Peces Criollos - Freshwater Fishes of Argentina Peces Criollos - Freshwater Fishes of Argentina
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Otocinclus arnoldi - a valid species from Argentina

Otocinclus arnoldi
Variation of colour pattern in Otocinclus arnoldi
(photo from publication 2006a)

a valid species from Argentina:
Otocinclus arnoldi Regan, 1909

Aquino (1996) considered Otocinclus arnoldi a synonym of O. flexilis. Lehmann (2006a) now states that this diagnosis has been made by error as Aquino compared O. arnoldi with non-type material of O. flexilis from localities in Argentina without including type-material of O. flexilis in her study. Lehmann limits the distribution of Otocinlus flexilis to tributaries of the Patos lagoon system and resurrects O. arnoldi from the synonymy with O. flexilis.
Records of Otocinclus flexilis from Argentina are now to be considered Otocinclus arnoldi
In his description of Otocinclus batmani Lehmann (2006b) identifies two lots of Otocinclus arnoldi from localities in Argentina within the list of comparative material:
- MCP 32565, 5, 1 c&s, 27.3-34.3 mm SL, Arroyo Nogoya, Entre Rios, approx. 32°50’S 59°50’W.
- MZUSP 51092, 18, Río Cayasta, tributary to Río San Javier, Santa Fé, approx. 31°10’S 60°10’W.

abstract (from publication 2006a):
Otocinclus arnoldi from the La Plata basin is resurrected from the synonymy of O. flexilis described from rio Jacuí basin, based on two diagnostic characters: the presence of five branched pectoral-fin rays vs. six in O. flexilis, and the presence of the raised tuft of enlarged odontodes at the tip of the supraoccipital posterior process, in juvenile as well as in adults of O. arnoldi

distribution (from publication 2006a):

distribution of Otocinclus arnoldi + Otocinclus flexilis
Geographic distribution of Otocinclus arnoldi (red squares) and O. flexilis (black dots).
(modified map from publication 2006a)

Otocinclus flexilis is restricted to the laguna dos Patos drainage basin…
Otocinclus arnoldi occurs in the tributaries of the lower Río Paraná drainage (below the former major Sete Quedas waterfalls), lower and middle Paraguay, Uruguay, La Plata and small coastal streams of Uruguay, south of the laguna dos Patos drainage.

published in:
Aquino, A.E. (1996): Redescripción de Otocinclus flexilis Cope, 1894 (Siluriformes, Loricariidae, Hypoptopomatinae) con un nuevo sinónimo. Iheringia, Série Zoologia 81: 13-22

Lehmann, P. (2006a): Anatomia e relações filogenéticas da família Loricariidae (Ostariophysi: Siluriformes) com ênfase na subfamília Hypoptopomatinae. Tese de doutorado. PUCRS, Porto Alegre, Brazil. ix + 420 p.
Usage of unpublished data authorized by Roberto Reis.

Lehmann, P. (2006b): Otocinclus batmani, a new species of hypoptopomatine catfish (Siluriformes: Loricariidae) from Colombia and Peru. Neotropical Ichthyology 4 (4): 379-383

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