TAXONOMY AND PALEOECOLOGY OF MID-CRETACEOUS RUDIST BIVALVES FROM PUERTO RICO

During the Cretaceous the Caribbean was home to vast carbonate platforms where rudist bivalves contributed extensively to reef development. These platforms have been well-studied in Mexico and Texas, but less so in some Caribbean islands. On the island of Puerto Rico, the Barrancas, Río Matón, and Aguas Buenas are limestone members within volcanic formations that can provide a snapshot of life in the paleotropics. These members have been dated to Albian based on stratigraphic position and the presence of sufficiently preserved forams and macrofossils. Samples were collected per stratigraphic unit and taxonomic analyses were conducted in the laboratory. The data were transferred to graphic representations of measured sections. The Barrancas yielded approximately 170 specimens with 110 resulting in identification to family level, 56 of which were identified to genus level. The Río Matón contained slightly fewer specimens with 160, 107 resulting in identification to family level and 41 identified to genus level. The Aguas Buenas contained 35 specimens resulting in 26 identifications to family level and 5 identifications to genus level. All members contained requieniid, radiolitid, and caprinid rudists. Barrancas and Río Matón also contained rare polyconitids. Caprinid specimens made up the majority of identifiable rudists, while requieniids and radiolitids were rarely identified beyond family level. Although the greater field collection included more rudist fossils, only specimens associated with stratigraphic levels were used to confirm the age of the members. Of all the rudists identified, the temporal ranges of caprinid specimens proved the most useful for correlation into regions with integrated macro-and microfossil zones. This research allows us to understand the life history and age ranges of these rudists more accurately from a regional perspective, and will be an important basis for future studies of marine ecosystems and connectivity during this time period.