Plicofollis

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

Plicofollis Kailola, 2004

(fig. 77)

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

Diagnosis. Plicofollis 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 , Cathorops (with exception of C. dasycephalus ), Galeichthys , Genidens and Netuma ]; (7) orbitosphenoid laterally expanded [shared with Arius , Brustiarius , Carlarius , Cinetodus , Genidens , Netuma , Notarius planiceps , Potamosilurus (with exception of P. latirostris ) and Sciades (with exception of S. couma , S. emphysetus , 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 , Genidens , Ketengus 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 , Carlarius , Cephalocassis , Cinetodus , Cochlefelis , Cryptarius , Doiichthys , Genidens , Nemapteryx , Neoarius , Netuma thalassinus , Pachyula , Potamarius and Sciades ); (12) first pharyngobranchial well developed, subrectangular and depressed (fig. 82) (shared with Cathorops dasycephalus , Cryptarius and Pachyula ); (13) posterior face of first epibranchial with a prominent process (fig. 82) (shared with Pachyula ); (14) 15 or more ribs present (shared with Bagre , Carlarius , Cochlefelis , Genidens , Neoarius , Netuma , Notarius and Sciades ); (15) base of adipose fin very short, less than one-half as long as anal-fin base (shared with Bagre , Brustiarius , Cathorops , Cryptarius and Netuma ); (16) origin of adipose fin located vertically above posterior half of anal fin (shared with Bagre , Brustiarius and Netuma ).

The distinction of Plicofollis 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 , Brustiarius , Cochlefelis , Hemiarius , Notarius , Sciades couma , S. emphysetus , S. herzbergii , 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 , Netuma thalassinus and Sciades platypogon ); metapterygoid longer than deeper [shared with Cathorops (with exception of Cathorops dasycephalus ), Cephalocassis , Cinetodus , Cryptarius , Pachyula and Potamarius ]; anterior process of metapterygoid truncate [shared with Cinetodus , Cochlefelis , Pachyula , Potamarius 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 and Aspistor ).

Skeleton preparations of Arius argyropleuron 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 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.