Total (live dead) ostacod assemblages are documented in five samples from the Coconut Field area, and eight from the Mahogany Field, SE of Trinidad and east of the Orinoco delta. Although the fields both lie in ∼70–80m of water, and Mahogany lies only 18 km NE of Coconut, they are situated in different biofacies: Bradleya ex gr. dictyon, the dominant species in the Coconut Field (46% of total recovery), forms only 7.6% of the fauna in the Mahogany Field. Assemblages in the Mahogany Field are dominated by Bairdoppilata dorsoangulata. Diversity (measured using both species richness and the Information Function) is greater at the Mahogany Field. This suggests greater water clarity at the Mahogany Field, which lies farther from the Orinoco delta. Bythoceratina carmoi, Callistocythere fossulata and Bairdoppilata dorsoangulata are recorded north of 4°N for the first time.