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…

Live colouration of this species was not included in the original description but the specimens in our images were identified by Dr. Ronald E. Watson, the principal author, as S. exallisquamulus. It's normally misidentified and traded as the Sri Lankan endemic species Sicyopus jonklaasi.

It is diagnosable from congeners by the following combination of characters: 14-15 pectoral-fin rays; both genders exhibit small, widely-spaced scales…

This apparently undescribed species was traded as 'Aequidens' sp. 'Orinoco' but following Musilová et al. (2009) appears to be a member of the genus Andinoacara.

This hypothetically-undescribed species appears to be a member of the Betta unimaculata complex of closely-related species within the genus, of which members share the following set of characters: body long and slender with depth at dorsal fin origin 18-25 % SL; head large and blunt with width 19-24 % SL; long maxilla and lower lip with distance from tip of lower jaw to posterior end of maxilla 27-54 % HL; caudal-fin rounded in shape, occasionally with elongated median rays; pelvic-fin short and filamentous; dorsal and anal fins relatively pointed.

This species is included in the Betta unimaculata complex of closely-related species within the genus, of which members share the following set of characters: body long and slender with depth at dorsal fin origin 18-25 % SL; head large and blunt with width 19-24 % SL; long maxilla and lower lip with distance from tip of lower jaw to poste…

This species is traded under several names of which others include 'sharp-nosed gourami', 'moonlight chocolate gourami', 'black-lined chocolate gourami' and 'black-tailed chocolate gourami', though it's far from common in the hobby. Its unique colour pattern makes it difficult to confuse with any of the three other members of the genus even in the absence of meristic data.

This species is traded under several names of which others include ‘Samurai gourami’ and ‘Samurai Zebra Chocolate Gourami’. Though the former of these is arguably the most common, these names are potentially misleading since the fish is neither especially combative nor from Japan.

Its unique colour pattern makes it difficult to confuse with any of the three other members of the genus even in the abse…

This species is sometimes traded under the names 'mini chocolate gourami', 'Burmese chocolate gourami' or mislabelled as the congener P. ocellatus, these two currently comprising the only known members of the genus.

P. lineatus can be told apart from P. ocellatus via the following combination of characters: smaller body size (maximum standard length 18.7 mm vs. 32.0 mm); absence of ocellus-type marking in middle of each flank (vs. presence); presence of dark, stripe (vs. abs…

This species is not traded commercially at present and the specimen pictured above was brought back from northern Papua New Guinea by private collectors in 2008. It's diagnosable from other members in the genus by possession of 10 segmented rays in the second dorsal fin, males with filamentous spines in the firstandusually with 14 rays. Colour patterning in males is also distinctive (see 'Sexual Dimorphism').

The Gobiidae is the most speciose vert…

This species was referred to as Dario sp. ‘Jaintia Hills’ or D. sp. ‘Bangladesh’ prior to its description.

Type locality is ‘India, Meghalaya, Jaintia Hills, Seinphoh stream at Umolong, 7 km from Jowai town, 25°31’36’’N 92°08’27’’E, 1320 m asl’, and in India it has not been found elsewhere to date.