Nedystoma

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 : 73

Nedystoma Ogilby, 1898

(fig. 63)

Nedystoma Ogilby, 1898: 32. Type species: Hemipimelodus dayi Ramsay & Ogilby, 1886. Type by original designation and also monotypy. Gender: neuter.

Diagnosis. Nedystoma can be distinguished from all other members of the Ariidae through the combination of exclusive (1 to 3) and shared (4 to 9) characters: (1) premaxillary anterior margin fringed; (2) third external branchiostegal ray in form of a spatula; (3) pharyngeal tooth plates very long and narrow (fig. 64); (4) accessory tooth plates absent (shared with Cephalocassis borneensis , Ketengus , Pachyula , Potamarius izabalensis and Potamosilurus velutinus ); (5) opercle anterior part trapezoid shaped, long and narrow (shared with Bagre , Cinetodus and Galeichthys ); (6) upper hyomandibular crest short and high (shared with Amphiarius , Arius , Aspistor , Batrachocephalus , Cathorops , Hemiarius , Ketengus , Notarius , Osteogeneiosus , Plicofollis platystomus and Potamosilurus ); (7) contact face between first epibranchial and first pharyngobranchial very conspicuous [shared with Arius arius , A. gagora , A. madagascariensis , Brustiarius , Osteogeneiosus , Plicofollis (with exception of P. platystomus ) and Potamosilurus ]; (8) lateral face of third pharyngobranchial conspicuous and acute (shared with Arius , Brustiarius , Neoarius , Netuma , Plicofollis and Potamosilurus ); (9) transversal crest of neural spine of fourth vertebra very high (shared with Amphiarius , Bagre , Batrachocephalus , Cathorops , Cinetodus , Cryptarius , Ketengus , Hemiarius , Nemapteryx , Notarius planiceps , Osteogeneiosus , Pachyula and Sciades platypogon ).

Supplementary morphological characters. Cephalic shield granulated visible under the skin; lateral ethmoid and frontal delimiting a large fenestra clearly visible under the skin; medial groove of neurocranium limited by frontal bones and/or on supraoccipital absent; posterior cranial fontanel well differentiated, large and oval shaped; 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, very long and narrow, 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; accessory tooth plates absent; 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 base of caudal-fin upper lobe; cleithrum narrow, with second dorsal process on its upper portion; posterior cleithral process short and distinct from second dorsal process of cleithrum.

Distribution and habitat. Southern New Guinea, predominantly freshwaters.