ABSTRACT
Molluscan biodiversity in the Paulinian Subprovince The southernmost subprovince of the Brazilian Province, the Paulinian, encompasses the northern half of the Southwestern Atlantic Shelf, a physiographic region that extends from the Cabo São Tome-Cabo Frio area of Rio de Janeiro State south to the Falkland Islands off Argentina. The Paulinian Subprovince is centered around the South Brazil Bight, a wide, broad, sheltered embayment that extends from Rio de Janeiro, Rio de Janeiro State (Figure 11.1) south to Florianopolis, Santa Catarina State, and contains complex marine environments composed of small coral and sponge bioherms and coralline algal ridges and rhodolith beds. Oceanographically, the South Brazil Bight is completely within the inuence of the warm Brazilian Current, which supports a eutropical molluscan fauna complete with almost all the tropical index taxa. South of Florianopolis on the Southwestern Atlantic Shelf, the Brazilian Current swings farther offshore and cool water eddies spinning off the subantarctic Falklands Current migrate up and down the coast (Matano, Palma, and Piola, 2010), creating only marginally paratropical conditions. South of Rio Grande, Rio Grande do Sul State, the northward-owing eddies off the Falklands Current become stronger and more dominant, and nine of the ten tropical index taxa groups dis appear. Only one cold-tolerant species of conid, Lamniconus carcellesi, occurs in this area and ranges as far south as the mouth of the Rio de la Plata in Uruguay and Argentina. This southernmost area of Brazilian inuence is here referred to as the Uruguayan Provinciatone, and the area is a broad transition zone between the tropical Brazilian Province and the subantarctic Patagonian Province.
