Lithoxus

Lithoxus
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Order:	Siluriformes
Family:	Loricariidae
Tribe:	Ancistrini
Genus:	Lithoxus C. H. Eigenmann, 1910
Type species
Lithoxus lithoides C. H. Eigenmann, 1910
Synonyms
Paralithoxus Boeseman, 1982

Paralithoxus Boeseman, 1982

Lithoxus is a genus of suckermouth armored catfishes native to tropical South America.

Lithoxus is supported as a monophyletic sister to Exastilithoxus. Together, these two genera form a well-supported clade.

There are currently eight recognized species in this genus:

Lithoxus range from the Oyapock drainage along the border between Brazil and French Guiana, through Suriname west to the Tacutu River along the border between Guyana and Brazil and south to the Uatama and Trombetas rivers of Brazil.

Lithoxus contains some of the most dorsoventrally flattened fishes in the world. They can be distinguished from most loricariids by having a round instead of oval lower lip. The lower lip is large and round as in Exastilithoxus with the edge sometimes frilled, but not with the barbels seen in Exastilithoxus.

Lithoxus species have a unique, enlarged, thin-walled stomach from which the intestine exits dorsally. The stomach is expanded, thin-walled, and clear and is used in breathing air. A thin, clear tube exits the main body of the stomach anterodorsally, terminating at the pylorus just anterior to the posterior extent of the stomach. The intestine tends to have less coils than other members of Ancistrini. The expanded stomach is slightly larger in males; this is due to the males having more space due to a difference in the relative size of the gonads.

Colouration in Lithoxus species is typically slate gray to tan with a few lighter markings on the body; there are occasionally bands in the pectoral and caudal fins. The ventral surface ranges from white to slightly lighter than the sides. The abdomen is naked (scaleless and unplated). The caudal fin is slightly forked.

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