Neoplecostomus altimontanus Uzeda, Paiola, Cesar, Okubo, Marques-Frisoni, Andrade & Langeani, 2024, new species

Neoplecostomus altimontanus, new species urn:lsid:zoobank.org:act: BD8EC52A-FBE3-47BD-BA8D-4CD1D62B22CE (Figs. 1–7; Tab. 1) Holotype. DZSJRP 24792, male, 90.2 mm SL, Brazil, Minas Gerais, Itamonte, rio Grande sub-basin, rio Sapucaí drainage, rio Capivari at Engenho da Serra district, 22º21’04.38”S 44º47’11.66”W, 1.357 m a.s.l., 12 Aug 2023, P. L. C. Uzeda & L. Sartori. Paratypes. All from Brazil, Minas Gerais, Itamonte, rio Grande sub-basin, rio Sapucaí drainage, rio Verde microbasin. Rio Capivari, affluent to rio Verde: CI-UFLA 1785, 2, 71.4–76.8 mm SL, DZSJRP 24793, 5, 52.5–93.2 mm SL (1 c&s, 85.5 mm SL), collected with the holotype. Instituto Alto-Montana da Serra Fina, Albert Heilmann waterfall at Córrego Pinhão Assado. CI-UFLA 2176, 35, 25 unmeasured, 10, 51.1–88.6 mm SL, DZSJRP 24794, 17, 54.8–93.5 mm SL, 22º21’22.21”S 44º47’50.73”W, 1.427 m a.s.l., Dec 2010, P. Pompeu, R. Loures, N. Tadini & C. Gandini. Diagnosis. Neoplecostomus altimontanus differs from all congeners, except N. bandeirante and Neoplecostomus sp. n. (described below), by having the exposed area of the first plates of mid-ventral and ventral series narrower than the naked area surrounding each plate (vs. all other congeners with exposed area of first plates of mid-ventral and ventral series equal to or wider than the naked area surrounding each plate) (Fig. 2). Furthermore, the new species differs from all congeners, except N. jaguari, N. langeanii, and N. sp. n., by presenting sexual dimorphism in dentition, with males having more robust and fewer teeth compared to females (Fig. 3) (vs. tooth morphology and number similar in both sexes in all other congeners). Additionally, N. altimontanus differs from N. bandeirante by the absence of azygous pre-adipose plates (vs. presence); from N. jaguari by having one or two posteronasal plates (vs. 5–7); from N. langeanii by the presence of an extra canal-bearing plate between supraopercle and dorsal opening of preopercular canal (Fig. 4) (vs. extra canal-bearing plate absent). Neoplecostomus altimontanus is most similar to Neoplecostomus sp. n., from which differs by having conspicuous dark spots over body and fins (vs. transverse light bars); presence of slightly hypertrophied odontodes on the posterior portion of the plates of dorsal, mid-dorsal, median and mid-ventral series, resembling discontinuous keels on caudal peduncle (vs. odontodes on caudal-peduncle plates roughly equal in size; caudal-peduncle surface smooth and rounded in cross-section) (Fig. 5); well-developed adipose fin, extending over four or five dorsal plates, usually five (vs. reduced adipose fin, extending over three or four plates, usually three) (Fig. 5); absence of a lateronasal plate (vs. lateronasal plate present) (Fig. 6); smaller nares (nare length 3.0–9.0% vs. 9.9–14.1% of HL); and by the higher premaxillary (31–42, modally 35 vs. 24–33, modally 26) and dentary (31–40, modally 31 vs. 22–31, modally 26) teeth counts in females. Description. Measurements and counts in Tab. 1. Body elongated and depressed. Greatest width at anterior portion of cleithrum, gradually narrowing towards caudal peduncle. Dorsal profile of body slightly convex, rising from snout tip to dorsal-fin origin, descending to procurrent rays of caudal fin. Body deepest at dorsal-fin origin. Trunk rounded and caudal peduncle polygonal in cross-section. Ventral profile depressed to origin of anal fin, slightly rounded to caudal fin. Body entirely covered with bony plates, except around dorsal-fin origin, ventral surface of head, lateral portion of trunk between pectoral and pelvic-fin base, and around ventral shield. Presence of minute keels on dorsal, mid-dorsal, lateral, and mid-ventral series of plates; exposed area of first plates on mid-ventral and ventral series narrower than naked areas surrounding each plate. Abdomen with small plates covered with odontodes, arranged into pentagonal to hexagonal shield between pectoral- and pelvic-fin origins. Head broad and rounded. Snout tip naked, without bony plates. Lateral margins of head and snout lacking hypertrophied odontodes and swollen skin. Interorbital region slightly convex in frontal view. Eyes dorsolaterally located and moderate sized. Head naked ventrally, except for cheek plate, not divided and with mesial projection. Extra canal-bearing plate between supraopercle and compound pterotic. Lips moderately developed and rounded; posterior margin of lower lip slightly convex, reaching or almost reaching pectoral girdle. Lower lip covered with small rounded papillae; two or three series of hypertrophied papillae immediately posterior to dentary teeth. Dentary rami angled towards each other at about 110º–115º. Maxillary barbel poorly developed, entirely coalesced to lower lip. All teeth bicuspid e copper colored; lateral cusp smaller than mesial cusp. Dorsal fin ii,7, originating slightly posterior to vertical through pelvic-fin origin. Spinelet always present and larger than base of unbranched ray; locking mechanism not functional. Posterior margin straight and roughly emarginate, reaching vertical through anal-fin origin when adpressed. Adipose fin well developed, extending over four or five dorsal plates; preadipose azygous plates absent; adipose-fin spine homogeneously covered with odontodes. Pectoral fin i,6; unbranched ray dorsoventrally depressed, curved posteriorly and shorter than first branched ray; posterior margin straight, surpassing first third of pelvic fin when adpressed. Pelvic fin i,5; unbranched ray slightly curved inwards; ventral surface flattened and covered with spatulate odontodes. Anal fin i,5; unbranched ray covered with small odontodes, except for naked area on anterior surface; posterior margin straight. Caudal fin i,7,7,i; inferior lobe longer than superior lobe; posterior margin concave. Supraorbital sensory canal with four pores; pore s1 at anteromesial margin of anterior nare; pore s3 at posteromesial margin of posterior nare; pore s6+s6 at interorbital region, approximately near middle of eye length in transverse line; pore s8 located posteromesially to eye, longitudinally aligned to nares. Infraorbital sensory canal with six pores; pore io1 at anterior margin of first infraorbital; pore io2 between posterior margin of first infraorbital and anterior margin of second infraorbital; pore io3 between second and third infraorbitals; pore io4 between third and fourth infraorbitals; io5 between fourth and fifth infraorbitals; io6 between superior margin of fifth infraorbital and inferior margin of sphenotic. Preoperculomandibular sensory canal with four pores; pore pm1 on ventral margin of cheek plate, pore pm2 between superior margin of cheek plate and inferior margin of preopercle; pore pm3 between superior margin of preopercle, and inferior margin of supraopercle; pore pm5+po1 rising on surface of extra canal-bearing plate. Three postotic sensory pores; pore po1 fused to pore pm5; pore po2 above branchial slit, and pore po3 on skin overlying opening of swim-bladder capsule. Coloration in alcohol. Coloration variable; body normally covered with dark spots bigger than eye diameter and fainted vermiculations over brownish to grayish background (see Discussion for comments on coloration patterns). Dark spots over fin rays, forming three to four diffuse bars; interradial membranes hyaline in life (Fig. 7). Juveniles present four conspicuous transverse light bars on dorsal region of body, located at predorsal region, dorsal-fin base, region between dorsal and adipose fin, and between adipose and caudal fin. Coloration in alcohol similar to that in life, but with slightly less contrasting patterns. Sexual dimorphism. Males have a urogenital papilla posterior to anal opening and a skin flap along the dorsal surface of unbranched pelvic-fin ray (both absent in females). Additionally, males have teeth short, robust and fewer in number (17–22 premaxillary and 12–19 dentary teeth) compared to females, which have slender and more numerous teeth (31–42 premaxillary and 31–40 dentary teeth). Geographical distribution. The new species is known from two streams on the northern slope of Serra da Mantiqueira, southeastern Brazil. These two streams are located in the rio Capivari within rio Verde microbasin, affluent to rio Sapucaí, rio Grande sub-basin, upper rio Paraná basin. The headwaters of rio Sapucaí are separated from those of the rio Paraíba do Sul basin by Serra da Mantiqueira, and the localities of N. altimontanus are situated approximately four kilometers from the latter basin (Fig. 8). Ecological notes. Neoplecostomus altimontanus is found in environments typically inhabited by members of Neoplecostomini: streams with shallow depth (<1 m), crystal clear water, high flow, low temperature and high oxygen levels. Specimens were more frequently captured at the portions with highest water flow, where small waterfalls are formed. The two streams where the species is known to occur have relatively high slope and drain valleys on the foothill of Parque Nacional do Itatiaia, at altitudes between 1.300 and 1.500 m above sea level, and are mainly composed of big boulders with sandy substrate. The localities mostly presented pristine riparian covering of upper montane Atlantic Forest, with high abundance of Bryophytes, Pteridophytes, and Orchidaceae associated to trees and exposed stones (Fig. 9). The aforementioned features make the streams to receive few moments of direct sunlight during the day. The only sympatric species found with N. altimontanus at the two localities was Trichomycterus (Paracambeva) sp. The invasive rainbow trout, Oncorhynchus mykiss (Walbaum, 1792), was also found in the type-locality, probably due to the high density of trout farms implemented along Serra da Mantiqueira. Etymology. The specific epithet “altimontanus” is given in reference to the Upper Montane Atlantic Forest (Mata Atlântica Alto-Montana in Portuguese), a vegetation type only found in few mountain