A new species of Pimelodella (Siluriformes: Heptapteridae) from the Paraguai basin, Brazil, with a discussion regarding its distribution

Uma nova espécie de Pimelodella é descrita da bacia do rio Paraguai, nos Estados de Mato Grosso do Sul e Mato Grosso, Brasil. A nova espécie se distingue de todas as suas congêneres por apresentar uma combinação exclusiva de características, que incluem: perfil da região anterior do corpo reto do focinho à nadadeira dorsal, barbilhão maxilar alcançando pelo menos o término da nadadeira anal quando paralelo ao eixo principal do corpo, espinho da nadadeira dorsal robusto e apresentando pequenas espínulas nos três-quartos distais da sua margem posterior, 41–42 vértebras totais (raramente 43 ou 44), espinho da nadadeira peitoral apresentando 13–23 lâminas grandes e retrorsas na sua margem posterior, e região dorsolateral do corpo ligeiramente mais escura que o restante. Este estudo também discute as similaridades entre a ictiofauna das bacias do Paraguai e Amazônica, abordando a história biogeográfica entre ambas as regiões. Adicionalmente, considerações acerca do dimorfismo sexual de Pimelodella são apresentadas, além de uma chave de identificação para as espécies de Pimelodella encontradas na bacia do Paraguai.

Palavras chave:
Bagres; Biogeografia; Chave de identificação; Dimorfismo sexual; Taxonomia

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Sociedade Brasileira de Ictiologia Neotropical Ichthyology, Departamento de Biologia Animal e Vegetal, CCB, Universidade Estadual de Londrina, Rodovia Celso Garcia Cid, Km 380, Cidade Universitária, 86055-900, Londrina, Paraná, Brazil, Phone +55(43)3371-5151 - Londrina - PR - Brazil
E-mail: neoichth@nupelia.uem.br

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Total length (mm)	97.1	47.5–161.2	42	99.9
Standard length (mm)	78.5	37.1–127.9	43	82.5
Percents of standard length
Body depth (dorsal)	17.6	15.0–20.8	43	17.9	1.3
Body width (dorsal)	12.0	11.1–14.1	43	12.9	0.8
Cleithral width	16.0	15.2–18.2	43	16.7	0.6
Head length	29.2	27.2–31.3	43	29.0	1.0
Maxillary-barbel length (left side)	87.1	81.0–113.6	42	94.6	7.4
Outer mental-barbel length (left side)	36.7	28.7–49.7	43	37.3	3.9
Inner mental-barbel length (left side)	21.2	16.8–32.3	43	22.0	3.0
Predorsal length	32.3	28.5–34.1	43	32.3	1.2
Distance between snout tip and terminus of dorsal-fin base	45.4	42.3–48.9	43	46.2	1.2
Distance between snout tip and dorsal-fin distal end	62.1	54.4–75.2	38	58.3	3.4
Dorsal fin to adipose fin	5.0	3.8–22.2	43	7.3	2.9
Dorsal-fin base	15.2	12.7–18.3	43	14.9	1.0
Length of first dorsal-fin ray (unbranched)	30.5	20.1–42.5	29	24.8	4.3
Length of rigid part of first dorsal-fin ray	20.4	14.3–20.7	38	18.5	1.4
Length of second dorsal-fin ray (first branched)	24.0	18.6–24.0	42	21.3	1.2
Length of third dorsal-fin ray (second branched)	19.3	16.4–23.3	42	19.4	1.6
Prepectoral length	23.2	20.0–27.5	43	24.0	2.0
Distance between snout tip and terminus of pectoral-fin base	24.7	22.5–29.0	43	25.9	1.7
Distance between snout tip and pectoral-fin distal end	43.0	38.8–46.0	42	42.4	1.7
Length of first left pectoral-fin ray (unbranched)	21.2	17.3–21.2	39	19.4	1.1
Length of rigid part of first left pectoral-fin ray	18.7	15.5–18.8	43	17.4	0.9
Length of second left pectoral-fin ray (first branched)	19.2	14.7–19.9	42	17.6	1.2
Length of third left pectoral-fin ray (second branched)	17.9	12.4–17.9	41	15.4	1.2
Prepelvic length	42.1	42.1–49.2	43	45.5	1.5
Distance between snout tip and terminus of pelvic-fin base	43.6	43.6–50.8	43	47.1	1.4
Distance between snout tip and pelvic-fin distal end	61.3	58.6–65.5	43	61.4	1.7
Distance between pelvic fins	3.7	2.7–6.4	43	4.3	0.8
Length of first left pelvic-fin ray (unbranched)	18.1	11.5–18.1	43	14.8	1.4
Length of second left pelvic-fin ray (first branched)	18.2	14.3–18.2	43	16.1	1.0
Length of third left pelvic-fin ray (second branched)	17.4	14.0–17.9	42	15.8	1.0
Anal-fin base	10.3	8.6–12.9	43	10.5	0.9
Preanal length	65.7	65.1–71.4	43	67.8	1.4
Distance between snout tip and terminus of anal-fin base	76.7	74.8–82.5	43	77.4	1.5
Distance between snout tip and anal-fin distal end	84.3	82.0–90.3	42	85.2	1.7
Adipose-fin length	39.1	32.5–39.4	43	36.4	1.5
Preadipose length	51.6	51.1–56.4	43	53.2	1.2
Distance between snout tip and adipose-fin base end	86.9	86.3–91.1	43	88.2	1.0
Adipose-fin depth	4.4	3.6–5.2	42	4.4	0.4
Caudal-peduncle length posterior to adipose-fin	10.9	8.1–12.9	43	10.5	0.9
Caudal-peduncle depth at adipose-fin terminus	8.2	6.5–9.2	43	8.0	0.5
Snout-anus distance	48.6	48.2–54.4	42	51.0	1.3
Snout-urogenital papilla distance	55.4	53.2–60.0	40	56.3	1.5
Anus-urogenital papilla distance	6.8	3.9–9.4	40	5.4	1.3
Dorsal lobe of caudal fin length	23.6	21.2–29.2	39	25.8	2.2
Ventral lobe of caudal fin length	26.7	20.8–29.8	42	25.1	1.9
Percents of head length
Head depth	48.4	42.3–63.5	43	51.4	4.0
Head width	48.9	46.1–57.7	43	51.8	3.1
Eye diameter (left)	19.3	17.6–25.3	43	20.3	1.6
Fleshy interorbital	28.2	22.1–28.4	43	24.9	1.7
Bony interorbital	18.0	12.0–20.5	43	17.2	1.5
Mouth gape	32.0	27.3–37.2	42	32.2	2.4
Snout length (left)	35.8	31.2–38.2	43	35.0	1.5
Distance between snout tip and posterior nare (left side)	18.6	15.6–21.5	43	18.5	1.3
Anterior internarial width	12.1	9.1–15.3	43	12.0	1.1
Posterior internarial width	12.1	11.3–15.5	43	13.7	1.0
Intranarial length (left side)	11.9	10.9–15.4	43	12.8	0.9