Phalloceros elachistos, the Córrego toothcarp, is a species of poeciliid fish native to Brazil.
Distribution.
"Phalloceros elachistos" is found in Brazil in the drainages of rio Doce, Santa Maria da Vitória, Jucu, and Timbuí, which are coastal drainages of Espírito Santo State of 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 = "elachis", small, or short or little; "–istos", meaning least, referring to small size.