Cephalocassis

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 : 46-47

Cephalocassis Bleeker, 1858

(fig. 36)

Cephalocassis Bleeker, 1858: 62, 98 and 246. Type species: Arius melanochir Bleeker, 1852. Type by subsequent designation by Bleeker, 1862: 7. Gender: feminine.

Hemipimelodus Bleeker, 1858: 205 and 236. Type species: Pimelodus borneensis Bleeker, 1851. Type by subsequent designation by Bleeker, 1862: 8 and 1863: 92. Gender: masculine.

Diagnosis. The presence of one exclusive (1) and twelve (2 to 13) shared characters define and distinguishes Cephalocassis from all other ariid genera: (1) presence of a fenestra between supraoccipital, pterotic and sphenotic (fig. 37); (2) mesethmoid very thin at median portion (fig. 37) [shared with Arius (with the exception of A. caelatus and A. madagascariensis ), Cathorops , Cinetodus , Ketengus , Osteogeneiosus , Pachyula and Potamarius ]; (3) vomer anterior margin acute and very conspicuous [shared with Amphiarius , Arius , Aspistor , Cinetodus , Potamarius , Osteogeneiosus , Plicofollis , Notarius (with exception of N. planiceps ), Pachyula and Potamosilurus macrorhynchus ]; (4) bony bridge formed by frontals and lateral ethmoid having frontals as its major component (fig. 37) (shared with Amphiarius , Cathorops and Hemiarius ); (5) contact face of transcapular process with basioccipital restricted and columnar [shared with Arius (with exception of A. gagora , A. maculatus and A. manillensis ), Batrachocephalus , Brustiarius , Carlarius , Cinetodus , Cochlefelis , Galeichthys , Genidens , Hemiarius , Ketengus , Neoarius , Netuma , Osteogeneiosus , Pachyula , Plicofollis (with exception of P. platystomus ), Potamarius , Potamosilurus (with exception of P. latirostris ) and Sciades ]; (6) dentary teeth restricted to 2/3 of the mesial portion of the bone (shared with Cryptarius and Genidens ); (7) premaxilla narrow, almost as long as wide (shared with Cathorops , Cinetodus and Potamarius ); (8) metapterygoid 1.5 times longer than higher (fig. 38) [shared with Cathorops (with exception of Cathorops dasycephalus ), Cinetodus , Cryptarius , Pachyula , Plicofollis and Potamarius ]; (9) lower crest of hyomandibular absent (fig. 38) (shared with Cathorops and Ketengus ); (10) anterior portion of second basibranchial cup shaped and moderately differentiated (shared with Bagre , Batrachocephalus , Brustiarius , Cinetodus , Cochlefelis , Cryptarius , Galeichthys , Genidens , Neoarius , Pachyula , Potamarius and Potamosilurus latirostris ); (11) posterior portion of second basibranchial moderately long and thin [shared with Arius (with exception of A. gagora and A. maculatus ), Batrachocephalus , Cathorops , Notarius , Osteogeneiosus , Potamosilurus (with exception of P. latirostris ) and Sciades ]; (12) accessory crest connecting transversal and median crests of neural spine of fourth vertebra present (shared with Amphiarius , Aspistor and Notarius ); (13) base of adipose fin very long, as long as anal-fin base (shared with Amphiarius , Aspistor , Cinetodus , Galeichthys , Hemiarius , Notarius and Pachyula ).

Supplementary external characters. Cephalic shield granulated, visible under the skin; lateral ethmoid and frontal limiting a wide fenestra very conspicuous under the skin; medial groove of neurocranium limited by frontal bones and/or on supraoccipital absent; posterior cranial fontanel well differentiated, large and oval; fenestra limited by supraoccipital, pterotic and sphenotic present; fossa limited by pterotic, supracleithrum and extrascapular present or absent; epioccipital not invading dorsal portion of cephalic shield; shape of occipital process varying considerably; anterior and median nuchal plates fused and indistinct forming a structure of semi-lunar aspect; tooth plates associated with vomer absent; accessory tooth plates present or absent, when present bearing conical teeth; maxillary barbel fleshy and cylindrical; two pairs of mental barbels; base of adipose fin very long, as long as anal-fin base; lateral line bifurcated or not at caudal region, reaching base of upper and sometimes of lower caudal-fin lobes; cleithrum thin with second dorsal process located at its upper portion; posterior cleithral process short and distinct from second dorsal process of cleithrum.

Remarks. Examination of Pimelodus borneensis Bleeker, 1851, type-species of Hemipimelodus indicated that this genus is synonym of Cephalocassis . Since the two generic names were proposed simultaneously, we here consider Cephalocassis as the valid generic name. The inclusion of C. bleekeri (Popta, 1900) and C. manillensis (Valenciennes, 1840) is also tentative and based on a few external supplementary morphological characters from the literature and distribution of the species and needs confirmation.

Distribution and habitat. South and southeast Asia, freshwaters.