Family Rivulidae Myers 1925 (Fig. 4F). New World Rivulins; Killies, Saltones, Olominas

Description: Body elongate, cylindrical; up to 20 cm, usually less than 8 cm; mouth short, wide, terminal to superior; eyes relatively large; head flattened; pelvic fins located on the belly; lateral line incomplete, underdeveloped; dorsal fin posterior, usually behind the origin of the anal fin; caudal fin usually rounded (Nelson et al. 2016, Angulo et al. 2021). Distribution: Freshwater (rarely brackish); southern Florida through much of Central America to Uruguay and northeastern Argentina (Nelson et al. 2016). One genus and one species in Nicaraguan freshwaters.