Chinchaysuyoa labiata

description

Description. Morphometric data in Table 1. Head depressed, profile elevated posteriorly, straight at frontal and parieto-supraoccipital area. Snout long and anteriorly pointed. Anterior nostril round, with fleshy edge, posterior nostril covered by flap of skin; nostrils relatively close to one another and distant to orbit, not connected by fleshy furrow. Eye lateral and large; eyes relatively close to one another. Three pairs of moderately long teretiform barbels; maxillary barbel usually reaching gill membrane edge, mental barbels not reaching gill membrane edge. Osseous bridge formed by lateral ethmoid and frontal relatively long and slender, little evident under skin. Cephalic shield exposed, gently granulated; long and moderately large on lateral ethmoid, frontal, and supracleithral areas. Anterior portion of dorsomedial groove of neurocranium fleshy, inconspicuous and not continuous to level of posterior nares; posterior portion of osseous groove shallow, with straight margins, narrowing posteriorly. Parietosupraoccipital process funnel-shaped, long and moderately wide on posterior portion, and profile straight. Nuchal plate crescent-shaped, long and moderately wide. Mouth sub

Chinchaysuyoa, a new genus of the fish family Ariidae (Siluriformes), with a redescription of Chinchaysuyoa labiata from Ecuador and a new species description from Peru

diagnosis

Diagnosis. Chinchaysuyoa labiata differs from C. ortegai by finer granulation homogeneously distributed in the cephalic shield (vs. thicker and irregularly distributed in the cephalic shield, especially in the sphenotic, pterotic and parieto-supraoccipital, Figs. 5 and 6), snout pointed anteriorly (vs. truncated anteriorly, Fig. 5), distance between the anterior nostrils 5.1 – 5.9 % SL (vs. 6.3 – 7.6 % SL, Table 1), distance between the posterior nostrils 5.2 – 6.2 % SL (vs. 6.4 – 7.5 % SL, rarely less than 6.4, Table 1), caudal – fin lobes relatively long, pointed posteriorly (vs. relatively short, rounded posteriorly, Fig. 4).

Chinchaysuyoa, a new genus of the fish family Ariidae (Siluriformes), with a redescription of Chinchaysuyoa labiata from Ecuador and a new species description from Peru

discussion

Remarks. Arius labiatus was described by Boulenger (1898) based on a single specimen deposited at Museo di Zoologia, Instituto di Zoologia e Anatomia Comparata Universitá di Torino, Italy (holotype, MZUT 1540, Fig. 4 a). Subsequently, Eigenmann (1922) described Hexanematichthys henni based on three specimens from Río Daule, Ecuador, considering that “ It is possible that these specimens are the young of Arius labiatus, the only known specimen of which is three times as large as our largest ”. While the descriptions of both species provide good details on the accessory tooth plates, which have a unique configuration in the ariids from the eastern Pacific, both have been considered as species inquirenda in the recent literature (Kailola & Bussing 1995; Marceniuk & Ferraris 2003; Marceniuk & Menezes 2007), due primarily to the small number of samples available in zoological collections and the lack of taxonomic studies of the ariid catfish of the west coast of South America. Here, Chinchaysuyoa labiata is recognized as a valid species and Hexanematichthys henni (Fig. 4) as its junior synonym, supported by the fine, homogeneous granulation of the cephalic shield (Figs. 4 and 6), the na

Chinchaysuyoa, a new genus of the fish family Ariidae (Siluriformes), with a redescription of Chinchaysuyoa labiata from Ecuador and a new species description from Peru

distribution

Distribution and habitat. Chinchaysuyoa labiata is known from middle Río Peripa (holotype of Chinchaysuyoa labiata), middle Río Daule (holotype of H. henni), middle Rio Guayas (paratype of H. henni), and middle Rio Vinces (non-type specimens) all from Guayas Basin. Based on the know distribution of the species, we infer that the distribution of Chinchaysuyoa labiata is restrict to freshwater habitat from west Ecuador (Fig. 7).

Chinchaysuyoa, a new genus of the fish family Ariidae (Siluriformes), with a redescription of Chinchaysuyoa labiata from Ecuador and a new species description from Peru