Catfishes of the genus Auchenipterichthys ( Osteichthyes : Siluriformes : Auchenipteridae ) ; a revisionary study

The Neotropical auchenipterid catfish genus Auchenipterichthys is reviewed and found to include four species. Auchenipterichthys thoracatus, formerly considered to be widely distributed throughout the Amazon River basin, is found to be restricted to the upper Madeira River basin. The widespread Amazonian species that had been misidentified as A. thoracatus is, instead, A. coracoideus; a species that also occurs in the upper Essequibo River. Auchenipterichthys longimanus, the most widely distributed species of the genus, is found through much of the Amazon and Orinoco River basins. The fourth species of the genus, A. punctatus (and its junior synonym A. dantei), is found in the upper portions of the Orinoco and Negro River basins in Venezuela and the central portions of the Amazon River basin in Brazil. All four species of Auchenipterichthys are redescribed and illustrated, and a key to the species is provided.


Introduction
The genus Auchenipterichthys was first proposed in Bleeker (1862-63) for a single species of Brazilian catfish that had been originally placed by Kner (1857) in Auchenipterus, a genus that at that time included many of the Neotropical catfishes that are currently recognized as the Auchenipteridae.Although Bleeker did not recognize a group equivalent to the Auchenipteridae, he clearly recognized that species then placed within Auchenipterus did not belong together in one genus.He created several new genera to accommodate species formerly placed in Auchenipterus among which was Auchenipterichthys, which included only A. thoracatus (Kner).
Shortly after the creation of Auchenipterichthys, Günther (1864) described a second species in the genus.The two species were reported to be widely distributed throughout the Amazon and Orinoco River basins by Soares-Porto (1994), who also named a third species as A. dantei.In a review of the types of auchenipterid catfishes held in MNHN, Royero and Hureau (1996) discovered that the species named by Soares-Porto had been named previously as Auchenipterus punctatus by Valenciennes (in Cuvier & Valenciennes, 1840).Examination of specimens identified as Auchenipterichthys thoracatus from the Guaporé River basin (the type locality of the species) and from other parts of the Amazon River basin led us to suspect that more than one species was included within that species complex, which prompted this revision.

Material and Methods
Unpaired fin-ray counts and vertebral counts were taken from radiographs.The two posterior most dorsal-and analfin rays articulating on the corresponding last pterygiophore of each fin were counted as separate rays.Caudal-fin ray counts report the principal rays (i.e., branched rays and the first unbranched ray of the dorsal and ventral lobes).Paired fin rays were counted under a stereomicroscope and include all elements.
Measurements were taken, point-to-point, as follows: the body depth was taken at the dorsal-fin origin and anal-fin origin; the head length was measured parallel to the body axis, from the tip of the snout to the posterior tip of the fleshy operculum; the cleithral width was measured across the bony cleithrum just anterior to the pectoral spine; the snout length was measured from the tip of the snout to the anterior margin of the eye; the bony interorbital width represents the shortest distance across the bony interorbit; the dorsal-fin spine length was measured from the junction point between the first spine (spinelet) and the second spine to the tip of the bony spine, but not including the fleshy or flexible bony terminal parts of the spine; and the anal-fin base length was measured from the origin of the anal fin to the insertion of the last anal-fin ray.
The following abbreviations are used in the text: SLstandard length; TL -total length; HL -head length; aslabove sea level.

Diagnosis.
A genus of the Auchenipteridae characterized by the following combination of characters: eye large, midlateral, and visible in both dorsal and ventral views; anal fin with long base and at least 18 branched fin rays; lateral surface of body with several vertically-oriented rows of pale spots above the lateral line; caudal fin emarginate or obliquely truncate; pelvic fin with eight or nine branched rays; and adipose fin present.
Remarks.At present, no derived characters have been identified that are unique to the species of Auchenipterichthys (see Ferraris, 1988;Soares-Porto, 1994;de Pinna, 1998).Instead, the characters listed in the diagnosis are derived characters within the Auchenipteridae (except for the presence of the adipose fin, which is primitive), each of which is also present in at least one other genus in the family, but that occur in common only in the species of Auchenipterichthys.
In the absence of an identified unique synapomorphy it is possible that Auchenipterichthys is non-monophyletic; however, no evidence has been advanced to date to suggest that the genus is not natural.In the absence of evidence to the contrary we continue to treat the included species as a single, presumably natural, genus.
Based on overall similarity, the species of Auchenipterichthys fall into two groups.One group, which consists of A. coracoideus and A. thoracatus, has the ventral surface of the coracoid bone covered only by a thin integument (Figs.1a, b) and thus appears to be exposed to the body surface, has eight branched pelvic-fin rays, and has an obliquely-truncate caudal-fin margin.The second group, which includes A. longimanus and A. punctatus, has a thick layer of integument superficial to the ventral margin of the coracoid, such that the coracoid is not visible on the body surface (Fig. 1c), has nine branched pelvic-fin rays, and, in most individuals, has a caudal fin that is emarginate and symmetrical (some larger specimens exhibit a truncate fin margin).Because the monophyly of Auchenipterichthys has yet to be established, future studies of the relationships within the Auchenipteridae should include a representative species from each of these two groups so as to determine whether the groups cluster together as a natural unit.

Sexual dimorphism.
Sexual dimorphism in the species of Auchenipterichthys includes the enlarged urogenital orifice in females, whereas the urogenital pore of males is located at the distal tip of an elongated tube that is bound by integument to the anterior margin of the anal fin.Males also have an elongated and enlarged posterior unbranched and anterior branched anal-fin rays and elongated spinules along the anterior and posterior margins of the distal part of the dorsal-fin spine.Nuptial males of at least one species (A.coracoideus) have an elongated dorsal-fin spine.Species of Auchenipterichthys lack the ossification of the maxillary barbel, elongation of the unbranched pelvic-fin ray, and presence of keratinaceous unculi on dorsal surface of the head, abdomen and maxillary barbel that are found in some other genera of auchenipterids (Ferraris and Vari, 1999, Vari and Ferraris, 1998, Akama and Ferraris, 2003).& Allen, 1942].-Fowler, 1945: 64 [in listing of species of fishes in Peru].-Fowler, 1951: 473 [literature compilation].Auchenipterichthys longimanus (not of Günther, 1864), Mees, 1974: 38 [in part, specimen from Nazareth, Peru].Auchenipterichthys thoracatum (not of Kner, 1857), Merona et al., 1987: 83 [Brazil, lower rio Tocantins; increasing relative abundance following closure of Tucuruí dam].Auchenipterichthys coracoideus, Ferraris, 2003: 472 [checklist].

Diagnosis.
A species of Auchenipterichthys with coracoid bone covered only by thin layer of integument and exposed ventrally (Fig. 1a), an obliquely truncated caudal-fin margin, typically 25 or fewer branched anal-fin rays (rarely 26; Table 1), eight branched pelvic-fin rays, anterior teeth on the premaxilla visible when the mouth is closed, and the body pigmentation dark gray dorsally and lighter (pale in some specimens) laterally and ventrally, body without distinct dark spots.
Auchenipterichthys coracoideus is most similar in appear-
ance to A. thoracatus, which typically has 26 or more branched anal-fin rays, and is readily distinguished from its other two congeners, A. longimanus and A. punctatus, which have coracoids that are covered ventrally by a thick layer of integument (Fig. 1c), the anterior teeth on the premaxilla that are not visible when mouth is closed and, typically, nine branched pelvic-fin rays.
Description.Body depth at dorsal-fin origin 0.23-0.26 of SL and slightly greater than body width at cleithrum.Body depth at anal-fin origin 0.23-0.25 of SL.Body compressed, with width at anal-fin origin 0.39-0.41 of body depth at that point.Ventral surface of coracoids exposed on ventral surface of body (see Fig. 1a).Lateral line complete and midlateral.Canal having irregular zigzag pattern, with oblique, posteriorly-directed branches extending off main canal.Lateral line canal extending short distance onto, and obliquely posterodorsally-directed on, caudal-fin base.Head depressed anteriorly; depth of head at vertical through middle of orbit approximately one-half of head width at middle of orbit.Head length 0.36-0.39 of SL.Dorsal profile of head broadly convex anteriorly and then straight from vertical running through anterior margin of orbit to dorsalfin origin.Distance from midpoint of snout to anterior margin of orbit slightly greater than horizontal diameter of orbit.Snout margin broadly rounded from dorsal view.Interorbital width approximately 0.55-0.58 of HL and approximately equal to distance from middle of eye to posterior margin of opercle.Eye large, lateral, and visible in both dorsal and ventral views.Orbit distinctly ovoid with horizontal axis longer.
Barbels slender and thread-like.Maxillary barbel long, ex-tending posteriorly slightly past margin of opercle.Medial mandibular barbel originating immediately posterior of lower lip; adpressed barbel extending posteriorly to point slightly short of vertical through transverse plane through origin of lateral mandibular barbel.Lateral mandibular barbel originating in plane slightly anterior of vertical through middle of orbit and extending posteriorly approximately to anterior portion of exposed cleithrum.Branchiostegal membrane broadly attached to isthmus; ventral margin of gill opening extending to anterior margin of exposed portion of cleithrum.
Mouth terminal, but with upper jaw extending slightly beyond margin of lower jaw.Anterior premaxillary teeth visible from ventral view when mouth is closed.Teeth on premaxilla minute and arranged in band.Band consisting of approximately 8 irregular series of teeth at symphysis and of 10 irregular series laterally.Dentary teeth slightly larger than those on premaxilla, with approximately 6 series of teeth at symphysis that progressively decrease to one tooth row posterolaterally.
Dorsal-fin origin at 0.37 of SL.Length of dorsal-fin base approximately one-half of length of first branched dorsalfin ray.Dorsal-fin spine pungent and slightly curved with convex anterior margin.Length of dorsal-fin spine approximately equal to HL except in nuptial males in which spine may be longer than 1.5 times HL.Basal half of anterior margin of dorsal-fin spine bearing two rows of small, blunt projections.Spine margin smooth or finely serrated distally.Posterior margin of spine with few, short, medial, obliquely distally-directed serrae; serrae proportionally longer in nuptial males.Dorsal-fin rays II,6.Adipose fin relatively small.Anal-fin base approximately 0.24-0.27 of SL.Anal-fin origin located distinctly posterior of middle of SL and at, or slightly posterior of, middle of TL.Anal-fin margin straight, with first ray longest and subsequent rays becoming progressively shorter, but with anterior rays in nuptial males extending beyond margin of rest of fin.Last anal-fin ray without membranous attachment to caudal peduncle.Anal-fin rays iii,20 to iii,26 (Table 1).

O F S
Distal margin of pelvic fin broadly convex with third branched ray longest.Pelvic-fin insertion at middle of SL.Tip of adpressed pelvic fin falling short of anal-fin origin.Pelvicfin rays i,8 (Table 1).
Pectoral fin with strong spine serrated along entire length of both margins.Serrae antrorse along anterior margin of spine and retrorse along posterior margin.Anterior pectoral-fin rays longest.Fin margin straight anteriorly and convex along posterior rays.Pectoral-fin rays typically I,8, rarely I,7 or I,9 (Table 1).
Pigmentation pattern in alcohol.Overall ground coloration most often grayish, with overall coloration darker on dorsal portion of head and body and in some individuals on midlateral portion of body posterior of head in region overlying swim bladder.Overall pigmentation pattern less intense in some individuals, most notably those from some locations in western portions of species distribution, albeit without any distinct geographic pattern to differences in coloration.Abdomen unpigmented.Snout, upper lip, and region ventral of margin of lower lip very dark in many, but not all, specimens.
Lateral and dorsolateral surface of body with several series of vertically-aligned, unpigmented, rounded spots of size most often approximately equal to one-fifth to one-quarter width of pupil or smaller.These series begin most often under, but in some individuals somewhat anterior of, base of dorsal-fin spine and extend posteriorly to beyond posterior terminus of base of adipose fin.Spots often difficult to discern in specimens of overall light ground pigmentation.Midlateral surface of body with irregular longitudinal series of unpigmented spots extending from rear of head to posterior margin of caudal peduncle.Unpigmented spots coalesce in some individuals into larger spots of irregular form.Region anterior of vertical of pelvic-fin origin and ventral of midlateral series of unpigmented spots with few, scattered, unpigmented spots.
Patch of dark to very dark pigmentation typically present anterior to base of dorsal fin.First and second interradial membranes of dorsal fin dark distally.Adipose fin with dark basal spot continuous with dark pigmentation of body in most individuals, other specimens with diffuse batch of dark chromatophores basally that do not form distinct spot.Caudal fin distinctly dusky basally and continuing pigmentation of body.Region of dark pigmentation on base of caudal fin with distinct, straight to slightly irregular, posterior margin; margin somewhat anteroventrally inclined.Some specimens with small, unpigmented spots within dusky, basal pigmentation field in region overlying central rays.
Basal region of dark caudal-fin pigmentation followed by hyaline region and then vertical band of less intense dark pigmentation along distal margin of fin.Anal fin with variably developed dark pigmentation.Some individuals with distinctly darker basal band on caudal fin formed of dark chromatophores comparable in size and form to those on adjoining region of body; when present, darker field of pigmentation often extending more distally on dorsal rays of mature males.Other individuals with less developed dark pigmentation continuous across fin.Most specimens with distal portions of fin darker than middle sections of rays.Dorsal surface of pelvic fin with diffuse dark pigmentation in some individuals, but without distinct patch of dark pigmentation.Distal portion of fin with dark pigmentation in most individuals.Margins and sometimes dorsal surface of pectoral-fin spine dark.Pectoral-fin rays variably outlined with dark chromatophores.
Color pattern in life.Dark pigmentation as in preserved specimens.Lateral and posterodorsal surface of head along with lateral surface of anterior portion of body, dorsolateral surface of body and basal one-half of caudal fin with variably intense yellowish coloration.Yellow coloration also apparent on basal one-half of dorsal-fin spine and rays and on adipose fin (Fig. 2).
Sexual dimorphism.Auchenipterichthys coracoideus demonstrates sexual dimorphism in the length of the dorsal spine and anterior rays of the anal fin as discussed above (see Figs. 3 and 4).
Distribution.Tocantins River, central and upper portions of Amazon River, and Essequibo River basins (Fig. 5).

P R O O F S
Fig. 4. Auchenipterichthys coracoideus, AMNH 12700, 100 mm SL, nuptial male; Brazil, rio Livramento, tributary of rio Madeira (7°17'S, 62°22'W).Posterior rays of anal fin folded over, which gives an incorrect impression of the fin margin.Remarks.Auchenipterichthys coracoideus was originally described as a species of Trachycorystes by Eigenmann & Allen (1942: 120) without a discussion of the basis for that generic assignment; however, the species is clearly a species of Auchenipterichthys.Auchenipterichthys coracoideus has been repeatedly misidentified as A. thoracatus by various authors who applied that name to samples of the genus with exposed coracoids that originated across the Amazon basin (see synonymies for those two species).All population samples of A. thoracatus examined in this study originated in a relatively restricted region in the upper portions of the Madeira River in eastern Bolivia and southwestern Brazil (Fig. 10; dots).We consequently treat all reports of A. thoracatus from the portions of the Amazon basin outside of the upper Madeira River system as A. coracoideus, which has a wide distribution across that river basin (Fig. 5).
In addition to the difference in the number of anal-fin rays between Auchenipterichthys coracoideus and A. thoracatus, the two species appear to differ in the shape of the head and the angle of divergence of the exposed portion of the coracoids.The ventral margin of the head of A. coracoideus is nearly horizontal, in contrast to the more oblique aspect of that region in A. thoracatus.The contralateral coracoids diverge more posteriorly in A. coracoideus, whereas they are more nearly parallel in A. thoracatus (see Figs. 1a-b).However, we found it impossible to quantify these differences sufficiently well to include them in the diagnoses of the respective species.Mees (1974: 36) Kner, 1857), Fisher, 1917: 424 [specimen from Manáos (=Manaus, Brazil)].-Mees, 1974: 38 [Fisher (1917)  Diagnosis.A species of Auchenipterichthys with coracoid bone covered with thick integument and not exposed ventrally (Fig. 1c), an emarginate or truncate caudal-fin margin, 25 or fewer branched anal-fin rays (modally 21; Table 1), nine (rarely eight) branched pelvic-fin rays (Table 1), the anterior teeth on premaxilla not visible when the mouth is closed, and the body pigmentation pattern not consisting of distinct dark spots on a gray background.Auchenipterichthys longimanus is most similar in appearance to A. punctatus, which differs from A. longimanus primarily in having dark spots that cover much of dorsolateral surface of the body.The possession of a coracoid bone that is not exposed ventrally (Fig. 1c), the anterior teeth on the premaxilla that are not visible when the mouth is closed, and nine (rarely eight) branched pelvic-fin rays (Table 1) distinguishes A. longimanus from its other two congeners, A. coracoideus and A. thoracatus, which have coracoids that are exposed ventrally (Figs.1a-b) rather than covered by a thick layer of integument, the anterior teeth on the premaxilla visible when mouth is closed and, typically eight branched pelvic-fin rays.
Description.Body depth at dorsal-fin origin 0.22-0.25 of SL and equal to, or slightly greater than, body width at cleithrum.Body depth at anal-fin origin 0.25-0.27 of SL and nearly equal to HL. Body compressed, with width at anal-fin origin approximately 0.48-0.51 of body depth at that point.Ventral surface of coracoids not exposed on ventral surface of body (see Fig. 1c).Lateral line complete and midlateral.Canal having irregular zigzag pattern, with oblique posteriorly-directed branches off main canal.Lateral line canal extending short distance onto, and directed posteriorly or obliquelyposterodorsally on, caudal-fin base.Head depressed anteriorly; depth of head at vertical through middle of orbit greater than distance from middle of eye to dorsal midline of head.Head length 0.25-0.27 of SL.Dorsal profile of head broadly convex anteriorly and then straight or very slightly convex from vertical running through Branchiostegal membrane broadly attached to isthmus; ventral margin of gill opening extending to vertical approximately one orbit length posterior of rear margin of orbit.
Mouth terminal.Anterior teeth on premaxilla not visible from ventral view when mouth closed.Teeth on premaxilla minute and arranged in band.Band consisting of approximately eight irregular series of teeth at symphysis and of ten irregular series laterally.Dentary teeth slightly larger than those on premaxilla, with approximately six series of teeth at symphysis that decrease to one tooth row posterolaterally.
Dorsal-fin origin at 0.31-0.34 of SL.Length of dorsal-fin base slightly less than one-half length of first branched dorsal-fin ray.Dorsal-fin spine pungent, with slightly curved, convex anterior margin.Length of dorsal-fin spine approximately equal to distance between anterior nares and posterior margin of opercle, without elongation apparent in examined mature males.Anterior surface of dorsal-fin spine with

O F S
single series of relatively well-developed, antrorse serrae extending nearly to tip of spine.Posterior margin of spine with medial row of retrorse serrae extending nearly to tip of spine.Serrae on posterior surface of spine shorter than those on anterior surface in juveniles and females; posterior serrae on distal portion of spine proportionally longer in mature males.Dorsal-fin rays II,6.Adipose fin relatively small.Caudal fin emarginate to obliquely truncate, with dorsal lobe longer than ventral lobe.Principal caudal-fin rays i,7,8,i.
Anal-fin base approximately 0.22-0.24 of SL and slightly shorter than HL.Anal-fin origin located distinctly posterior of middle of SL and slightly posterior of middle of TL.Analfin margin straight, with first ray longest and subsequent rays becoming progressively shorter, but with anterior rays in mature males extending slightly beyond margin of rest of fin.Last anal-fin ray without membranous attachment to caudal peduncle.Anal-fin rays typically iii,18 to iii,23 (iii,25 in one of 87 specimens; Table 1).
Distal margin of pelvic fin broadly convex, with third branched ray longest.Pelvic-fin insertion slightly posterior of middle of SL.Tip of adpressed pelvic fin barely reaching anal-fin origin.Pelvic-fin rays typically i,9, rarely i,8 (Table 1).
Pectoral fin with strong spine serrated along entire length of both margins with antrorse serrae along anterior margin and retrorse serrae along posterior margin.Anterior pectoral-fin rays longest.Fin margin straight anteriorly and convex along posterior rays.Pectoral-fin rays I,7, or I,8, rarely I,9 (Table 1).
Pigmentation pattern in alcohol.Overall ground coloration ranging from light to dark brown, with overall ground coloration darker on dorsal portion of head and body and in some individuals on midlateral portion of body posterior of head in region overlying swimbladder.Abdomen unpigmented.Snout and upper lip darkly pigmented to some degree in all specimens.Lower lip with curved patch of dark coloration along margin in more darkly pigmented individuals.
Lateral surface of body with small, unpigmented, rounded spots of approximately one-fifth width of pupil or sometimes smaller.Number and distribution of unpigmented spots varies greatly in different population samples, with spots and their arrangement difficult to discern in some individuals, particularly those of fainter overall coloration.Unpigmented spots in some individuals form variably-developed row or sometimes narrow band along midlateral region of body from rear of head to hypural joint, but with anterior and posterior portions of such row or band variably present in different specimens.Individual spots or series of vertically-aligned spots present on dorsolateral portion of body in region from vertical through base of rear of dorsal fin, or posterior of that point, to area under base of adipose fin.Some specimens, often those with very dark overall pigmentation, with individual spots or series of vertically-aligned spots present on dorsolat-eral portion of body from vertical through base of rear of dorsal fin, or posterior of that point, to area under base of adipose fin.Number of such unpigmented spots highly variable in different specimens, with spots nearly completely absent in some individuals.
Dorsal fin with dark pigmentation on distal portion of first (lightly pigmented individuals) or first and second (more darkly pigmented individuals) interradial membranes.Adipose fin dusky to dark.Caudal fin ranges from dusky basally and lighter posteriorly to dark overall with little decrease in degree of pigmentation posteriorly.Some specimens with small white spots within dark, basal pigmentation field in region overlying central rays.Anal fin with variably developed dark pigmentation basally.Such pigmentation more obvious in overall more darkly pigmented individuals.Dorsal surface of pelvic fin hyaline or with diffuse field of small, dark chromatophores in darker individuals with chromatophores not, however, forming distinct spot.Margins and sometimes dorsal surface of pectoral-fin spine dark; interradial membranes with diffuse fields of small, dark chromatophores.
Maxillary and mandibular barbels typically hyaline, but with few small, dark chromatophores present in overall darkly pigmented individuals.
Sexual dimorphism.Although a number of mature males of 126 to 140 mm SL (as indicated by the possession of an elongated urogenital tube adhering to the anterior margin of the anal fin) were examined, none demonstrated an elongation of the dorsal-fin spine beyond the condition present in females of comparable sizes.It is uncertain whether this observation reflects the absence of sexual dimorphism in the species or the lack of nuptial males in the available samples.Serrae on the posterior surface of the distal one-half of the dorsal-fin spine are proportionally longer in mature males than they are in juveniles and females.
Distribution.Orinoco River basin in Venezuela, lower and middle portions of Amazon and Tocantins Rivers in Brazil (Fig. 7).

Diagnosis.
A species of Auchenipterichthys with coracoid bone overlain by thick layer of skin ventrally and not visible ventrally (see Fig. 1c), an emarginate or obliquely truncate caudal-fin margin, 21 to 24 branched anal-fin rays (Table 1), nine branched pelvic-fin rays (Table 1), the anterior teeth on the premaxilla not visible in the closed mouth, and a pattern of body pigmentation consisting of variablysized spots of dark pigmentation scattered over the dorsal and lateral surface of the body and fins.Auchenipterichthys punctatus is most similar in appearance to A. longimanus, which differs from A. punctatus primarily in lacking distinct, dark spots covering the head or body.
Auchenipterichthys punctatus is readily distinguished from its other two congeners, A. coracoideus and A. thoracatus, which have coracoids that are covered ventrally only by a thin layer of integument and appear to be exposed to the surface (Figs.1a-b), the anterior teeth on premaxilla are visible in the closed mouth and, typically, eight (rarely nine) branched pelvic-fin rays (Table 1).
Description.Body depth at dorsal-fin origin 0.25-0.27 of SL and equal to, or slightly greater than body width at cleithrum.Body depth at anal-fin origin approximately 0.25 of SL and equal to HL. Body compressed, with width at anal-fin origin slightly less than one-half of body depth at that point.Ventral surface of coracoids not exposed on ventral surface of body (Fig. 1c).Lateral line complete and midlateral.Canal having irregular zigzag pattern, with oblique posteriorly-directed branches off main canal.Lateral line canal extending short distance onto caudal fin base and branched with both obliquely posterodorsal and obliquely posteroventral branches.Head depressed anteriorly; height of head at vertical through middle of orbit greater than distance from middle of eye to dorsal midline of head.Head length 0.23-0.26 of SL.Dorsal profile of head broadly convex anteriorly and then straight or very slightly convex from vertical running through anterior margin of orbit to dorsal-fin origin.Distance from midpoint of snout to anterior margin of orbit approximately 1.5 times horizontal diameter of orbit.Snout margin broadly rounded from dorsal view.Interorbital width approximately 0.57-0.65 of HL and approximately equal to distance from middle of eye to posterior margin of opercle.Eye large, lateral, and visible in both dorsal and ventral views.Orbit distinctly ovoid with horizontal axis longer.
Barbels slender and thread-like.Maxillary barbel long, extending posteriorly slightly past middle of length of cleithral spine.Medial mandibular barbel originating immediately posterior of lower lip; adpressed barbel extending posteriorly to point slightly past transverse plane through origin of lateral mandibular barbel.Lateral mandibular barbel originating in plane slightly anterior of vertical through middle of orbit and extending posteriorly approximately to transverse line through pectoral-spine origin.
Branchiostegal membrane broadly attached to isthmus; ventral margin of gill opening extending to vertical approximately one orbit length posterior of rear margin of orbit.
Mouth terminal.Anterior teeth on premaxilla not visible from ventral view of closed mouth.Teeth on premaxilla minute and arranged in band.Band consisting of approximately eight irregular series of teeth at symphysis and of ten irregular series laterally.Dentary teeth slightly larger than those on premaxilla, with approximately six series of teeth at symphysis that progressively decrease to one tooth row posterolaterally.Caudal fin emarginate to obliquely truncate with dorsal lobe longer than ventral lobe.Principal caudal-fin rays i,7,8,i.
Anal-fin base approximately 0.23-0.26 of SL and approximately equal to HL. Anal-fin origin located distinctly posterior of middle of SL and slightly posterior of middle of TL.Anal-fin margin straight, with first ray longest and subse-quent rays becoming progressively shorter.Last anal-fin ray without membranous attachment to caudal peduncle.Analfin rays iii,21 to iii,24 (Table 1).
Distal margin of pelvic fin broadly convex, with third branched ray longest.Pelvic-fin insertion situated at middle of SL.Tip of adpressed pelvic fin extending posterior of analfin origin and approximately to base of first branched anal-fin ray.Pelvic-fin rays i,9 (Table 1).
Pectoral fin with strong spine serrated along entire length of both margins with antrorse serrae along anterior margin and retrorse serrae along posterior margin.Anterior pectoral-fin rays longest.Fin margin straight anteriorly and convex along posterior rays.Pectoral-fin rays I,8 (Table 1).ing narrow, irregularly-margined, horizontal stripe.Lateral and dorsolateral surface of body with series of unpigmented, rounded spots of size most often approximately equal to one-fifth of width of pupil or smaller.Lateral surface of body ventral of lateral line tan to light brown and overlain by variably sized and distributed spots of dark pigmentation.Dark spots proportionally larger in small specimens.Abdomen and lower portion of head posterior of lateral mandibular barbel pale.Margin of lower lip darkly pigmented.First, second, and sometimes third interradial membranes of dorsal fin dark distally with remainder of fin in larger individuals with scattered, dark spots similar in size to those on lateral surface of body.Adipose fin generally dark with single darker subterminal spot within field of dark pigmentation, but with pale margin.Caudal fin typically dark on basal portion of rays and membranes, with dark basal region bordered by lighter, near vertical band, and distal tip of fin somewhat darker than coloration of vertical band.Spots of darker pigmentation scattered over all of fin; spots on basal onehalf of fin larger than those on remainder of fin.Ground coloration of anal fin comparable to that of adjoining ventral portion of body, but with broad, darker, distal margin on fin.Anal fin with scattered, small, darker spots over entire surface.Ground coloration of pelvic fin comparable to that of adjoining portions of body; with small, scattered, darker spots throughout.Pectoral fin darkly pigmented on distal portions of first two interradial membranes and generally lighter across remainder of fin.Pectoral spine dark along entire dorsal surface.

Pigmentation pattern in
Maxillary and lateral mandibular barbels darkly pigmented throughout.Medial mandibular barbel more lightly pigmented.
Color pattern of juvenile specimens similar to that described above, but patterning bolder and spots proportionally larger than those found in adults (Fig. 8).

Sexual dimorphism.
No nuptial males were examined in the course of this study and as such it is uncertain whether Auchenipterichthys punctatus demonstrates the sexually-dimorphic features occurring in some congeneric species.Soares-Porto (1994: 285) noted that the males she examined in her description of A. dantei did not demonstrate any sexual differences relative to females other that for their urogenital modifications.
Distribution.Examined specimens originated in the upper portions of the Orinoco and Negro River basins in Venezuela and the central portions of the Amazon River basin in Brazil (Fig. 10; triangles).Soares-Porto (1994, fig. 6) also examined material of the species that originated along the length of the Brazilian portion of the Negro River.
Remarks.Auchenipterus punctatus appears not to have been cited in the literature following its description by Valenciennes (in Cuvier & Valenciennes, 1840) until it was discussed by Royero & Hureau (1996), who first recognized that it represented a species of Auchenipterichthys.Perhaps as a consequence of that situation, this species was subsequently redescribed as A. dantei by Soares-Porto (1994).
Description.Body depth at dorsal-fin origin 0.25-0.29 of SL and slightly greater than width at cleithrum.Body depth at anal-fin origin 0.27 of SL.Body compressed, with width at anal-fin origin 0.38-0.40 of body depth at that point.Ventral surface of coracoids exposed on ventral surface of body (see Fig. 1b).Lateral line complete and midlateral.Canal having irregular zigzag pattern, with oblique, posteriorly-directed branches off main canal.Lateral line canal extending short distance onto, and directed obliquely-posterodorsally on, caudal-fin base.Head depressed anteriorly; height of head at vertical through middle of orbit approximately equal to distance from middle of eye to dorsal midline of head.Dorsal profile of head broadly convex anteriorly and then slightly concave from vertical running through anterior margin of orbit to dorsal-fin origin.Distance from midpoint of snout to anterior margin of orbit approximately equal to horizontal diameter of orbit.Snout margin broadly rounded from dorsal view.Interorbital width approximately 0.65-0.70 of HL and approximately equal to distance from middle of eye to posterior margin of opercle.Eye large, lateral, and visible in both dorsal and ventral views.Orbit distinctly ovoid with horizontal axis longest.
Barbels slender and thread-like.Maxillary barbel long, extending posteriorly slightly past margin of opercle.Medial mandibular barbel originating immediately posterior of lower lip; adpressed barbel extending posteriorly only to vertical through transverse plane through lateral mandibular barbel.Lateral mandibular barbel originating in plane slightly anterior of vertical through middle of orbit and extending posteriorly approximately to anterior portion of exposed cleithrum.
Branchiostegal membrane broadly attached to isthmus;

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ventral margin of gill opening extending to anterior margin of exposed portion of cleithrum.Mouth terminal, but with upper jaw extending very slightly beyond margin of lower jaw.Anterior teeth on premaxilla visible from ventral view in closed mouth.Teeth on premaxilla minute and arranged in band.Band consisting of approximately eight irregular series of teeth at symphysis and of ten irregular series laterally.Dentary teeth slightly larger than those on premaxilla, with approximately six series of teeth at symphysis that progressively decrease to one tooth row posterolaterally.
Dorsal-fin origin at 0.36-0.39 of SL.Length of dorsal-fin base approximately one-half of length of first branched dorsal-fin ray.Dorsal-fin spine pungent with slightly convexly curved anterior margin.Length of dorsal spine approximately equal to HL in specimens of both sexes.Basal one-half of anterior margin of dorsal-fin spine bearing two rows of small, blunt projections with spine margin smooth or finely serrated distally.Posterior margin of spine with few, short, medial, obliquely distally-directed serrae.Dorsal-fin rays II,6.Adipose fin relatively small.
Anal-fin base approximately 0.28-0.31 of SL.Anal-fin origin located distinctly posterior of middle of SL and slightly anterior of middle of TL.Anal-fin margin straight, with first ray longest and subsequent rays becoming progressively shorter.Last anal-fin ray without membranous attachment to caudal peduncle.Anal-fin rays iii,25 to iii,28 (Table 1).
Distal margin of pelvic fin broadly convex with middle branched ray longest.Pelvic-fin insertion situated anterior of middle of SL.Tip of adpressed anal fin falling short of anal-fin origin.Pelvic-fin rays typically i,8, rarely i,9 or i,10 (Table 1).
Pectoral fin with strong spine serrated along entire length of both margins with antrorse serrae along anterior margin and retrorse serrae along posterior margin.Anterior pectoralfin rays longest.Fin margin straight anteriorly and convex along posterior rays.Pectoral-fin rays typically I,8, infrequently I,7 (Table 1).
Pigmentation pattern in alcohol.Overall ground coloration ranging from brown to dark brown, with coloration darker on dorsal portion of head and body and in some individuals on midlateral portion of body posterior of head in region overlapping swimbladder.Abdomen unpigmented.Snout, upper lip, and region ventral of margin of lower lip very dark.Patch of very dark pigmentation present anterior to base of dorsal fin.Lateral and dorsolateral surface of body with series of unpigmented spots of size approximately equal to one-quarter width of pupil or smaller.Unpigmented spots arranged in several series.Midlateral surface of body with irregular longitudinal series of light spots extending from rear of head to posterior margin of caudal peduncle.Anterior portion of this midlateral series overlies several series of approximately vertically-aligned pairs of unpigmented spots.Dorsolateral surface of body with irregularly spaced, vertically-aligned series of unpigmented spots; these series begin under, or posterior of, base of dorsal fin and typically extend posteriorly to beyond base of adipose fin, but in some individuals continue posteriorly to rear of caudal peduncle.Dorsal fin-rays dark distally.Adipose fin with dark basal spot continuous with dark pigmentation of body.Caudal fin dark basally with pigmentation continuing that of body.Some specimens with small, unpigmented spots within dark basal pigmentation field in region overlying central caudal-fin rays.Darkly pigmented region with distinct, straight to slightly irregular, posterior margin; margin of dark pigmentation ranges from approximately vertical to somewhat anteroventrally inclined.Dark region at base of caudal fin followed posteriorly by hyaline region and then by band of less intense dark pigmentation along distal margin of fin.Anal fin with variably developed dark pigmentation basally.Distal margin of dark pigmentation usually of irregular form, but sometimes smoothly convex.Dorsal surface of basal portion of pelvic fin with variably dark patch of pigmentation.Distal portion of fin with dark pigmentation in most individuals; pigmentation intense in well pigmented specimens.Margins and sometimes dorsal surface of pectoral fin spine dark; fin rays variably outlined with dark chromatophores.
Sexual dimorphism.Although a number of mature males of Auchenipterichthys thoracatus of 94 to 109 mm SL (as indicated by the possession of an elongated urogenital tube adhering to the anterior margin of the anal fin) were examined, none demonstrated an elongation of the dorsal-fin spine beyond the condition present in females of comparable sizes.It is uncertain whether this observation reflects the absence of sexual dimorphism in the species or the lack of nuptial males in the available samples.Serrae on the posterior surface of the distal one-half of the dorsal-fin spine are proportionally longer in mature males than they are in juveniles and females of the species.
Distribution.Upper portions of the Madeira River basin in Bolivia and Brazil (Fig. 10; dots).
Various authors have misidentified samples of Auchenipterichthys coracoideus as A. thoracatus as is well exemplified in the synonymies for both of these species.One of the major consequences of the failure to discriminate these two species was the erroneous broad purported range for A. thoracatus that was thought to range across major portions of the Amazon River basin.Our results rather indicate that A. thoracatus is limited to the upper portions of the Madeira River basin in southwestern Brazil and eastern Bolivia (Fig. 10, dots); with A. coracoideus having an extensive distribu-

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tion along the length of the Amazon River basin into the Tocantins River system and upper portions of the Essequibo River basin in Guyana (Fig. 5).
anterior margin of orbit posteriorly as far as dorsal-fin origin.Distance from midpoint of snout to anterior margin of orbit approximately 1.5 times horizontal diameter of orbit.Snout margin broadly rounded from dorsal view.Interorbital width approximately 0.65-0.68 of HL and approximately equal to distance from middle of eye to posterior margin of opercle.Eye large, lateral, and visible in both dorsal and ventral views.Orbit distinctly ovoid with horizontal axis longer.Barbels slender and thread-like.Maxillary barbel very long, extending posteriorly nearly to posterior tip of cleithral spine.Medial mandibular barbel originating immediately posterior of lower lip; adpressed barbel extending posteriorly to point slightly short of vertical through transverse plane through origin of lateral mandibular barbel.Lateral mandibular barbel originating in plane slightly anterior of vertical through middle of orbit and extending posteriorly approximately to transverse line through pectoral-spine origin.