Celestichthys, Roberts, 2007

Roberts, Tyson R., 2007, The “ Celestial Pearl Danio ”, A New Genus And Species Of Colourful Minute Cyprinid Fish From Myanmar (Pisces: Cypriniformes), Raffles Bulletin of Zoology 55 (1), pp. 131-140 : 132

Celestichthys , new genus

Type species. – Celestichthys margaritatus , new species, by monotypy.

Diagnosis. – Celestichthys differs from all previously-known Asian Cyprinidae in its distinctive head and body shape, small upturned mouth with shortened jaws, unique colouration, and 9/8 principal caudal fin rays (whereas Microrasbora rubescens , type species of the genus Microrasbora , has 10/9, the usual count for the family Cyprinidae ; and “ Microrasbora ” erythromicron has 9/9). It is further distinguished by caudal fin moderately rather than deeply forked; pharyngeal teeth conical, three-rowed; scales in lateral series 25–26; and body without lateral line canal (no scales with lateral line pores).

In size and shape of head, jaws, body and fins it is most similar to another diminutive and highly colourful cyprinid, “ Microrasbora ” erythromicron Annandale, 1918, endemic to Inle Lake. That species, which may represent the same or another new genus, has entirely different colouration and 9/ 9 principal caudal fin rays. All other Asian cyprinids so far as known, including Microrasbora rubescens Annandale, 1918 (type species of Microrasbora Annandale, 1918 ) have 10/9 principal caudal fin rays except for Danionella translucida Roberts, 1986 , and D. mirifica Britz, 2003 , and “ Microrasbora ” erythromicron with 9/9 and Paedocypris Kottelat, Britz, Tan & Witte, 2005 , with only 8/8. While they also are danioins, Danionella and Paedocypris apparently are not closely related to the new genus and species. They are relatively slender fish, even smaller than Celestichthys , but with increased numbers of post-abdominal vertebrae and elongate lower jaw.

A 24.8 mm Microrasbora rubescens has numerous fine tubercles of about equal size in three or four rows extending the length of the ventrolateral margin of the mandibles. The mandible in Celestichthys apparently is non-tuberculate. The anal fin of M. rubescens , with ii 111 / 2 rays, has a distinctly concave posterior margin, giving it almost a falcate shape. This differs from the anal fin of Celestichthys , which has a convex margin and only ii 81 / 2 – 91 / 2 rays. The caudal peduncle, similar in both sexes, is much more elongate than in Celestichthys . In these respects, “ Microrasbora ” erythromicron is again like Celestichthys .