Potamosilurus, Alexandre P. Marceniuk & Naércio A. Menezes, 2007

Alexandre P. Marceniuk & Naércio A. Menezes, 2007, Systematics of the family Ariidae (Ostariophysi, Siluriformes), with a redefinition of the genera., Zootaxa 1416, pp. 1-126 : 100-101

Potamosilurus new genus

(fig. 88)

Type species: Hemipimelodus macrorhynchus Weber, 1913.

Diagnosis. The combination of the following shared characters distinguishes Potamosilurus from all other members of the Ariidae : (1) wing-like process of parasphenoid formed by a single long and thin process [shared with Amphiarius , Aspistor , Bagre , Cathorops (with exception of C. dasycephalus ), Cochlefelis , Hemiarius , Notarius (with exception of N. planiceps ), Pachyula , Plicofollis platystomus , Potamarius , Sciades emphysetus , S. passany and S. proops ]; (2) metapterygoid anterior process truncate (shared with Cinetodus , Cochlefelis , Pachyula , Plicofollis and Potamarius ); (3) tip of uncinate process of third epibranchial pointed (shared with Cephalocassis , Cinetodus , Doiichthys , Galeichthys , Hemiarius stormii , Nedystoma and Pachyula ).

Supplementary morphological characters. Cephalic shield granulated visible under the skin; lateral ethmoid and frontal limiting a moderately developed fenestra visible under the skin; medial groove of neurocranium very distinct, limited by frontal bones and/or on supraoccipital (except in P. latirostris ); posterior cranial fontanel moderately developed, long and narrow (except in P. latirostris ); fenestra limited by supraoccipital, pterotic and sphenotic absent; fossa limited by pterotic, supracleithrum and extrascapular relatively large; epioccipital not invading dorsal portion of cephalic shield; occipital process triangular, moderately long and wide, progressively narrower toward its posterior part; anterior and median nuchal plates fused and indistinct, forming a structure of semi-lunar aspect; tooth plates associated with vomer absent (except in P. latirostris ); accessory tooth plates absent (except in P. latirostris ); maxillary barbel fleshy and cylindrical; two pairs of mental barbels; base of adipose fin moderately long, about half as long as anal-fin base; lateral line not bifurcated at caudal region, reaching caudal-fin upper lobe; cleithrum wide, with second process on its upper portion; posterior cleithral process moderately long and distinct from dorsal process of cleithrum.

Remarks. Marceniuk (2003) hypothesizes that Potamosilurus macrorhynchus and P. latirostris form a monophyletic unit. In the present study five freshwater species from New Guinea are included in the genus. The inclusion of P. coatesi (Kailola, 1990) and P. robertsi (Kailola, 1990) is based on the presence of diagnostic characters depicted from the literature, since these species were not examined and P. velutinus (Weber, 1907) was tentatively assigned to the genus, but it needs to be confirmed as it is based only on supplementary morphological characters. In Kailola (2004) these species are considered to belong in Arius or in Ariopsis (herein considered synonymous with Sciades ). All Potamosilurus species can be distinguished from the species belonging in Arius by the absence of accessory tooth plates (with exception of P. latirostris ) and by the lateral line not bifurcated at caudal region, reaching caudal-fin upper lobe and from members of Sciades (= Ariopsis ) by having the large fenestra visible under the skin limited by the lateral ethmoid and frontal bones, the posterior cranial fontanel conspicuous and the fossa limited by pterotic, supracleithrum and extrascapular large (see also diagnosis of the genus).

Distribution and habitat. Southern New Guinea, freshwaters.

Etymology. The first part of the generic name potamo is from the Greek word potamos meaning river, and silurus is from Latin, a generic name applied in the past to many catfish taxa, alluding to the fact that all the included species are from freshwater. Gender: masculine.