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: 89-92

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Plicofollis  ZBK  Kailola, 2004

(fig. 77)

Plicofollis  ZBK  Kailola, 2004: 141. Type species: Arius argyropleuron  ZBK  Valenciennes, 1840. Type by original designation. Gender: not clear from original description.

Diagnosis. Plicofollis  ZBK  can be distinguishes from all other members of the Ariidae  by the following combination of unique (1 to 5) and shared (6 to 16) characters: (1) tooth plates associated with vomer isolated and very distant from each other; (2) lachrymal thin (fig. 78); (3) anterior part of interopercle compressed with anterior end notched (fig. 79); (4) interopercle subrectangular shaped and elongated (fig. 79); (5) lateral margin of uncinate process of third epibranchial notched (fig. 80); (6) posterior cranial fontanel absent or reduced to a small opening (fig. 81) [shared with Bagre  , Brustiarius  ZBK  , Cathorops  (with exception of C. dasycephalus  ), Galeichthys  ZBK  , Genidens  ZBK  and Netuma  ]; (7) orbitosphenoid laterally expanded [shared with Arius  ZBK  , Brustiarius  ZBK  , Carlarius  , Cinetodus  ZBK  , Genidens  ZBK  , Netuma  , Notarius planiceps  , Potamosilurus  (with exception of P. latirostris  ) and Sciades  (with exception of S. couma  , S. emphysetus  ZBK  , S. passany  , S. proops  , S. seemanni  and S. sagor  )]; (8) anterior edge of opercle straight (fig. 79) (shared with Cathorops  ); (9) posteroventral portion of opercle little pronounced posteriorly [shared with Bagre panamensis  , Carlarius  (with exception of C. heudelotii  ), Galeichthys  ZBK  , Genidens  ZBK  , Ketengus  ZBK  and Sciades  (with exception of S. couma  and S. felis  )]; (10) posterior margin of interopercle angulated (fig. 79) (shared with Cathorops  ); (11) hyomandibular upper crest long and low (shared with Brustiarius  ZBK  , Carlarius  , Cephalocassis  ZBK  , Cinetodus  ZBK  , Cochlefelis  ZBK  , Cryptarius  ZBK  , Doiichthys  ZBK  , Genidens  ZBK  , Nemapteryx  ZBK  , Neoarius  ZBK  , Netuma thalassinus  , Pachyula  ZBK  , Potamarius  ZBK  and Sciades  ); (12) first pharyngobranchial well developed, subrectangular and depressed (fig. 82) (shared with Cathorops dasycephalus  , Cryptarius  ZBK  and Pachyula  ZBK  ); (13) posterior face of first epibranchial with a prominent process (fig. 82) (shared with Pachyula  ZBK  ); (14) 15 or more ribs present (shared with Bagre  , Carlarius  , Cochlefelis  ZBK  , Genidens  ZBK  , Neoarius  ZBK  , Netuma  , Notarius  ZBK  and Sciades  ); (15) base of adipose fin very short, less than one-half as long as anal-fin base (shared with Bagre  , Brustiarius  ZBK  , Cathorops  , Cryptarius  ZBK  and Netuma  ); (16) origin of adipose fin located vertically above posterior half of anal fin (shared with Bagre  , Brustiarius  ZBK  and Netuma  ).

The distinction of Plicofollis  ZBK  is also supported by four unique characters within the Ariidae  , not present in P. platystomus  and Plicofollis tenuispinis  : lateral ethmoid expanded (fig. 81); vomer oval shaped (fig. 83); lateral processes of vomer very short (fig. 83); uncinate process of third pharyngobranchial longer and wider than mesial portion of epibranchial (fig. 80).

Supplementary morphological characters. Cephalic shield granulated visible under the skin; a small fenestra limited by lateral ethmoid and frontal bones scarcely visible under the skin; medial groove of neurocranium very distinct, limited by frontal bones and/or on supraoccipital; posterior cranial fontanel in many cases closing entirely during ontogenetic growth; fenestra limited by supraoccipital, pterotic and sphenotic absent; fossa limited by pterotic, supracleithrum and extrascapular relatively large; epioccipital invading dorsal portion of cephalic shield (except in C. tenuispinis  and C. platystomus  ); occipital process triangular, moderately long and large, narrowing continuously toward its posterior end, its lateral margins convex; anterior and median nuchal plates fused and indistinct, forming a structure of semi-lunar aspect; accessory tooth plates longitudinally elongated, bearing molar-like teeth; maxillary barbel fleshy and cylindrical; two pairs of mental barbels; base of adipose fin very short, less than one-half length of anal-fin base; lateral line bifurcated at caudal region, reaching base of caudal-fin upper and lower lobes; cleithrum wide, with second dorsal process on its upper portion; posterior cleithral process moderately long and distinct from second dorsal process of cleithrum.

Remarks. The genus is defined by characters shared by all the species directly examined, except P. platystomus  (Day, 1877). The inclusion of this species is preliminary and supported by a series of characters shared between P. platystomus  and all other members of the genus: parasphenoid wide in ventral view (shared with Amphiarius  , Aspistor  ZBK  , Brustiarius  ZBK  , Cochlefelis  ZBK  , Hemiarius  ZBK  , Notarius  ZBK  , Sciades couma  , S. emphysetus  ZBK  , S. herzbergii  ZBK  , S. passany  and S. proops  ); maxilla with the margins parallel in the proximal 2/3, slightly narrower in the distal 1/3 and posteriorly truncate (shared with Carlarius heudelotii  , Genidens  ZBK  , Netuma thalassinus  and Sciades platypogon  ); metapterygoid longer than deeper [shared with Cathorops  (with exception of Cathorops dasycephalus  ), Cephalocassis  ZBK  , Cinetodus  ZBK  , Cryptarius  ZBK  , Pachyula  ZBK  and Potamarius  ZBK  ]; anterior process of metapterygoid truncate [shared with Cinetodus  ZBK  , Cochlefelis  ZBK  , Pachyula  ZBK  , Potamarius  ZBK  and Potamosilurus  (with exception of P. velutinus  )]; mesial portion of ceratohyal well developed; urohyal lateral processes 1/3 as long as medial process; posterior portion of second basibranchial short and robust (shared with Arius gagora  , A. maculatus  ZBK  and Aspistor  ZBK  ).

Skeleton preparations of Arius argyropleuron  ZBK  Kuhl & van Hasselt, 1840, type-species of the genus and also of P. crossocheilos  (Bleeker, 1846) and P. magatensis  (Herre, 1926) were not examined and their recognition as members of Plicofollis  ZBK  is based on the supplementary morphological characters observed in preserved specimens and data from the literature.

Distribution and habitat. Eastern Africa, south and southeast Asia, southern New Guinea and northern Australia, marine and brackish waters.