Aspidoras aldebaran, Tencatt & Britto & Isbrücker & Pavanelli, 2022

Tencatt, Luiz Fernando Caserta, Britto, Marcelo R., Isbrücker, Isaäc Jan Hendrik & Pavanelli, Carla Simone, 2022, Taxonomy of the armored catfish genus Aspidoras (Siluriformes: Callichthyidae) revisited, with the description of a new species, Neotropical Ichthyology (e 220040) 20 (3), pp. 1-159 : 9-23

Aspidoras aldebaran , new species urn:lsid:zoobank.org:act:E3ABD342-36E5-49EA-B86A-00EC247315AF

( Fig. 2 )

Aspidoras taurus (non Lima, Britto, 2001 ): — Lima, Britto, 2001:1011 (paratypes of Aspidoras taurus ; partim).

Holotype. LIRP 16933 , 30.0 mm SL, Brazil, Mato Grosso State, Alto Araguaia Municipality, ribeirão do Sapo, upstream the Couto de Magalhães Waterfall , rio Araguaia basin, 17°31’10”S 53°15’33”W, 7‒8 Aug 2002, A. L. A. Melo and L. S. F. Martins.

Paratypes. All from Brazil , Mato Grosso State , Alto Araguaia Municipality , except when indicated. Rio Paraguay basin. CPUFMT 700 , 11 , 21.5‒28.8 mm SL, córrego Pinguelinha, 17°19’17”S 53°34’55”W, 18 Nov 2010, F. Machado and A. Ribeiro .

CPUFMT 703 , 3 , 15.1‒29.7 mm SL, córrego Pinguela , 17°18’37”S 53°32’23”W, 18 Nov 2010 , F. Machado and A. Ribeiro. CPUFMT 724 , 1 , 15.7 mm SL, córrego São José , 17°26’26”S 53°37’44”W, 18 Nov 2010 , F. Machado and A. Ribeiro. MZUSP 41417 , 2 , 19.2‒27.1 mm SL, córrego da Pinguela , 17°18’37”S 53°32’22”W, 9 Mar 1989 , L. P. S. Portugal and F. Langeani. MZUSP 41488 , 2 , 27.2‒27.4 mm SL, córrego do Mato , 9 Mar 1989 , L.P.S. Portugal and F. Langeani. Rio Araguaia basin. LIRP 4477 , 1 , 23.7 mm SL, Goiás State , Santa Rita do Araguaia Municipality, rio Araguaia, 17°19’42”S 53°13’00”W, 5‒7 Aug 2002 , A. L. A. Melo and L. S. F. Martins. MZUSP 41404 , 22 , 15.1‒22.6 mm SL, córrego do Rancho , approx. 17°15’S 53°23’W, 8 Mar 1989 , L. P. S. Portugal and F. Langeani. MZUSP 73248 , 1 , 16.3 mm SL, córrego Gordura , 17°18’20”S 53°16’22”W, 15 May 2001 , C. L. R. Moreira and F. C. T. Lima . MZUSP 73278 , 8 , 10.4‒33.1 mm SL, stream tributary to the córrego Gordura , 17°17’55”S 53°16’34”W, 17 May 2001 , C. L. R. Moreira and F. C. T. Lima . MZUSP 73261 , 6 , 15.7‒22.8 mm SL, stream tributary to the córrego Gordura , 17°19’02”S 53°15’49”W, 16 May 2001 , C. L. R. Moreira and F. C. T. Lima . MZUSP 73265 , 24 , 10.5 ‒25.0 mm SL, córrego Boiadeiro , 17°20’01”S 53°14’52”W, 16 May 2001 , C. L. R. Moreira and F. C. T. Lima . MZUSP 73283 , 1 , 12.1 mm SL, stream tributary to the córrego Gordura 17°17’42”S 53°17’12”W, 17 May 2001 , C. L. R. Moreira and F. C. T. Lima . MZUSP 73293 , 4 , 14.3‒22.7 mm SL, stream tributary to the córrego Boiadeiro , 17°20’31”S 53°14’41”W, 18 May 2001 , C. L. R. Moreira and F. C. T. Lima . MZUSP 73302 , 3 , 22.1‒31.7 mm SL, stream tributary to the córrego Tapera , 17°21’58”S 53°14’51”W, 18 May 2001 , C. L. R. Moreira and F. C. T. Lima . MZUSP 73306 , 1 , 19.0 mm SL, córrego Tapera , 17°22’19”S 53°14’30”W, 18 May 2001 , C. L. R. Moreira and F. C. T. Lima . MZUSP 73331 , 6 , 12.3 ‒18.0 mm SL, córrego do Sapinho , 17°25’35”S 53°14’20”W, 21 May 2001 , C. L. R. Moreira and F. C. T. Lima . CITL 381 , 5 , 24.9–29.6 mm SL ; LIRP 4437 , 34 of 36, 10.6‒30.5 mm SL, 2 CS of 36, 25.0‒ 25.6 mm SL; LIRP 4494 , 26 of 28, 14.7‒27.6 mm SL, 2 CS of 28, 26.0‒27.0 mm SL; NUP 23487 , 5 , 22.4–26.9 mm SL, collected with the holotype .

Diagnosis. Aspidoras aldebaran can be distinguished from its congeners, with exception of A. belenos , A. kiriri , and A. raimundi , by having parapophysis of the complex vertebra well developed (vs. moderately developed in A. depinnai , A. lakoi , A. maculosus , A. mephisto , A. poecilus , A. psammatides , and A. velites ; poorly or moderately developed in A. albater and A. fuscoguttatus ; poorly developed in A. azaghal ); it can be distinguished from A. belenos , A. kiriri , and A. raimundi by having inner laminar expansion of infraorbital 1 ranging from well developed to extremely well developed (vs. moderately developed). Additionally, it can be distinguished from A. albater , A. azaghal , A. gabrieli , A. lakoi , A. mephisto , A. psammatides , and A. rochai by having a narrow frontal bone, with width slightly smaller than half of entire length (vs. relatively wide, with width equal to or slightly larger than half of entire length in A. albater , A. azaghal , A. gabrieli , A. lakoi , A. mephisto , and A. rochai ; extremely narrow, with width conspicuously smaller than half of entire length in A. psammatides ); from A. azaghal , A. depinnai and A. kiriri by the presence of small black spots on dorsal fin (vs. absence).

Description. Morphometric data presented in Tab. 2. Head compressed with convex dorsal profile; somewhat trapezoid in dorsal view. Snout moderately developed and pointed; variably relatively well developed. Head profile convex from tip of snout to anterior nares; region of mesethmoid slightly concave in some specimens; ascending slightly convex from this point to dorsal-fin origin. Dorsal margin of orbit slightly elevated in some specimens. Profile nearly straight to slightly convex along dorsal-fin base. Postdorsal-fin body profile slightly concave to adipose-fin spine; slightly concave from this point to caudal-fin base. Ventral profile of body slightly convex from isthmus to pelvic-fin origin; region of gill opening slightly concave in some specimens; nearly straight from this point to anal-fin origin; slightly concave until caudal-fin base. Body roughly elliptical in cross section at pectoral girdle, gradually becoming more compressed toward caudal fin.

Eye rounded, located dorso-laterally on head; orbit delimited dorsally by lateral ethmoid, frontal and sphenotic, ventrally by infraorbitals. 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 equal to or slightly smaller than naris diameter. Mouth small, subterminal, width slightly larger than bony orbit diameter. Maxillary barbel moderate in size, not reaching anteroventral limit of gill opening. Outer mental barbel slightly larger than maxillary barbel. Inner mental barbel fleshy, with base slightly separated from its counterpart. Lower lip moderately developed, forming small semicircular or triangular fleshy flap. Small, rounded papillae covering entire surface of all barbels, upper and lower lips, snout and isthmus.

Mesethmoid short; anterior tip poorly developed, slightly smaller than 50% of bone length (see Britto, 2003:123, ch. 1, state 1; fig. 1B); posterior portion wide, partially exposed. Nasal slender, curved laterally, inner margin with moderately developed laminar expansion; outer margin with reduced laminar expansion; mesial border contacting frontal and mesethmoid.

Frontal elongated, narrow, with width slightly smaller than half of entire length ( Fig. 3A ); anterior projection ranging from short, with size smaller than nasal length, to long, with size slightly larger than nasal length; anterior margin generally exposed. Frontal fontanel relatively small, ellipsoid or somewhat rhomboid; posterior tip extension not entering anterior margin of parieto-supraoccipital. Sphenotic somewhat trapezoid, contacting parieto-supraoccipital dorsally, pterotic-extrascapular posteriorly, second infraorbital ventrally and frontal anteriorly. Pterotic-extrascapular roughly pipe-shaped, with posteriormost portion contacting first lateral-line ossicle, and ventral margin contacting opercle and cleithrum; posterior expansion almost entirely covering lateral opening of swimbladder capsule, leaving slender pseudotympanic area on dorsal margin covered only by thick layer of skin. Parieto-supraoccipital wide, posterior process strongly reduced to poorly developed, not contacting nuchal plate. Parieto-supraoccipital medial keel expanded ventrally; laminar, with posterior portion at same level as posterior process tip; expanded posteriorly in some specimens, slightly surpassing tip of posterior process. Parieto-supraoccipital fontanel small, roundish; located medially on parieto-supraoccipital.

Two laminar infraorbitals with minute odontodes; infraorbital 1 large, ventral laminar expansion poorly to moderately developed; anterior portion with laminar expansion ranging from poorly developed, slightly surpassing posterior margin of nasal capsule, to moderately developed, reaching middle of nasal capsule ( Fig. 4 ); inner laminar expansion ranging from well developed to extremely well developed ( Fig. 5A,B ); small portions of external surface covered by thick layer of skin; infraorbital 2 small, slender; with posterior laminar expansion generally poorly developed; inner laminar expansion ranging from moderately to well developed; posteroventral margin close but not directly contacting posterodorsal ridge of hyomandibula; contacting in some specimens; dorsal tip contacting only sphenotic; small portions of external surface covered by thick layer of skin ( Fig. 4 ). Posterodorsal ridge of hyomandibula, close to its articulation with opercle, oblong, relatively slender; exposed, bearing small odontodes; dorsal ridge of hyomandibula, between pterotic-extrascapular and opercle, covered by thick layer of skin. Interopercle entirely covered by thick layer of skin; with posterior portion variably exposed; somewhat triangular, anterior projection moderately developed. Preopercle relatively slender, elongated, minute odontodes sparse on external surface. Opercle compact in shape, width larger than half of its length; free margin convex; posterodorsal region variably with smoothly concave area; without serrations and covered by small odontodes; some portions of bony distal margin irregular in some specimens.

Four branchiostegal rays decreasing in size posteriorly. Hypobranchial 2 somewhat triangular, tip ossified and directed towards anterior portion, posterior margin cartilaginous; ossified portion well developed, about twice size of cartilaginous portion. Five ceratobranchials with expansions increasing posteriorly; ceratobranchial 1 with strongly reduced process on anterior margin of mesial portion; process variably absent; ceratobranchial 3 with continuous postero-lateral margin; ceratobranchial 5 toothed on postero-dorsal surface, 20 to 26 (4) teeth aligned in one row. Four epibranchials with similar size; epibranchial 2 slightly larger than others, with strongly reduced pointed process on laminar expansion of posterior margin; process variably absent; epibranchial 3 with triangular uncinate process on laminar expansion of posterior margin. Two wide pharyngobranchials (3 and 4), pharyngobranchial 3 with triangular laminar expansion on posterior margin; triangular laminar expansion with notches in some specimens. Upper tooth plate oval, with 23 to 31 (4) teeth aligned in two rows on postero-ventral surface.

Lateral-line canal entering neurocranium through pterotic-extrascapular, branching twice before entering sphenotic: pterotic branch with single pore; preoperculomandibular branch conspicuously reduced, with single pore opening close to postotic main canal; more developed, with pore opening closer to anteroventral border of pterotic-extrascapular in some specimens; postotic main canal widens just posterior to pterotic branch. Sensory canal continuing through pterotic-extrascapular, entering sphenotic as temporal canal, which splits into two branches: one branch giving rise to infraorbital canal, another branch entering frontal through supraorbital canal, both with single pore. Supraorbital canal branched, running through nasal bone. Epiphyseal branch of supraorbital canal relatively long, with pore opening close to frontal fontanel; or slightly shorter, with pore opening closer to supraorbital main canal. Nasal canal with three openings, first on posterior edge, second on posterolateral portion and third on anterior edge; second pore generally fused with first pore. Infraorbital canal running through entire second infraorbital, extending to infraorbital 1 and opening into two or three 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 somewhat triangular, located just posterior to third dorsolateral body plate. Dorsal-fin rays II,7(1), II,8*(19), posterior margin of dorsal-fin spine smooth. Nuchal plate moderately developed in length; almost entirely exposed, with minute odontodes on exposed area; anterior tip covered by thick layer of skin ( Fig. 6 ); spinelet short, partially exposed; spine relatively well developed, adpressed distal tip reaching or surpassing posterior origin of dorsal-fin base; anterior margin with small odontodes. Pectoral fin roughly triangular, its origin just posterior to gill opening. Pectoral-fin rays I,7(1), I,8*(19); posterior margin of pectoral spine with 21 to 27 moderately-developed serrations along almost its entire length; small region just posterior to origin of spine lacking serrations; some serrations directed towards origin of spine, perpendicularly directed or directed towards tip of spine; presence of bifid serrations in some specimens; base of branched rays with reduced laminar expansions on inner margin, generally more evident on first rays; laminar expansions variably with irregular margins ( Fig. 7 ). Anteroventral portion of cleithrum partially exposed; posterolateral portion of scapulocoracoid reduced, externally visible. Pelvic fin oblong, located just below third ventrolateral body plate, and at vertical through second dorsal-fin branched ray. Pelvic-fin rays I,5*(20). Adipose fin roughly triangular, separated from posterior origin of dorsal-fin base by seven or eight dorsolateral body plates. Anal fin somewhat triangular, located just posterior to 12 th or 13 th ventrolateral body plates, and at vertical through region of preadipose platelets. Anal-fin rays, ii,5(3), ii,4,i(2), ii,6(2), ii,5,i*(13). Caudal-fin rays I,11,I(1), I,12,I*(19), four or five dorsal and/or ventral procurrent rays; caudal fin bilobed, dorsal and ventral lobes generally with similar size; dorsal lobe variably slightly larger than ventral lobe.

Two or three laterosensory canals on trunk; first ossicle tubular, second ossicle laminar, third lateral-line canal, if present, encased in third dorsolateral body plate. Body plates with conspicuous line of relatively large odontodes confined to posterior margins; dorsolateral body plates 24(5), 25*(12), 26(3); ventrolateral body plates 21(1), 22*(13), 23(6); dorsolateral body plates along dorsal-fin base 5(2), 6*(15), 7(3); dorsolateral body plates between adipose-fin spine and caudal-fin base 7(13), 8*(7); preadipose platelets 2(2), 3*(8), 4(9), 5(1); small platelets covering base of caudal-fin rays; small platelets disposed dorsally and ventrally between junctions of lateral plates on posterior portion of caudal peduncle. Ventral surface of trunk naked.

Vertebral count 23(4); ribs 6(3), 7(1), first pair conspicuously large; parapophysis of complex vertebra well developed ( Fig. 8A ).

Coloration in alcohol. Ground color of body light or brownish yellow, with top of head dark brown. Posterodorsal portion of head, region below eye, opercle and cleithrum with scattered dark brown or black chromatophores. Snout covered dark brown or black chromatophores on its dorsal surface; chromatophores densely disposed in some specimens; generally forming dark brown or black rounded, striated or irregular relatively large spots; or forming conspicuously smaller spots; generally, with dark brown or black diffuse or conspicuous stripe from anteroventral portion of orbit to upper lip lateral area; ventrolateral portion of snout with dark brown or black chromatophores, variably forming spots, in some specimens. Upper lip and maxillary barbel with dark brown or black chromatophores; area of lateral portion of upper lip generally with conspicuous concentration of dark brown or black chromatophores; outer mental barbel with dark brown or black chromatophores, generally more evident on its proximal portion; region of isthmus around lower lip with dark brown or black chromatophores in some specimens. Dorsal series of four to five dark brown or black blotches, first on anterior portion of dorsal-fin base, second on posterior portion of dorsal-fin base, third, if present, between dorsal and adipose fins, fourth on adipose-fin base, and fifth on caudal-fin base; blotches variably diffuse. Dorsal portion of body with conspicuous concentration of dark brown or black chromatophores between counterparts of dorsolateral body plates in some specimens. Ventral surface of trunk, generally on region close to pectoral- and pelvic-fin origins, and region posterior to urogenital opening with dark brown or black chromatophores in some specimens. First dorsolateral body plate with conspicuous concentration of dark brown or black chromatophores; posterior margin of some dorso- and ventrolateral body plates, and lateral line pores with conspicuous concentration of dark brown or black chromatophores in some specimens. Midline of flank with longitudinal series of three to six medium-sized conspicuous dark brown or black blotches; blotches rounded, oblong or irregular; blotches variably fused, forming longitudinally elongated bars. Dorsal half of dorsolateral body plates with dark brown or black chromatophores; region of anterior and posterior portions of dorsal-fin base, between dorsal and adipose fins, adipose-fin base, and base of caudal peduncle with more concentrated chromatophores, forming conspicuous blotches in some specimens; blotches variably fused to flank midline blotches. Ventral half of dorsolateral body plates and dorsal half of ventrolateral body plates with concentration of dark brown or black chromatophores, forming conspicuous blotches in some specimens; blotches generally more evident on anterior portion of body and on area of flank midline blotches. Mid-ventral portion of ventrolateral body plates on area of flank midline blotches with concentration of dark brown or black chromatophores, generally forming conspicuous blotches; blotches generally more evident posteriorly to pelvic-fin origin; variably fused to flank midline blotches; ventral portion of ventrolateral body plates with concentration of dark brown or black chromatophores, generally more evident posterior to anal-fin anterior origin, in some specimens. Dorsal fin with dark brown or black spots; aligned spots, forming oblique bars in some specimens; membranes with dark brown or black chromatophores, generally more evident on region of first and second branched rays proximal portion; dorsal-fin base with conspicuous concentration of dark brown or black chromatophores, generally more concentrated on bases of first and last branched rays; spine covered by dark brown or black chromatophores. Pectoral fin with dark brown or black chromatophores on its dorsal surface, generally more evident on spine and branched rays; conspicuous concentration of dark brown and black chromatophores on proximal portion of branched rays; covered by dark brown or black spots in some specimens; spots aligned, forming oblique bars in some specimens; spots variably diffuse or more evident on first branched rays; region of body around dorsal portion of pectoral-fin origin generally with concentration of dark brown or black chromatophores. Pelvic fin with conspicuous concentration of dark brown or black chromatophores on its dorsal surface, generally forming one to three oblong dark brown or black patches; anteriormost patch generally larger and more intensely pigmented; region of body around dorsal portion of pelvic-fin origin with concentration of dark brown or black chromatophores in some specimens. Adipose-fin membrane with dark brown or black chromatophores; conspicuous concentration of dark brown or black chromatophores in some areas of membrane, generally more evident close to spine, forming isolated patches in some specimens; adipose-fin spine generally with dark brown or black chromatophores. Anal fin with conspicuous concentrations of dark brown or black chromatophores in some areas, generally more evident on its middle portion and bases of last branched rays; variably forming one to three dark brown or black blotches. Middle portion of caudal-fin base, posteriorly to last flank midline blotch, generally with small- to medium-sized dark brown or black blotch; blotch variably diffuse or fused with last midlateral blotch. Caudal fin with three to six transversal dark brown or black slender to wide bars.

Coloration in life. Similar to that observed in preserved specimens but with clearer ground color of body. Iris orangish brown. Body covered with whitish yellow and green iridescent coloration ( Fig. 9A ).

Geographical distribution. Aspidoras aldebaran is known from the upper rio Araguaia basin in Goiás and Mato Grosso states, and upper rio Paraguay basin in Mato Grosso State, Brazil ( Fig. 10 ).

Ecological notes. The córrego Gordura, where some of the paratypes were collected, is a medium-sized tributary to the upper rio Araguaia basin with highly transparent and clear water, width ranging from less than one meter to about 15 m, and depth ranging from about 10 cm to nearly two meters. Aspidoras aldebaran was found in shallow (up to about 20 cm) stretches in the upper portion of the córrego Gordura, with moderate current and substrate composed mainly by sand and gravel ( Fig. 9B ). At this site, the species was found in syntopy with Aspidoras velites , Characidium sp. , and Hypostomus cf. careopinnatus Martins, Marinho, Langeani & Serra, 2012 . Aspidoras aldebaran and A. velites were placed in a small biotope aquarium (i.e., one that recreates the natural habitat) to record their color pattern in life. During this event, a specimen of A. velites displayed an aggressive behavior towards an A. aldebaran specimen, chasing and pushing it throughout the aquarium. The A. aldebaran specimen did not react aggressively but tried to evade the assaults by the A. velites specimen. Interestingly, A. aldebaran is generally larger and a clearly more robust species than A. velites . In nature, such confrontations seem unlikely considering that the new species was generally found associated with the sandy substrate of small shores whereas A. velites was most commonly captured in areas associated with marginal and/or submerged vegetation.

Etymology. The epithet “ aldebaran ” refers to the red giant Aldebaran or Alpha Tauri (α Tauri), the brightest star of the Taurus constellation, deriving from the Arabic al Dabarān, which means “the follower”. The star presents a bright orange glow and it is positioned at the left eye of the mythological bull. The name alludes to the fact that A. aldebaran was firstly found among Aspidoras taurus type series (see Remarks below), being promptly recognized as a different and new species by its peculiar morphology and color pattern. A noun in apposition.

Conservation status. The Extent of Occurrence of A. aldebaran was estimated to be

864 km 2. Additionally, the species is known only from two relatively small subareas,

one of them with streams draining to the rio Araguaia basin, and the other one with streams draining to the rio Paraguay basin. Although the number of specimens in fish collections is relatively large, the region where the new species was found, the Southern portion of the border between Mato Grosso and Goiás states, close to Mato Grosso Sul State limits, is severely impacted by anthropic action, especially for agricultural and cattle raising purposes. Therefore, it is expected that such a relatively restricted species, essentially inhabiting headwater streams, will be negatively affected in the near future. According to the International Union for Conservation of Nature (IUCN) categories and criteria (IUCN Standards and Petitions Subcommittee, 2019), Aspidoras aldebaran can be classified as Near Threatened (NT), approximating the Endangered (EN) category by criterion B1b(iii).

Remarks. The analysis of the Aspidoras taurus type series revealed the presence of two species, one that included the holotype of A. taurus , and a second one under the vouchers MZUSP 41404, MZUSP 41417 and MZUSP 41488, which is clearly distinct from all congeners (see Diagnosis). Although Lima, Britto (2001:1011) stated that A.

taurus only occurs in the upper rio Paraguay basin, the data available for MZUSP 41404

showed that its collecting site, the do Rancho Stream, is in fact a tributary to the upper rio Araguaia basin, and not upper rio Paraguay basin, as stated by the authors.

As explained by Tencatt, Evers (2016:20), the C- and CW-number coding system was implemented by the fishkeeping hobby for putative new species to avoid the creation of nomina nuda in taxonomy. The species coded as CW141 is said to be from the same area as A. aldebaran , the rio Araguaia basin at Alto Araguaia, Mato Grosso, and strikingly resembles the new species. Therefore, considering the clear compatibility between locality data and general morphology and color pattern, we attribute CW141 to A. aldebaran .

Figures

FIGURE 2 | Aspidoras aldebaran, holotype, LIRP 16933,30.0 mm SL, Brazil, Mato Grosso State, Alto Araguaia Municipality, ribeirão do Sapo, upstream Couto de Magalhães Waterfall. Dorsal (top), lateral (middle) and ventral (bottom) views. Photos by Celso Ikedo.

FIGURE 3 | Dorsal view of the head of CS specimens showing the three patterns of paired frontal bones (outlined in black) in Aspidoras: (A) narrow, with width of each frontal slightly smaller than half of its entire length (Aspidoras maculosus, UFBA 3291, 30.7 mm SL), (B) relatively wide, with width equal to or slightly larger than half of entire length (Aspidoras albater, MZUSP 40793, 29.4 mm SL), and (C) extremely narrow, with width clearly smaller than half of entire length (Aspidoras psammatides, UNT 9604, 27.3 mm SL). Scale bars = 1 mm.

FIGURE 4 | Lateral view of the head of CS paratype of Aspidoras aldebaran, LIRP 4494, 27.0 mm SL, showing general pattern of infraorbitals. Abbreviations: io1: infraorbital 1, io2: infraorbital 2, sph: sphenotic, pes: pteroticextrascapular. Scale bar = 1 mm.

FIGURE 5 | Dorsal view of the infraorbital series of CS specimens showing the four patterns of size and shape of the inner laminar expansion of infraorbital 1 (white arrows) in Aspidoras: (A) extremely well developed (Aspidoras albater, MNRJ 13080, 30.9 mm SL), (B) well developed (Aspidoras fuscoguttatus, NUP 12677, 36.1 mm SL), (C) moderately developed (Aspidoras poecilus, UNT 6249, 30.9 mm SL), and (D) poorly developed (Aspidoras psammatides, UNT 9604, 27.3 mm SL). Abbreviations: io1: infraorbital 1, io2: infraorbital 2. Scale bars = 1 mm.

FIGURE 6 | Aspidoras aldebaran, LIRP 4494, CS paratype, 27.0 mm SL, showing predorsal region of trunk in dorsal view. Dotted lines indicate the limits of the tip of the posterior process of the parieto-supraoccipital and anterior tip of the nuchal plate. Abbreviations: np: nuchal plate, pso: parieto-supraoccipital. Scale bar = 1 mm.

FIGURE 7 | Aspidoras aldebaran, LIRP 4494, CS paratype, 27.0 mm SL, showing dorsal view of the pectoral fin. Arrows indicate the reduced laminar expansions at the base of branched rays. Scale bar = 1 mm.

FIGURE 8 | Ventral view of the complex vertebra in CS specimens of (A) Aspidoras belenos, paratype, UFRJ 4419 (ex-UFRJ 3861), 22.1 mm SL, with well-developed parapophysis, (B) Aspidoras albater, MNRJ 12571, 35.3 mm SL, with poorly-developed parapophysis, and (C) Aspidoras albater, MNRJ 12581 (disarticulated, indeterminate size), with moderately-developed parapophysis. Abbreviations: ccv: centrum of the complex vertebra, pcv: parapophysis of the complex vertebra. Scale bars = 1 mm.

FIGURE 9 | Aspidoras aldebaran, uncataloged specimen photographed alive (A), and the córrego Gordura, rio Araguaia basin, showing the typical habitat of the new species (B). Photos by Hans Evers.

FIGURE 10 | Map showing the geographical distribution of Aspidoras albater (type locality: red circle; non-type localities: black circles), A. aldebaran (type locality: red star; non-type localities: white stars), A. azaghal (purple triangle), A. belenos (type locality: purple diamond), A. brunneus (possible region of type locality: grey diamond), A. carvalhoi (type locality: purple circle), A. depinnai (type locality: red square; nontype localities: black squares), A. fuscoguttatus (type locality: red triangle; non-type localities: white triangles), A. gabrieli (type locality: red pentagon; non-type locality: white pentagon), A. kiriri (black cross), A. lakoi (type locality: red diamond; non-type locality: black diamond), A. maculosus (red cross), and A. mephisto (type locality: white cross). Each symbol may represent more than one locality.