Seasonal killifish species from the Mid-Northeastern Caatinga ecoregion, northeastern Brazil. Live specimens of Cynolebias microphthalmus male (A) and female (B) collected in May 2019 in Apodi-Mossoró river basin (locality 14), Rio Grande do Norte State; live specimens of Hypsolebias antenori male (C) and female (D) collected in June 2018 in Córrego da Mata coastal basin (locality 12), Furna Feia National Park, Rio Grande do Norte State; and preserved specimens of H . martinsi male (E) and female (F) collected in February 2019 in Mundaú river basin (locality 2), Ceará State.