The Antarctic Shortcut – a possible explanation for increased mid-Cenozoic faunal exchange between New Zealand and South America

NIELSEN S.N.; CASADÍO, S.

Viena

Congreso; Jahrestagung Paläontologische Gesellschaft; 2011

Close faunal links between Cenozoic marine faunas of New Zealand and southern South America (Chile and Argentina), especially in mollusks, have been known for some time. Between New Zealand and Argentina 46 shared molluscan genera were identified for the Cenozoic, with a dispersal peak in the late Oligocene to early Miocene. At least 18 of these do also appear in Chile, but there are certain genera which are shared with either one of them but not with both. Chile and Argentina share e.g. Struthiochenopus, Adelomelon and Olivancillaria, while Chile and New Zealand share e.g. Lamprodomina, Bedeva and Austrotoma. In all three occur e.g. Fusitriton, Austrocominella and Zeacuminia. Apart from mollusks there is additional evidence for paleobiogeographic connections from cinctoporid bryozoans, echinoids and brachiopods. Cinctoporids are a bryozoan family thought exclusive to New Zealand which, however, has recently been reported also from the Oligo-Miocene of Patagonia. It is proposed that a locally still low Andean Cordillera and Oligocene alignment of New Zealand, Antarctica and South America provided several migration pathways possibly until as late as the late Miocene. These shelf or shallow water areas provided dispersal possibilities 1) between New Zealand and Chile along the Antarctic shelf, 2) between New Zealand and Argentina across the West Antarctic Rift system, and between Chile and Argentina across the Andes. Rafting on macro-algae or driftwood enhanced dispersal ability for several taxa without long-lived larvae.