Corydoras aurofrenatus

description

Description. Morphometric data presented in Tab. 1. Head compressed with convex dorsal profile, roughly triangular in dorsal view. Snout conical, conspicuously pointed. Head profile slightly concave from tip of snout to anterior nares, ascending slightly convex from this point to tip of posterior process of parieto-supraoccipital. Profile slightly convex along dorsal-fin base. Postdorsal-fin body profile concave to adipose-fin spine; concave from this point to caudal-fin base. Ventral profile of body nearly straight from isthmus to pectoral girdle, and slightly convex from this point until pelvic girdle. Profile nearly straight from pelvic girdle to base of first anal-fin ray, concave from this point until caudal-fin base. Body roughly elliptical in cross section at pectoral girdle, gradually becoming more compressed toward caudal fin. Eye rounded, located dorsolaterally on head. Orbit delimited anteriorly by lateral ethmoid, anterodorsally by frontal, posterodorsally by sphenotic, posteriorly by infraorbital 2, and ventrally by infraorbital 1. Anterior and posterior nares close to each other, only separated by flap of skin. Anterior naris tubular. Posterior naris close to anterodo

Taxonomic review of the typical long-snouted species of Corydoras (Siluriformes: Callichthyidae) from the río de La Plata basin

diagnosis

Diagnosis. Corydoras aurofrenatus can be distinguished from its congeners, except for the species within lineage 1, by the presence of the following features: temporal sensory canal in sphenotic with two pores anterior to the branch that gives rise to infraorbital canal (vs. with a single pore), upper tooth plate of branchial arch with three to four series of teeth (vs. two series of teeth), area at the corner of the mouth, ventral to maxillary barbel, with a fleshy flap (vs. fleshy flap absent). Corydoras aurofrenatus can be distinguished from the species of the lineage 1, except for C. acutus, C. areio, C. cervinus, C. coriatae Burgess, 1997, C. desana Lima & Sazima, 2017, C. filamentosus Nijssen & Isbrücker, 1983, C. fowleri Böhlke, 1950, C. geoffroy Lacépède, 1803, C. maculifer, C. negro Knaack, 2004, C. ourastigma Nijssen, 1972, C. oxyrhynchus, C. sarareensis Dinkelmeyer, 1995, C. semiaquilus Weitzman, 1964, C. septentrionalis Gosline, 1940, C. simulatus Weitzman & Nijssen, 1970, C. solox, C. stenocephalus Eigenmann & Allen, 1942, C. treitlii Steindachner, 1906 and C. zawadzkii by the absence of a dark brown or black stripe transversally crossing the eye (vs. presence of such

Taxonomic review of the typical long-snouted species of Corydoras (Siluriformes: Callichthyidae) from the río de La Plata basin

discussion

Remarks. In a revisionary study for Callichthyidae, Ellis (1913) mentioned the presence of C. flaveolus Ihering, 1911 (described from the rio Tietê basin) in the río Paraguay basin, at Sapucay, Paraguay. In the illustration of one of the examined specimens (Ellis, 1913: Pl. XXVIII, fig. 1), it is possible to observe that the specimen presents a long and conical snout, contrary to C. flaveolus, which displays a short and rounded snout (Tencatt et al., 2014 a: 93, fig. 4). Ellis’s (1913) confusion is probably due to the comparison between C. aurofrenatus and C. flaveolus made by Ihering (1911: 386), which stated that his new species is morphologically similar to C. aurofrenatus, from which it differs by its color pattern. Gosline (1940) also conducted a review on Callichthyidae, in which he described Corydoras ellisae based on that material identified as C. flaveolus by Ellis (1913: 407, pl. 28, fig. 1). Gosline (1940) mentioned that C. ellisae and the other new species described therein (C. septentrionalis) are remarkably similar but regarded them as different species by some morphological features and geographic distribution (Gosline, 1940: 18). As previously discussed by Axenrot,

Taxonomic review of the typical long-snouted species of Corydoras (Siluriformes: Callichthyidae) from the río de La Plata basin

distribution

Geographical distribution. Corydoras aurofrenatus is known from several tributaries of the rio Paraguay basin in Brazil and Paraguay (Fig. 5). Ecological notes. During collecting trips for the Proyecto Vertebrados del Paraguay (1992 – 1999) conducted by the NRM and the Museo Nacional de Historia Natural del Paraguay (MNHNP), C. aurofrenatus was captured from small streams to the main channel of rivers within Paraguayan territory. The arroyo Laguna Penayo (Fig. 10 A) is a stream with about 20 m width and 0.5 m deep, very slight to stagnant current, turbid water, and substrate composed mainly by clay. An unnamed stream tributary from the río Apa (Fig. 10 B) with about 25 m width and 1 m deep, stagnant current, dark brown, very turbid water, and substrate composed by sand, rocks and trunks. The río Araguay-Guazú (Fig. 10 C) is relatively small river with about 35 m width and 1 m deep, moderate current, turbid water, and substrate composed mainly by sand. The río Jejuí-Guazú (Fig. 10 D) is a small river with brown semitransparent water, and substrate composed mainly by sand, gravel and leaf heaps. A small, unnamed stream tributary from the río Paraguay (Fig. 10 E) with light brown wate

Taxonomic review of the typical long-snouted species of Corydoras (Siluriformes: Callichthyidae) from the río de La Plata basin