Euryochus thysanos Pereira and Reis, new species
Creators: name: Pereira, Edson H. L.
name: Reis, Roberto E.
Publisher: name: Zenodo
Year: 2017
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Actinopterygii
Siluriformes
Astroblepidae
Euryochus
Euryochus thysanos

description: Euryochus thysanos Pereira and Reis, new species
http://zoobank.org/urn:lsid:zoobank.org:act:A8EAE615-8A9F-4A5A-B151-3E478804F2F2 Figure 41, Table 1
Holotype. MCP 50000, male, 104.2 mm SL, Brazil, Espirito Santo State, córrego Limoeiro near Praça Oito, Itarana, Rio Doce basin, 19°54'42"S 40°50'10"W, 8 February 2001, R. L. Teixeira and P. S. Miller.
Paratypes. All from Brazil, Rio Doce basin, Espirito Santo State: MCP 31334, (1, 79.3 mm SL), same data as holotype. MCP 27341, (3, 56.3–88.9 mm SL), same locality as holotype, 19 August 2000, R. L. Teixeira. MCP 31316, 2, 42.7–63.9 mm SL (1, 63.9 mm SL), same locality as holotype, 18 October 2000, R. L. Teixeira and P. S. Miller. MCP 31327, (2, 69.8–85.0 mm SL), rio Jaboticabas, Itarana, 19°55'58"S 40°52'00", 19 August 2000, R. L. Teixeira. MCP 31307, 4, 58.5–95.7 (3, 78.4–95.7 mm SL), rio Santa Joana, fazenda Coser, Itaguaçú, 19°48'S 40°52'W, 28 September 2001, R. L. Teixeira and P. S. Miller. MCP 31328, (2, 75.1–93.5 mm SL), rio Santa Joana, fazenda Coser, Itaguaçu, 19°44'07"S 40°50'42"W, 8 September 2001, R. L. Teixeira and P. S. Miller. MCP 42076, 3, 56.4–88.5 mm SL (2, 85.5–88.5 mm SL), rio Santa Joana, fazenda Coser, Itaguaçú, 19°48'S 40°52'W, 18 January 2001, R. L. Teixeira. Minas Gerais State: MCP 13755, 2, 67.7–79.7 mm SL, rio Santo Antonio near Ferros, 19°13'36"S 43°01'08"W 8 Set 1989, C. Lucena, E. H. Pereira, J. F. Pezzi & P. V. Azevedo. MCP 18047, 2, 31.5– 87.2 (1, 87.2 mm SL), rio Suaçuí at highway BR-116, Frei Inocêncio, 18°34'21"S 41°54'42"W, 18 January 1995, R. E. Reis, S. Schaefer, W. G. Saul and E. Pereira. ANSP 174077, 2, 34.6–67.6 mm SL, rio Suaçuí at highway BR- 116, Frei Inocêncio, 18°34'21"S 41°54'42"W, 18 January 1995, R. E. Reis, S. Schaefer, W. G. Saul and E. Pereira. MCP 42460, (2, 67.0– 88.3 mm SL), córrego Passa Sete on road from Conceição do Mato Dentro to Serro, Alvorada de Minas, 18°51'40"S 43°23'56"W, 10 January 2008, T. P. Carvalho, F. C. Jerep and C. A. Cramer. MCP 43794, 4, 69.6–93.0 mm SL (3, 84.3–93.0 mm SL), rio Doce near Baguari, 19°00'29"S 42°06'55"W, 1 November 2006, T. Pessali. MCP 49287, 8, 51.2–82.7 mm SL (2, 78.6–82.7 mm SL), creek tributary to rio Santo Antônio on road from Morro do Pilar to Itambé Mato Dentro, Morro do Pilar, 19°13'11"S 43°22'22"W, 29 July 2015, E. H. L. Pereira, P. Lehmann and R. E. Reis. MNRJ 18034, (2, 82.0– 86.6 mm SL), rio Santo Antônio near mouth of ribeirão Pitangas, Braúnas, March 1998, F. A. Bockmann, E. L. Sábato and M. A. L. Sábato. MZUSP 52555, 2, 19.1–99.4 mm SL, 1 c&s, 99.4 mm SL, ribeirão Pitangas, ca 2 km upstream from confluence with rio Santo Antônio, Braúnas, 19°05'14"S 42°40'34"W, 8 November 1997, P. M. C. Araújo and F. A. Bockmann. MZUSP 52562, (1, 105.7 mm SL), rio Santo Antônio at córrego do Gaúcho, near the hydroelectric plant of Salto Grande, Joanésia, 19°06'17"S 42°42'47"W, 11 August 1997, P. M. C. Araújo and F. A. Bockmann. MZUSP 52565, (1, 115.5 mm SL), rio Santo Antônio near mouth of ribeirão Pitangas, Braúnas, 19°05'44"S 42°39'51"W, 8 November 1997, P. M. C. Araújo and F. A. Bockmann.
Non-types. All from Brazil, Rio Doce basin: MCP 31305, 2, 38.9–61.5 mm SL, rio Jaboticabas, Itarana, Espirito Santo, 19°55'58"S 40°52'00"W, 18 October 2000, R. L. Teixeira and P. S. Miller. MCP 31310, 1, 33.7 mm SL, córrego Limoeiro near Praça Oito, Itarana, Espirito Santo, 19°55'S 40°50'W, 18 October 2000, R. L. Teixeira and P. S. Miller. MZUSP 52540, 7, 13.1–48.7 mm SL, ribeirão Pitangas near confluence with rio Santo Antônio, Braúnas, Minas Gerais, 19°05'44"S 42°39'51"W, 7 November 1997, P. M. C. Araújo and F. A. Bockmann. MCP 41829, 2, 42.8–45.6 mm SL, ribeirão Panquinhas, Fazenda Breda, Pancas, Espírito Santo, approx. 19°13'S 40°51'W, 4 February 2003, R. L. Teixeira.
Rio São Mateus basin: MCP 26709, 2, 58.8–59.9 mm SL, rio Itaúnas at Barra do São Francisco, tributary to rio São Mateus, Barra de São Francisco, Espirito Santo, 18°49’52”S 40°54’42”W, 26 August 2000, R. L. Teixeira. MCP 26700, 2, 66.0– 66.1 mm SL, rio Itaúnas at Barra do São Francisco, tributary to rio São Mateus, Barra de São Francisco, Espirito Santo, 18°49’52”S 40°54’42”W, 27 August 2000, R. L Teixeira. MCP 26689, 1, 72.6 mm SL, rio Itaúnas at Barra do São Francisco, tributary to rio São Mateus, Barra de São Francisco, Espirito Santo, 18°46’19”S 40°52’43”W, 26 August 2000, R. L. Teixeira. MCP 41872, 6, 51.5–78.5 mm SL, rio Itaúnas at waterfall, Barra de São Francisco, Espírito Santo, 18 June 2001, R. L. Teixeira. MCP 18040, 1, 63.5 mm SL and ANSP 174082, 1, 76.1 mm SL, rio Cricaré, tributary to rio São Mateus, ca 1 km upstream from Nova Venecia, Espírito Santo, 18°42’02”S 40°24’58”W, 26 January 1995, R. E. Reis and others. MCP 27689, 4, 56.4–104.5 mm SL, 1 c&s, 75.2 mm SL, córrego do Ouro at Barra de São Francisco, tributary to rio São Mateus, Barra de São Francisco, Espírito Santo, 18°43’17”S 40°49’27”W, 27 March 2001, R. L. Teixeira. MCP 27701, 22, 51.2–82.7 mm SL, 3 c&s, 63.8–78.7 mm SL, rio Itaúnas at Cachoeirinha de Itaúnas, tributary to rio São Francisco, rio São Mateus basin, Barra de São Francisco, Espírito Santo, approx. 18°51’S 40°54’W, 27 March 2001, R. L. Teixeira. Rio Mucuri basin: MCP 18049, 2, 74.7–105.0 mm SL and ANSP 174078, 2, 82.6–93.3 mm SL, rio Santana, tributary to rio Mucuri, on road BR-418 from Teófilo Otoni to Carlos Chagas, ca 22 km E of Teófilo Otoni, Minas Gerais, 17°50'39"S 041°20'54"W, 19 January 1995, R. Reis, S. Schaefer and E. H. L. Pereira. MCP 18048, 1, 90.4 mm SL and ANSP 174079, 2, 48.5–50.2 mm SL, waterfalls of rio Teófilo Otoni, tributary to rio Mucuri, near road from Teófilo Otoni to Potá, Teófilo Otoni, Minas Gerais, 17°50’30”S 41°36’39”W, 19 January 1995, W. G. Saul, J. C. Garavello and A. S. Santos. MCP 18038, 3, 61.8–75.4 mm SL, 2 c&s, 67.6–72.9 mm SL and ANSP 174080, 5, 56.0– 68.2 mm SL, rio Mucuri on road from Ladainha to Teofilo Otoni next to old railroad, Teófilo Otoni, Minas Gerais, 19 January 1995, 17°43'20"S 41°40'25"W, W. G. Saul, J. C. Garavello and A. S. Santos. MCP 17793, 1, 68.9 mm SL, rio Todos os Santos, tributary to rio Mucuri ca 30 km E of Teófilo Otoni, Teófilo Otoni, Minas Gerais, 17°53’25”S 041°17’13”W, 19 January 1995, R. E. Reis and others.
Rio dos Frades basin: MCP 18034, 20, 30.0– 68.1 mm SL, 3 c&s, 31.9–67.8 mm SL and ANSP 174085, 15, 27.6–61.8 mm SL, rio dos Frades on road BR-101 between Guaratinga and Monte Pascoal, Bahia, 16°37’09”S 39°32’25”W, 24 January 1995, W. G. Saul and others. MCP 18037, 5, 64.5–81.4 mm SL, 1 c&s, 73.7 mm SL and ANSP 174081, 5, 54.7–79.4 mm SL, rio Barrigudas, tributary to rio dos Frades, ca 13 km from road BR-101 towards Cajuíta, Guaratinga, Bahia, 16°39’32”S 39°37’03”W, 24 January 1995, R. E. Reis and others.
Other smaller basins: MCP 44948, 2, 82.1–95.3 mm SL, creek tributary to rio Santa Maria, Luiz Portraz, Espírito Santo, Brazil, 20°03’23”S 40°46’29”W, 23 January 2010, R. E. Reis and others. MCP 27682, 3, 58.2–83.0 mm SL, rio Santa Maria at Cachoeira do Pastor, Santa Maria do Jetibá, Espírito Santo, 20°04'24"S 40°47'01"W, 17 January 2001, R. L. Teixeira. MCP 31323, 8, 74.7–119.7 mm SL, 1 c&s, 87.1 mm SL, rio Santa Maria at Cachoeira do Pastor, Santa Maria do Jetibá, Espírito Santo, Brazil, 20°04'24"S 40°47'01"W, 17 January 2001, R. L. Teixeira. MCP 29478, 5, 87.9–115.8 mm SL, 1 c&s, 102.7 mm SL, rio Santa Maria da Vitória at Cachoeira do Pastor, Santa Maria do Jetibá, Espírito Santo, 20°04'24"S 40°47'01"W, 14 March 2001, R. L. Teixeira. MCP 27705, 3, 85.6– 116.2 mm SL, rio Santa Maria at Cachoeira do Pastor, Santa Maria do Jetibá, Espírito Santo, 20°04’24”S 040°47’01”W, 14 March 2001, R. L. Teixeira. MCP 31308, 2, 79.4–84.7 mm SL, rio Santa Maria at Cachoeira do Pastor, Santa Maria do Jetibá, Espírito Santo, 20°04’24”S 040°47’01”W, 27 July 2000, R. L. Teixeira. MCP 41870, 2, 52.9–86.4 mm SL, rio Santa Maria da Vitória at Cachoeira do Pastor, Santa Maria do Jetibá, Espírito Santo, Brazil, 20°04’24”S 040°47’01”W, 17 January 2001, R. L. Teixeira. MCP 29491, 1, 111.2 mm SL, upper rio Santa Maria da Vitória, Santa Maria do Jetibá, Espírito Santo, 20°07’35”S 040°53’27”W, 14 March 2001, R. L. Teixeira. MCP 27332, 3, 85.7–98.2 mm SL, rio Santa Maria da Vitória, Santa Maria do Jetibá, Espírito Santo, approx. 20°02’S 40°44’W, 27 July 2000, R. L. Teixeira. MCP 29471, 1, 72.2 mm SL, córrego Rico, Muniz Freire, Espírito Santo, 20°23’33”S 41°24’46”W, 27 March 2001. R. L. Teixeira. MCP 37336, 17, 57.7–113.7 mm SL, córrego Palmeira at Fazenda Cafenorte, tributary to rio Jucuruçu, Prado, Bahia, 17°10’30”S 39°32’10”W, 29 November, 2004, J. F. P. da Silva.
Diagnosis. As for genus.
Description. Counts and proportional measurements in Table 1. Large sized neoplecotomine with standard length of measured specimens reaching to 115.5 mm SL. Body elongate, wide anteriorly and moderately depressed. Greatest body width at cleithrum, progressively tapering to end of caudal peduncle. Dorsal profile of body continuously convex from snout tip to dorsal-fin origin, straight to slightly concave from that point to adipose fin, and slightly concave from adipose spine to caudal fin. Greatest body depth at dorsal-fin origin. Least body depth at shallowest portion of caudal peduncle. Trunk and caudal peduncle somewhat trapezoidal in cross-section, flattened ventrally between dorsal-fin origin and adipose fin, more compressed caudally. Lateral-line canal in median series complete, pored tube visible from compound pterotic to caudal-fin base. Ventral profile almost straight between snout tip and pelvic girdle, slightly convex at pelvic and straight to slightly concave along caudal peduncle. Dorsal and lateral surfaces of body and ventral surface of caudal peduncle covered by dermal plates. Predorsal area covered by plates arranged in two or more frequently three series of predorsal plates. Five lateral rows of dermal plates covering body. Dorsal series forming inconspicuous ridge between dorsal and adipose fins and ventral series bent and forming strong ridge on caudal peduncle. All body plates and posterior portion of head with odontodes clearly aligned and forming lines. Ventral surface of head and abdomen totally naked up to anal-fin origin. Plates of ventral series not meeting counterparts in midline in front of anal fin.
Head broad and depressed. Outline of head widely round, in dorsal view, more so in males. Interorbital space wide and flat to slightly concave. Three weakly elevated ridges on snout, one in front of each orbit and central ridge anterior to nares formed by underlying bones, without emerging hyperthrophied odontodes. Snout convex in lateral profile; completely covered by dermal plates but lacking rostral plate. Snout tip with small area devoid of odontodes. Eye large, dorsolaterally placed; orbital diameter 16.1–19.7% HL. Iris operculum present. Nares triangular, wider anteriorly and narrow posteriorly, positioned much closer to anterior margin of orbit than to snout tip. Lips well developed, widely oval transversely. Lower lip wide and comparatively short, never reaching pectoral girdle. Surface of lower lip densely covered by minute papillae; papillae decreasing in size towards edge. Margin of lower lip ornated with dense but fine fringes and sometimes elongated papillae. Upper lip smaller and usually bent posteriorly, concealing papillae. Maxillary barbel small and free. Teeth series in both premaxillae and dentaries with mesial ends slightly curved inwards. Teeth slender, asymmetrically bifid, medial cusp long and rounded; lateral cusp small and pointed, with about one third to one fifth length of medial cusp in unworn teeth.
Dorsal-fin origin along vertical passing through origin of unbranched pelvic-fin ray. Dorsal fin short, not contacting preadipose azygous plates when adpressed. Nuchal plate crescent-shaped and exposed in front of dorsal fin. Dorsal-fin spinelet present. Dorsal-fin spine moderately flexible, followed by seven branched rays. Adipose fin with large and well-ossified leading spine bearing odontodes. Adipose-fin membrane well developed, short or extended slightly beyond tip of adipose-fin spine. Adipose fin preceeded by one to three median preadipose azygous plates (usually one or two). Pectoral fin large, with spine slightly curve and flattened, covered by minute odontodes. Pectoral fin with six branched rays, first equal to or slightly longer than spine. Subsequent branched rays decrease gradually in size, last ray two thirds length of first ray. Distal margin of pectoral fin straight to slightly rounded, reaching between one third and one half of pelvic-fin spine when adpressed. Pelvic fin with one unbranched and five branched rays, not reaching to anal-fin origin when adpressed. Pelvic-fin unbranched ray depressed, covered with minute odontodes and with small dermal flap on dorsal surface in males. Anal fin small with one unbranched and five branched rays. Anal-fin origin along vertical slightly anterior to tip of depressed dorsal-fin rays. Caudal fin concave; lower lobe slightly longer than upper; 14 branched rays. Upper caudal-fin lobe with five and lower lobe with four plate-like procurrent rays, posteriormost elongate. Total vertebral centra 29; hypural plate slightly asymmetrical, with hypurals 1+2 extending slightly beyond posterior margin of hypurals 3+4+5.
Color in alcohol. Body mostly light or medium brown dorsally with four darker dorsal saddles; first on anterior portion of dorsal-fin base, second on last rays and immediately posterior to dorsal fin, third at origin of adipose fin, and fourth at end of caudal peduncle. All dark saddles on dorsal and middorsal series of plates, merging laterally on conspicuous darker longitudinal stripe. Ventral half of plates in midventral series and entire plates in ventral series pale yellow, highlightening dark longitudinal stripe. Head mostly plain dark brown, with crest in front of each eye slightly lighter. Ventral surface of head and trunk pale yellow; upper lip and sometimes skin in front of opercular opening darkened. Dorsal-fin rays pale, with three or four inconspicuous lines of darker spots. Pectoral- and pelvic-fin rays with three or four lines of dark brown spots. Anal fin mostly unpigmented. Caudal fin with transverse, dark brown band basally and two or three irregular transverse dark brown bands across rays. Interradial membranes hyaline on all fins (Fig. 41).
Sexual dimorphism. Males of Euryochus thysanos possess the typical conical urogenital papilla of neoplecostomines and hypoptopomatines behind the anal opening and a small dermal flap on the dorsal surface of the pelvic-fin spine, which are absent in females. In addition, mature males also have the odontodes on the lateral margins of the head and on the exposed process of the cleithrum above the pectoral-fin insertion slightly hypertrophied, when compared to females.
Etymology. Euryochus thysanos is named from the Greek thysanos, meaning fringe or tassel; in allusion to the finely fringed margin of the lower lip. A noun in apposition.
Geographic distribution. Euryochus thysanos occurs in the coastal rivers of eastern Brazil from the Itapemirim River in the south, and including the larger basins of the Doce and Mucuri rivers in Espirito Santo and Minas Gerais states, to the Frades River in the north, in Bahia State (Fig. 42).
Habitat notes. Euryochus thysanos is known from many localities in coastal rivers of eastern Brazil, where it occurs in a variety of habitats like small creeks to large rivers. Water current is typically medium to high and substrate is composed of small to large rocks and boulders. The species has been collected in places where water quality was not very good and where riparian forest has been removed. For this reason, and considering its wide distribution, E. thysanos can be assessed as Least Concern according to the IUCN criteria (IUCN, 2016).
Remarks. Although all populations of Euryochus thysanos are believed to be conspecific, they are distributed in various independent coastal basins of eastern Brazil, and slight morphometric differences were detected among those populations (see values in boldface in Table 1). For this reason, only specimens inhabiting the Doce River basin were used as type-material.
description: Published as part of Pereira, Edson H. L. & Reis, Roberto E., 2017, Morphology-based phylogeny of the suckermouth armored catfishes, with emphasis on the Neoplecostominae (Teleostei: Siluriformes: Loricariidae), pp. 1-104 in Zootaxa 4264 (1) on pages 77-81, DOI: 10.5281/zenodo.574211