Species: Poecilia mexicana, Shortfin molly

Poecilia mexicana Steindachner, 1863

Shortfin molly, Mexican molly

Body variable in proportions, torpedo shaped to deep, compressed; head depressed;front nostril not tubular; covering of eye not continuous with skin of head; mouth small, at front, slightly oblique, lower jaw slightly projecting, top jaw protractile; jaw teeth consist of an outer row of large backward curved teeth with expanded tips, and several rows of small pointed teeth, inner row of teeth with 1 point; 21-26 gill rakers; with 2 pairs of pores on top of snout before eyes; 1 dorsal fin with short base, origin behind pelvic origin, 9-10 rays, fin small in male; pelvic origin well behind pectoral base, near anal fin; tip of pelvic fin of males swollen, elongate;  pectorals high on flank, 5th ray not scalloped in male; anal fin 9 rays, origin under (female) or a little behind (male) dorsal fin origin; 3rd anal ray unbranched; anal fin modified in male to form an elongate sex organ, that organ relatively short, with straight tip that has small spines, a small claw & a fleshy palp; tail base relatively narrow; tail fin rounded, without elongate sword; scales smooth and relatively large; 18 scales around tail fin base; 29 (26-30) lateral scale rows.

There is considerable geographic variation in the color patterns of males of  this species: N Mexico upper body bluey grey, with more blue below; tail and dorsal fins – black inner half + orange outer part; Yucatan body with rows of orange spots along scale rows; dorsal fin with black and yellow reticulations; tail fin with base bluey white, center with several  vertical rows of black spots, rear margin broadly orange. Female grey-brown above, whitish below; base of dorsal fin with a row of dense black spots, tail fin with a few scattered black spots. Costa Rica: several rows of yellow spots on flanks, those spots black in females of some brackish water areas; dorsal and anal fins of male more heavily pigmented than in female.

Reaches 14.4 cm.

Fresh to brackish water nearly full strength salt water, in lagoons and estuaries on the coast.

Depth range: 0-1 m.

SW Gulf of Mexico to Colombia.