Eurycheilichthys coryphaenus, Reis, 2017

Reis, Roberto E., 2017, Unexpectedly high diversity in a small basin: A taxonomic revision of Eurycheilichthys (Siluriformes: Loricariidae), with descriptions of seven new species, Neotropical Ichthyology 15 (1), No. e 160068, pp. 1-28 : 13-15

Eurycheilichthys coryphaenus , new species

u r n: l s i d: z o o b a n k. o rg: a c t: 6 C 1 D 3 5 4 A - C E 4 0 - 4 8 B 9 - 96FF-B48025296287

Fig. 10; Tabs. 1, 3, 4

Eurycheilichthys sp. 7 .- Reis, Carvalho, 2007: 84 [listed]. Holotype. MCP 40665, 46.7 mm SL, female, Brazil, Rio Grande do Sul, Tainhas, arroio Contendas, rio Taquari basin (approx. 29º17’S 50º14’W), 4 Dec 2002, J. P. Silva & J. Anza.

Paratypes. Brazil: Rio Grande do Sul: upper rio Taquari drainage: MCP 31160, 3 , 16.5-43.6 mm SL (2, 39.1-43.6 mm SL), collected with the holotype. MCP 35044, 2 (2, 36.2-44.3 mm SL) and 15 tis, 25.4-33.2 mm SL, arroio Contendas, ca. 1 km NE of road from Aratinga to Tainhas , Tainhas (29º16’41”S 50º14’42”W), 23 May 2004, R. E. Reis. UFRGS 6905 , 1 , 35.3 mm SL, MCP 40667, 1 c&s, 51.8 mm SL, MZUSP 92427 , 1 , 35.1 mm SL, AMNH 238576 , 2 , 34.1-36.3 mm SL, creek tributary to rio Tainhas , ca. 4 km North of Tainhas, Tainhas (29°15’06”S 50°16’39”W), 27 Nov 2004, J. Anza et al. MCP 22375, 3 , 33.8-49.7 mm SL (1, 49.7 mm SL), and MNRJ 18341 , 4 , 17.5-37.7 mm SL (2, 36.4-37.7 mm SL), creek tributary to rio Tainhas , 1.7 km NW of roads intersection near Tainhas, Tainhas (29º15’44”S 50º19’54”W), 16 Dec 1998, R. E. Reis et al. MCP 25674, 2 , 1 c&s, 30.1 mm SL (2, 36.8-42.0 mm SL), arroio Contendas on road from Aratinga to Tainhas, Tainhas (approx. 29º17’S 50º15’W), 20 Mar 2000, W. Bruschi Jr. UFRGS 5075 , 2 , 31.0- 42.7 mm SL, creek tributary to rio Tainhas on road RS-230 ca. 2 km West of Tainhas, Tainhas (29°15’47”S 50°19’56”W), 30 Mar 2001, L. R. Malabarba et al. UFRGS 5022 , 1 , 44.2 mm SL, rio Tainhas near Tainhas (29º15’30”S 50º13’12”), 11 Sep 1999, G. B. Buckup et al. MCN 18563, 3, 33.8-44.8 mm SL, rio Tainhas at Passo da Ilha , São Francisco de Paula (29º07’24.8”S 50º21’29.9”W), 6 Mar 2006, M. Azevedo & R. Hirano .

Genseq- 2 16S. MCP 35044; GenBank accession number KX355633 .

Non-types. Brazil: Rio Grande do Sul: upper rio Taquari drainage: UFRGS 5077 , 3 , 30.8 -44.0 mm SL, rio Tomé at road RS-020, Vacaria (29º02’21”S 50º34’12”W), 31 Mar 2001, L. R. Malabarba et al .

Diagnosis. Eurycheilichthys coryphaenus is distinguished from all congeners by having the parieto-supraoccipital conspicuously elevated ( Fig. 3) (vs. parieto-supraoccipital without a conspicuous elevation); and the abdominal plates granular and partially embedded in skin such that mostly only odontodes are visible (vs. abdominal plates absent or large and conspicuous). Eurycheilichthys coryphaenus is further distinguished from E. castaneus and E. limulus by the spotted pattern of its body and fins (vs. body plain dark brown, without blotches or spot, and with a light stripe from snout tip, crossing above the eye and predorsal area), and 25-26 plates in middle lateral series (vs. 27-29 plates); from E. planus , E. luisae , and E. vacariensis by having the abdomen completely covered by small platelets (vs. naked, partially plated with a middle stripe of platelets, or incompletely covered with granular platelets); from E. planus by the longer dorsal-fin spine (21.8-24.0 vs. 16.5-21.6% SL) and deeper head (47.8-54.0 vs. 41.6-46.9% HL); from E. paucidens and E. apocremnus by the shorter pelvic-fin spine (64.4-80.2 vs. 80.6-100.6% of the pectoralfin spine) and 25-26 plates in middle lateral series (vs. 27- 30 plates, occasionally 26); from E. paucidens by larger orbital diameter (13.8-18.5 vs. 9.3-12.4% HL); and from E. pantherinus by the lower lip hardly reaching the anterior margin of the pectoral girdle (vs. lower lip clearly extending past the anterior margin of the pectoral girdle).

Description. Proportional measurements and counts in Tabs. 1, 3 and 4. Dorsal body profile straight to gently arched from snout tip to parieto-supraoccipital, straight from that point to dorsal-fin origin; parieto-supraoccipital with conspicuous elevation, more salient in larger individuals. Trunk generally straight and tapering slightly toward caudal-fin base. Trunk and caudal peduncle rounded in cross section, slightly flattened at and behind base of dorsal and anal fins, and compressed caudally. Greatest body depth at parieto-supraoccipital bone or dorsal-fin origin. Head and snout broad and rounded anteriorly, with body progressively narrowing caudally from cleithrum. Interorbital space flat to slightly concave; superior margin of orbits slightly elevated. Snout flat to slightly convex anterior to nares. Nostrils located at posterior terminus of pair of elongate, shallow depressions beginning close to snout tip. Eye comparatively large, orbit diameter 13.8-18.5% HL, dorsolaterally placed.

Pectoral fin of moderate size, spine slightly arched, posterior fin-margin straight to slightly rounded; extending to between middle and distal third of pelvic fin when depressed. Fleshy flap along posterodorsal margin of pectoral-fin spine low in adult males, and absent in females. Pectoral-fin axillary slit present, with large opening ventral to tip of posterior process of cleithrum. Pelvic fin of females short, extending to point midway between anus and analfin origin when depressed. Thickened first pelvic-fin ray of males longer, typically extending to anal-fin origin. Males with well-developed fleshy flap along posterodorsal margin of thickened first pelvic-fin ray. Dorsal-fin origin at or slightly posterior to vertical line through end of pelvicfin base; spinelet present, reduced and plate-like; dorsal-fin locking mechanism non-functional. Adipose fin absent.

Body entirely covered by dermal plates except for area around anus, opening of swimbladder capsule posteroventrally to compound pterotic, around pectoral- and pelvic-fin insertions, and ventral surface of head around lips. Body and head without crests. Coracoid and cleithrum exposed laterally, covered medially by skin and few isolated platelets. Arrector fossa open. Lateral abdominal plates absent. Middle abdominal plates granular and somewhat embedded in skin, irregularly arranged and interspaced, covering most of abdominal surface between pectoral girdle and anal opening ( Fig. 2e). Posterior tip of parietosupraoccipital with conspicuous patch of enlarged and raised odontodes compared to those of remainder of head and predorsal area, especially in smaller individuals. Head and body plates covered with odontodes, these larger on ventral face of pelvic and pectoral spines. Odontodes on head and trunk otherwise of uniform size and distribution, not arranged in conspicuous rows.

Lips roundish and wide, papillose, extending posteriorly to a point between end of canal-bearing lateral cheek plate and anterior margin of pectoral girdle. Lower lip margin fringed. Maxillary barbel short, mostly adnate to lower lip. Teeth slender, bifid; major (medial) cusp large, bladelike, and slightly rounded; minor (lateral) cusp minute, pointed. Accessory patch of unicuspid teeth on premaxilla and dentary, attached to dermal bone posterior (premaxilla) and anterior to (dentary) margin of tooth cup, which encloses main series of emergent and pre-emergent bifid teeth. Accessory teeth large, elongate, sharply pointed, directed posteroventrally (premaxilla) and anteroventrally (dentary).

Color in alcohol. Background color of dorsal surface of head and body tan to brown with few large, dark brown spots throughout head and body; yellowish tan, mostly unpigmented ventrally. Head primarily dark, predorsal region lighter; two inconspicuous lighter saddles on dorsum, at end of dorsal-fin base and caudal peduncle. Hypertrophied odontodes on tip of parieto-supraoccipital bone lighter than background. First thickened ray of dorsal, pectoral, pelvic, and anal fins and external rays of caudal fin with chromatophores arranged in four to six discernible blotches. Branched rays in these fins with similar color pattern. Caudal fin with three or four irregular dark vertical bands.

Distribution and habitat. Eurycheilichthys coryphaenus is known from localities in the upper reaches of the rio Tainhas basin, which is a tributary to the rio das Antas, rio Taquari basin, Rio Grande do Sul, Brazil ( Fig. 11), an area located at the extreme eastern headwaters of the rio Taquari basin, in the Araucaria forest area. One lot from rio Tomé (UFRGS 5077) is tentatively assigned to this species and specimens are considered non-types. The localities are small creeks with medium flowing clear water and substrate covered with rocks and stones. Despite dense vegetation including marginal grasses and aquatic macrophytes being present in these localities, fishes are found dwelling among loose stones on the substrate.

Etymology. The specific epithet of Eurycheilichthys coryphaenus is from the Greek koryphe, meaning head, crown, top, or highest point, in allusion to the distinctly elevated parieto-supraoccipital bone. An adjective.

Conservation status. Eurycheilichthys coryphaenus is not abundant and is known from tributaries to the rio Tainhas and the rio Tomé, with Extent of Occurrence (EOO) of approximately 104 km 2. Despite the continuing decline in habitat quality because of land use change, especially agriculture and Pinus reforestation, the population is neither severely fragmented nor presenting extreme fluctuations, and the species can be categorized as Near Threatened (NT) according to IUCN criteria B1b(iii) (IUCN, 2016).