Fossil remains of clupeomorph fishes are commonly found in Cretaceous and Tertiary deposits from the northeastern Brazil. The taxonomic diversity is relatively high and include tellimmichthyiforms, early clupeiforms, and advanced clupeoids. However, well-preserved specimens are very scarce so that very little is known about affinities of most taxa. Recently, new localities containing clupeomorphs have been discovered and prospected in Alagoas State, in Northeastern Brazil. From them, Atol Quarry, in which Barremian shales from the Coqueiro Seco Formation crop out, has demonstrated to be meaningful by having a diverse fish assemblage. It contains holosteans, coelacanths, gonorynchiforms, and enchodontids besides clupeomorphs. Most of fishes correspond to new taxa. In this paper, an early clupeiform fish, †Pseudoellimma gallae gen. et sp. nov., is described from those shales. The fish shows many informative characters and revealed to be advanced in comparison with other early and relatively well-known clupeomorphs such as † Spratticeps and † Santanaclupea. Although lacking pleurostyle, it shares with clupeoids derived features such as accessory anterior foramen of temporal canal, hidden post-orbital branch of supraorbital canal on frontal, longitudinal and parallel ridges sculpturing the skull roof, and reduced first ural centrum. If so, many derived features found in advanced extant clupeoids appeared early in the history of clupeiform fishes. Furthermore the present study indicates divergence between Clupeoidei and Denticipitoidei lineages older than Barremian age.