The Black Lyretail Sailfin Molly, is an aquarium strain of hybrid mollies. Parental species include Poecilia latipinna, P. sphenops and possibly other molly species. The lack of a species name here indicates that this fish is a hybrid of unknown origin within the genus Poecilia and not a natural species. We originally acquired this strain from a commercial source in 1999. We out crossed those original fish to our P. latipinna, Coleto Creek and P. latipinna, Rio San Antonio fish to improve the dorsal fins. Males reach 12.5cm (5 in.). Females grow somewhat larger and much heavier. Both sexes have solid black bodies and fins. The male’s dorsal fin is immense, often showing a thin orange distal margin. Both sexes sport the lyretail that gives the strain its name. The lyretail characteristic is controlled by a dominant gene. This gene originally occurred in fish of P. sphenops heritage and, therefore, all mollies with the characteristic carry genes. Since this species has males with small dorsals, most lyretails don’t have sailfin dorsal fins. We have diligently worked to improve dorsal size through selection and out-crossing to P. latipinna. This fish has no natural range since it is a hybrid among species that range from the Carolinas to Central America.