Pariolius maldonadoi, Faustino-Fuster & López-Castaño & Quiñones & Meza-Vargas, 2024

Faustino-Fuster, Dario R., López-Castaño, Jeisson A., Quiñones, Jhonatan M. & Meza-Vargas, Vanessa, 2024, Increasing the species diversity of the monotypic genus Pariolius Cope 1872 (Siluriformes: Heptapteridae) after more than 150 years, Zootaxa 5433 (3), pp. 389-403 : 396-399

Pariolius maldonadoi new species

urn:lsid:zoobank.org:act:13482E78-62CF-494C-B942-87BB3836BA72

(Figs. 10 a–c, Tables 1 , 2 )

Holotype. MHNU-I 3257 , 29.9 mm SL, Colombia, Guaviare State, Retorno Municipality, Caño Potosí, tributary of the Inírida River , Orinoco River basin, 2°10’50.8”N; 72°38’48.8”W, 27 February 2021, J. M. Vásquez-Ramos, M. A. Cortés-Hernández, J. M. Quiñones-Montiel, Y. A. Rojas-Molina, J. A. López-Castaño.

Paratype. Thirty specimens, all from Colombia: Amazon River basin: Guaviare State: MPUJ 13074 , 11, 19.3–38.8 mm SL, Calamar Municipality, Caño Bálsamo , tributary of the Unilla River , Upper Negro River , 1°57’59.0”N; 72°37’16.5”W, 11 January 2017, C. Moreno-Arias. Orinoco River basin: Meta State: IAvH-P-16263 , 1, 22.5 mm SL, La Macarena Municipality, unnamed creek tributary to El Silencio Lake , Guayabero River , 02°14’57.5”N; 73°45’33.8”W, 28 October 2016, L. Mesa Salazar, C. A. Lasso, P. Herrera. IAvH-P-16293 , 1, 26.6 mm SL, La Macarena Municipality, Canoas creek, tributary to Guayabero River , 02°28’29.8”N; 73°44’33.2”W, 31 October 2016, C. A. Lasso, M. Morales-Betancourt, P. Herrera. Guaviare State: MPUJ 13075 , 1, 33.5 mm SL, El Retorno Municipality, Caño Platanales, tributary of Inírida River , 2°10’50.81”N; 72°38’48.80”W, 11 January 2011, C. Moreno-Arias. MPUJ 13076 , 5, 23.2–35.4 mm SL, El Retorno Municipality, Caño Blanco, tributary of the Inírida River , 2°11’1.72”N; 72°41’26.99”W, 12 January 2017, C. Moreno-Arias. MPUJ 13077 , 5, 17.8–27.3 mm SL, El Retorno Municipality, Caño Potosí, tributary of the Inírida River , 2°12’18.40”N; 72°38’14.71”W, 12 January 2017, C. Moreno-Arias. MHNU-I 3250 , 6, 20.7–32.6 mm SL, same data as holotype. MUSM 71200 , 2, 20.5–28.5 mm SL, same data as holotype .

Genseq-2 coI. GenBank accession number. Obtained from paratypes MUSM 71200 (PP057715).

Diagnosis. Pariolius maldonadoi is distinguished from all congeners by having six branched pectoral-fin rays (vs. seven branched rays) and narrower head (64.3–68.3 % SL vs. 69.0–73.0% in P. pax and 68.3–94.2% SL in P. armillatus ). It is further distinguished from P. pax by having well-defined white nuchal collar (vs. very faint or undistinguishable white nuchal collar), five branched caudal-fin rays on dorsal lobe (vs. six branched rays), deeper body (9.5–13.2% SL vs. 13.3–17.0% SL), deeper head at supraoccipital (35.7–41.6% SL vs. 48.0–51.5% SL), deeper head at interorbital (26.3–29.9% SL vs. 34.5–43.5% SL). Additionally, Pariolius maldonadoi can be distinguished from P. armillatus by having longer adipose fin vs. 17.1–21.0% SL).

Description. Morphometric data present in Table 1 . Body moderately elongated. Cylindrical in cross section at dorsal-fin origin and compressed on caudal peduncle. Dorsal body profile straight from snout tip to supraoccipital, nearly convex from supraoccipital to dorsal-fin origin, straight from dorsal-fin origin to adipose-fin origin, slightly convex from adipose-fin origin to caudal-fin origin. Ventral profile of head gently convex from snout tip to pectoral-fin origin, convex from pectoral-fin origin to pelvic-fin origin, straight from pelvic-fin to anal-fin origin, and from anal-fin origin to caudal-fin origin. Anus pore located at level of one third of pelvic fin length, urogenital papilla close to anus pore (separated approximately eye diameter).

Head small (0.2–0.3 times of SL), depressed (ascending to supraoccipital), and trapezoidal in dorsal view (Figure 10). Mouth wide and subterminal. Snout short and rounded in dorsal view. Barbels shorts, slender, flatted. Maxillary barbel longest; inserted dorsal to upper lip, lateral and gently posterior to anterior nostrils; anterior portion extending in superficial groove under anterior- and posterior-nostril region; tip of maxillary barbel surpassing pectoral-fin origin (one third pectoral-fin length). Mental barbels inserted midway between the anterior border of lower jaw and gular fold. Inner mental barbel shorter than outer barbel and inserted posterior to third pore of preoperculomandibular laterosensory canal (pm3); tip of inner mental barbel reaching pectoral-fin origin. Outer mental barbel inserted approximately posterior to midway between fourth and fifth pore of preoperculomandibular laterosensory canal; tip of outer mental barbel surpassing the pectoral-fin origin. Eye small, elliptical horizontally, slightly dorsal, and anterior to midpoint of head length. Orbital margin not free and pupil rounded. Nostrils arranged as in vertices of squared, anterior internostril distance similar than posterior internostril distance. Anterior nostril tubular, closer to upper lip than posterior nostril. Posterior nostril closer to anterior margin of eye than anterior nostril, anterior margin with flap.

Pectoral fin rays i +6 (16), distal margin rounded; unbranched pectoral-fin ray soft and short (0.8–0.9 times length of pectoral-fin ray); second pectoral-fin ray (first branched rays) as long as third ray (second branched ray); last branched rays short and decreasing gradually; tip of pectoral fin behind vertical through pelvic-fin origin. Pelvic fin rays i + 5 (16), distal margin rounded; unbranched pectoral -fin rays soft and short (0.7 times length of pelvic-fin ray); second pelvic-fin ray (first unbranched ray) shorter than third ray (second branched rays); third pelvic-fin ray (second branched ray) as long as and fourth ray (third branched ray); last two branched rays short and decreasing gradually; pelvic-fin origin anterior to midpoint body (excluding caudal fin) and anterior to vertical through dorsal-fin origin; tip of pelvic fin surpassing the urogenital papilla (one half its length). Insertion of first pelvic-fin ray on basipterygium at vertical through between centra 13–14.

Dorsal fin rays i + 6 (16), distally rounded in lateral profile, unbranched dorsal-fin soft and short (0.8–0.96 times length of longest dorsal-fin rays) followed by six branched rays; dorsal-fin origin anterior to vertical through pelvic-fin origin. First dorsal-fin pterygiophore inserted on bifid neural spine of vertebrae 13 (2). Last dorsal-fin pterygiophore inserted between space of neural spine of vertebrae 16–17 (2) or 17–18 (1). Anal fin rays iv + 7 (1), iii + 8 (2), iv +8 (12), v + 8 (1). Anal fin convex and short (0.1–0.2 times its standard). Anal-fin origin anterior to vertical through adipose-fin origin, and last anal-fin ray slightly anterior to half adipose-fin base length. First anal-fin pterygiophore inserted between hemal spines of vertebrae 24–25 (3). Last anal-fin pterygiophore inserted between hemal spines of vertebrae 31–32(3). Anal fin with 12 (2) pterygiophores. Adipose fin short (0.2–0.25 times its standard length), rectangular and slightly convex in lateral profile (Figure 1a); adipose-fin base longer than dorsal to adipose fin distance (1.1–1.5 times its length) and anal-fin base (1.2–1.6 times its length). Adipose-fin origin posterior of anal-fin origin and terminus not continuous with dorsal procurrent caudal-fin rays. Insertion of adipose fin at vertical through vertebrae centra 28–29 (2); and terminus of adipose fin at vertebrae 39–40 (2). Caudal fin gently emarginate, dorsal lobe longer and pointed than ventral lobe; dorsal caudal lobe with rarely four (2) or usually with five (13) branched rays; ventral lobe with rarely four (4) or usually five (11) branched rays. Total caudal-fin rays 36 (2) or 37 (1); with 18 (2) or 19 (1) rays on dorsal lobe and 18 (3) rays on ventral lobe (Figure 2B).

Canals of laterosensory system with simple pores and arrangement according to Figure 11. Supraorbital canal with four branches: s1, s2, s3 and s8; each supraorbital laterosensory opening into a single pore, except branch s2 fused with antorbital branch (s2+i2). Infraorbital canals with six branches: i1, i2, i3, i4, i5 and i6; all opening into its own, except branch i2 fused with s2 opening into a single pore (s2+i2). Preoperculomandibular canal with 11 branches: pm1, pm2, pm3, pm4, pm5, pm6, pm7, pm8, pm9, pm10 and pm11; all opening into its own pore except branch pm11, fused with branch po1 (pm11+po1). Postotic canal with three branches: po1, po2 and po3; all opening into its own pore except branch po1 fused with pm11 opening into a single pore (pm11+po1). Lateral line incomplete, last pore approximately at vertical through end of dorsal-fin base.

Total of vertebrae 41 (1) or 41 (2). 14 (1) or 15 (1) vertebrae with incomplete hemal spine. 27 (1) or 28 (2) vertebrae with complete hemal spine. Six (3) pair ribs.

Osteology. Cranial skeleton (Figure 12) not ornamented; dorsal surface straight or slightly convex and without crests; orbital region well defined dorsally; slightly concave and limited by lateral ethmoid anteriorly, frontal laterally, and sphenotic posteriorly; interorbital region similar its length; two cranial fontanels separated by epiphyseal bar; anterior fontanel wider than anterior one; posterior fontanel longer than anterior in length; anterior and posterior edge of anterior fontanel slightly rounded; anterior region of posterior fontanel triangular and posterior region rounded; epiphyseal bar located to anterior to midpoint of frontal length. Mesethmoid with dorsal and ventral horizontal plane; anterolateral mesethmoid in dorsal horizontal plane, anterolateral mesethmoid ramus shorter, narrower, and more blunt-tipped than posterolateral mesethmoid, and anterolaterally directed; posterolateral mesethmoid anterolaterally projected forming a conspicuous cornu. Vomer arrow-shape, posterior portion longer than lateral arms, anterior margin of vomer at same level of posterolateral mesethmoid cornu. Lateral ethmoid slightly quadrangular; posterior and anterior face straight and lateral face concave; posterior portion longer than anterior portion; posterolateral angle more pointed than anterolateral angle. Premaxilla rectangular, size three times its width, anterior margin continuous and without process, posterolateral angle not pronounced; five or six rows of villiform teeth on premaxilla. Maxilla small and trapezoidal (distal margin longer than proximal margin), distal region forming bony tubule attached to maxillary barbel. Autopalatine rod-like, shorter than orbital region. Nasal bone poorly ossified, and shorter and narrower than autopalatine. Antorbital poorly ossified triangular, and shorter than autopalatine. Frontal smooth and lacking any process; anteriorly limited by lateral ethmoid, posterolaterally limited by sphenotic and posteriorly limited by supraoccipital; posterior portion slightly wider than anterior portion; orbital face straight. Sphenotic longer and gently narrower than pterotic length; anterior portion with anterior and lateral process. Pterotic shorter and wider than sphenotic; anterior and posterior portion with similar width. Supraoccipital limited laterally by posterior portion of sphenoid and the pterotic; supraoccipital process thin and not reaching the anterior region of complex centra (in dorsal view).

Complex anterior vertebra (Figure 5B). Composed by vertebrae 1, 2, 3, 4 and 5; vertebrae 1 disc-like element and attached to complex vertebra with tissues ventrally; complex vertebra (vertebrae 2 to 4) attached to vertebra 5 with suture ventrally; neural spine of vertebra 4 not covering neural spine of vertebra 5. Transverse process of vertebra 4 divided in anterior and posterior branches. Anterior branch of transverse process of vertebra 4 wide, laminar, and expanded laterally; proximal portion wider than distal portion. Posterior branch of transverse process of vertebrae 4 arborescent; proximal region wider than distal region; distal region divided in anterior and posterior portion; anterior portion laminar, rectangular, notched and joined to distal region of the posterior portion; posterior portion triangular. Transverse process of vertebra 5 is expanded and not branched.

Suspensory (Figure 6B). Entopterygoid small and rectangular; posterior edge concave and attached to anterior margin of metapterygoid. Metapterygoid rectangular, smooth, and approximately three times entopterygoid size; dorsal margin convex; posteroventral and medial margin of metapterygoid attached with dentate suture and cartilaginous bar to dorsal margin of quadrate; posterodorsal margin joint with dentate suture to anterodorsal margin of hyomandibula and ventral margin joint with anterodorsal process of quadrate. Quadrate approximately rectangular and similar size than hyomandibula; anterior and posterior portion separates; anterior margin of quadrate with long and strong anterodorsal process covering ventrolateral margin of metapterygoid; dorsal margin straight along its free dorsal margin; posterior and ventral margin join to hyomandibula with denticulate suture and cartilaginous bar; dorsal margin joint to posterodorsal margin of metapterygoid and anteroventral margin of hyomandibula; anteroventral portion of quadrate with rectangular process to articulate to angulo-retroarticular. Hyomandibula quadrangular; mostly smooth; anterodorsal margin slightly concave; posterodorsal hyomandibular process triangular with posterior margin very pointed. Opercle triangular and less than two times interopercle size; anterior and posterior margins rounded, ventral margin slightly convex, posterior and dorsal margin slightly concave. Interopercle triangular; anterior, posterior, and dorsal margin pointed; ventral margin convex, anterodorsal straight and posterodorsal margin concave.

Branchial arches (Figure 7B). Three basibranchial series: bb2, bb3, and bb4 (basibranchial 1 absent). Basibranchial 2 anteroposteriorly elongate, largely ossified, anterior portion wider than posterior, size is three times bigger than bb3 length, anterior portion wider than posterior portion. Basibranchial 3, completely cartilaginous, size two times its anterior width size, anterior portion wider than posterior region. Basibranchial 4 completely cartilaginous, rectangular shape; bordered by cartilaginous heads of hb3 anteriorly, cb5 posteriorly and cb4 laterally. Three hypobranchial series: hb1, hb2, hb3. Hypobranchial 1 laterally elongate, largely ossified, size three times its greatest width, cartilage just in proximal and distal extremities, anterior portion with uncinate process. Hypobranchial 2 slightly elongate, L-shape, anterior portion ossified and posterior portion cartilaginous with two times ossified size. Hypobranchial 3 completely cartilaginous, triangular, elongate laterally. Five ceratobranchial series: cb1, cb2, cb3, cb4, cb5; fully ossified with cartilage at their extremities; ceratobranchial 1, 2 and 3 similar size and longer than ceratobranchial 4 and 5. Ceratobranchial 1 to 4 with similar width along its length. Ceratobranchial 5 expanded anteromedially to support patch of conical teeth, teeth with similar size and covering one-half of cb5 length. Four epibranchial series plus accessory element of ceratobranchial 4: eb1, eb2, eb3, eb4, and plus accessory element of ceratobranchial 4; first four epibranchials rod-shaped, anteromedial narrower than posterolateral portion; eb1, eb2, eb3 and eb4 mostly ossified; aecb4 cartilaginous; epibranchial 1 and 2 similar size and longer than epibranchial 3 and 4. Epibranchial 3 with rectangular posterior uncinate process. Epibranchial 4 expanded at anterior and posterior portion. Two pharyngobranchial series: pb3 and pb4; pharyngobranchial 1 and 2 absent. Pharyngobranchial 3 rod-like, ossified, anterior portion narrower than posterior portion; posterior margin mostly expanded. Pharyngobranchial 4 ossified; rectangular and anteroposteriorly elongate.

Colour in alcohol. Dorsal and lateral surface of body dark brown (Figure 9) and dark grey in life (Figure 8B). Ventral body surface cream. Upper portion of head covered by brown pigment, surface between posterior eye margins and supraoccipital more intense; cheeks with brown scattered melanophores fading ventrally. Cream bar (collar) above pectoral fins contacting each other dorsally. Region between posterior margin of eye and maxillary barbel insertion with dark brown bar. Maxillary barbel pigmented with dark brown dorsally (one half its length) and ventrally unpigmented. Outer mental barbel pigmented with dark brown dorsally (until one third its length) and ventrally unpigmented. Inner mental barbel unpigmented (some brown melanophores at base). At least twenty-four brown chevron-shape lines marking the myosepta at the posterior region of the body, progressively narrower, more angled, and intense posteriorly. Dorsal-, anal-, pectoral-, and pelvic-fin with some dispersal brown (preserved) and grey (life) melanophores along rays and inter-radial membranes devoid of melanophores. Caudal- and adipose-fin with marbled. Caudal-fin base with triangular spot dark brown (preserved) and dark grey (life). Lateral line with dark brown and narrow stripe; nearly convex above pectoral fin and straight along midbody from that point to caudal-fin base and more intense anteriorly.

Geographic distribution. Pariolius maldonadoi is distributed is small tributaries to the Inírida and Guayabero rivers in the Orinoco River basin, Meta State and Vaupes River in the Rio Negro basin, Guaviare State, Colombia (Figure 9).

Etymology. The specific name is in honor of the authors’ colleague and friend in memoriam; to Javier Maldonado-Ocampo, professor of the Pontificia Universidad Javeriana in Bogotá, Colombia for his great contribution and devotions to the Colombian and Neotropical Ichthyology. Treated as a noun in the genitive case.