Tlaloc, named for the Aztec rain god, is a small genus of Middle American killifish found in Mexico, Guatemala, and Honduras, part of the diverse cluster of egg-laying cyprinodontiform genera that were split out of the older, broader Profundulus grouping as researchers worked through the region's freshwater fish diversity. The atlas covers 3 species, 2.5–4.5 in, sharing the elongate body and upward-pointing mouth typical of surface-feeding killifish adapted to small streams and spring-fed pools.
This genus sits well outside the mainstream aquarium hobby - it is known mainly to killifish specialists and regional ichthyologists rather than general fishkeepers, and data on husbandry and behaviour stay sparse in the literature reviewed for this atlas. The conservation picture is mixed and concerning within a narrow footprint: of the 3 species, one (Tlaloc portillorum, the Uluan killifish) is assessed Endangered, reflecting the vulnerability that comes with living in small, geographically restricted Middle American waterways exposed to habitat degradation.