Typically, western Melanesia is viewed as a critical series of stepping stones in an eastward biotic flow of colonisers from Asia or Australia out into the Pacific islands. This traditional view relegates western Melanesia to a position of little importance in the actual generation of biodiversity and assumes a largely one-way flow of taxa from rich continental source areas out into depauperate insular recipient areas. In contrast, recent evidence makes clear that modern New Guinea is far too geologically recent to have served in this role, and that the Melanesian islands have been important since the Oligocene (34–23 Mya) as source areas generating taxonomic radiations, some of which have then gone on to colonise continental or insular areas to the west.

 

It is increasingly clear that insular landforms of a size sufficient to generate endemic radiations have long occupied the southwestern Pacific and have been overlooked in explaining the origins of some of the megadiversity in southeastern Asia, Australia, and the intervening islands of western Melanesia, especially New Guinea. However, the details of where these landforms occurred, their subaerial ages, their geological histories, and which taxa arose on them remain uninvestigated, with most studies treating Sahul, wrongly, as a single entity.

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Using herpetofauna to construct dated phylogenetic trees will help identify areas and times of origin for each clade and trace their expansion to new regions. Cross-validation between these results and updated geological models will illuminate tectonic events that drove speciation and dispersal in the region.