Pseudotocinclus Nichols, 1919

Takako, Adriana Kazue, Oliveira, Claudio & Oyakawa, Osvaldo Takeshi, 2005, Revision of the genus Pseudotocinclus (Siluriformes: Loricariidae: Hypoptopomatinae), with descriptions of two new species, Neotropical Ichthyology 3 (4), pp. 499-508 : 500-501

Pseudotocinclus Nichols, 1919

Pseudotocinclus Nichols, 1919: 533 . Type species: Pseudotocinclus intermedius Nichols, 1919:534 , by monotypy. Gender: masculine.

Diagnosis. The genus Pseudotocinclus can be diagnosed from other Hypoptopomatinae by the presence of a caudal peduncle that is nearly square in cross section from the posterior base of the dorsal fin to the caudal fin, and the following combination of characters: 26 or more plates along the lateral line, a dorsally positioned eye, an exposed preopercle, and an abdomen covered with numerous small platelets.

Description. Dorsal surface of trunk near the dorsal fin forming a depression, which becomes progressively posteriorly flattened near caudal peduncle; ventral surface of trunk between the anal fin and caudal peduncle flattened; dorsal series of plates extending from origin of dorsal-fin to end of caudal peduncle. Mid-dorsal series of plates interrupted; only four to five plates counting from origin of dorsal-fin. Plates of median series dorsally expanded and touching dorsal series of plates. Median series complete. Mid-ventral series of plates interrupted at 17-22 plates, counting from compound pterotic. Ventral series of plates complete, counting from near origin of ventral-fin unbranched ray to end of caudal peduncle; dorsal and ventral series of plates forming distinct longitudinal keels; second nuchal plate large and fused to first proximal radial; first dorsal-fin unbranched ray present; non-functional dorsal-fin locking mechanism. Abdomen entirely covered by numerous platelets; area between pelvic fin and urogenital pore scarcely covered by platelets. Dorsal fin I,7; pectoral fin I,6; ventral fin i,5; anal fin i,5; caudal fin i,14,i. Adipose fin absent. Snout tip naked or covered with small platelets, with odontodes; all teeth bicuspid, inner cusp greater than outer cusp; maxillary barbel present. Major area of scapular bridge covered with skin with platelets, leaving only small ventrolateral portion of coracoid exposed; males with urogenital papilla and dermal flap on entire length of dorsal surface of pelvic-fin unbranched ray; pelvic-flap distinctly higher near pelvic-fin base. Proximal tips of first and last pterygiophores of anal fin lying ventral to hemal spines of vertebrae 15 and 19 respectively; total vertebrae 32-33; perforated plates of lateral line 23-32; dark-brown midlateral stripe extending from snout to end of caudal peduncle. Three to four transverse dark-brown bands on dorsal region of body coalesced with midlateral stripe.

Distribution. Species of this genus are found in the upper rio Tietê basin, São Paulo, in the ribeirão Grande, a tributary of the middle course of the rio Paraíba do Sul, Pindamonhangaba, São Paulo, in the headwaters of rio Itatinga, a coastal river of São Paulo, and in the upper and lower courses of the rio Juquiá, rio Ribeira de Iguape basin, São Paulo ( Fig. 1 ).

Key to the species of Pseudotocinclus :

1. Orbital ring not prominent or conspicuous; parieto-supraoccipital and paired compound pterotic with low crest; parieto-supraoccipital bordered posteriorly by 3-6 large plates..……………………………………..……………….2

1’. Orbital ring very prominent and conspicuous; parieto-supraoccipital and paired compound pterotic with very high crest; parieto-supraoccipital bordered posteriorly by ten or more small plates …..................…..........… P. juquiae

2. Frontal in contact with compound pterotic at orbital margin, separating sphenotic from orbit margin; snout tip usually covered by small platelets with odontodes ............... ................…....................................................... P. parahybae

2’. Frontal separated from compound pterotic at orbital margin by sphenotic, which contributes to the orbital margin; snout with small naked area at tip ................... P. tietensis

Figures

Fig. 1. Southern part of São Paulo, Brazil, showing the geographic distribution of P. tietensis (squares), P. juquiae (triangles), and P. parahybae (circle). Some symbols represent more than one lot or locality. Open symbols = type locality. The precise type locality of P. tietensis is not known. 1- rio Paraíba do Sul basin; 2 - rio Tietê basin; 3 - rio Ribeira de Iguape basin.