Rediscovering species: redescription of <i>Bryconops gracilis</i> (Characiformes: Iguanodectidae), an often-misidentified species

Silva-Oliveira, Cárlison; Ota, Rafaela P.; Lima, Flávio C. T.; Py-Daniel, Lúcia Rapp

doi:10.1590/1982-0224-2021-0054

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Original article • Neotrop. ichthyol. 19 (4) • 2021 • https://doi.org/10.1590/1982-0224-2021-0054 copy

Rediscovering species: redescription of Bryconops gracilis (Characiformes: Iguanodectidae), an often-misidentified species

Authorship SCIMAGO INSTITUTIONS RANKINGS

ABSTRACT

A redescription of Bryconops gracilis is provided, a species poorly known for more than a century. Bryconops gracilis differs from all congeners by having the following combination of features: eight branched pelvic-fin rays, 31-36 anal-fin rays, 15-17 predorsal scales arranged in a regular series, two rows of premaxillary teeth, and 53-60 lateral-line scales. The species was often misidentified as B. alburnoides by sharing an overall elongated body shape, caudal fin yellowish in life, and a high number of lateral-line scales. A diagnosis between B. alburnoides and B. gracilis is provided. The holotype of B. gracilis which for many years had whereabouts unknown, was recovered, examined and illustrated by CT-Scan. Additionally, more detailed information about the type locality, morphology, color pattern (including in living specimens), habitat and distribution pattern of species are provided.

Keywords:
Amazon basin; Bryconops alburnoides; Bryconops melanurus; Taxonomy; Thayer expedition

	H	N	Range	Mean	SD
Standard length (mm)	61.8	42	36.4-129.8	94.8	-
Percents of standard length
Snout to dorsal-fin origin	50.2	42	46.9-53.7	50.0	1.5
Snout to anal-fin origin	59.9	42	56.4-65.6	62.2	2.0
Snout to pelvic-fin origin	46.9	42	44.6-49.7	47.5	1.2
Pelvic-fin length	-	31	9.9-14.6	12.8	1.2
Snout to pectoral-fin origin	22.7	42	21.8-26.9	23.4	1.0
Pectoral-fin length	-	31	14.3-21.9	16.8	1.5
Dorsal-fin base length	12.1	42	10.5-13.9	12.1	0.9
Depth at dorsal-fin origin	19.4	42	18.4-24.8	23.0	1.4
Dorsal-fin terminus- adipose origin	25.9	42	24.0-29.2	26.5	1.4
Dorsal-fin origin- adipose origin	38.8	42	35.4-41.2	38.8	1.3
Adipose terminus to hypural plate	10.5	42	10.2-15.0	11.9	1.1
Anal-fin base length	29.1	42	24.7-33.5	30.7	1.7
Caudal-peduncle length	9.7	42	7.8-13.3	10.2	1.1
Caudal-peduncle depth	7.3	31	6.3-8.2	7.3	0.4
Head length	21.0	42	19.6-26.1	21.6	1.4
Maxillary length	9.7	42	8.2-12.4	9.7	0.8
Snout length	6.8	42	4.7-6.9	5.6	0.5
Horizontal orbit diameter	8.1	42	7.3-10.7	8.5	0.8
Percents of head length
Maxillary length	46.2	42	40.2-50.6	45.1	2.5
Snout length	-	42	23.0-28.9	26.1	1.4
Horizontal orbit diameter	38.4	42	35.5-42.7	39.4	1.7
Tip of snout to tip of supraoccipital	92.3	42	91.4-102.4	94.9	2.1
Posterior margin of orbit to end of opercle	-	42	28.9-36.9	33.2	1.8

Sociedade Brasileira de Ictiologia Neotropical Ichthyology, Núcleo de Pesquisas em Limnologia, Ictiologia e Aquicultura, Universidade Estadual de Maringá., Av. Colombo, 5790, 87020-900, Phone number: +55 44-3011-4632 - Maringá - PR - Brazil
E-mail: neoichth@nupelia.uem.br

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[1] Edited by

George Mattox