A new megatrigonid, Anditrigonia britoi n.sp., is described from three new fossiliferous localities from Riachuelo and Divina Pastora Districts. Northwest Brazil. The specimens come from conglomeratic sandstones from Angico Member of Riachuelo Formation from Sergipe Basin. Anditrigonia britoi was problably a infaunal vagile bivalve that vertically burrowing in soft bottom as a suspension feeder free-living primary dweller (sensu Seilacher, 1984) in a shallow marine transitional environment, whit normal oxygen level, high turbidity and low salinity, characteristic from aluvial fandelta that occurred in the region during the Early Albian. The genus, hitherto unknown in Brazilian or South Atlantic basins, is typical of the North and South American Pacific coast, during Bajocian to Hauterivian stages. The present state name occurrence, associated to ammonite Douvilleiceras sp., enlarge the geographic and temporal occurrence of the genus, now established from the Bajocian (Early Jurassic) to Early Albian (Early Cretaceous).
