The Early Origin of the Antarctic Marine Fauna and Its Evolutionary Implications

• Published in: PloS one Vol. 9; no. 12; p. e114743
• Main Authors: Crame, J Alistair, Beu, Alan G, Ineson, Jon R, Francis, Jane E, Whittle, Rowan J, Bowman, Vanessa C
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 10-12-2014; Public Library of Science (PLoS)
• Subjects: Animals; Antarctic radiation; Antarctic Regions; Aquatic Organisms; Biodiversity; Biological Evolution; Biology and Life Sciences; Bivalvia; Climate change; Cretaceous; Cretaceous period; Earth Sciences; Eocene; Evolution; Evolution (Biology); Fauna; Fossils; Gastropoda; Gastropods; Global cooling; Global temperature changes; Global warming; Marine animals; Marine fauna; Mass extinction; Mass extinctions; Mollusca; Mollusks; Neogene; Paleocene; Paleogene; Paleogene period; People and Places; Polar environments; Radiation; Source-sink relationships; Species extinction; Antarctic Peninsula; United Kingdom > UK; United States > US; Denmark; Seymour Island; Antarctica; Chicago Illinois
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0114743

The extensive Late Cretaceous - Early Paleogene sedimentary succession of Seymour Island, N.E. Antarctic Peninsula offers an unparalleled opportunity to examine the evolutionary origins of a modern polar marine fauna. Some 38 modern Southern Ocean molluscan genera (26 gastropods and 12 bivalves), representing approximately 18% of the total modern benthic molluscan fauna, can now be traced back through at least part of this sequence. As noted elsewhere in the world, the balance of the molluscan fauna changes sharply across the Cretaceous - Paleogene (K/Pg) boundary, with gastropods subsequently becoming more diverse than bivalves. A major reason for this is a significant radiation of the Neogastropoda, which today forms one of the most diverse clades in the sea. Buccinoidea is the dominant neogastropod superfamily in both the Paleocene Sobral Formation (SF) (56% of neogastropod genera) and Early - Middle Eocene La Meseta Formation (LMF) (47%), with the Conoidea (25%) being prominent for the first time in the latter. This radiation of Neogastropoda is linked to a significant pulse of global warming that reached at least 65°S, and terminates abruptly in the upper LMF in an extinction event that most likely heralds the onset of global cooling. It is also possible that the marked Early Paleogene expansion of neogastropods in Antarctica is in part due to a global increase in rates of origination following the K/Pg mass extinction event. The radiation of this and other clades at ∼65°S indicates that Antarctica was not necessarily an evolutionary refugium, or sink, in the Early - Middle Eocene. Evolutionary source - sink dynamics may have been significantly different between the Paleogene greenhouse and Neogene icehouse worlds.