At time of writing there exists no scientific evidence that the different populations of this species seen in the aquarium trade (see 'Distribution') represent anything other than a single, widely-distributed species although some exibit minor morphological differences including relative body depth, longer fin rays in the unpaired fins and yellow or orange colouration in the paired fins. There is apparently a form from the upper rio Negro which may turn out to be distinct but it's…

This species is a member of the putative A. nasutus group of closely-related species within the genus alongside A. nasutus, A. maculipinna and A. isalineae.

These are all characterised by possession of two dark, longitudinal stripes, one running from the tip of the snout to the base and the other from the posterior edge of the lower maxilla to the underside of the caudal peduncle.

This species is a member of the putative A. nasutus group of closely-related species within the genus alongside A. nasutus, A. maculipinna and A. isalineae.

These are characterised by possession of two dark, longitudinal stripes, one running from the tip of the snout to the base and the other from the posterior edge of the lower maxilla to the underside of the caudal peduncle.

The genus Ageneiosus was at one point classified in the family Ageneiosidae alongside the genus Tetranematichthys, but this was not accepted by all authors. The grouping remains poorly-studied with the last major revision having been conducted by Watson (1990) in his unpublished dissertation, in which A. inermis was included under the currently synonymous name A. brevifilis. It can be separated from the majority of the genus (except A. marmoratus) by possession of a truncate caudal fin, and from…

T. stellatus is superficially similar to its only congener T. securis, but can immediately be identified by the presence (vs. absence) of a prominent dark spot in the dorsal-fin. It is sometimes traded as ‘platinum hatchetfish’.

The genus Thoracocharax was originally erected by Fowler in 1906 as a subgenus of Gasteropelecus, but was elevated to generic status by Weitzman (1960).

This species may be referred to using a variety of names including ‘scomb’, ‘sabre tooth tetra’, ‘sabre tusk barracuda’, ‘dog tooth characin, ‘vampire fish’, ‘Cachorra’ or Pirandirá (the latter two names being used in Brazil where they’re also applied to congeners).

It’s regularly confused with the payara, H. armatus, though that species grows considerably larger, is pop…

Recorded throughout much of the Amazon basin, with its range extending eastwards from the Ucayali system in Peru as far as the Tocantins drainage which flows into the Atlantic alongside the Amazon at its delta. The southern extremity of its range appears to be the Río Mamoré in Bolivia, a tributary of the rio Guaporé, and the northern limit the Essequibo basin, Guyana.

C. guapore is a sought after aquarium fish although it is not often traded. It exhibits slightly different behaviour to the majority of congeners in that it tends to form aggregations in midwater and spends a large proportion of its time away from the substrate. Its morphology exhibits corresponding adaptations towards a pelagic existence with a relatively large eye, a more terminal mouth position, more strongly-forked caudal-fin, and more symmetrical body shape than most other Corydoras species.

This species is not well-documented but is said to differ from the comparable C. punctatus by possessing larger dark markings on the body which may form an irregular midlateral stripe in some specimens.

Unfortunately diagnostic characters cannot be provided since we’ve been unable to obtain the type description, and little has been written about the species since it was published.

This species is also referred to as ‘South American puffer’, ‘SAP’, ‘Amazonian puffer’, ‘Peruvian puffer’, or ‘Brazilian puffer’ in the ornamental trade.

Within the genus Colomesus, C. asellus can be immediately identified by possessing a unique transverse row of dermal flaps across the chin which is absent in its congeners C. psittacus and C. tocantinensis.