Studies on Australian Gastropods have only begun recently. Before that, the molluscan fauna of this large continent was almost unknown. Till date, the direction and rate of studies on gastropods have varied remarkably usually driven by the interest of one or a few individuals (Beechey, 2012). The initial studies of Australian gastropods were a collection of shells by naturalists of the Cook expedition in Botany Bay, New South Wales in1770. Early European exploratory voyages to the continent thus herald the studies on these Australian gastropods.
The fossil history of gastropod groups is not equally represented in the fossil record. One of the reasons is due to the size of shell. Small shells are not well recorded and are generally scarce in the fossil records. However, large, heavy shelled groups such as the Vetigastropoda and Caenogastropoda are the most diverse in the fossil assemblages.
The superfamily Trochoidea have an extensive fossil record, which starts from Middle Triassic (228–245 Mya; Hickman & McLean, 1990).
There is a well-represented fossil record of Turban shells, however, their taxonomic assignment and documentation is poor (Williams, 2007). Their shell morphology is usual characteristic, thus, misidentification of extant and recent species are reduced (Williams, 2007).
In the Cenozoic 65 Mya), and the Neogene (23Mya) in particular, there was a radiation of diversity of both marine and terrestrial organisms (Carme & Roson 2002). This radiation was concentrated in the tropics, with a strong latitudinal gradient (Crame, 2000).This parallel trend in many organisms indicated that the driving force is from a single factor or group of associated factors (Signor, 1990). Tectonic activity are one of the causes. In the beginning of the Cenozoic, there was auniform tropical realm, the Tethys Sea which stretches from the East Pacific across the Caribbean and Mediterranean into the Indian Ocean (Harzhauser, Piller and Steininger, 2003). Collision of Laurasia and India saw the disruption of the Tethys Sea in the Eocene and in the early Miocene by the collision of New Guinea and Australia with South East Asia.
Approximately 18-19Mya, a large land barrier separating Indo-West Pacific from the proto-Mediterranean closed and terminated the Tethys Sea (Vrielynck, Odin and Dercourt, 1997). The gene flow between the tropical seas were greatly affected by the vicarant events. At the same time, the collision of South east asia with new Guinea and Australia resulted in the creation of a lot of new shallow water habitats in the central IWP (Crame and Rosen, 2002).
Concurently, a proliferation of reef building corals occurred in the last 20-25Myr (Crame and Rosen, 2002;Wilson and Roson, 1998).
The tectonic events also caused global cooling (Crame and Rosen, 2002) causing the lost of 40-50% of tropical habitats (Adams, Lee and Rosen, 1990).
All Turbo species in the Indo-west pacific form a single clade approximately 68Myr in age. This predates the clousure of the Tethys Sea. Thus, they evolved before the physical separation of the Indo-west pacific from other biogeographical regions (Williams,2007). Fossil evidence indicates that at least some Turbo lineage were previously more widespread but now restricted to the Indo-west pacific (Williams,2007).
The use of both fossil evidence and phylogeny indicates that the current diversity of Turbo in the Indo-west Pacific is a result of evolutionary persistence within the Indo-west Pacific although some lineages were more widespread in the Oligocene (Williams, 2007). In the early Miocene, there was a significant increase in diversity, a resultof the increase shallow water habitats and increased carbonate platform (due to diversification of zooxanthellae corals) in the central Indo-west Pacific. Temperate habitats are found to be the ancestral character. Temperature has an effect on speciation rates with tropical clades showing greater diversity than temperate Turbininae (Williams, 2007).
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