Hoplias maranhensis Guimaraes, Rosso, Gonzalez-Castro, do Nascimento Andrade, Brito, Guimaraes, Diaz de Astarloa & Rodrigues 2025, sp. nov.

Hoplias maranhensis Guimarães, Rosso, González-Castro, do Nascimento Andrade, Brito, Guimarães, Díaz de Astarloa & Rodrigues sp. nov. Fig. 2, Table 1 Hoplias malabaricus [non Bloch 1794]. Cardoso et al. (2018); Guimarães et al. (2022): (Brazil, Maranhão, Itapecuru River; supported by distinct molecular methods as a putative new undescribed species in the H. malabaricus species-group). Type materials. Holotype. Brazil • UFOPA -I 001760, 260 mm SL; Maranhão State, Itapecuru basin: Aldeias Altas Municipality, Alagadiço Stream; coordinates: -4.55256, -43.32781; F. Lopes, 10 June 2024; BOLD: ACR 9466. Paratypes. All from Brazil, Maranhão State: Itapecuru Basin: Gonçalves Dias Municipality, Codozinho River: -5.11683, -44.09703, J. O. Sousa, 9 August 2023: • UNMDP 5375, 1, 240 mm SL • UNMDP 5376, 1, 258 mm SL • UNMDP 5377 (osteologic), 1, 280 mm SL • Caxias Municipality, Itapecuru River: -4,870 50, -43,361 16, A. Lima, 3 December 2021: • UFOPA -I 001757, 4, 161– 325 mm SL • UNMDP 5393, 1, 195 mm SL • UNMDP 5378, 1, 180 mm SL • UNMDP 5394, 1,198 SL • Cajazeira Stream: -4.99417, -43.47751, K. Guimarães, 5 February 2023: • UNMDP 5379, 1, 184 mm SL • UNMDP 5380 (osteologic), 1, 116 mm SL • UFOPA -I 001761, 1, 155 mm SL • Itapecuruzinho Stream: -4,926 69, -43,352 62, F. Lopes, 10 October 2023: • UNMDP 5381-5384, 4, 138-180 mm SL • Ouro Stream: -4.81575, -43.25931, F. Lopes, 9 June 2024: • UFOPA -I 001758, 3, 178– 212 mm SL; Aldeias Altas Municipality, Alagadiço Stream: -4.55256, -43.32781, F. Lopes, 10 June 2024: • UFOPA -I 001759, 2, 222– 240 mm SL; Gonçalves Dias Municipality, Codozinho River: -5.11683, -44.09703, J. O. Sousa, 9 August 2023: • UFOPA / LGBIO–GCD 1, 1, 225 mm SL • UFOPA -I 001762, 1, 258 mm SL. Non-type specimens. All from Brazil, Maranhão State: Itapecuru Basin: Gonçalves Dias Municipality, Codozinho River: -5.11683, -44.09703, J. O. Sousa, 9 August 2023: • UFOPA / LGBIO–GCD 3, 1, 204 mm SL • UFOPA / LGBIO–GCD 4, 1, 195 mm SL • UFOPA / LGBIO–GCD 8, 1, 283 mm SL; Caxias Municipality, Itapecuru River: Cajazeira Stream: -4.99417, -43.47751, K. Guimarães, 5 February 2023: • UFOPA / LGBIO–CAX 8, 1, 100 mm SL • UFOPA / LGBIO–CAX 9, 1, 115 mm SL • UFOPA / LGBIO–CAX 10, 1, 122 mm SL • UFOPA / LGBIO–CAX 11, 1, 95 mm SL • UFOPA / LGBIO–CAX 12, 1, 130 mm SL • UFOPA / LGBIO–CAX 13, 1, 120 mm SL • UFOPA / LGBIO–CAX 14, 1, 99 mm SL • UFOPA / LGBIO–CAX 15, 1, 102 mm SL • UFOPA / LGBIO–CAX 16, 1, 113 mm SL • UFOPA / LGBIO–CAX 19, 1, 80 mm SL • UFOPA / LGBIO–CAX 23, 1, 156 mm SL; Peritoró Municipality, Preitoró River: -4,514 78, -44,319 54, E. C. Guimarães & P. S. Brito, 4 September 2021: • UFOPA / LGBIO–MPI 005, 1, 61 mm SL; MEARIM BASIN: Formosa da Serra Negra Municipality, Ribeirão Tamboril: -6.42949, -45.99744, E. C. Guimarães & P. S. Brito, 7 September 2021: • UFOPA / LGBIO–MPI 013 H 1, 1, 51.45 mm SL. Diagnosis. Hoplias maranhensis is distinguished from other species of the H. malabaricus species-group by the following combination of characters: 14–16 predorsal scales, 37–40 lateral-line scales, 39–40 vertebrae, 15 branched caudal-fin rays, ii-iii unbranched anal-fin rays, a straight line formed by the last vertical series of scales at the base of the caudal-fin rays, a marked ridge in the posterior angular end of the ascending process of premaxilla, postcleithrum 1 with an anterior expansion and in contact or nearly in contact with an elongated postcleithrum 2, the first proximal pterygiophore of the dorsal fin widely bifurcated, the number of principal caudal-fin rays articulating with lower hypural bones, foramen not in contact with premaxilla border and ascending process of the premaxilla expanded medially and with a dorsoposterior tip. The number of predorsal scales (14–16), lateral-line scales (37–40), and vertebrae (39–40) distinguishes H. maranhensis from H. argentinensis (17–19, 41–44, and 42–43, respectively). H. maranhensis can be distinguished from H. microlepis by predorsal scales (14–16 vs. 17–19), lateral-line scales (43–46), and vertebrae (42–43). Pre-dorsal scales (14–16 vs. 18), lateral-line scales (37–40 vs. 40–41), and vertebrae (39–40 vs. 42) differentiate H. maranhensis from H. teres. The count of lateral-line scales (37–40) and vertebrae (39–40) distinguishes H. maranhensis from H. mbigua (41–44 and 42, respectively). H. maranhensis is distinguished from H. auri by the number of branched caudal-fin rays (15 vs. 12–15), unbranched anal-fin rays (iii – iv vs. ii), lateral-line scales (37–40 vs. 39–40), and vertebrae (39–40 vs. 38–39). Hoplias maranhensis differs from H. misionera by having a straight line formed by the last vertical series of scales at the base of the caudal-fin rays (vs. curved) and two vertical rows of scales on caudal fin (vs. four). The shape of the ascending process of the premaxilla distinguishes H. maranhensis from H. malabaricus (with a marked ridge vs. poorly developed) (Fig. 3). H. maranhensis also differs from H. auri and H. argentinensis in some osteological traits: from H. auri it differs in postcleithrum 1 (with an anterior expansion vs. no anterior expansion), postcleithrum 2 (more elongated and positioned closer to the base of postcleithrum 1 vs. shorter and more distinctly separated from postcleithrum 1), the first two proximal pterygiophores of the dorsal fin (a bifurcation with a widely divergent “V” shape vs. a parallel bifurcation, with a less separation between branches), articulation pattern of principal caudal-fin rays with lower hypural bones (one ray with parahypural, five rays with hypural 1, one ray with hypural 2 vs. two rays with parahypural, three rays with hypural 1 and two rays with hypural 2) (Fig. 4), foramen not in contact with premaxilla border vs. foramen in contact; dorsoposterior margin of premaxilla projecting medially with an ascending and pointed process vs. not projecting medially and lacking ascending and pointed process) (Fig. 5). From H. argentinensis it differs in postcleithrum 2 (round-shaped and positioned closer to the base of postcleithrum 1 vs. a triangular-shaped and more distinctly separated from postcleithrum 1), the first two proximal pterygiophores of the dorsal fin (a bifurcation with a widely divergent “ V ” shape vs. a parallel bifurcation), and articulation pattern of principal caudal-fin rays with lower hypural bones (one ray articulates with parahypural, five rays with hypural 1, one ray with hypural 2 vs. two rays with parahypural, three or four rays with hypural 1, and one or two rays with hypural 2) (Fig. 3). Compared to H. mbigua, H. maranhensis exhibits a straight or slightly convex dorsal head profile (vs. markedly concave) and a longer interorbital width (22.8–30.7 %, mean 27.2 % vs. 18.5–28.6 %, mean 24.3 %). Morphometric differences also separate H. maranhensis from other species in the group. A longer dorsal-fin base (17.3–21 %, mean 19 %, vs. 16.2–17.7 %, mean 16.9 %), a narrower snout (snout width 20.4–25.7 %, mean 23 %, vs. 29.4–29.5 %, mean 29.4 %), greater body depth (20.1–24.4 %, mean 22.1 %, vs. 17–20.6 %, mean 18.8 %), and greater upper jaw length 54.4 (50.1–58 %, mean 54.4 %, vs. 50.5–51 %, mean 50.7 %) distinguish H. maranhensis from H. teres. Hoplias maranhensis differs from H. microlepis in snout width (20.4–25.7 %, mean 23 % vs. 23.6–28.6 %, mean 26.8 %), pre-nasal length (11.8–18.5 %, mean 16.0 % vs. 15.4–23.8 %, mean 21.4 %), pre-dorsal length (45–50 %, mean 47.8 % vs. 47.7–52.2 %, mean 49.8 %), and upper jaw length (50.1–58 %, mean 54.4 % vs. 47.7–53.4 %, mean 50.1 %). Compared to H. malabaricus, H. maranhensis differs in having a shorter predorsal length (45–50 %, mean 47.8 %, vs. 48.4–54.4 %, mean 50.8 %), a longer dorsal-fin (29.5–34.1 %, mean 32.0 % vs. 28.9–31.1 %, mean 32 %), a longer dorsal-fin base (17.3–21 %, mean 19.0 % vs. 15.3–19.2 %, mean 17.6 %), a longer pre-nasal length (11.8–18.5 %, mean 16 % vs. 12.5–16.2 %, mean 13.8 %), and a shorter pre-pelvic length (48.5–55.7 %, mean 53 % vs. 52.1–58.1 %, mean 54.3 %). H. maranhensis also differs from H. auri by a greater body depth (20.1–24.4 %, mean 22.1 %, vs. 16.2–23 %, mean 19.9 %), a longer dorsal-fin base (17.3–21 %, mean 19.0 % vs. 15.1–19.5 %, mean 17.5 %), and a shorter pre-pelvic length (48.5–55.7 %, mean 53 % vs. 53.5–58.8 %, mean 55.7 %) (Fig. 6). Description. Morphometric data are summarized in Table 1. Body cylindrical, dorsal profile of head straight or slightly convex. Anterior profile of the head angular to slightly rounded in lateral view, with the greatest body depth at dorsal-fin origin. Dorsal surface of the head with a pronounced ridge at the posterior angular end of the ascending process of the premaxilla, in contact with the mesethmoid medially and the nasal bone laterally (see Fig. 2). The medial margins of the contralateral dentaries converge at the midline in a V-shaped angle. Both upper and lower lips, fleshy. Anterior nostrils with an incomplete tubular skin flap partially covering the opening, while posterior nostril without fleshy flap and equidistant from the anterior nostril and anterior bony margin of the orbit. Infraorbitals 3 and 4 completely excluded from orbital ring. Teeth caniniform in both jaws. Premaxilla with a single tooth row containing 9 (1), 10 (23 *), or 11 (1) teeth. First two medial teeth large, followed by three to five smaller teeth, ending with two larger canines. First and last canines in this series, the largest. One or two small teeth posterior to last large premaxillary canine, nearly in contact with the first small maxillary tooth. Maxillary row with four to six anterior teeth, progressively increasing in size, followed by 37–46 smaller teeth. External dentary series with one symphyseal tooth, followed by two smaller teeth, another large tooth equal in size to the symphyseal tooth, and largest dentary canine. This is succeeded by three to seven small teeth and a series of six to 11 teeth arranged in a repetitive pattern of one large tooth followed by one, two, or three small