Thicklip pupfish
The thicklip pupfish ("Cyprinodon labiosus"), known in Spanish as "Cachorrito cangrejero", is a species of fish in the family Cyprinodontidae. Thicklip pupfish is endemic to Lake Chichancanab in Quintana Roo, Mexico. In almost all places, different "Cyprinodon" species do not overlap in their range, but there are two notable exceptions and one of these is Lake Chichancanab, which is inhabited by "C. labiosus", "C. beltrani", "C. esconditus", "C. maya", "C. simus", "C. suavium" and "C. verecundus" (the other place where several "Cyprinodon" species live together are lakes in San Salvador Island, the Bahamas). Among the endemic "Cyprinodon" species  in Lake Chichancanab, only "C. beltrani" and "C. labiosus" still occur in some numbers in their habitat, while the remaining are virtually—if not fully—extinct in the wild (at least some of these still survive in captivity). They usually live in a tropical climate with temperatures ranging from 22°C to 26°C. The max length of this fish is 7cm.