The modern distribution of rocks containing Australian (Lacazinella) and Sundaland to wider Tethyan (APB) microfossil faunas on the whole follows expected patterns, with ophiolite complexes and major fault zones occurring along zones of collision between these once separate plates (e.g. in Papua, see Figure 3, modified from Hamilton 1979). The identity and tectonic evolution of the major plate units are not in doubt. It is in assigning Sundaland or Australian origins to the minor plate fragments that these fossils will be of most use.

Many islands that make up the Banda Arc, including Sumba, parts of Timor, and Seram have records of the APB fauna. This similarity indicates that they were separate from the Australian plate and at low latitudes in Eocene times. Assuming the palaeomagnetic anomaly "M25", end mid-Jurassic rift-drift event was the last known cause for separation of micro-plate fragments from the Australian margin (cf. Veevers et al. 1991), then these fragments would have been carried north and become accreted onto the subducting margin south of Sundaland within the Cretaceous. Such a model does not match tectonic histories proposed in many recent publications. For example, Hall (1996) reconstructed Seram but did not display Sumba. Subsequent models by Hall (2001), however, incorporated Sumba as a fragment of Sundaland based on geological criteria, which is consistent with the faunal data presented here. Other areas are more hotly contested, with differing geological interpretations. For instance there are many proposed tectonic models for Timor, which can be tested with the biogeographic model proposed here. The Eocene fossil data favors the model of mixed Sundaland terrains over-thrusting the colliding Australian plate, as discussed in the many papers of Audley-Charles (1968) and Barber. This model contrasts with those having Timor as a wholly Australian derived fragment, such as that of Chamalaun and Grady (1978), which concluded that "there should be continuity between the stratigraphy of Timor and that of the Sahul Shelf" (p. 107 op.cit); - a summary inconsistent with the data presented here.