381 Neogene Paleontology of the Northern Dominican Republic 24

Based on approximately 25,00 specimens from the Miocene and Pliocene of the Cibao Valley, northern Dominican Republic, the bivalve family Propeamussiidae is represented by two genera and four species, including two new species Cyclopecten acuminatus and C. zalaya; the family Pectinidae is represented by three subfamilies, six tribes, 18 genera, and 35 species.  

Assemblages of the two families change composition going upward in stratigraphic sections measured along each major river, reflecting increasing depth of deposition, changing bottom conditions, and association with coral reefs or marine grasses and algae. Evolutionary changes within particular lineages help to resolve several previous biostratigraphic uncertainties and controversies, including the age of limestones on the Rio Yaque del Norte and in the Guayubin area.