The marine ostracod genus Tasmanocypris from the Neogene of southeastern Australia: Systematic and palaeoceanographical relationships, palaeoecology and palaeobiogeography

Abstract

Abstract A new fossil paracypridine ostracod, Tasmanocypris lochardi sp.nov. is described from late Miocene shallow marine strata of southeastern Australia. It has morphological features similar to a number of modern southern Australian and southwest African Tasmanocypris species, here termed the dartnalli-group. This species group was likely present in early Cenozoic temperate, shallow seas around Antarctica. The first appearance of Tasmanocypris lochardi in late Miocene marine strata of the Bass Strait hinterland of SE Australia, equates to a late Miocene (9–7 Ma) intensification and northward latitudinal shift of the Antarctic Circumpolar Current (ACC). Late Miocene occurrences of Tasmanocypris lochardi in southeast Australia were likely associated with temperate eastward flows of the ACC north of the Subantarctic Front. During the early Pliocene, the warm Zeehan Current (aka Leeuwin Current) replaced the ACC as the dominant easterly flowing current across Bass Strait, and this 4.4 Ma palaeoceanographical event correlates with the temporary, but widespread disappearance of T. lochardi from southeast Australian marine waters. However, the presence of refugia populations of T. lochardi along the east Australian continental shelf between 4.4 and 3.4 Ma, likely enabled the brief re-establishment of T. lochardi in the east of Bass Strait during the late Pliocene (3.2–3.0 Ma). Tasmanocypris lochardi became permanently extinct in this region during the latest Pliocene to early Pleistocene (