Editorial Type:
Article Category: Research Article
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Online Publication Date: 27 May 2020

A New Miniature Species of Acanthobunocephalus (Silurifomes: Aspredinidae) from the Lower Purus River Basin, Amazon Basin, Brazil

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Page Range: 347 – 357
DOI: 10.1643/CI-19-309
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A second species of Acanthobunocephalus is described from tributaries of the lower Purus River in the Amazon Basin, Brazil. Acanthobunocephalus scruggsi, new species, is distinguished from all other aspredinid species by its reduced number of fin rays: four pectoral-fin rays (vs. five or more), two dorsal-fin rays (vs. three or more, except Amaralia hypsiura), five pelvic-fin rays (vs. six), four to five anal-fin rays (vs. six or more, except Bunocephalus verrucosus), and nine caudal-fin rays (vs. 10, except Hoplomyzontinae, Amaralia, Platystacus, Bunocephalus chamaizelus, and Bunocephalus minerim). Osteological aspects of the new species of Acanthobunocephalus are described using cleared and stained specimens and high-resolution x-ray computed tomography (HRXCT), and compared with Acanthobunocephalus nicoi and other aspredinids. Generic assignment is based on putative apomorphic shared features and a morphological diagnosis for Acanthobunocephalus is presented.

Uma segunda espécie de Acanthobunocephalus é descrita de tributários do baixo rio Purus, na Bacia Amazônica, Brasil. Acanthobunocephalus scruggsi, espécie nova, se distingue de todas as outras espécies de aspredinídeos pelo número extremamente reduzido de raios nas nadadeiras: quatro raios na nadadeira peitoral (vs. cinco ou mais), dois raios na nadadeira dorsal (vs. três ou mais, exceto Amaralia hypsiura), cinco raios da nadadeira pélvica (vs. seis), quatro a cinco raios da nadadeira anal (vs. seis ou mais, exceto Bunocephalus verrucosus) e nove raios da nadadeira caudal (vs. 10, exceto Hoplomyzontinae, Amaralia, Platystacus, Bunocephalus chamaizelus e Bunocephalus minerim). Aspectos osteológicos da nova espécie de Acanthobunocephalus são descritos usando diafanização e tomografia computadorizada de raios-X de alta resolução e comparados com Acanthobunocephalus nicoi e outros aspredinídeos. A posição genérica da nova espécie baseia-se em características compartilhadas apomórficas dela e Acanthobunocephalus nicoi e aqui é apresentado uma diagnose morfológica para Acanthobunocephalus.

Copyright: © 2020 by the American Society of Ichthyologists and Herpetologists
Fig. 1.
Fig. 1.

HRXCT model of Acanthobunocephalus nicoi, paratype, ANSP 168816, 12.6 mm SL. (A) Dorsal view and (B) ventral view. br = branchiostegal rays; cl = cleithrum; cv = parapophysis of complex vertebrae; den = dentary; dfr1 = dorsal-fin spine; dfs = dorsal-fin spinelet; dp = distal portion of pectoral-fin spine; fr = frontal; hc = hemal canal; le = lateral ethmoid; lpv = lateral vertebral process associated with last vertebrae; me = mesethmoid; mx = maxilla; pcl = posterior process of cleithrum; pmx = premaxilla; pp = proximal portion of pectoral-fin spine; psc = posterior process of scapulocoracoid; pso = parietosupraoccipital; pto = pterotic; pv5 = parapophysis of fifth vertebra; r6 = sixth rib; sc = scapulocoracoid; scl = posttemporal-supracleithrum; spo = sphenotic. Limits between selected bones are highlighted in black.

Fig. 2.
Fig. 2.

HRXCT model of skull and anterior body of Acanthobunocephalus scruggsi, holotype, INPA 57946, 21.7 mm SL. (A) Dorsal view, (B) lateral view, and (C) ventral view. br = branchiostegal rays; cl = cleithrum; cv = parapophysis of complex vertebrae; db = dorsal blade of complex vertebrae; den = dentary; df = dorsal fin; dp = distal portion of pectoral-fin spine; fr = frontal; hc = hemal canal; me = mesethmoid; mnp = middle nuchal plate; mx = maxilla; op = opercle; p = premaxilla; pcl = posterior process of cleithrum; pfs = pectoral-fin spine; po = preopercle; pp = proximal portion of pectoral-fin spine; psc = posterior process of scapulocoracoid; pso = parieto-supraoccipital; pto = pterotic; pv5 = parapophysis of fifth vertebra; r6 = sixth rib; sco = scapulocoracoid; scl = posttemporal-supracleithrum; spo = sphenotic; tf = temporal fontanel. Limits between selected bones are highlighted in black.

Fig. 3.
Fig. 3.

Holotype of Acanthobunocephalus scruggsi, INPA 57946, 21.7 mm SL, Brazil, Amazonas, Beruri, Igarapé Caipirinha, tributary of Lago Ayapuá. Scale bar = 10 mm.

Fig. 4.
Fig. 4.

Paratype of Acanthobunocephalus scruggsi, INPA 42229, 20.6 mm SL, Amazonas, Tapauá, Igarapé dos Caetanos, tributary to Rio Ipixuna. Scale bar = 10 mm.

Fig. 5.
Fig. 5.

Lateral view of left suspensorium of Acanthobunocephalus scruggsi, INPA 34666, 22.1 mm SL. ang = anguloarticular; den = dentary; hyo = hyomandibula; iop = interopercle; mc = ossified tubule of preopercle-mandibular canal; op = opercle; pop = preopercle; qu = quadrate. Scale bar = 1 mm.

Fig. 6.
Fig. 6.

Dorsal view of hyoid and branchial arches of Acanthobunocephalus scruggsi, INPA 34666, 22.1 mm SL. ab = anterior blade of anterior ceratohyal; ach = anterior ceratohyal; bb2 = second basibranchial; br = branchiostegal rays; ch1 = first ceratobranchial; eb = epibranchial; ih = interhyal; hb = hypobranchial; pb3 = third pharyngobranchial; pch = posterior ceratohyal; vh = ventral hypohyal. Scale bar = 1 mm.

Fig. 7.
Fig. 7.

Ventral view of pectoral-fin girdle of Acanthobunocephalus scruggsi, INPA 34666, 22.1 mm SL. cl = cleithrum; dp = distal portion of anterior margin of pectoral-fin spine; dpc = dorsal process of cleithrum; pcl = posterior process of cleithrum; pfr = pectoral-fin rays; pfs = pectoral-fin spine; prd = pectoral-fin radials; psc = posterior process of scapulocoracoid; sco = scapulocoracoid. Scale bar = 2 mm.

Fig. 8.
Fig. 8.

Geographic distributions of species of Acanthobunocephalus. Circles = A. nicoi, squares = A. scruggsi. Black symbols refer to type localities. Amazon River basin highlighted in green.

Contributor Notes

1 Laboratorio de Ictiología, Unidad de Ecología y Sistemática (UNESIS), Departamento de Biología, Facultad de Ciencias, Pontificia Universidad Javeriana, Carrera 7 No. 43-82, Bogotá D.C., Colombia; Email: pitiago@javeriana.edu.co. Send reprint requests to this address.
2 Departamento de Zoologia, Programa de Pós-Graduação em Biologia Animal, Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves, 9500–Bloco IV–Prédio 43433, 91501-970 Porto Alegre, RS, Brazil.
3 Research Associate, Department of Ichthyology, The Academy of Natural Sciences, 1900 Benjamin Franklin Parkway, 19103-1195 Philadelphia, Pennsylvania.
4 Pontifícia Universidade Católica do Rio Grande do Sul, PUCRS, Av. Ipiranga, 6681, 90619-900 Porto Alegre, RS, Brazil; Email: reis@pucrs.br.

Associate Editor: W. L. Smith.

Received: 21 Oct 2019
Accepted: 13 Jan 2020
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