infraorbital 2, extending to infraorbital 1 and typically opening into two pores.Preoperculomandibular branch giving rise to preoperculo-mandibular canal, which runs through entire preopercle with three openings, leading to pores 3, 4, and 5, respectively.Dorsal fin subtriangular, located just posterior to second or third dorsolateral body plate.Dorsal-fin rays II,5 (1), II,7 (2), II,8* (17), posterior margin of dorsal-fin spine with seven to 14 strongly reduced to poorly-developed serrations; most serrations directed towards tip of spine; some serrations variably perpendicularly directed; serrations absent close to origin of spine; small odontodes on anterior and lateral surfaces of spine (Fig. 6A).Nuchal plate moderately developed, almost entirely exposed, with minute odontodes.Spinelet short; spine ranging from moderately developed, with adpressed distal tip surpassing middle portion of dorsal-fin base, to well developed, with adpressed distal tip slightly surpassing posterior origin of dorsal-fin base.Pectoral fin roughly triangular, its origin just posterior to gill opening.Pectoral-fin I,5 (1), I,8 (15), I,9* (4), posterior margin of pectoral spine with 20 to 27 poorly-to moderately-developed serrations along almost its entire length, absent close to origin of spine; most serrations directed towards tip of spine; some serrations perpendicularly directed and/or bifid; variably with some trifid and/or fused serrations; small odontodes on anterior, dorsal and ventral surfaces of spine (Fig. 6B).Anteroventral portion of cleithrum exposed; posterolateral portion of scapulocoracoid moderately developed, exposed, with anterior portion slightly expanded anteriorly, not in contact with anteroventral portion of cleithrum; exposed areas bearing small odontodes.Opening of axillary gland sensu Kiehl et al. (2006) located just posterior to pectoral-fin spine base.Pelvic fin oblong, located just below second or third ventrolateral body plate, and at vertical through first or second branched dorsal-fin ray.Pelvic-fin rays i,4,i (2), i,5* (18).Anterior internal process of basipterygium well developed and ranging from slightly to conspicuously laterally expanded, with obliquely placed dorsal lamina, converging mesially towards anterior edge of process; anterior internal process conspicuously narrow in specimen CITL 430, 45.6 mm SL, apparently due to malformation; anterior external process laminar, moderately developed, ranging from not to slightly expanded posteriorly; dorsal ischiac process well developed, with anterior laminar expansion poorly to moderately expanded anteriorly, and posterior laminar expansion conspicuously expanded posteriorly; anterior and posterior laminar expansions of ischiac process roughly triangular; ventral ischiac process clearly smaller than dorsal process, roughly triangular, slightly bent anteriorly (Figs.7A, B).Adipose fin roughly triangular, separated from base of last dorsal-fin ray by eight or nine dorsolateral body plates.Anal fin subtriangular, located just posterior to 12 th or 13 th ventrolateral body plates, and at vertical through region of preadipose platelets.Anal-fin rays ii,4,i (1), ii,5,i (2), ii,6 (16), ii,7* (1).Caudal fin bilobed, with dorsal and ventral lobes similar in size or dorsal lobe slightly larger than ventral lobe.Caudal-fin rays i,7,i (1), i,12,i* (18), i,13,i (1), with generally five dorsal and ventral procurrent rays; small cartilage between upper principal and procurrent caudal-fin rays (presumably opisthural cartilage (Monod, 1968;McDowall, 1999)) (Fig. 7C).
Vertebral count 23 (3); ribs 6 (1), 7 (1); first pair conspicuously large, its middle portion closely connected to first ventrolateral body plate; its tip not connected to anterior external process of basipterygium; nearly contacting in some specimens.Parapophysis of complex vertebra moderately or well developed.Color in alcohol.Overall color of body in Fig. 1.Ground color of body pale-to brownish yellow or beige, with top of head dark brown.Dorsal and lateral surface of head, and lateral surface of cleithrum covered by dark brown or black chromatophores, not forming blotches; posterior margin of cleithrum with conspicuous concentration of dark brown or black chromatophores, forming thin dark line, which is more evident on dorsal half of cleithrum.Border of pores of laterosensory canals typically with conspicuous concentration of dark brown or black chromatophores.Anterodorsal portion of flank, just below anterior portion of dorsal-fin base, with large, conspicuous dark brown or black blotch, ranging from somewhat rounded to roughly diamond shaped.Remaining portions of dorso-and ventrolateral body plates covered by dark brown or black chromatophores, not forming blotches; ventral portion of ventrolateral body plates, especially on region around pelvic-fin origin, devoid of or with sparse chromatophores.Posterior margin of body plates with conspicuous concentration of dark brown or black chromatophores, forming thin dark lines, typically more evident on dorsal portion of dorsolateral body plates, azygous precaudal and preadipose plates, and on dorsolateral body plates below dorsal-fin base.Dorsal and adipose fins entirely covered by numerous brown or black chromatophores, not forming blotches.Pectoral, pelvic, anal and caudal fins with conspicuous concentrations of brown or black chromatophores on rays, not forming blotches; membranes typically devoid of or with sparse chromatophores.
Color in life.Similar to color pattern of preserved specimens, but with ground color of body typically brownish orange (Fig. 8A); variably greyish orange or reddish orange (Figs.9A, B).Dorsal fin reddish orange in some specimens (Fig. 9C).Body covered by greenish yellow iridescent coloration, with anterior portion of first dorsolateral body plate typically with orange or yellow bright patch.(Figs.9D, E).

Geographical distribution.
Corydoras maclurei is currently known from tributaries to the rio Araza, an affluent of the rio Inambari, itself a tributary to the rio Madre de Dios, rio Madeira basin, Camanti District, Quispicanchi Province, Cusco Region, Peru (Fig. 10).

Ecological notes.
Corydoras maclurei was captured in clearwater creeks and smaller rivers tributaries to the rio Madre de Dios drainage around the town of Quince Mil (Fig. 8B).The habitats are mostly very shallow, raising their water levels only after stronger rainfalls, which return to normal levels after a few hours.The water temperatures measured by HGE lay between 22.3 to 24.9°C during the daytime at different times of the year (June, September).During the night, the air temperatures fall significantly and so do the water temperatures.On June 17th, 2015 at 8 pm the water temperature at the type locality was 18.5 °C.The conductivity lies between 53 µS/cm with a pH at 6.0 (June 17, 2015) and 29 µS/cm with a pH of 7.0 (September 22, 2016).In these sites, the crystal-clear water flows over a bed of pebbles, rocks and boulders, with smaller  areas of fine sand.Especially in the very small and narrow creeks, there is also a dense leaf litter covering the ground.During the day, single specimens of C. maclurei could be observed resting between the rocks and quickly hiding under the leaves in case of danger.Night collecting efforts could not be performed as the dense vegetation and rough terrain make collecting fish extremely difficult at this time of day.Even after extensive collecting activities, for several hours, only a few specimens of C. maclurei were captured, suggesting that the new species is naturally not very abundant in the aforementioned biotopes, while the syntopic Corydoras weitzmani Nijssen, 1971 can be observed in pairs or small groups foraging along the river edges.Etymology.Corydoras maclurei is named in honor of Robert "Rob" McLure, dear friend and renowned Corydoradinae breeder.Rob has been the main English-language reviewer of the first author's publications, in addition to providing valuable information and live photos of several species of Corydoradinae.A genitive noun.

Conservation status.
Even with the extensive survey efforts throughout the region, C. maclurei was exclusively found in some of the small streams draining to the rio Araza around Quince Mil, a small Peruvian community.With the currently available data, the Extent of Occurrence of C. maclurei was roughly estimated to be 5 km 2 .All habitats in the vicinity of Quince Mil are vulnerable due to human activities, especially illegal goldmining and road building (see Lujan et al., 2013), increasing problems in the whole rio Inambari basin (Hans -G. Evers, 2016, pers. obs.).Additionally, the new species is desirable in the aquarium hobby, making some fishermen from the Cusco area to perform regular collecting efforts in the Quince Mil area, where they even use rotenone to collect both C. maclurei and C. weitzmani, mostly at night (Hans -G. Evers, 2022, pers. obs.).Considering that the new species seems to occur in low abundance, it is possible that its populations are being overfished, which is aggravated by its restricted geographic distribution and the collecting method applied by the local fishermen (i.e., rotenone).Therefore, according to the International Union for Conservation of Nature (IUCN) categories and criteria (IUCN Standards and Petitions Subcommittee, 2022), Corydoras maclurei can be classified as Near Threatened (NT), approximating the Critically Endangered (CR) category by criterion B1b(iii).

Remarks.
Corydoras maclurei has been bred under aquarium conditions by one of the authors (HGE), who documented its ontogenetic development from 8 to 28 mm LT, showing general changes in external morphology and color pattern (Fig. 11).Specimen with 8.0 mm TL in yolk-sac stage (Fig. 11A); head slightly depressed, with short and conspicuously rounded snout; barbels moderate in size and with well-developed papillae, which will gradually become less developed along individual's growth; eye large; median fin fold present, extending from postcephalic region to genital opening; Specimen with 12.0 mm TL in final flexion stage (Fig. 11B); dorsal-and caudal-fin rays distinct, but fins not detached from fin fold; pectoral-fin rays distinct; anal, pelvic and adipose fins not distinct; caudal-fin asymmetrical, dorsal portion distinctly longer than ventral; hypural plates visible by transparency; conspicuous, oblique dark stripe from anteroventral margin of orbit to upper lip lateral area.Specimen with 16.0 mm TL in early post-flexion stage (Fig. 11C) displays more pronounced snout; reduction of median fold, with dorsal, anal and caudal fins partially detached; pectoral fin slightly more developed; pelvic-and anal-fin rays distinct; adipose fin indistinct; beginning of formation of lateral body plates; slightly more pigmented body, with diffuse dark patches.Juvenile specimens with 21.0 and 28.0 mm TL (Figs. 11D, E), respectively, are strongly similar to each other, except for except for gradual development of lateral body plates and fin spines, and conspicuous dark patch on anterodorsal portion of flank in larger specimen; snout slightly more pronounced; median fold absorbed, with distinct adipose, caudal and anal fins.

DISCUSSION
Corydoras maclurei presents both general morphological and color patterns typical to the species within lineage 7 sensu Alexandrou et al. (2011), which harbors C. aeneus, C. eques Steindachner, 1876, C. melanotaenia, C. rabauti LaMonte, 1941, and C. zygatus Eigenmann & Allen, 1942.The species from this group can be distinguished from remaining congeners by having the following features: (I) mesethmoid ranging from short to moderate in size (vs.conspicuously short, large or extremely large in size); (II) posterior margin of pectoral-fin spine with all or nearly all serrations directed towards the tip of the spine or perpendicularly directed (vs.mostly directed towards the origin of spine, variably with some serrations perpendicularly directed or directed towards tip of spine); (III) posterior laminar expansion of infraorbital 2 conspicuously well developed, in contact with pterotic-extrascapular (vs.ranging from strongly reduced to relatively well developed, typically not in contact with pterotic-extrascapular); and (IV) ground color of body in shades of orange or yellow, with only a single, large dark patch on flanks; all fins devoid of dark spots (vs.ground color of body pale yellow, brownish yellow or greyish yellow, typically with small dark spots at least in some part of the body).In addition to the aforementioned species, such color and morphological patterns can also be observed in C. hephaestus, suggesting that this species possibly composes this group.
Considering overall color and morphological patterns, the most similar congeners to C. maclurei are C. hephaestus and C. melanotaenia (Fig. 12).The new species can be distinguished from both species by details in color pattern (see Diagnosis section).Additionally, C. maclurei can be distinguished from C. hephaestus by having comparatively smaller ventral laminar expansion of infraorbital 1 (vs.larger ventral laminar expansion, see Ohara et al. (2016:544, fig.3)), posterior margin of dorsal-fin spine with seven to 14 serrations (vs.posterior margin of dorsal spine smooth, lacking serrations), and posterior margin of pectoral-fin spine with more serrations (20 to 27 vs.nine to 14).Although additional differences between C. maclurei and C. melanotaenia are more subtle, the new species can be distinguished from C. melanotaenia by having a comparatively more rounded snout (vs.more pointed), and ground color of body in life in shades of orange (vs.ground color of body, especially fins, intensely yellow).
Regarding the remaining lineage 7 species, C. maclurei can be promptly distinguished from C. eques, C. rabauti, and C. zygatus by having a single, large conspicuous dark brown or black blotch on anterodorsal portion of flank, with remaining areas of the flanks clearly paler; blotch somewhat rounded to roughly diamond shaped (vs.extremely large dark patch almost entirely covering flanks in C. eques; dark stripe running in parallel to the dorsal profile of the body, extending from the region just anterior to dorsal fin to caudal-fin base).The new species can be further distinguished from the three aforementioned congeners by having posterolateral portion of scapulocoracoid moderately developed, poorly expanded medially, with counterparts conspicuously distant in ventral surface of trunk (vs.posterolateral portion of scapulocoracoid strongly well developed, conspicuously expanded medially, with counterparts contacting in ventral surface of trunk).
The last valid species within lineage 7 is C. aeneus (Fig. 13), which surely presents one of the most complex taxonomic problems among the Corydoradinae.Although this species was described from Trinidad Island, West Indies, several populations throughout South and 2, and a relatively well-developed pectoral spine are also useful to differ the typical C. aeneus from some populations attributed to it.
Although preliminary analyzes seem promising for elucidating the taxonomic status of C. aeneus, a solid resolution of its identity can only be accomplished through an extensive taxonomic revision.In any case, even considering the morphological variation in populations attributed to C. aeneus, the absence of contact between posterior process of the parieto-supraoccipital and nuchal plate plus serration pattern of pectoral spine are useful to distinguish the new species from C. aeneus.Nevertheless, it is important to point out that one of the paralectotypes (USNM 92819; Fig. 13C), presents a conspicuous malformation on predorsal region (also affecting the dorsal fin), which clearly caused the absence of contact between the posterior process of the parieto-supraoccipital and the nuchal plate in this specimen.
.br | scielo.br/niA new Corydoras from the rio Madre de Dios basin .br | scielo.br/niLuiz Fernando C. Tencatt, Vandergleison C. Gomes and Hans-Georg Evers on flank anterior half; remaining areas of dorsolateral body plates with conspicuous concentration of dark brown or black chromatophores, more evident on flank anterior half; dorsal half of ventrolateral body plates, except for small brownish yellow roundish areas, with conspicuous concentration of dark brown or black chromatophores in C. latus; wide, longitudinal dark stripe almost entirely covering dorsal and middle portion of flank in C. melanotaenia; dorsal portion of flank with a long, continuous, regular, longitudinal dark brown or black stripe, which runs in parallel to body dorsal profile,

FIGURE 8 |
FIGURE 8 | Uncatalogued aquarium specimen of Corydoras maclurei (A) showing its typical color pattern in life (lateral view), collected in its type-locality (B), a small stream tributary to the rio Araza, rio Madre de Dios basin, rio Madeira basin in Peru.
FIGURE 9 | Uncatalogued aquarium specimens of Corydoras maclurei (not measured) showing variations of the color pattern in life: specimens can variably present greyish orange (A) or reddish orange (B) ground color of body.In C, the detail of a conspicuously reddish orange dorsal fin.Anterior portion of first dorsolateral body plate typically with orange (D) or yellow (E) bright patch.Photographs (D) and (E) by Ian Fuller.
FIGURE 10 | Map showing the geographical distribution of Corydoras maclurei (yellow star).The symbol represents more than one locality.

FIGURE
FIGURE 11 | Ontogenetic series of Corydoras maclurei (bred under aquarium conditions) showing general changes in external morphology and color pattern in specimens with 8.0 mm TL (A), 12.0 mm TL (B), 16.0 mm TL (C), 21.0 mm TL (D), and 28.0 mm TL (E).
FIGURE 12 | Uncatalogued specimens (not measured) of (A) Corydoras hephaestus and (B) C. melanotaenia photographed alive in lateral view, showing general color and morphological patterns.Photograph (A) by Fernando Dagosta and (B) by Robert McLure.

FIGURE 13 |
FIGURE 13 | Type specimens of Corydoras aeneus, showing the lectotype (A, USNM 1116) and paralectotypes (B, C, USNM 205649 and USNM 92819, respectively) of Hoplosoma aeneum.Red arrows in C indicates the area affected by a malformation on predorsal region of body.Photographs by Sandra Raredon.Scale bar = 1 mm.

TABLE 1 |
Morphometric data of the holotype and 19 paratypes of Corydoras maclurei.SD = Standard deviation.