The Rajidae of Southwest Atlantic: an overview

FIGUEROA, DANIEL E.; BARBINI, SANTIAGO A.; SCENNA, LORENA; DELPIANI, GABRIELA; SPATH, M. CECILIA; IZZO, LUCIANO

Minnesota

Congreso; Joint Meeting of Ichthyologists and Herpetologists.; 2011

The Rajidae of the Southwestern Atlantic shows at the genus level an astonishing endemic diversity related to its ecology. Two biogeographic provinces constitute the southwestern Atlantic: the northern warm-temperate Argentinean Province and the southern cold-temperate Magellan Province. Skates from the former are endemic of southern South America; instead, genera from the latter are cosmopolitans related to the Antarctic ichthyofauna, with Gondwanic distribution, and one of its genus is invader of the Argentine Province. The Argentine continental shelf, one of the largest in the world, possesses ideal conditions for the development of skates: smooth slopes, little relief, 65% sand-covered, located in a temperate transition zone. However, since this region is one of the youngest in the world, its colonization is also recent. Considering the environmental features from its formation in the Cretacic --where Chondrychthyes Batoid teeth are already found-- to nowadays, its evolution has been traumatic. At the beginning, temperate waters arrived to Antarctica and even Oceania, the opening of the Drake Passage in the Paleogene permitted the entrance of cold waters that severely affected the South American cone, and lastly, during the Pleistocenic ice age, the subtropical sub Antarctic convergence zone moved farther north than at the present time. The endemic skates of the Argentine Province could be the most ancient settlers of the region. The wide temperature and salinity tolerance range they exhibit is really surprising.