A New Poecilia (Pamphorichthys) Species (Cyprinodontiformes: Poeciliidae) and Its Conservation Implications at the Chapada Diamantina, Bahia, Brazil

A new species of Poecilia, subgenus Pamphorichthys, is described from the Cachoeirinha River, a tributary of the upper Paraguaçu River basin in the Chapada Diamantina, Bahia, Brazil. Pamphorichthys is diagnosed among the Poecilini by the strongly pigmented gonopodium in mature males and the equally pigmented urogenital region in females. The new species exhibits four diagnostic features defining the Pamphorichthys clade within Poeciliidae. Males display a unique combination of a reticulated body pattern with diffuse vertical bars and a highly modified pelvic fin. The male pelvic fin possesses a subterminal process on the second ray, similar to that found in the limbs of Pamphorichthys, but highly modified. Although it shares the unique pelvic-fin processes of Pamphorichthys, its gonopodium exhibits reduced ornamentation, resembling the condition in P. pertapeh and P. akroa. Its discovery in an isolated drainage within the Chapada Diamantina underscores the notable endemism of the region. However, the species faces an imminent conservation crisis. Its only known habitat has undergone severe degradation in the last few decades. An excessive water withdrawal has collapsed the Utinga River, one of the main tributaries of the upper Paraguaçu River, and anthropogenic degradation can lead to the disappearance of species, even before it becomes known.