Pterophyllum leopoldi can be differentiated from other members of the genus by the presence of up to 11 vertical stripes on the body, though often only the 3 largest, boldest stripes can be seen. This species also shows a dark patch over the operculum.

In adult specimens, a red/maroon hue over the back and fins is characteristic of the species, leading some to believe the most colourful natural form Angelfish.

The name-sake roman nose possessed by the fish is also very distinctive and used as a meristic feature.

The genus Centromochlus is diagnosable by members having the proximal anal-fin radials enlarged and fused to each other at the base, forming a single ossified structure.

It’s sometimes included in the putative subfa…

It’s known by various vernacular names including ‘Pirá-pacu’, ‘Pira-pucu’ or ‘Diente de cao’ (central Amazon), ‘Bicuda’ or ‘Uena’ (rio Tocantins), ‘Bicuda’ (rio Tapajós), ‘Aguejeta’ or ‘Picua’ (Venezuela), and ‘Moruwi’ or ‘Pirapoko’ (Guyana).

The entire dorsal-fin base is located anteriorly to a vertical through the anal-fin origin and this character distinguishes it from all other ctenolucids except B. lucius and B. xyrekes.

This species is rare in the aquarium trade but is arguably more suitable for the home aquarium than some of its better-known relatives given its adult size and relatively docile behaviour.

Other vernacular names include ‘Dientón’ (Peru), ‘Perrito’ (Ecuador), ‘Payara-chata’ or ‘Payarin’ (Venezuela) and ‘Icanga’, ‘Minguilista’ or ‘Peice-cachorro’ (Brazil), some of which are also applied to related species.

Native to the central Amazon basin with records existing from the Madeira, Branco, Trombetas, and Tapajós river drainages, plus the Rupununi basin in Guyana. Although an affluent of the rio Essequibo and thus not officially part of the Amazon basin, the latter is connected to the rio Takutu, a tributary of the upper rio Branco, during the annual wet season.

Type locality is given by Fowler as ‘Rio Madeira about 200 miles east of W. Long. 62°20′, Brazil’.

C. strigata is an enduringly popular species in the aquarium hobby but is not bred on a commercial basis with all fish offered for sale collected in the wild.

It can be told apart from other members of the genus by its larger adult size and dark, marbled colour pattern appearing as a series of dark and light stripes running diagonally across the body below the lateral line.

This colour pattern is variable and popul…

R. vulpinus is the most widely-distributed member of the family Cynodontidae.

Type locality is given simply as ‘Brazilian rivers’, but this species is currently understood to be distributed in the Amazon basin from the Río Ucayali system in Peru, eastward as far as the rio Xingu in Brazil, plus the rio Tocantins and Rio Capim basins.

It’s also known from the Río Orinoco ba…

Type locality is ‘Río Yuruari, 3 kilometers east of El Callao, 7°18’N, 61°50’W, Bolivar, Venezuela’, and this species is also known from the Rupununi River drianage in Guyana and the Courantyne/Corantijn system in Suriname.

The Yuruari, an affluent of the Río Cuyuni, an…

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.

There also exist a number of minor differences in colour pattern between populations. For example some Peruvian forms have yellow pigmentation on the body and fins, and those from Guyana and Suriname possess a short red stripe on vertical scale rows 6-9, above the central dark stripe on the body.

Rio Negro forms have a similar red stripe but overlapping the central dark stripe and extending along most of the flank, while a form from Colombia has an elongate red stripe which is broken in two beneath the dorsal-fi…