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: 69-72

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Ketengus  ZBK  Bleeker, 1847

(fig. 58)

Ketengus  ZBK  Bleeker, 1847: 167. Type species: Ketengus typus  ZBK  Bleeker, 1847. Type by monotypy. Gender: masculine.

Diagnosis. Ketengus  ZBK  can be differentiated from all other members of the Ariidae  by exclusive (1 to 9) and shared (10 to 19) characters: (1) fenestra delimited by mesethmoid and lateral ethmoid wide and filled with cartilage (fig. 59); (2) vomer diamond shaped (fig. 60); (3) vomerine lateral processes absent (fig. 60); (4) a single point of contact between lateral ethmoid and frontal (fig. 59); (5) lachrymal with three anterior branches (fig. 61); (6) tooth band on dentary reaching posterior end of bone; (7) dorsal crest of premaxilla, delimiting contact area between mesethmoid and premaxilla absent; (8) second and third basibranchials indistinct(fig. 62); (9) first and second hypobranchials boomerang shaped (fig. 62); (10) posterior horn of mesethmoid tubular and thin (fig. 59) [shared with Cathorops  (with exception of C. dasycephalus  )]; (11) mesethmoid posterior branches thin (fig. 59) [shared with Bagre  (with exception of B. panamensis  ), Cathorops  , Cephalocassis  ZBK  , Doiichthys  ZBK  , Nedystoma  ZBK  and Nemapteryx  ZBK  ]; (12) mesethmoid posterior branches parallel over their entire length (fig. 59) (shared with Cathorops  , Cephalocassis  ZBK  , Doiichthys  ZBK  , Nedystoma  ZBK  and Nemapteryx  ZBK  ); (13) accessory tooth plates absent (shared with Cephalocassis borneensis  , Nedystoma  ZBK  , Pachyula  ZBK  , Potamarius izabalensis  ZBK  and Potamosilurus velutinus  ); (14) anterior portion of opercle subtriangular (shared with Cochlefelis  ZBK  , Sciades emphysetus  ZBK  , S. passany  and S. proops  ); (15) posteroventral portion of opercle little pronounced posteriorly [shared with Bagre panamensis  , Carlarius  (with exception of C. heudelotii  ), Galeichthys  ZBK  , Genidens  ZBK  , Plicofollis  ZBK  (with exception of P. platystomus  ) and Sciades  (with exception of S. couma  and S. felis  )]; (16) hyomandibular lower crest absent (shared with Cathorops  and Cephalocassis  ZBK  ); (17) second epibranchial overlaying first (shared with Bagre  and Galeichthys  ZBK  ); (18) third pharyngobranchial not mesially angulated hourglass shaped (shared with Doiichthys  ZBK  and Potamarius grandoculis  ); (19) seventh vertebra anterior most element free from lower superficial ossification (shared with Amphiarius  , Aspistor  ZBK  , Cathorops  , Cephalocassis  ZBK  , Cinetodus  ZBK  , Cryptarius  ZBK  , Doiichthys  ZBK  , Galeichthys  ZBK  , Hemiarius  ZBK  , Nedystoma  ZBK  , Nemapteryx  ZBK  and Pachyula  ZBK  ).

Supplementary morphological characters. Cephalic shield granulated visible under the skin; fenestra between lateral ethmoid and frontal absent; medial groove of neurocranium very distinct, limited by frontal bones and/or on supraoccipital; posterior cranial fontanel moderately developed, long and narrow; 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, short and moderately large, 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; two pairs of mental barbels; base of adipose fin moderately long, about half as long as anal-fin base length; lateral line bifurcated at caudal region, reaching base of caudal-fin upper and lower lobes; cleithrum wide with second dorsal process on upper its portion; posterior cleithral process of moderate size, distinct from dorsal process of cleithrum.

Distribution and habitat. South and southeast Asia, brackish waters.