Uma nova espécie do recentemente descoberto tridentíneo miniatura, Rhinotridens, é descrita da bacia Amazônica no Brasil, Colômbia e Peru. A nova forma difere de Rhinotridenschromocaudatus, espécie-tipo do gênero, pela nadadeira caudal hialina, o barbilhão rictal vestigial ou externamente ausente, a nadadeira anal longa, com 22–29 raios segmentados, além de várias outras características do esqueleto. Uma descrição osteológica da nova espécie é fornecida com base em exemplares diafanizados e corados, e características de morfologia externa são revelados através de microscopia eletrônica de varredura (MEV), que pela primeira vez mostram detalhes da estrutura labial de Tridentinae. Os sete caracteres morfológicos previamente listados como sinapomorfias de Rhinotridens são confirmados na espécie aqui descrita, corroborando sua alocação genérica. Uma característica adicional da morfologia do processo lateral do autopalatino é proposta como uma nova sinapomorfia do gênero.

Palavras chave:
Bagre; Candiru; Miniatura; Sistemática; Taxonomia

Autoria

Mário de Pinna

Conceptualization

Data curation

Formal analysis

Investigation

Methodology

Project administration

Writing-original draft

Writing-review and editing

Museu de Zoologia da Universidade de São Paulo, Caixa Postal 42494, 04218-970 São Paulo, SP, Brazil. (MP) pinna@ib.usp.br (corresponding author), (VR) carvalhvinicius@gmail.com, (MNLP) mpastana@usp.br, (AD) adatovo@usp.br.Universidade de São PauloBrazilSão Paulo, SP, BrazilMuseu de Zoologia da Universidade de São Paulo, Caixa Postal 42494, 04218-970 São Paulo, SP, Brazil. (MP) pinna@ib.usp.br (corresponding author), (VR) carvalhvinicius@gmail.com, (MNLP) mpastana@usp.br, (AD) adatovo@usp.br.

https://orcid.org/0000-0003-1711-4816

Vinícius Reis

Data curation

Investigation

Methodology

Visualization

https://orcid.org/0000-0001-7163-9889

Murilo N. L. Pastana

Data curation

Formal analysis

Visualization

Writing-review and editing

https://orcid.org/0000-0003-3906-0863

Aléssio Datovo

Conceptualization

Data curation

Investigation

Methodology

Writing-review and editing

https://orcid.org/0000-0001-9117-7343

Edited-by

Carlos DoNascimiento

Correspondence

Mário de Pinna pinna@ib.usp.br

Competing Interests

The author declares no competing interests.

Ethical Statement

Not applicable.

SCIMAGO INSTITUTIONS RANKINGS

Figuras | Tabelas

Figuras (12)
Tabelas (2)

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FIGURE 1 |
Rhinotridens britskii, holotype, ZUEC 18281, 15.2 mm SL. Brazil, Amazonas State, Igarapé Boa Vista (rio Purus drainage). A. Lateral view; B. Dorsal view; C. Ventral view.

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FIGURE 2 |
Scanning electron microscopy of the head and anterior part of body of Rhinotridens britskii, paratype, MZUSP 36303, 13.4 mm SL. A. Lateral view; B. Dorsal view; C. Ventral view. Scale bar = 0.1 mm.

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FIGURE 3 |
Upper jaw and autopalatine of Rhinotridens britskii, paratype, MZUSP 129867, 15.2 mm SL; ventral view. Left anterior autopalatine cartilage damaged. Arrow indicates lateral process of autopalatine. Ap, autopalatine; LbT, labial teeth; Mx, maxilla; MxB, maxillary barbel; PmT, premaxillary teeth; Pmx, premaxilla; RcB, rictal barbel; SPT, symphyseal premaxillary teeth. Scale bar = 0.2 mm.

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FIGURE 4 |
Gill arches of Rhinotridens britskii, paratype, MZUSP 129867, 15.2 mm SL; dorsal view. ABb, additional basibranchial element; Bb2-4, basibranchials 2 to 4; Cb1-5, ceratobranchials 1 to 5; Eb1-4, epibranchials 1 to 4; Hb1-3, hypobranchials 1 to 3; Pb3-4, pharyngobranchials 3 to 4; Utp, upper pharyngeal tooth plate. Scale bar = 0.1 mm.

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FIGURE 5 |
Neurocranium and associated structures of Rhinotridens britskii, paratype, MZUSP 129867, 15.2 mm SL; A. Lateral view; B. Dorsal view; C. Ventral view. Boc, basioccipital; Ep, epioccipital; Fr, frontal; Le, lateral ethmoid; Me, mesethmoid; Osph, orbitosphenoid; Psph, parasphenoid; Psoc, parieto-supraoccipital; Ptscl, postemporo-supracleithrum; Pro, prootic; Pt, pterotic; Sph, sphenotic-prootic-pterosphenoid; Vo, vomer; WeC, Weberian capsule. Scale bar = 0.5 mm.

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FIGURE 6 |
Scanning electron microscopy of the opercular region of Rhinotridens britskii, paratype, MZUSP 36303, 13.4 mm SL. Arrows indicate opercular odontodophore (dorsally) and interopercular odontodophore (ventrally). Scale bar = 0.1 mm.

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FIGURE 7 |
Suspensorium and opercular series of Rhinotridens britskii, paratype, MZUSP 129867, 15.2 mm SL; left lateral view. Arrow indicates distal process of hyomandibula. Hy, hyomandibular; Iop, interopercle; Op, opercle; Pop, preopercle; Qd, quadrate. Scale bar = 0.2 mm.

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FIGURE 8 |
Hyoid arch of Rhinotridens britskii, paratype, MZUSP 129867, 15.2 mm SL; ventral view. AC, anterior ceratohyal; Br, branchiostegal rays; PC, posterior ceratohyal; Uh, urohyal; VH, ventral hypohyal. Scale bar = 0.2 mm.

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FIGURE 9 |
Pectoral skeleton of Rhinotridens britskii, paratype, MZUSP 129867, 15.2 mm SL; ventral view. Cle, cleithrum; Pcr, pectoral-fin rays; Pr1-2, proximal radials 1-2; Sco, scapulocoracoid. Scale bar = 0.3 mm.

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FIGURE 10 |
Pelvic girdle and fin of Rhinotridens britskii, paratype, MZUSP 129867, 15.2 mm SL. Arrows indicate ossified tips of basipterygium arms. Bpt, basipterygium; Pvr, pelvic-fin rays. Scale bar = 0.2 mm.

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FIGURE 11 |
Geographic distribution of Rhinotridens britskii. Dotted circle, holotype; white circle, paratypes and non-type specimens.

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FIGURE 12 |
Type-locality of Rhinotridens britskii, igarapé Boa Vista (rio Javari drainage), Atalaia do Norte Municipality. Photo by Flávio C. T. Lima.

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TABLE 1 |
Morphometric data for holotype and paratypes of Rhinotridens britskii; range includes holotype. N = number of specimens; SD = Standard deviation.

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TABLE 2 |
Morphometric data for five non-type specimens of Rhinotridens britskii (MZUSP 72977; MZUSP 121256; MCZ 52186). N = number of specimens.

FIGURE 1 | Rhinotridens britskii, holotype, ZUEC 18281, 15.2 mm SL. Brazil, Amazonas State, Igarapé Boa Vista (rio Purus drainage). A. Lateral view; B. Dorsal view; C. Ventral view.

FIGURE 2 | Scanning electron microscopy of the head and anterior part of body of Rhinotridens britskii, paratype, MZUSP 36303, 13.4 mm SL. A. Lateral view; B. Dorsal view; C. Ventral view. Scale bar = 0.1 mm.

FIGURE 3 | Upper jaw and autopalatine of Rhinotridens britskii, paratype, MZUSP 129867, 15.2 mm SL; ventral view. Left anterior autopalatine cartilage damaged. Arrow indicates lateral process of autopalatine. Ap, autopalatine; LbT, labial teeth; Mx, maxilla; MxB, maxillary barbel; PmT, premaxillary teeth; Pmx, premaxilla; RcB, rictal barbel; SPT, symphyseal premaxillary teeth. Scale bar = 0.2 mm.

FIGURE 4 | Gill arches of Rhinotridens britskii, paratype, MZUSP 129867, 15.2 mm SL; dorsal view. ABb, additional basibranchial element; Bb2-4, basibranchials 2 to 4; Cb1-5, ceratobranchials 1 to 5; Eb1-4, epibranchials 1 to 4; Hb1-3, hypobranchials 1 to 3; Pb3-4, pharyngobranchials 3 to 4; Utp, upper pharyngeal tooth plate. Scale bar = 0.1 mm.

FIGURE 5 | Neurocranium and associated structures of Rhinotridens britskii, paratype, MZUSP 129867, 15.2 mm SL; A. Lateral view; B. Dorsal view; C. Ventral view. Boc, basioccipital; Ep, epioccipital; Fr, frontal; Le, lateral ethmoid; Me, mesethmoid; Osph, orbitosphenoid; Psph, parasphenoid; Psoc, parieto-supraoccipital; Ptscl, postemporo-supracleithrum; Pro, prootic; Pt, pterotic; Sph, sphenotic-prootic-pterosphenoid; Vo, vomer; WeC, Weberian capsule. Scale bar = 0.5 mm.

FIGURE 6 | Scanning electron microscopy of the opercular region of Rhinotridens britskii, paratype, MZUSP 36303, 13.4 mm SL. Arrows indicate opercular odontodophore (dorsally) and interopercular odontodophore (ventrally). Scale bar = 0.1 mm.

FIGURE 7 | Suspensorium and opercular series of Rhinotridens britskii, paratype, MZUSP 129867, 15.2 mm SL; left lateral view. Arrow indicates distal process of hyomandibula. Hy, hyomandibular; Iop, interopercle; Op, opercle; Pop, preopercle; Qd, quadrate. Scale bar = 0.2 mm.

FIGURE 8 | Hyoid arch of Rhinotridens britskii, paratype, MZUSP 129867, 15.2 mm SL; ventral view. AC, anterior ceratohyal; Br, branchiostegal rays; PC, posterior ceratohyal; Uh, urohyal; VH, ventral hypohyal. Scale bar = 0.2 mm.

FIGURE 9 | Pectoral skeleton of Rhinotridens britskii, paratype, MZUSP 129867, 15.2 mm SL; ventral view. Cle, cleithrum; Pcr, pectoral-fin rays; Pr1-2, proximal radials 1-2; Sco, scapulocoracoid. Scale bar = 0.3 mm.

FIGURE 10 | Pelvic girdle and fin of Rhinotridens britskii, paratype, MZUSP 129867, 15.2 mm SL. Arrows indicate ossified tips of basipterygium arms. Bpt, basipterygium; Pvr, pelvic-fin rays. Scale bar = 0.2 mm.

FIGURE 11 | Geographic distribution of Rhinotridens britskii. Dotted circle, holotype; white circle, paratypes and non-type specimens.

FIGURE 12 | Type-locality of Rhinotridens britskii, igarapé Boa Vista (rio Javari drainage), Atalaia do Norte Municipality. Photo by Flávio C. T. Lima.

TABLE 1 | Morphometric data for holotype and paratypes of Rhinotridens britskii; range includes holotype. N = number of specimens; SD = Standard deviation.

	Holotype	Range	Mean	SD	N
Standard length (mm)	15.2	13.4–16.5	–	–	12
Percentage of standard length
Body depth	14.9	13.1–18.2	15.7	1.5	12
Caudal peduncle length	10.2	8.4–11	9.9	0.7	12
Caudal peduncle depth	8.0	7.4–8.9	8.3	0.4	12
Predorsal length	73.6	67.5–74.2	71.5	2.0	12
Preanal length	61.8	55.5–62.7	59.8	2.1	12
Dorsal-fin base length	8.4	6.9–10.2	8.9	1.0	12
Anal-fin base length	31.4	29–35.1	32.4	1.9	12
Distance between dorsal-fin origin and caudal-fin base	31.1	29.5–34.1	31.4	1.5	12
Distance between anal-fin origin and caudal-fin base	41.6	38.8–44.4	41.8	1.7	12
Pectoral girdle width	11.6	11.1–13.7	12.3	0.8	12
Pectoral fin length	7.9	7.1–10.4	8.8	0.8	12
Prepelvic length	47.4	42.7–47.4	45.2	1.3	12
Percentage of head length
Head length	17.3	17.3–19.9	18.6	0.8	12
Head width	71.8	66.2–73.5	71.2	1.9	12
Head depth	56.5	43.2–56.5	50.4	3.4	12
Interorbital distance	32.9	31.2–39.4	34.9	1.9	12
Snout length	37.2	37.2–43.2	40.2	1.7	12
Maxillary-barbel length	-	8.3–20.1	8.0	3.6	7
Mouth width	51.6	37.7–51.6	45.0	3.8	12
Eye diameter	28.8	26.1–29.7	28.1	0.9	12

TABLE 2 | Morphometric data for five non-type specimens of Rhinotridens britskii (MZUSP 72977; MZUSP 121256; MCZ 52186). N = number of specimens.

	MZUSP 72977	MZUSP 121256	MCZ 52186 (N = 3)
Standard length (mm)	14.8	15.2	14.1–15.3
Percentage of standard length
Body depth	14.8	12.7	12.8–13.8
Caudal peduncle length	11.9	9.6	7.9–11.9
Caudal peduncle depth	7.7	6.9	6.5–6.8
Predorsal length	69.6	67.3	70.2–72.1
Preanal length	59.0	56.8	59.5–61.4
Dorsal-fin base length	8.9	7.9	8.0–10.7
Anal-fin base length	30.7	32.9	29.6–32.6
Distance between dorsal-fin origin and caudal-fin base	33.0	30.8	30.2–31.6
Distance between anal-fin origin and caudal-fin base	43.0	42.1	39.5–40.8
Pectoral girdle width	12.4	9.7	11.1–11.8
Pectoral fin length	8.5	7.5	8.2–8.7
Prepelvic length	41.7	42.4	45.2–45.9
Percentage of head length
Head length	19.0	18.7	18.9–19.5
Head width	70.1	62.6	63.8–65.7
Head depth	49.0	39.9	42.4–45.6
Interorbital distance	28.9	29.4	29.3–31.4
Snout length	38.3	40.2	41.7–42.7
Maxillary-barbel length	–	–	8.7–10.8
Mouth width	45.4	42.5	34.5–37.3
Eye diameter	24.6	30.2	24.5–26

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