Leporinus lignator, Boaretto & Ohara & Souza-Shibatta & Olivan Birindelli, 2024

Leporinus lignator , new species urn:lsid:zoobank.org:act:2BD29D53-528F-47CE-A69E-649E8658675A

( Fig. 5; Tab. 5)

Holotype. MZUEL 21727, 152.96 mm SL, Igarapé Vasquin , a tributary of Comemoração River , Machado River drainage, Madeira River basin, 12°12’18”S 60°37’23”W, Pimenta Bueno, Rondônia, Brazil, 25 Jan 2022, W. M. Ohara. GoogleMaps

Paratypes. All from Brazil, Madeira River basin . MCP 41342 View Materials , 1 View Materials , 92.0 mm SL, São Domingos River, tributary of Guaporé River, 12°03’18”S 63°59’51”W, São Domingos do Guaporé , Rondônia, 16 Jul 2004 GoogleMaps , R. E. Reis, F. Langeni , F. C . T. Lima, and E. H. L. Pereira . MZUEL 21726 , 5 , 91.74–117.01 mm SL; 1 CS, 91.74 mm SL, collected with holotype. NUP 7736, 1, 132.6 mm SL, 10°06’35”S 59°26’12”W, tributary of Guaribal River, Aripuanã River basin, Aripuanã , Mato Grosso, 19 May 2008 GoogleMaps , I. M. Fernandes. MNRJ 36227 View Materials , 1 View Materials , 78.1 mm SL, Aripuanã River, below Cachoeira de Dardanelos, 10°09’43”S 59°26’31”W, Aripuanã , Mato Grosso, 27 Oct 2007 GoogleMaps , F. Pupo. ZUEC-PIS 10514 , 2,65.1– 78.1 mm SL mm SL, Aripuanã River, below Cachoeira de Dardenelos, 10°09’43”S 59°26’31”W, Aripuanã , Mato Grosso, 7 Oct 2004 GoogleMaps , F. A. Machado et al.

Diagnosis. Leporinus lignator is distinguished from all other anostomids except L. affinis , L. altipinnis , L. bleheri , L. desmotes , L. enyae , L. fasciatus , L. jatuncochi , L. pearsoni , L. tigrinus , L. villasboasorum , and L. y-ophorus, by having dark vertical bars encircling the body in adults and nine branched pelvic-fin rays (vs. horizontal bars, dark blotches or dark transversal bars not encircling the body, and eight branched pelvic-fin rays). Leporinus lignator is distinguished from the formers except for L. bleheri and L. tigrinus by having three unicuspid teeth on the premaxillary and four on the dentary (vs. 3/3 or 4/4). Leporinus lignator is distinguished from L. bleheri and L. tigrinus by having 12 scales around the caudal peduncle (vs. 16).

Description. Morphometric and meristic values in Tab. 5. Small-sized species for the genus, largest examined specimen 153.0 mm SL. Greatest body depth at dorsal-fin origin. Body rounded, slightly robust. Dorsal profile convex from snout tip to dorsal-fin origin, somewhat concave from dorsal-fin insertion to adipose-fin origin, then distinctly concave to caudal fin. Ventral profile convex from lower jaw to anal-fin origin, concave from anal fin to caudal fin. Three teeth on premaxillary and four on dentary, stair-like,

unicuspid, and incisiform. Lateral line complete from supracleithrum to caudal-fin base.

Dorsal-fin origin slightly anterior to middle of body. Adipose fin small, rounded, origin slightly behind anal-fin origin. Pectoral-fin origin at opercle border. Pelvic-fin origin slightly anterior to body middle. Anal-fin origin ahead of adipose-fin origin. Caudal fin forked, dorsal lobe a bit longer.

Osteology. Infraorbital series composed of six infraorbitals, nasal, antorbital, and supraorbital, all plate-like ( Fig. 6A). Antorbital without canal, as long as first infraorbital,

C-shaped and inclined relative to horizontal body axis, with small plate-like lamina.

Nasal large, with a canal and two intermediate pores. Supraorbital located posteriorly to nasal and much smaller than latter, with no canals. First infraorbital somewhat triangular, immediately ventral to antorbital, with a small quadripartite canal located on anteriormost portion of plate-like bone. Second infraorbital triangular, with canal extended on middle of bone and bearing two intermediate pores. Third infraorbital largest, axe-shaped, with canal bearing an intermediate pore close to anteriormost opening. Fourth infraorbital somewhat rectangular, with canal bifurcate at dorsal portion and horizontal branch extended to posterior edge of bone. Fifth infraorbital with straight canal bearing a tiny branch at midlength. Sixth infraorbital smallest, beanshaped, bearing Y-shaped canal.

Premaxillary bone trapezoidal with rounded borders, bearing three unicuspid incisiform teeth, decreasing gradually in size laterally ( Figs. 6C–D). Maxillary bone located on posterolateral edge of premaxillary, positioned vertically relative to body axis, with acute dorsal end and enlarged ventral portion. Lower jaw trapezoidal, larger, and more rounded than premaxillary. Dentary with four unicuspid incisiform teeth, decreasing gradually in size laterally. Fourth dentary tooth considerably smaller than anteriormost ones. Retroarticular tiny; anguloarticular with dorsal portion slightly expanded and curved anteriorly, but not dorsally surpassing dorsal limit of dentary.

Suspensorium L-shaped, laterally compressed and with horizontal portion longer than vertical one ( Fig. 6G). Autopalatine bearing a large and rounded anterodorsal process, ectopterygoid vertically aligned and constricted near its dorsal edge. Entopterygoid small, associated with quadrate, metapterygoid, ectopterygoid and autopalatine. Metapterygoid large, dorsal to quadrate, forming an irregular fenestra with quadrate. Metapterygoid-quadrate fenestra shaped as a fallen eight, with a median constriction. Quadrate large and triangular. Symplectic elongate and thin. Hyomandibular large, bearing a pointy process on ventral-anterior margin anteriorly-directed towards quadrate. Preopercle large and L-shaped, with a horizontal ventrolateral shelf. Two small canal-like bones between preopercle and lower jaw. Interopercle and subopercle small. Opercle large, posterior margin rounded, resembling a semicircle.

Mesethmoid triangular, anteriorly forming attachment site for premaxillae ( Figs. 7A–C). Anterior and posterior cranial fontanel large and wide, encased by mesethmoid, frontals, parietals, and supraoccipital. Frontal large, rectangular-shaped. Lateral ethmoid long with a distinct ventrally-directed triangular process. Parietal wide, much shorter than frontal. Sphenotic and pterotic sightly triangular and forming ventrolateral acute projections of the neurocranium. Supraoccipital C-shaped anteriorly and with small triangular process on posterior border. Epiotic bears three distinct bony bridges at posterior border of neurocranium, exoccipital posterior to it. Vomer triangular in ventral view, rounded borders. Parasphenoid long and thin, extended from vomer to basioccipital and bearing two posteriorly elongated horizontal processes ventral to basioccipital. Orbitosphenoid, pterosphenoid, and prootic dorsal to parasphenoid, ventral to frontal and parietal, forming the ventral wall of the braincase. Basioccipital thin and rounded, posterior to prootic and ventral to exoccipital.

Hyoid arch composed of dorsal and ventral hypohyals, anterior and posterior ceratohyals, urohyal, interhyal, and four branchiostegals ( Fig. 8A). Branchiostegals long and thin, spatula-shaped, three articulated to posterior ceratohyal, and last articulated with anterior ceratohyal. Branchial apparatus composed of basihyal, three basibranchials, three hypobranchials, five ceratobranchials, four epibranchials, and four pharyngobranchials ( Figs. 8C–D). Basihyal long and thin, with a toothplate on anterior margin and posteriorly connected to the first basibranchial. Basibranchials rod-like, connected by cartilage to hypobranchials, which are square-shaped with rounded borders, also connected to ceratobranchials by cartilage. Four ceratobranchials long, rod-like, with small rakers on anterior and posterior margins, and the fifth ceratobranchial with rakers only on anterior margin, bearing a tooth plate on lenticular posterior expansion with two irregular rows of approximately ten acicular teeth. Four epibranchials, with the fourth bearing a tooth plate with two irregular rows of around eight acicular teeth, connected by cartilage to ceratobranchials and pharyngobranchials.

Dorsal fin with two unbranched and ten branched rays ( Fig. 9A), first pterygiophore inserted between neural spines of 9 and 10 vertebral centra. Pelvic bone supporting a pelvic splint, one unbranched ray, and nine branched rays; ischiatic process elongated ( Fig. 9C).

Anal fin with two unbranched and nine branched rays ( Fig. 10A), first pterygiophore inserted between haemal spines of 25 and 26 vertebral centra. Pectoral fin connected to neurocranium through extrascapular and posttemporal, with one unbranched plus thirteen to fifteen branched rays ( Fig. 10C). Cleithrum large and somewhat triangular, with a small bump on anterior margin. Coracoid rectangular with triangular posterior process. Scapula large and somewhat triangular. Three postcleithra present, first rounded, posterior to cleithrum, second triangular, posterior to cleithrum and scapula, third largest with ventrally-directed thin process.

Caudal skeleton comprises a compound center, pleurostyle, three epurals, two uroneurals, opisthural cartilage, parhypural, and six hypurals ( Fig. 11A). Parhypural, first and second hypurals on lower lobe. Opisthural cartilage, uroneurals, epurals, pleurostyle, and four hypurals on upper lobe.

Coloration in alcohol. Body with a light tan background and dark brown vertical bars. Two bars on head, nine bars on trunk. First bar at snout, second along eyes, third at opercle, fourth and fifth before dorsal-fin origin, connected only in their middle portion, forming an “X”. Sixth bar at dorsal fin and seventh bar posterior to dorsal fin,

also connected only at their middle portion forming an “X”. Eighth bar between dorsal fin and adipose fin, bifurcated dorsally, “V” shaped. Ninth bar at adipose fin and tenth bar between adipose and caudal fins, connected only at their middle portion, forming an “X”. Eleventh bar on caudal peduncle separated from ninth bar. Dorsal and adipose fins dark brown at base, adipose fin with a dark strip at tip, yellow in middle. Pelvic and anal fins with a dark brown stripe in middle, yellow at base. Caudal fin slightly yellow at base ( Figs. 5A–B).

Coloration in life. Live specimens yellowish, slightly darker dorsally than ventrally.

Dark black vertical bars conspicuous. Dorsal fin dark at base. Adipose fin black at base and tip, yellow in-between. Pelvic and anal fin with a black strip in the middle, yellow at the base. Caudal fin slightly yellow at the base ( Fig. 5C).

Geographical distribution. Leporinus lignator is only known from the tributaries of the Madeira drainage, including the Guaporé, the Aripuanã, and the Machado basins in the Amazon basin ( Fig. 12).

Etymology. The specific epithet, lignator , is allusive to its type-locality, the Machado

River, part of the Madeira River basin. In Portuguese, Machado means axe, and Madeira means wood. Lignator is Latin (m.) for a lumberjack who cuts trees into logs, often using axes. A noun in apposition.

Ecological notes. The type-locality of Leporinus lignator is a clear water stream, 3–5 m wide, 0.3–1.8 m deep, with rocks, pebbles, sand bottoms, and riparian vegetation, located at 300 m altitude ( Fig. 5). Sintopic species included Ancistrus verecundus Fisch-Muller, Cardoso, da Silva & Bertaco, 2005 , Cichlasoma boliviense Kullander, 1983 , Moenkhausia mikia Marinho & Langeani, 2010 , Moenkhausia cf. pankilopteryx Bertaco & Lucinda, 2006 .

Conservation status. Leporinus lignator is known only from a few specimens collected in a few sites, all of which are located in areas relatively well-preserved and close to several preservation areas, including the Parque do Aripuanã, the Parque Estudual de Corumbiara, and many indigenous regions. Therefore, although the species distribution is poorly known, we suggest that the conservation status of Leporinus lignator is likely to be Least Concern (LC) at this moment, according to IUCN criteria (IUCN, 2022).