The ichthyofaunistic colonization and complex biogeographic history of the southern portion of the Southwest Atlantic Ocean

Abstract

Here, we highlight the geological processes that resulted in the current conformation of the southern Southwest Atlantic Ocean, and explore the heterogeneous composition of the marine ichthyofauna found between 33° and 56° from a paleobiological perspective. During the early Cretaceous (140 Mya), the South Atlantic was still not formed, and Gondwana was probably a set of united plates with shallow continental waters. In the middle Cretaceous (112 Mya), the major Gondwanan plates started diverging from each other, allowing shallow marine intrusions and the diversification of an endemic fish fauna. By the end of the Mesozoic (66 Mya), the proto‐South Atlantic connected with the North Atlantic, which was still part of the Tethys Sea, allowing its ichthyofauna to colonize the south and reach the Antarctic region. The opening of the Drake Passage in the Oligocene (33 Mya) enabled the cold waters of the Pacific Ocean to reach the South Atlantic, causing drastic effects on the thermophilic fauna and favoring the dispersion of cold‐water species. Successive glaciations during the Quaternary (2 Myr to 10,000 years ago) resulted in the prevalence of Antarctic climatic conditions in the southern Southwest Atlantic. The long history of changing scenarios in the constitution of the southern Southwest Atlantic is reflected in the heterogeneous composition of the marine ichthyofauna between 33° and 56°S, which is characterized by a mixture of cosmopolitan, Tethyan, Pacific, Gondwanan, Antarctic, and endemic origins.

A Faunistic Revision of Longnose Skates of the Genus Dipturus (Rajiformes: Rajidae) from the Southern Southwestern Atlantic Ocean, Based on Morphological and Molecular Evidence

“…Further comprehensive studies are imperative to enhance our understanding of the diversity and distribution of Dipturus and Dipturus-like taxa worldwide. Particularly, in the Southwest Atlantic, which comprises two biogeographic provinces where the diversity of skates is notable [44]. In this region, a wide range of skates can be found, from the largest in the world (Dipturus trachyderma) to one of the smallest (Psammobatis rutrum) [44].…”

“…Particularly, in the Southwest Atlantic, which comprises two biogeographic provinces where the diversity of skates is notable [44]. In this region, a wide range of skates can be found, from the largest in the world (Dipturus trachyderma) to one of the smallest (Psammobatis rutrum) [44]. It includes two endemic genera (Atlantoraja and Rioraja) and several cosmopolitan genera, with one of them showing a surprising radiation (Bathyraja) and another (Zearaja) considered Gondwanan [12,44].…”

“…In this region, a wide range of skates can be found, from the largest in the world (Dipturus trachyderma) to one of the smallest (Psammobatis rutrum) [44]. It includes two endemic genera (Atlantoraja and Rioraja) and several cosmopolitan genera, with one of them showing a surprising radiation (Bathyraja) and another (Zearaja) considered Gondwanan [12,44]. Moreover, a deeper understanding of skate biodiversity, along with accurate species definitions, are crucial for the development of effective fisheries management measures.…”