Phalloceros heptaktinos, the seven ray toothcarp, is a species of poeciliid fish native to Brazil.
Distribution.
"Phalloceros heptaktinos" is known only from the tributarues of the arroio dos Ratos, in the Jacuí basin of the Rio Grande do Sul, Brazil.
Size.
The females of this species grow to a total length of , while males remain smaller at .
Habitat.
The fish live in tropical freshwater; and are benthopelagic. 
Etymology.
The fish is named in Latin = "hepta-", seven; "aktinos", rays, referring to number of dorsal-fin rays of the females.