Hoplosternum Gill 1858

Type-species: Callichthys laevigatus Valenciennes, 1840 (=H. littorale).
See the Complete Catalogue for authorships, synonyms, type-localities, and references.

Diagnosis

No uniquely derived features were found for Hoplosternum, but a posterior triangular expansion of the second infraorbital bone, towards the pterotic-supracleithrum, is a derived condition. This character, however, is shared by the species of Brochis and some Corydoras.

Distribution

Hoplosternum littorale is the species of Callichthyidae with widest distribution. It is present in all of South America east of the Andes and north of Buenos Aires, including the Río Orinoco, Trinidad, coastal rivers of the Guianas, Río Amazonas drainage, Río Paraguay, lower Río Paraná and coastal systems in southern Brazil. One single lot is known from the upper rio Paraná (MZUSP 40336) and the rio São Francisco drainage (MCP 16715). Oliveira (1991) suggested that these occurrences may represent introduced populations. Very recently (December, 1995) I received from Dr. Leo Nico a lot of this species collected in Florida (USA).

Hoplosternum magdalenae occurs west of the Andes, in the Lago Maracaibo basin in Venezuela, and in the drainages of Río Sinu and Río Magdalena in Colombia.
Finally, Hoplosternum punctatum is only found in the Río Atrato basin in Colombia and in the Pacific coastal drainages of Panamá, in southern Central America.

Key to species of Hoplosternum

• 1a. Second infraorbital bone narrow, not articulating with the pterotic-supracleithrum and leaving a naked skin area between eye and opercle; coracoids strongly developed in fully matured males, contacting and sometimes overlapping ventrally; only first scute of upper lateral series with lateral line perforation .....2
• 1b. Second infraorbital bone extremely developed, articulating with the pterotic-supracleithrum and covering the entire area of skin between eye and opercle; coracoids exposed ventrally but not in contact in the midline even in fully matured males; 4-6 scutes of upper lateral series with lateral line perforations .....Hoplosternum littorale
• 2a. Interopercle exposed in a small roundish area ventrally to the opercle; caudal peduncle deeper (17.4-19.5% of standard length in specimens larger than 55.0 mm SL) .....Hoplosternum magdalenae
• 2b. Interopercle covered by skin, not visible externally; caudal peduncle shallower (14.3-17.2% of standard length in specimens larger that 55.0 mm SL) .....Hoplosternum punctatum