Valenciennes in G. Cuvier & Valenciennes, 1840
Defining the limits so that Arius can form a natural grouping has always been a problem. The genus was never properly defined, and many species previously classified in Arius are now in other genera. Recent authors have recognized this genus as nonmonophyetic, rejecting that the genus is a natural grouping. Two unnamed groups are distinguished by accessory tooth plates, which are either very elongated and bearing molar-like teeth, or are oval shaped or subtriangular and bearing acicular (needle-like) or conic teeth. A. jatius lacks these tooth plates, but has been included in this genus based on its adipose fin and lateral line. The recognition of Arenarius as a junior synonym of Arius is tentative and needs to be further investigated.
Arius species have three pairs of barbels, including the fleshy and cylindrical maxillary barbels and two pairs of mental barbels. The base of the adipose fin is moderately long, about half the length of the base of the anal fin.
Currently, 25 living species are recognized for this genus.
- Arius acutirostris F. Day, 1877
- Arius africanus Günther, 1867 (African sea catfish)
- Arius arenarius (J. P. Müller & Troschel, 1849) (sand catfish)
- Arius arius (F. Hamilton, 1822) (threadfin sea catfish)
- Arius brunellii Zolezzi, 1939
- Arius cous Hyrtl, 1859
- Arius dispar Herre, 1926 (fleshysnout catfish)
- Arius festinus H. H. Ng & Sparks, 2003
- Arius gagora (F. Hamilton, 1822) (Gagora catfish)
- Arius gigas Boulenger, 1911 (giant sea catfish)
- Arius jella F. Day, 1877 (blackfin sea catfish)
- Arius latiscutatus Günther, 1864 (roughhead sea catfish)
- Arius leptonotacanthus Bleeker, 1849
- Arius macracanthus Günther, 1864
- Arius maculatus (Thunberg, 1792) (spotted catfish)
- Arius madagascariensis Vaillant, 1894 (Madagascar sea catfish)
- Arius malabaricus F. Day, 1877
- Arius manillensis Valenciennes, 1840 (Manila sea catfish)
- Arius microcephalus Bleeker, 1855 (squirrelheaded catfish)
- Arius nudidens M. C. W. Weber, 1913
- Arius oetik Bleeker, 1846
- Arius subrostratus Valenciennes, 1840 (shovelnose sea catfish)
- Arius sumatranus (Anonymous, referred to E. T. Bennett, 1830) (goat catfish)
- Arius uncinatus H. H. Ng & Sparks, 2003
- Arius venosus Valenciennes, 1840 (veined catfish)
- Sepkoski, Jack (2002). "A ompendium of fossil marine animal genera". Bulletins of American Paleontology. 364: 560. Archived from the original on 2011-07-23. Retrieved 2008-01-08.
- Marceniuk, Alexandre P.; Menezes, Naércio A. (2007). "Systematics of the family Ariidae (Ostariophysi, Siluriformes), with a redefinition of the genera" (PDF). Zootaxa. 1416: 1–126.
- Froese, Rainer and Pauly, Daniel, eds. (2011). Species of Arius in FishBase. December 2011 version.