Sciades

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: 102-104

publication ID

z01416p001

publication LSID

lsid:zoobank.org:pub:FFC65592-D8DB-41BE-AEAC-A41EAB6C6185

persistent identifier

http://treatment.plazi.org/id/FE963D3F-4239-056C-104E-BC11F36DB885

treatment provided by

Thomas

scientific name

Sciades
status

 

Sciades  Müller & Troschel, 1849

(fig. 89)

Sciades  Müller & Troschel, 1849: 6. Type species: Bagrus (Sciades) emphysetus  ZBK  Müller & Troschel, 1849. Type by subsequent designation. Type apparently designated first by Bleeker 1862: 8 (subgenus of Bagrus  ZBK  ). Gender: masculine.

Hexanematichthys  ZBK  Bleeker, 1858: 61, 126. Type species: Bagrus sondaicus  ZBK  Valenciennes, 1840. Type by monotypy. Gender: masculine.

Sciadeichthys  ZBK  Bleeker, 1858: 62, 66. Type species: Bagrus (Sciades) emphysetus  ZBK  Müller & Troschel, 1849. Type by monotypy. Gender: masculine.

Selenaspis  ZBK  Bleeker, 1858: 62. Type species: Silurus herzbergii  ZBK  Bloch, 1794. Type by subsequent designation by Jordan & Evermann (1896: 119). Gender: feminine.

Ariopsis  ZBK  Gill, 1861: 56. Type species: Arius milberti  ZBK  Valenciennes, 1840. Type by monotypy. Gender: feminine.

Leptarius  ZBK  Gill, 1863: 170. Type species: Leptarius dowii  ZBK  Gill, 1863. Type by monotypy. Gender: masculine.

Diagnosis. The species of Sciades  can be differentiated from all other genera of the Ariidae  by the combination of the following exclusive (1 to 5) and shared (6 to 8) characters: (1) medial groove of neurocranium delimited mostly or exclusively by frontal bones (fig. 90); (2) temporal fossa very reduced or entirely closed during ontogenetic development (fig. 90) (with exception of Sciades leptaspis  ); (3) otic capsules little developed; (4) space between transcapular process and otic capsule very wide; (5) subvertebral process indistinct or little differentiated; (6) posterior cranial fontanel absent (fig. 90) (with exception of Sciades platypogon  and shared with Batrachocephalus  ZBK  ); (7) epiphyseal bar indistinct (with exception of Sciades platypogon  and shared with Batrachocephalus  ZBK  ); (8) exoccipital posterior process sutured to Muller’s ramus (with exception of Sciades platypogon  and shared with Potamarius izabalensis  ZBK  ).

Supplementary morphological characters. Cephalic shield conspicuously granulated visible under the skin; lateral ethmoid and frontal limiting a small fenestra not visible under the skin; medial groove of neurocranium limited by frontal bones and/or on supraoccipital distinct or not very distinct; posterior cranial fontanel always closed (except in S. platypogon  ); fenestra limited by supraoccipital, pterotic and sphenotic absent; fossa limited by pterotic, supracleithrum and extrascapular absent (except in S. leptaspis  ); epioccipital not invading dorsal portion of cephalic shield; occipital process triangular, its length and width variable, progressively narrower toward its posterior part; anterior and median nuchal plates fused and indistinct, forming a structure of semi-lunar aspect or broad in form of shield; tooth plates associated with vomer round; accessory tooth plates large, oval shaped or subtriangular, bearing conical teeth; 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 (with exception of S. couma  ); cleithrum wide, with second process on its upper portion; posterior cleithral process moderately long and distinct from dorsal process of cleithrum.

Remarks. Sciades  contains the largest number of ariid species from the eastern and western Americas, south and southeast Asia, southern New Guinea and northern Australia. The nominal genera Hexanematichthys  ZBK  , Selenaspis  ZBK  and Ariopsis  ZBK  represented by the respective type-species Pimelodus sagor  ZBK  Hamilton, 1822, Silurus herzbergii  ZBK  Bloch, 1794 and Arius milberti  ZBK  Valenciennes, 1840 (= Silurus felis  ZBK  Linnaeus, 1766), are considered junior synonyms of Sciades  . The genus Sciades  and Sciadeichthys  ZBK  are based on the same type-species, Bagrus (Sciades) emphysetus  ZBK  Müller & Troschel, 1849 and the latter is considered an objective synonym of the former. The osteology of Leptarius dowii  ZBK  Gill, 1863, the type-species of Leptarius  ZBK  , was not examined but morphological information from preserved specimens indicates that this genus is junior synonym of Sciades  . In addition to S. mastersi  (Ogilby, 1898), S. paucus  (Kailola, 2000) and S. utarus  (Kailola, 1990) were considered to belong in the genus based on the presence of external diagnostic morphological characters available in the literature. The inclusion of S. sona  (Hamilton, 1822) is only tentative.

The species Sciades couma  (Valenciennes, 1840), S. emphysetus  ZBK  , S. herzbergii  ZBK  , S. passany  (Valenciennes, 1840) and S. proops  (Valenciennes, 1840), form a subgroup well supported by the following exclusive characters, indicating that they might be considered a separate genus in future studies: lateral margin of premaxillary with a conspicuous concavity; mesopterygoid irregularly shaped (fig. 91); ectopterygoid very elongated (fig. 91); posterior nostrils connected by a groove (with exception of S. emphysetus  ZBK  and S. proops  ).

Distribution and habitat. Eastern and western America, south and southeast Asia, southern New Guinea and northern Australia.