Peces Criollos - Freshwater Fishes of Argentina Peces Criollos - Freshwater Fishes of Argentina
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Hisonotus aky comb.nov.

Epactionotus aky, dorsolateral view (photo Ingo Seidel)
Hisonotus aky, topotype (photo: I. Seidel)

new combination:
Hisonotus aky (Azpelicueta, Casciotta, Almirón & Koerber, 2004)
from: Epactionotus aky

published in:
Carvalho, T.P. & R.E. Reis (2009):
Four new species of Hisonotus (Siluriformes: Loricariidae) from the upper rio Uruguay, southeastern South America, with a review of the genus in the rio Uruguay.
Zootaxa 2113:1-40

abstract (from publication):
Four new species of Hisonotus are described from the upper course of the rio Uruguay basin in Brazil: Hisonotus iota from the rio Chapecó drainage; Hisonotus leucophrys from rio Rancho Grande and rio Ariranhas; Hisonotus megaloplax from the rio Passo Fundo drainage; and Hisonotus montanus from the rio Canoas drainage. The species Epactionotus aky, described from the arroyo Yabotí-Guazú drainage in Argentina, is transferred to Hisonotus and rediagnosed. Hisonotus candombe is considered a junior synonym of H. ringueleti. The new taxa, together with H. nigricauda, H. ringueleti, H. charrua, and H. aky represent the genus Hisonotus in the rio Uruguay basin. A taxonomic key for Hisonotus in the rio Uruguay basin is provided. Their distributions are discussed under biogeographic patterns previously proposed for the rio Uruguay basin.

remarks on new combination (from publication):
Hisonotus aky (Azpelicueta, Casciotta, Almirón & Koerber, 2004) was originally described in Epactionotus Reis & Schaefer, 1998 because of its supposed possession of three synapomorphies of that genus: absence of an expanded fleshy flap on the dorsal surface of the first pelvic-fin ray in males, neural spine of seventh vertebra not contacting the nuchal plate dorsally (contacting unpaired predorsal plates), and first dorsal proximal radial contacting the eighth vertebral centrum. However, the examination of type specimens of Epactionotus aky indicated the absence of most diagnostic features of Epactionotus. The first pelvic-fin ray without a dorsal skin flap in males is a derived feature that independently evolved three times in the hypoptopomatinae (Schizolecis, Epactionotus, and the clade formed by Acestridium, Oxyropsis, Hypoptopoma, and Nannoptopoma), according to the topology proposed by Schaefer (1998:382) and Gauger & Buckup (2005:511). The presence of a fleshy flap on the dorsal surface of the first pelvic-fin ray of mature males is plesiomorphic and shared by all species of Hisonotus, most hypoptopomatines, and Epactionotus aky (Fig 17). The character-states: neural spine of seventh vertebra not contacting the nuchal plate dorsally, and the first proximal radial of dorsal fin contacting the eighth vertebra (Fig. 18A), are not present in H. aky. Hisonotus aky shares with remaining Hisonotus species and other hypoptopomatines (except Microlepidogaster) the neural spine of the seventh vertebra contacting the nuchal plate, at least posteriorly, and the first proximal radial of dorsal fin contacting the seventh vertebra (Fig. 18B). Another character, discussed by Azpelicueta et al. (2004), suggesting the inclusion of H. aky in Epactionotus is the presence of light longitudinal stripes on head and trunk. Because the presence of light stripes is more widespread among hypoptopomatines and appears in several species of Hisonotus, that feature does not diagnose H. aky as belonging to the genus Epactionotus. Moreover, Epactionotus aky shares with two species of Hisonotus (H. iota and H. montanus) the presence of an infraorbital canal entering the infraorbital series via the compound pterotic, which is a derived feature and suggests a close relationship between these three species. For these reasons, Epactionotus aky is here transferred to the genus Hisonotus.

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