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Listrura urussanga sp. nov. http://zoobank.org/act: F703D95A-0F7E-4261-8B97-5EAAAD9BD698 (Figures 3d–f, 6, 7; Table 1) Holotype UFRJ 6914, 35.5 mm SL; Brazil: Estado de Santa Catarina: Municipality of Balneário Rincão: village of Urussanga Velha: stream tributary to Lagoa Urussanga Velha, Rio Urussanga basin, 28.791°S, 49.238°W; C.R.M. Feltrin, 27 April 2020. Paratypes All from Brazil: Estado de Santa Catarina: Município de Balneário Rincão: Rio Urussanga basin. UFRJ 6915, 1, 27.6 mm SL; UFRJ 6916, 3, 30.7–37.6 mm SL (C&S); CICCAA 04080, 2, 31.9–37.2 mm SL; collected with holotype. UFRJ 6917, 3, 35.9–39.6 mm SL; stream tributary to Lagoa Urussanga Velha, 28.786°S, 49.231°W; C.R.M. Feltrin, 27 April 2020. Additional material (non-type specimens) UFRJ 6930, 6; UFRJ 6931, 1 (C&S); Brazil: Santa Catarina State: Municipality of Içara: village of Cristo Rei: stream belonging to the Rio Três Ribeirões subdrainage, Rio dos Porcos drainage, Rio Araranguá basin, Cristo Rei, Içara, 28.713°S, 49.321°W; C.R.M. Feltrin, 27 April 2020. Diagnosis Listrura urussanga differs from all other species of the genus, except L. depinnai and L. gyrinura, by having a deep caudal peduncle, deeper than the preanal region of the body, as the result of an expanded skin fold involving procurrent caudal-fin rays (vs caudal peduncle slender, its depth about equal to preanal depth). Listrura urussanga is distinguished from L. depinnai by the presence of a dorsal fin (vs absence), and by having more vertebrae (48 or 49 vs 45 or 46), and from Listrura gyrinura having fewer vertebrae (48 or 49 vs 51 or 52), dorsal-fin origin at a vertical between the centra of the 29th and 30th vertebrae (vs between the centra of the 31st to 33rd vertebrae), anal-fin origin at a vertical between the centra of the 30th and 31st vertebrae (vs between the centra of the 32nd and 33rd vertebrae), presence of a process on the dorsal surface of the autopalatine articular facet for the mesethmoid (vs absence), presence of a ventral projection on the hyomandibula articular facet for the opercle (vs absence), a longer parhypural posterior process, its length about equal to the length between the anterior margin of the parurohyal head and the proximal limit of the posterior process (vs about half as long as, or slightly shorter than that length), and mesethmoid cornu nearly straight (vs slightly folded posteriorly). Listrura urussanga is also distinguished from L. boticario and L. camposae by having more procurrent caudal-fin rays (dorsal procurrent rays 38 or 39 vs 28–30 in L. boticario, 31–34 in L. camposae; ventral procurrent rays 35 or 36, vs 28 in L. boticario and 26–28 in L. camposae). Description Morphometric data appear in Table 1. Body slender, subcylindrical anteriorly, compressed posteriorly. Greatest body depth approximately at middle region of caudal peduncle. Dorsal and ventral profiles slightly convex, slightly expanded on caudal peduncle. Skin papillae minute. Anus and urogenital papilla slightly anterior to anal fin base. Head trapezoidal in dorsal view. Anterior profile of head straight in dorsal view. Eye small, dorsally positioned in head, just anterior to midway between snout and posterior limit of head. Posterior nostril located nearer orbit than anterior nostril. Barbels long, reaching basal portion of first pectoral-fin ray. Mouth subterminal. Jaw teeth pointed, arranged in two rows; total premaxillary teeth 16–20, outer row 6–8, inner row 10–12; total dentary teeth 15–16, outer row 7–8, inner row 7–9. Branchial membrane attached to isthmus only at its anterior point. Branchiostegal rays 6. Dorsal and anal fins minute; total dorsal-fin rays 7 (i–ii + V–VI), total anal-fin rays 6–7 (i–ii + 5–6); dorsal-fin origin at vertical slightly posterior to anal-fin base, through centrum of 29th or 30th vertebra; anal-fin origin at vertical through centrum of 30th or 31st vertebra. Pectoral fin narrow, total pectoral-fin rays 2–3 (II–III), first ray well developed, second and third rays rudimentary, second ray half first ray length or less, third ray when present hardly visible. Pelvic fin and girdle absent. Caudal fin spatula-shaped, with dorsal and ventral procurrent rays anteriorly extending to area close to dorsal and anal-fin base, respectively; total principal caudal-fin rays 13 (I + 9 + II), total dorsal procurrent rays 38–39 (xxxvi–xxxvii + I–II), total ventral procurrent rays 35–36 (xxxiv–xxxv + I). Vertebrae 48–49. Ribs 2 or 3. Single dorsal hypural plate, corresponding to hypurals 3–5; single ventral hypural plate corresponding to hypurals 1–2 and parhypural. Latero-sensory system Cephalic sensory canal minute, restricted to short postorbital canal with 2 pores just above opercular patch of odontodes, connected to short lateral line of body, with 1 pore just posterior to pectoral-fin base. Osteology (Figure 3 d-f) Mesethmoid thin, posteriorly widening, with distinctive lateral expansion; cornu narrow and straight. Antorbital rectangular, with a narrow posterior process; sesamoid supraorbital minute. Premaxilla sub-triangular in dorsal view, with narrow lateral extremity. Maxilla moderate in length, nearly equal to premaxilla length. Autopalatine sub-rectangular in dorsal view, compact, lateral and medial margins slightly concave; autopalatine posterolateral process minute, with narrow process dorso-medially directed; articular facet for mesethmoid wide, with distinctive dorsal process. Metapterygoid minute. Quadrate slender, dorsal process narrow, without posterior outgrowth. Hyomandibula long, with anterior outgrowth anteriorly terminating in sharp tip; articular facet for opercle robust, with distinctive ventral expansion. Opercle relatively robust, transverse length of odontode patch slightly shorter than transverse length of interopercular odontode patch; interopercle compact, with prominent postero-dorsal expansion; opercular odontodes 6–8, interopercular odontodes 6–8; odontodes pointed, nearly straight. Preopercle narrow and long. Parurohyal slender, lateral process narrow and pointed, latero-posteriorly directed; parurohyal head small, with minute anterolateral paired process; middle foramen small and rounded; posterior process long, its length about equal to length between anterior margin of parurohyal head and proximal limit of posterior process. Colouration in alcohol Trunk and head light brownish grey, with brown chromatophores irregularly arranged on dorsum, flank and head, often forming irregularly shaped spots, darker on flank longitudinal midline, almost black, often forming interrupted longitudinal stripe; on head, brown chromatophores extending over base of barbels; unpigmented area below orbit and branchiostegal region. Venter greyish white with few sparse brown chromatophores. Fins hyaline with brown chromatophores forming minute spots, often melanophores forming black spots between dorsal limit of caudal peduncle muscles and skin fold supporting dorsal procurrent caudal-fin rays. Distribution, habitat and conservation Listrura urussanga is known from two neighbouring areas, one in streams tributary to the Lagoa Urussanga Velha, Rio Urussanga basin, the type locality, and the other in the Rio dos Porcos drainage, Rio Araranguá basin (Figure 4). Specimens were found close to the leaf litter bottom over fine gravel sediment on the stream bottom (Figure 5b). The region where this species was found is undergoing an intense process of urbanisation, and many areas are occupied by livestock and agriculture activities, leaving few areas with natural conditions. In addition, neighbouring streams are under intense environmental decline caused by new roads and urban pollution, making the habitat of the new species highly vulnerable. Etymology The name urussanga is a reference to the type locality of the new species near the Lagoa Urussanga Velha, Rio Urussanga basin. It is a non-Latin noun used in apposition. The name is probably derived from the Tupi-Guarani, meaning very cold water., Published as part of Costa, Wilson J. E. M., Feltrin, Caio R. M. & Katz, Axel M., 2023, Field studies in small streams of the Atlantic Forest of southern subtropical Brazil reveal two new interstitial microcambevine catfishes of the genus Listrura (Siluriformes: Trichomycteridae), pp. 475-489 in Journal of Natural History 57 (9 - 12) on pages 482-487, DOI: 10.1080/00222933.2023.2196450, http://zenodo.org/record/7924564

Listrura urussanga sp. nov. http://zoobank.org/act: F703D95A-0F7E-4261-8B97-5EAAAD9BD698 (Figures 3d–f, 6, 7; Table 1) Holotype UFRJ 6914, 35.5 mm SL; Brazil: Estado de Santa Catarina: Municipality of Balneário Rincão: village of Urussanga Velha: stream tributary to Lagoa Urussanga Velha, Rio Urussanga basin, 28.791°S, 49.238°W; C.R.M. Feltrin, 27 April 2020. Paratypes All from Brazil: Estado de Santa Catarina: Município de Balneário Rincão: Rio Urussanga basin. UFRJ 6915, 1, 27.6 mm SL; UFRJ 6916, 3, 30.7–37.6 mm SL (C&S); CICCAA 04080, 2, 31.9–37.2 mm SL; collected with holotype. UFRJ 6917, 3, 35.9–39.6 mm SL; stream tributary to Lagoa Urussanga Velha, 28.786°S, 49.231°W; C.R.M. Feltrin, 27 April 2020. Additional material (non-type specimens) UFRJ 6930, 6; UFRJ 6931, 1 (C&S); Brazil: Santa Catarina State: Municipality of Içara: village of Cristo Rei: stream belonging to the Rio Três Ribeirões subdrainage, Rio dos Porcos drainage, Rio Araranguá basin, Cristo Rei, Içara, 28.713°S, 49.321°W; C.R.M. Feltrin, 27 April 2020. Diagnosis Listrura urussanga differs from all other species of the genus, except L. depinnai and L. gyrinura, by having a deep caudal peduncle, deeper than the preanal region of the body, as the result of an expanded skin fold involving procurrent caudal-fin rays (vs caudal peduncle slender, its depth about equal to preanal depth). Listrura urussanga is distinguished from L. depinnai by the presence of a dorsal fin (vs absence), and by having more vertebrae (48 or 49 vs 45 or 46), and from Listrura gyrinura having fewer vertebrae (48 or 49 vs 51 or 52), dorsal-fin origin at a vertical between the centra of the 29th and 30th vertebrae (vs between the centra of the 31st to 33rd vertebrae), anal-fin origin at a vertical between the centra of the 30th and 31st vertebrae (vs between the centra of the 32nd and 33rd vertebrae), presence of a process on the dorsal surface of the autopalatine articular facet for the mesethmoid (vs absence), presence of a ventral projection on the hyomandibula articular facet for the opercle (vs absence), a longer parhypural posterior process, its length about equal to the length between the anterior margin of the parurohyal head and the proximal limit of the posterior process (vs about half as long as, or slightly shorter than that length), and mesethmoid cornu nearly straight (vs slightly folded posteriorly). Listrura urussanga is also distinguished from L. boticario and L. camposae by having more procurrent caudal-fin rays (dorsal procurrent rays 38 or 39 vs 28–30 in L. boticario, 31–34 in L. camposae; ventral procurrent rays 35 or 36, vs 28 in L. boticario and 26–28 in L. camposae). Description Morphometric data appear in Table 1. Body slender, subcylindrical anteriorly, compressed posteriorly. Greatest body depth approximately at middle region of caudal peduncle. Dorsal and ventral profiles slightly convex, slightly expanded on caudal peduncle. Skin papillae minute. Anus and urogenital papilla slightly anterior to anal fin base. Head trapezoidal in dorsal view. Anterior profile of head straight in dorsal view. Eye small, dorsally positioned in head, just anterior to midway between snout and posterior limit of head. Posterior nostril located nearer orbit than anterior nostril. Barbels long, reaching basal portion of first pectoral-fin ray. Mouth subterminal. Jaw teeth pointed, arranged in two rows; total premaxillary teeth 16–20, outer row 6–8, inner row 10–12; total dentary teeth 15–16, outer row 7–8, inner row 7–9. Branchial membrane attached to isthmus only at its anterior point. Branchiostegal rays 6. Dorsal and anal fins minute; total dorsal-fin rays 7 (i–ii + V–VI), total anal-fin rays 6–7 (i–ii + 5–6); dorsal-fin origin at vertical slightly posterior to anal-fin base, through centrum of 29th or 30th vertebra; anal-fin origin at vertical through centrum of 30th or 31st vertebra. Pectoral fin narrow, total pectoral-fin rays 2–3 (II–III), first ray well developed, second and third rays rudimentary, second ray half first ray length or less, third ray when present hardly visible. Pelvic fin and girdle absent. Caudal fin spatula-shaped, with dorsal and ventral procurrent rays anteriorly extending to area close to dorsal and anal-fin base, respectively; total principal caudal-fin rays 13 (I + 9 + II), total dorsal procurrent rays 38–39 (xxxvi–xxxvii + I–II), total ventral procurrent rays 35–36 (xxxiv–xxxv + I). Vertebrae 48–49. Ribs 2 or 3. Single dorsal hypural plate, corresponding to hypurals 3–5; single ventral hypural plate corresponding to hypurals 1–2 and parhypural. Latero-sensory system Cephalic sensory canal minute, restricted to short postorbital canal with 2 pores just above opercular patch of odontodes, connected to short lateral line of body, with 1 pore just posterior to pectoral-fin base. Osteology (Figure 3 d-f) Mesethmoid thin, posteriorly widening, with distinctive lateral expansion; cornu narrow and straight. Antorbital rectangular, with a narrow posterior process; sesamoid supraorbital minute. Premaxilla sub-triangular in dorsal view, with narrow lateral extremity. Maxilla moderate in length, nearly equal to premaxilla length. Autopalatine sub-rectangular in dorsal view, compact, lateral and medial margins slightly concave; autopalatine posterolateral process minute, with narrow process dorso-medially directed; articular facet for mesethmoid wide, with distinctive dorsal process. Metapterygoid minute. Quadrate slender, dorsal process narrow, without posterior outgrowth. Hyomandibula long, with anterior outgrowth anteriorly terminating in sharp tip; articular facet for opercle robust, with distinctive ventral expansion. Opercle relatively robust, transverse length of odontode patch slightly shorter than transverse length of interopercular odontode patch; interopercle compact, with prominent postero-dorsal expansion; opercular odontodes 6–8, interopercular odontodes 6–8; odontodes pointed, nearly straight. Preopercle narrow and long. Parurohyal slender, lateral process narrow and pointed, latero-posteriorly directed; parurohyal head small, with minute anterolateral paired process; middle foramen small and rounded; posterior process long, its length about equal to length between anterior margin of parurohyal head and proximal limit of posterior process. Colouration in alcohol Trunk and head light brownish grey, with brown chromatophores irregularly arranged on dorsum, flank and head, often forming irregularly shaped spots, darker on flank longitudinal midline, almost black, often forming interrupted longitudinal stripe; on head, brown chromatophores extending over base of barbels; unpigmented area below orbit and branchiostegal region. Venter greyish white with few sparse brown chromatophores. Fins hyaline with brown chromatophores forming minute spots, often melanophores forming black spots between dorsal limit of caudal peduncle muscles and skin fold supporting dorsal procurrent caudal-fin rays. Distribution, habitat and conservation Listrura urussanga is known from two neighbouring areas, one in streams tributary to the Lagoa Urussanga Velha, Rio Urussanga basin, the type locality, and the other in the Rio dos Porcos drainage, Rio Araranguá basin (Figure 4). Specimens were found close to the leaf litter bottom over fine gravel sediment on the stream bottom (Figure 5b). The region where this species was found is undergoing an intense process of urbanisation, and many areas are occupied by livestock and agriculture activities, leaving few areas with natural conditions. In addition, neighbouring streams are under intense environmental decline caused by new roads and urban pollution, making the habitat of the new species highly vulnerable. Etymology The name urussanga is a reference to the type locality of the new species near the Lagoa Urussanga Velha, Rio Urussanga basin. It is a non-Latin noun used in apposition. The name is probably derived from the Tupi-Guarani, meaning very cold water.

Listrura gyrinura sp. nov. http://zoobank.org/act: F68F2A3E-B5F7-418E-BFA6-EA6752BAB543 (Figures 1–3a–c; Table 1) Holotype UFRJ 6927, 39.9 mm SL; Brazil: Santa Catarina State: Municipality of Paulo Lopes: village of Sertão do Campo: stream tributary to Rio da Madre, 27.920°S, 48.692°W; C.R.M. Feltrin and F.R. Colonetti, 10 July 2020. Paratypes UFRJ 6928, 10, 27.6–41.6 mm SL; UFRJ 6929, 4 (C&S), 29.7–38.4 mm SL; CICCAA 02658, 5, 29.7–37.0 mm SL; collected with holotype. Diagnosis Listrura gyrinura is distinguished from all congeners, except L. depinnai and L. urussanga, by having a deep caudal peduncle,deeper than the preanal region of the body, as the result of an expanded skin fold involving procurrent caudal-fin rays (vs caudal peduncle slender, its depth about equal to preanal depth). Listrura gyrinura is distinguished from L. depinnai and L. urussanga by having more vertebrae (51 or 52 vs 45 or 46 in L. depinnai and 48 or 49 in L. urussanga), absence of a process on the dorsal surface of the autopalatine articular facet for the mesethmoid (vs presence),and by the mesethmoid cornu being slightly posteriorly folded (vs straight). Listrura gyrinura also differs from L. depinnai by the presence of a dorsal fin (vs absence), and from L. urussanga by having the dorsal-fin origin at a vertical between the centra of the 31st to 33rd vertebrae (vs between centra of the 29th and 30th vertebrae), anal-fin origin at a vertical between the centra of the 32nd and 33rd vertebrae (vs between the centra of the 30th and 31st vertebrae), absence of a ventral projection on the hyomandibula articular facet for the opercle (vs presence), and a shorter parhypural posterior process, its length about half or slightly less of the length between the anterior margin of the parurohyal head and the proximal limit of the posterior process (vs about equal to that length). Listrura gyrinura is also distinguished from L. boticario and L. camposae by having more ventral procurrent caudal-fin rays (31–36, vs 28 in L. boticario and 26–28 in L. camposae). Description Morphometric data appear in Table 1. Body slender, subcylindrical anteriorly, compressed posteriorly. Greatest body depth approximately at middle region of caudal peduncle. Dorsal and ventral profiles slightly convex, slightly expanded on caudal peduncle. Skin papillae minute. Anus and urogenital papilla slightly anterior to anal fin base. Head trapezoidal in dorsal view. Anterior profile of head straight in dorsal view. Eye small, dorsally positioned in head, just anterior to midway between snout and posterior limit of head. Posterior nostril located nearer to orbit than to anterior nostril. Barbels long, reaching basal portion of first pectoral-fin ray. Mouth subterminal. Jaw teeth pointed, arranged in two rows; total premaxillary teeth 18–23, outer row 7–10, inner row 11–13; total dentary teeth 15–18, outer row 6–7, inner row 7–11. Branchial membrane attached to isthmus only at its anterior point. Branchiostegal rays 5–7. Dorsal and anal fins minute; total dorsal-fin rays 6–8 (i–ii + V–VI), total anal-fin rays 8 (ii–iii + 5–6); dorsal-fin origin at vertical slightly posterior to anal-fin base, between centra of 31st to 33rd vertebrae; anal-fin origin at vertical through centrum of 32nd or 33rd vertebra. Pectoral fin narrow, total pectoral-fin rays 3 (III), first ray well developed, second and third rays rudimentary, second ray half first ray length or less, third ray slightly shorter than second ray. Pelvic fin and girdle absent. Caudal fin spatula-shaped, narrowing posteriorly; dorsal and ventral procurrent rays anteriorly extending to area close to dorsal- and anal-fin base, respectively; total principal caudal-fin rays 12 or 13 (I–II + 7–9 + II–III), total dorsal procurrent rays 33–38 (xxxii–xxxvii + I–II), total ventral procurrent rays 31–36 (xxx–xxxiv + I–III). Vertebrae 51–52. Ribs 2 or 3. Single dorsal hypural plate, corresponding to hypurals 3–5; single ventral hypural plate corresponding to hypurals 1–2 and parhypural. Latero-sensory system Cephalic sensory canal minute, restricted to short postorbital canal with 2 pores just above opercular patch of odontodes, connected to short lateral line of body, with 1 pore just posterior to pectoral-fin base. Osteology (Figure 3a–c) Mesethmoid thin, posteriorly widening, with distinctive lateral expansion; cornu narrow and slightly posteriorly folded. Antorbital pentagonal; sesamoid supraorbital minute. Premaxilla sub-triangular in dorsal view, with narrow lateral extremity. Maxilla moderate in length, slightly longer than premaxilla length. Autopalatine sub-rectangular in dorsal view, compact, lateral and medial margins slightly concave; autopalatine posterolateral process minute, with narrow process dorso-medially directed; articular facet for mesethmoid wide, without distinctive dorsal process. Metapterygoid minute. Quadrate slender, dorsal process narrow, without posterior outgrowth. Hyomandibula long, with anterior outgrowth anteriorly terminating in sharp tip; articular facet for opercle robust, without distinctive ventral expansion. Opercle slender, transverse length of odontode patch about three quarters of transverse length of interopercular odontode patch; interopercle compact, with minute postero-dorsal process; opercular odontodes 5–7, interopercular odontodes 8–10; odontodes pointed, nearly straight. Preopercle narrow and long. Parurohyal slender, lateral process narrow and pointed, latero-posteriorly directed; parurohyal head small, with prominent anterolateral paired process; middle foramen small and rounded; posterior process short, its length about half or slightly less of length between anterior margin of parurohyal head and proximal limit of posterior process. Colouration in alcohol Dorsum and dorsal portion of flank and head light brownish grey, with brown chromatophores irregularly arranged, often forming small irregularly shaped spots, darker on flank longitudinal midline; on head, brown chromatophores extending over base of barbels; unpigmented area below orbit. Venter and ventral portion of flank and head greyish white, often with brown chromatophores irregularly arranged on posterior region of flank, sometimes a few brown chromatophores on ventral portion of head and venter. Fins hyaline with brown chromatophores forming minute spots. Distribution, habitat and conservation Listrura gyrinura is only known from the type locality, a clear-water stream tributary to the Rio da Madre, a small isolated coastal river basin (Figure 4). It was found close to the leaf litter over gravel sediment on the stream bottom (Figure 5a). The habitat of this species may be considered highly endangered by mining activities that use explosives. About 100 m below the type locality, the stream is highly impacted by both mining sediments and rice planting. Etymology From the Greek gyrinus (tadpole) and ura (tail), referring to the shape of the caudal fin and caudal peduncle of the new species, similar to that occurring in tadpoles., Published as part of Costa, Wilson J. E. M., Feltrin, Caio R. M. & Katz, Axel M., 2023, Field studies in small streams of the Atlantic Forest of southern subtropical Brazil reveal two new interstitial microcambevine catfishes of the genus Listrura (Siluriformes: Trichomycteridae), pp. 475-489 in Journal of Natural History 57 (9 - 12) on pages 477-481, DOI: 10.1080/00222933.2023.2196450, http://zenodo.org/record/7924564

Listrura gyrinura sp. nov. http://zoobank.org/act: F68F2A3E-B5F7-418E-BFA6-EA6752BAB543 (Figures 1–3a–c; Table 1) Holotype UFRJ 6927, 39.9 mm SL; Brazil: Santa Catarina State: Municipality of Paulo Lopes: village of Sertão do Campo: stream tributary to Rio da Madre, 27.920°S, 48.692°W; C.R.M. Feltrin and F.R. Colonetti, 10 July 2020. Paratypes UFRJ 6928, 10, 27.6–41.6 mm SL; UFRJ 6929, 4 (C&S), 29.7–38.4 mm SL; CICCAA 02658, 5, 29.7–37.0 mm SL; collected with holotype. Diagnosis Listrura gyrinura is distinguished from all congeners, except L. depinnai and L. urussanga, by having a deep caudal peduncle,deeper than the preanal region of the body, as the result of an expanded skin fold involving procurrent caudal-fin rays (vs caudal peduncle slender, its depth about equal to preanal depth). Listrura gyrinura is distinguished from L. depinnai and L. urussanga by having more vertebrae (51 or 52 vs 45 or 46 in L. depinnai and 48 or 49 in L. urussanga), absence of a process on the dorsal surface of the autopalatine articular facet for the mesethmoid (vs presence),and by the mesethmoid cornu being slightly posteriorly folded (vs straight). Listrura gyrinura also differs from L. depinnai by the presence of a dorsal fin (vs absence), and from L. urussanga by having the dorsal-fin origin at a vertical between the centra of the 31st to 33rd vertebrae (vs between centra of the 29th and 30th vertebrae), anal-fin origin at a vertical between the centra of the 32nd and 33rd vertebrae (vs between the centra of the 30th and 31st vertebrae), absence of a ventral projection on the hyomandibula articular facet for the opercle (vs presence), and a shorter parhypural posterior process, its length about half or slightly less of the length between the anterior margin of the parurohyal head and the proximal limit of the posterior process (vs about equal to that length). Listrura gyrinura is also distinguished from L. boticario and L. camposae by having more ventral procurrent caudal-fin rays (31–36, vs 28 in L. boticario and 26–28 in L. camposae). Description Morphometric data appear in Table 1. Body slender, subcylindrical anteriorly, compressed posteriorly. Greatest body depth approximately at middle region of caudal peduncle. Dorsal and ventral profiles slightly convex, slightly expanded on caudal peduncle. Skin papillae minute. Anus and urogenital papilla slightly anterior to anal fin base. Head trapezoidal in dorsal view. Anterior profile of head straight in dorsal view. Eye small, dorsally positioned in head, just anterior to midway between snout and posterior limit of head. Posterior nostril located nearer to orbit than to anterior nostril. Barbels long, reaching basal portion of first pectoral-fin ray. Mouth subterminal. Jaw teeth pointed, arranged in two rows; total premaxillary teeth 18–23, outer row 7–10, inner row 11–13; total dentary teeth 15–18, outer row 6–7, inner row 7–11. Branchial membrane attached to isthmus only at its anterior point. Branchiostegal rays 5–7. Dorsal and anal fins minute; total dorsal-fin rays 6–8 (i–ii + V–VI), total anal-fin rays 8 (ii–iii + 5–6); dorsal-fin origin at vertical slightly posterior to anal-fin base, between centra of 31st to 33rd vertebrae; anal-fin origin at vertical through centrum of 32nd or 33rd vertebra. Pectoral fin narrow, total pectoral-fin rays 3 (III), first ray well developed, second and third rays rudimentary, second ray half first ray length or less, third ray slightly shorter than second ray. Pelvic fin and girdle absent. Caudal fin spatula-shaped, narrowing posteriorly; dorsal and ventral procurrent rays anteriorly extending to area close to dorsal- and anal-fin base, respectively; total principal caudal-fin rays 12 or 13 (I–II + 7–9 + II–III), total dorsal procurrent rays 33–38 (xxxii–xxxvii + I–II), total ventral procurrent rays 31–36 (xxx–xxxiv + I–III). Vertebrae 51–52. Ribs 2 or 3. Single dorsal hypural plate, corresponding to hypurals 3–5; single ventral hypural plate corresponding to hypurals 1–2 and parhypural. Latero-sensory system Cephalic sensory canal minute, restricted to short postorbital canal with 2 pores just above opercular patch of odontodes, connected to short lateral line of body, with 1 pore just posterior to pectoral-fin base. Osteology (Figure 3a–c) Mesethmoid thin, posteriorly widening, with distinctive lateral expansion; cornu narrow and slightly posteriorly folded. Antorbital pentagonal; sesamoid supraorbital minute. Premaxilla sub-triangular in dorsal view, with narrow lateral extremity. Maxilla moderate in length, slightly longer than premaxilla length. Autopalatine sub-rectangular in dorsal view, compact, lateral and medial margins slightly concave; autopalatine posterolateral process minute, with narrow process dorso-medially directed; articular facet for mesethmoid wide, without distinctive dorsal process. Metapterygoid minute. Quadrate slender, dorsal process narrow, without posterior outgrowth. Hyomandibula long, with anterior outgrowth anteriorly terminating in sharp tip; articular facet for opercle robust, without distinctive ventral expansion. Opercle slender, transverse length of odontode patch about three quarters of transverse length of interopercular odontode patch; interopercle compact, with minute postero-dorsal process; opercular odontodes 5–7, interopercular odontodes 8–10; odontodes pointed, nearly straight. Preopercle narrow and long. Parurohyal slender, lateral process narrow and pointed, latero-posteriorly directed; parurohyal head small, with prominent anterolateral paired process; middle foramen small and rounded; posterior process short, its length about half or slightly less of length between anterior margin of parurohyal head and proximal limit of posterior process. Colouration in alcohol Dorsum and dorsal portion of flank and head light brownish grey, with brown chromatophores irregularly arranged, often forming small irregularly shaped spots, darker on flank longitudinal midline; on head, brown chromatophores extending over base of barbels; unpigmented area below orbit. Venter and ventral portion of flank and head greyish white, often with brown chromatophores irregularly arranged on posterior region of flank, sometimes a few brown chromatophores on ventral portion of head and venter. Fins hyaline with brown chromatophores forming minute spots. Distribution, habitat and conservation Listrura gyrinura is only known from the type locality, a clear-water stream tributary to the Rio da Madre, a small isolated coastal river basin (Figure 4). It was found close to the leaf litter over gravel sediment on the stream bottom (Figure 5a). The habitat of this species may be considered highly endangered by mining activities that use explosives. About 100 m below the type locality, the stream is highly impacted by both mining sediments and rice planting. Etymology From the Greek gyrinus (tadpole) and ura (tail), referring to the shape of the caudal fin and caudal peduncle of the new species, similar to that occurring in tadpoles.