Three new species of the loricariid catfish genus Loricariichthys (Teleostei : Siluriformes) from southern South America

Sixteen species of Loricariichthys Bleeker, 1862 are currently recognized i n South America, four of which inhabit the continent portions south of the Amazon basin: Loricariichthys anus (Valenciennes, 1836) from lower rio Para na, rio Uruguai, and coastal streams in southern Brazil; Loricariichthys ca staneus (Castelnau, 1855) from coastal streams of southeastern Brazil; Lori cariichthys labialis (Boulenger, 1895) from rio Paraguay and lower rio Para na; and Loricariichthys platymetopon Isbrucker and Nijssen, 1979, from Rio de Ia Plata basin. Three additional new species are described from this reg ion, Loricariichthys edentatus n. sp. from the Province of Entre Bios, Arge ntina, Loricariichthys melanocheilus n. sp. from the rio Uruguai basin, and Loricariichthys rostratus n. sp. from the Itaipu Hydroelectric reservoir, in the rio Parana. Loricariichthys edentatus n. sp. has no teeth on the pre maxilla, a feature unique in the genus. The monophyly of the genus Loricari ichthys is discussed and it is provisionally diagnosed by having (1) the th ird infrapharyngobranchial with a triangular lateral flange; (2) ventral sh elf of the antero- and posterohyal tall, deflected posteriorly so that it n early forms a 180 degrees angle with the main bodies of the bones; (3) the upper lip coalesced with the premaxillary region medially, never having bar bel-like fringes along the transverse, medial portion and (4) the lower lip of immature males and females formed by two thick, cushionlike structures. Loricariichthys spixii (Steindachner, 1881) is regarded as a junior synony m of L. castaneus.