FIGURE 4. Palaeogeographic Setting for the early Austrobalanidae. 4a in A review of the subfamily Eliminiinae (Cirripedia: Thoracica: Austrobalanidae), including a new genus, Protelminius nov., from the Oligocene of New Zealand

FIGURE 4. Palaeogeographic Setting for the early Austrobalanidae. 4a: Sketch depicting the oceanic systems that are likely to have operated in the south Pacific region during the late Palaeocene-early Eocene. At this time, the Antarctic continent was kept essentially ice-free by a large south Pacific warm-water gyre; counter-currents operating off Antarctic provided an opportunity for westward dispersal of Austrobalanus (to the McMurdo region and the proto-New Zealand land mass "NZ"). The dashed line represents a likely mobile transitional zone between marine regression and transgression. 4b: Southern ocean conditions during the Oligocene to early Miocene, after the initiation of the Antarctic Circumpolar Current. With the loss of the southern pacific warm-water gyre, glaciation of the Antarctic continent began (e.g. Kennett, 1977), with the resultant regional extinction of austrobalanid barnacles. The heavier dotted blue line represents the likely position of the cold and temperate water systems convergence. (Reconstruction adapted from Markwick et al., 1999; Barron and Peterson, 1991; Nelson and Cooke, 2001).