Eurycheilichthys paucidens, 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 : 19-22

Eurycheilichthys paucidens , new species

urn:lsid:zoobank.org:act:2F206D68-6F47-4ADE-9931-4A92E0FD2CB2

Fig. 13; Tabs. 2-4

Eurycheilichthys sp. 5 .- Reis, Carvalho, 2007: 84 [listed].

Holotype. MCP 40661, 61.8 mm SL, female, Brazil, Rio Grande do Sul, Muitos Capões, arroio Tavoqua, rio Taquari basin, near fazenda Cambará (28º21’51”S 51º17’53”W), 3 Apr 1999, V. A. Bertaco et al.

Paratypes. Brazil: Rio Grande do Sul: upper rio Taquari drainage: MCP 22800, 4 , 50.9-59.7 mm SL, 2 c&s, 46.1- 51.4 mm SL (2, 56.7-59.7 mm SL), MZUSP 92423 , 2 (2, 47.9-56.7 mm SL), AMNH 238572 , 2 (2, 42.4-55.7 mm SL), collected with the holotype. MCP 22374, 3 , 35.8-48.1 mm SL (1, 48.1 mm SL), and MNRJ 18342 , 3 , 20.0- 43.5 mm SL (2, 40.3-43.5 mm SL), rio Lageado Grande near Lageado Grande , on road RS-476 to Jaquirana , Lageado Grande (29º05’34”S 50º37’30”W), 16 Dec 1998, R. E. Reis et al. MCP 22202, 1 (1, 37.0 mm SL), rio da Prata at Passo do Respraiado , on road between Guabiju and André da Rocha, Guabiju (28º38’04”S 51º36’53”W), 20 Jan 1999, R. E. Reis et al. MCP 29958, 2 , 35.5-49.7 mm SL (1, 49.7 mm SL), arroio São Gonçalo next to bridge on road RS- 020, between São José dos Ausentes and Cambará do Sul, Cambará do Sul (28º52’11”S 50º01’11”W), 21 Jul 2002, G. M. Mauricio & C. M. Joenck. MCP 20688, 3 (3, 49.3- 50.6 mm SL), rio Lageado Grande, downstream Certaja hydroelectric dam and upstream waterfall, São Francisco de Paula , 11 Mar 1998, W. Koch. MCP 20689, 3 , 36.5-45.2 mm SL (1, 45.2 mm SL), arroio dos Moreira, downstream Certeja hydroelectric dam, São Francisco de Paula , 11 Mar 1998, W. Koch. MCN 14843, 3 (3, 42.2-47.4 mm SL), rio Tomé , tributary to rio das Antas, São Francisco de Paula , 21 Jun 1997, W. R. Koch & L. F. Guterrez. MCN 14901, 1, 36.1 mm SL, arroio dos Novilhos on Road to Capão Alto, São Francisco de Paula , 11 Jul 1997, W. R. Koch & L. F. Guterrez. MCN 14925, 1 (1, 49.4 mm SL), rioTomé, tributary to rio das Antas, São Francisco de Paula , 11 Jul 1997, W. R. Koch & L. F. Guterrez. UFRGS 4882 , 2 (2, 44.4-53.7 mm SL), rio das Antas, near São José dos Ausentes (28º49’43”S 50º00’42”W), 6 Apr 2000, L. R. Malabarba et al. UFRGS 4853 , 1 (1, 52.6 mm SL), creek tributary to rio das Antas, São José dos Ausentes (28º49’21”S 49º59’52”W), 6 Jan 2000, A. Schwarzbold et al. UFRGS 7865 , 5 , 39.8-56.3 mm SL, rio das Antas downstream from Sítio Vale das Trutas, near road from Cambará to São José dos Ausentes, São José dos Ausentes (28°47’08”S 49°58’55”W), 1 Jan 2001, D. Gelain et al. UFRGS 7877 , 8 , 32.8-48.6 mm SL, rio das Antas downstream from Sítio Vale das Trutas, near road from Cambará to São José dos Ausentes, São José dos Ausentes (28°47’08”S 49°58’55”W), 16 May 2001, J. Anza et al. UFRGS 7897 , 12 , 32.2-54.1 mm SL, rio das Antas downstream from Sítio Vale das Trutas, São José dos Ausentes (28º47’08”S 49°58’55”W), 21 Apr 2001, A. Cardoso et al. UFRGS 7876 , 12 , 40.0- 58.9 mm SL, rio das Antas downstream from Sítio Vale das Trutas, near road from Cambará to São José dos Ausentes, São José dos Ausentes (28°47’08”S 49°58’55”W), Jul 2001, J. Anza et al. MCP 35119, 1 tis, 46.6 mm SL, arroio Tavoqua, near fazenda Cambará, Muitos Capões (28º21’51”S 51º17’53”W), 23 May 2004, R. E. Reis et al .

Genseq- 2 16S. MCP 35119; GenBank accession number KX231811 .

Genseq-2 COI. Sequences deposited in GenBank by Cristian Cramer for COI ( MCP 22800; GenBank accession number EU370994 and MCP 22374; GenBank accession number EU370992 ).

Non-types. Brazil: Rio Grande do Sul: upper rio Taquari drainage: MCP 35040, 1 tis, 47.8 mm SL, rio Turvo near Turvo, on road from André da Rocha to Barretos, Turvo

(28º24’19”S 51º29’25”W), 22 May 2004, R. E. Reis et al. MCP 43344, 1 , 53.1 mm SL, arroio Governador, tributary to rio das Antes near Bom Jesus (28º44’23”S 50º40’42”W) , 4 Oct 2008, J. F. Pezzi et al. UFRGS 4896 , 1 , 30.9 mm SL, creek tributary to rio das Antas, São José dos Ausentes (28º49’11”S 49º59’40”W) , 6 Apr 2000, L. R. Malabarba et al. UFRGS 7898 , 5 , 37.2-48.7 mm SL, rio das Antas downstream from Sítio Vale das Trutas, near road from Cambará to São José dos Ausentes, São José dos Ausentes (28°47’08”S 49°58’55”W) , 22 Jun 2001, J. Anza et al. UFRGS 7885 , 1 , 30.2 mm SL, rio das Antas downstream from Sítio Vale das Trutas, near road from Cambará to São José dos Ausentes, São José dos Ausentes (28°47’08”S 49°58’55”W) , 2 Jun 2001, J. Pezzi da Silva et al. UFRGS 7893 , 2 , 40.1-53.5 mm SL, rio das Antas downstream from Sítio Vale das Trutas, near road from Cambará to São José dos Ausentes, São José dos Ausentes (28º47’08”S 49º58’55”W) , 16 Jan 2001, D. Gelain et al. UFRGS 7894 , 5 , 36.5-47.4 mm SL, rio das Antas downstream from Sítio Vale das Trutas, near road from Cambará to São José dos Ausentes, São José dos Ausentes (28º47’08”S 49º58’55”W) , 17 Mar 2001, L. R. Malabarba et al. UFRGS 7875 , 2 , 47.5-48.4 mm SL, rio das Antas downstream from Sítio Vale das Trutas, near road from Cambará to São José dos Ausentes, São José dos Ausentes (28°47’08”S 49°58’55”W) , 29 Sep 2000, J. Anza et al. UFRGS 7869 , 1 , 33.4 mm SL, rio das Antas downstream from Sítio Vale das Trutas, near road from Cambará to São José dos Ausentes, São José dos Ausentes (28°47’08”S 49°58’55”W) , 28 Jul 2000, J. Anza et al. UFRGS 7939 , 1 , 31.1 mm SL, rio das Antas downstream from Sítio Vale das Trutas, near road from Cambará to São José dos Ausentes, São José dos Ausentes (28º47’08”S 49º58’55”W) , 25 Nov 2000, D. Gelain et al. UFRGS 7937 , 3 , 40.6-50.3 mm SL, rio das Antas downstream from “Pesque-Pague” near road from Cambará to São José dos Ausentes, São José dos Ausentes (28°47’08”S 49°58’55”W) , 20 Dec 2000, J. Anza et al. UFRGS 6906 , 1 , 44.8 mm SL, rio Camisa at road RS- 020, Cambará do Sul (29°05’00”S 50°10’48”W) , 27 Nov 2004, J. Anza et al.

Diagnosis. Eurycheilichthys paucidens is distinguished from all congeners by possessing few (2-10) accessory teeth on the premaxilla in one irregular series (vs. numerous, 14-62 accessory teeth on the premaxilla in two to several irregular series). It is also distinguished from five other species by the relatively small orbital diameter (9.3-12.4% HL vs. 13.8- 18.5 in E. coryphaenus , 13.4-18.8 in E. pantherinus , 12.4- 14.9 in E. planus , 12.5-16.9 in E. vacariensis , and 12.1- 14.5 in E. luisae ), and by possessing 27-29 (one specimen with 26 on one side) plates in middle lateral series (vs. 23- 26 in E. coryphaenus , E. pantherinus (one specimen with 27 in one side), E. planus , E. vacariensis and E. luisae ). Eurycheilichthys paucidens is further distinguished from E. limulus and E. castaneus by exhibiting many dark, irregularly shaped blotches and spots on the body and head (vs. body and head plain dark brown without blotches or spots); from E. planus by the longer pelvic-fin spine (19.4- 24.2 vs. 15.6-19.2% SL) and longer anal-fin spine (18.2- 22.2 vs. 13.9-17.0% SL); and from E. luisae by the shorter mandibular ramus (7.0-10.8 vs. 11.1-14.7% HL).

Description. Proportional measurements and counts in Tabs. 2, 3, and 4. Dorsal body profile gently arched from snout tip to dorsal-fin origin. 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 located at dorsal-fin origin. Head and snout broad and flat, rounded anteriorly; body progressively narrowing caudally from cleithrum. Interorbital space flat to slightly convex; superior margin of orbits slightly elevated. Snout slightly convex anterior to nares. Nostrils located at posterior terminus of pair of elongate, shallow depressions beginning close to snout tip. Eye comparatively very small, orbit diameter 9.3-12.4% HL, dorsolaterally placed.

Pectoral fin of moderate size, spine strongly arched, posterior fin-margin straight or slightly concave; extending to middle to second third of pelvic fin when depressed. Fleshy flap along posterodorsal margin of pectoral-fin spine in both male and female adults. 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 anal-fin origin when depressed. Thickened first pelvic-fin ray of males longer, slightly extending past anal-fin origin. Males with welldeveloped fleshy flap along posterodorsal margin of thickened first pelvic-fin ray; females exhibit smaller flap. Dorsal-fin origin slightly posterior to vertical line through end of pelvic-fin base; spinelet present, reduced and platelike; 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 lacking crests. Coracoid and cleithrum exposed laterally, covered medially by skin and abdominal platelets. Arrector fossa open. Lateral abdominal plates absent. Middle abdominal plates small, irregularly arranged and covering most of abdominal surface between pectoral girdle and anal opening ( Fig. 2g). Posterior tip of parietosupraoccipital lacking a conspicuous patch of enlarged odontodes. 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, with posterior margin falling short of or extending posteriorly to end of canal-bearing lateral cheek plate. Lower lip margin smooth. 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 (dentary) margin of tooth cup, which encloses main series of emergent and pre-emergent bifid teeth. Accessory teeth elongate, sharply pointed and very small, arranged in single series and directed posteroventrally (premaxilla) and anteroventrally (dentary).

Color in alcohol. Background color of dorsal surface of head and body tan to light brown with many dark brown blotches of irregular shape, larger on caudal peduncle; head

primarily dark with thin lighter lines, especially on snout and cheeks; yellowish tan, mostly unpigmented ventrally. First thickened ray of dorsal, pectoral, pelvic, and anal fins and external rays of caudal fin with chromatophores arranged in two or three discernible blotches. Branched rays in these fins with similar color pattern. Caudal fin variably spotted, with middle light vertical band and lighter distal half.

Distribution and habitat. Eurycheilichthys paucidens is known from various tributaries to the rio Turvo and rio das Antas, of the rio Taquari basin, Rio Grande do Sul, Brazil ( Fig. 11). All localities are creeks or small rivers with medium to fast flowing water and substrate covered with rocks and stones. Fish are commonly found among the loose stones on the substrate.

Etymology. The specific epithet of Eurycheilichthys paucidens is from the Latin paucus, meaning few, little, and dens, meaning tooth, in allusion to the small number of accessory teeth in both premaxilla and dentary. An adjective in the nominative.

Conservation status. Eurycheilichthys paucidens is frequent and moderately abundant in the upper rio Taquari basin. Despite the Extent of Occurrence (EOO) is approximately 7,500 km 2 and hydroelectric dams exist and are planned in that basin, no specific threats were detected, and the species can be categorized as Least Concern (LC) according to IUCN criteria (IUCN, 2016).