An undescribed Danionella. Picture by Choy Heng Wah.
Danionella mirifica, new species, is distinguished from its only congener D. translucida in having a more elongate body (body depth 12.2-14.8 % SL vs. 18.5-24.4 % SL), 36-37 vertebrae (vs. 32-33), 17-20 anal-fin rays (vs. 12-14), a single ventromedian row of large melanophores between pelvic fins and tips of cleithra (vs. paired ventral paramedian rows of smaller melanophores between pelvics and tips of cleithra), and in lacking scattered small melanophores on ventrolateral side of abdomen (vs. presence of these melanophores). Although slightly larger than D. translucida, D. mirifica is still one of the smallest freshwater fishes.
Britz, Ralf. 2003. Danionella mirifica, a new species of miniature fish from Upper Myanmar (Ostariophysi: Cyprinidae). Ichthyol. Explor. Freshwaters 14 (3): 217–222. http://www.pfeil-verlag.de/04biol/pdf/ief14_3_03.pdf