Antarctic history of the family Rajidae

FIGUEROA DANIEL E.; BARBINI SANTIAGO; SCENNA LORENA; DELPIANI GABRIELA; SPATH CECILIA; BELLEGGIA MAURO

Vancouver

Congreso; World Congress of Herpetology; 2012

American Society of Ichthyologist and Herpertologists (ASIH)

Skates are a group of fish of an ancient lineage, a high specific diversity, a cosmopolitan distribution and a non-migratory mode of life, given that they are benthic fishes all along their ontogeny, which starts from the embryo stage in ovarian capsules with adhesive filaments. They constitute a valuable analytical tool when associated to geological processes. In modern Antarctica, the family Rajidae is represented by two cosmopolitan genera, Amblyraja with two species, and the most speciose genus in the world, Bathyraja, with approximately seven species. Climate of the late Cretaceous and early Tertiary times in the Antarctica was much more temperate than nowadays. Of coastal waters and extensive shelves, fossil records reveal the presence of siluriform, gadiform, cupleoid, trichiurid and labrid fishes, all typical modern exponents of the Buenos Aires District north of the Argentine continental shelf. This southwestern Atlantic sector shows at world level one of the oddest overlapping of endemic genera of skates. The fossil rays teeth found in the Eocene La Meseta Formation would probably belong to this group of skates instead of to Bathyraja and Amblyraja, as stated by some other authors. Both these two genera of rays accompanied by two families of bony fish (Zoarcidae and Liparidae), of sympatric distribution with these genera of skates in the Northern Hemisphere, probably joined the opening of Drake Passage in the late Tertiary, together with the incoming of the Pacific deep cold waters.