Common names: toothcarp (English), livebearer (English), guatopote (Espanol), olomina (Espanol)
Poeciliopsis fasciatus (Meek, 1904)
San Jeronimo livebearer, Dorsal-spot toothcarp
Head small, flattened above; body slender; dorsal I, 6; anal II, 5; scales large, smooth, 28-32 along mid-side; relatively small mouth; jaw teeth conical, in bands, outer teeth larger; pelvic rays 7 & 8 distorted, converging or in contact at midlength; male sex organ a tube on left side formed by folded (but not spiralled) anal fin rays, long (reaches to or nearly to the base of the tail fin) and slender.
Olive grey above; body with 2-6 narrow dark bars from top to mid side, sometimes 1-2 of them reach lower body; a black spot on base of first two dorsal rays; a black blotch just before anal fin and on basal half of first anal rays; a dark line along underside of tail base; iris black.
Size: grows to 5.5 cm.
Habitat: freshwater streams and brackish lagoons.
Depth: 0-2 m.
Southern Mexico - Acapulco to the Gulf of Tehuantepec.