Fig 1.
Approach to identify potential fossil areas with combined models.
For a given taxon, the areas with greatest potential to yield new fossils (red map) are those where the species used to live (brown map), where its fossils could be preserved (blue map), and where it is now possible to find its fossils (green map). (a) We used palaeo-climate data and fossil records with reliable ages to model the climate envelope of different genera of the Australian megafauna, geological variables to model the suitability for fossil preservation (b) and erosion proxies to model the suitability for fossil discovery (c). The average of the suitability rankings predicted by the climate-envelope, preservation, and discovery models can be used as an indicator of the potential of an area to yield new fossils of a given taxon. We cross-validated each model and used an independent subset of the data to validate the final predictions of each model and their combination.
Table 1.
Climate-envelope models cross-validations.
Table 2.
Data used to train climate-envelope models and validation steps for Diprotodon, Zygomaturus, Protemnodon, Thylacoleo, and Genyornis.
Fig 2.
Effect of combining models on probability of finding fossils.
Probability of finding a grid cell with independent fossil sites of five genera in areas predicted by the climate-envelope models (blue bars), in the area predicted by fossil preservation and discovery models (green bars), and in the area predicted by all models (i.e., climate-envelope, preservation, and discovery). Each probability is divided by the probability of finding the grid cells in all of Australia to emphasise usefulness of model combinations compared to finding fossils by chance. For example, a value of one (horizontal dashed line) would mean that the probability of finding a fossil using the model is the same as the probability of finding it by chance.
Fig 3.
Multi-temporal climate suitability for Diprotodon, Zygomaturus, Protemnodon, Thylacoleo, and Genyornis.
Maps display the climate suitability rankings (rescaled between 0 and 1) for each genus averaged across all time-slices during which the genus was still alive. Darker colours correspond to higher climate suitability. We used fossils with reliable ages (black circles) for model training and those without (black crosses) for validation. Diagonal lines indicate areas of extrapolation in model predictions (i.e., where there are values outside of the climate envelope used to train the model).
Fig 4.
Combined-model prediction of where to search for fossils of Diprotodon, Zygomaturus, Protemnodon, Thylacoleo, and Genyornis.
The places most likely to yield fossils of a given genus are the grid cells with the highest suitability. Maps display the climate suitability, suitability for fossil-preservation, and suitability for fossil-discovery rankings (rescaled between 0 and 1 and averaged) for each genus. Darker colours correspond to places more likely to yield new fossils. We used fossils with reliable ages (black circles) for climate-envelope model training and those without (black crosses) for validation of all models. Diagonal lines indicate areas of extrapolation in climate-envelope model predictions (i.e., where there are values outside of the climate envelope used to train the model). The yellow starts in map ‘e’ show the location of recent findings of new Genyornis eggshell remains [52], which provide an additional independent validation of our approach.