ABSTRACT
Introduction .............................................................................................................................................. 81 Geological Setting and Relationships of Fauna ....................................................................................... 82 Australia in the Indo-West Pacic ........................................................................................................... 83 North and South Biogeographic Regions ................................................................................................ 84 ‘ Traditional’ Biogeographic Regions ...................................................................................................... 84
Solanderian and Great Barrier Reef .................................................................................................... 84 Peronian .............................................................................................................................................. 84 Maugean .............................................................................................................................................. 87 Flindersian .......................................................................................................................................... 87 Dampierian .......................................................................................................................................... 87
Bioregionalisation .................................................................................................................................... 88 Conicting Classications ....................................................................................................................... 88 Taxonomic Groups ................................................................................................................................... 89
Molluscs .............................................................................................................................................. 89 Echinoderms ....................................................................................................................................... 89 Crustaceans ......................................................................................................................................... 90 Polychaetes ......................................................................................................................................... 91 Corals .................................................................................................................................................. 92 Sponges ............................................................................................................................................... 93 Tunicates ............................................................................................................................................. 93 Lophophorates .................................................................................................................................... 94
Bryozoa .......................................................................................................................................... 94 Brachiopoda ................................................................................................................................... 94 Phoronida ....................................................................................................................................... 94
References ................................................................................................................................................ 94
The current distributions of marine invertebrate species are the result of both contemporary physicalecological processes and the effects of events in geological history, the former being the domain of ecological biogeography and the latter of historical biogeography. Although the overall latitudinal distributions of modern species are consistent with present-day environmental variables in strong
north-south faunal differences, these differences have their roots in the Cretaceous during the breakup of Gondwana. During the Cretaceous, the northern supercontinent Laurasia and southern supercontinent Gondwana were separated by the equatorial Tethys Sea, within which a tropical fauna evolved. The present-day western margin of Australia essentially formed part of the northern Gondwanan coastline bounding the southern Tethys. Conversely, in Early Cretaceous times, present-day eastern Australia was much farther south, contiguous with eastern Antarctica, developing a separate Austral fauna. The sequential breakup of Gondwana saw the separation of Australia from Zealandia about 80 Ma and the beginnings of the break of Australia from Antarctica about 70 Ma. Australia’ s break from Antarctica started in what is now southwestern Australia, with the progressive opening of a north-facing seaway that increasingly exposed the newly forming ‘ southern’ Australian coastline to a tropical Tethyan biota (Crame 1999). By 40 Ma, Tasmania had also separated from eastern Antarctica, allowing the development of the southern circumpolar current. Australia’ s northwards movement and rotation towards its present position exposed more of the now northern coastline to warm-water Tethyan faunas, and prompted the transition of the formerly warm southwest towards a cooler-water palaeoaustral fauna that evolved in the southeast. Palaeoaustral remnants, especially in southeast temperate Australia, persist to this day. The collision of Australia with Southeast Asia about 20 Ma during the Miocene nally merged the northern Australian fauna and tropical Indo-West Pacic fauna, whose origin was in the Tethys. Thus, although the distribution of the Australian marine modern biota is governed by present-day physical-ecological conditions, its composition nevertheless carries the distinct signature of the past.
