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| Sahul Megafauna
in Hocknull, Lewis, Arnold, et al., 2020.
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Abstract
Explanations for the Upper Pleistocene extinction of megafauna from Sahul (Australia and New Guinea) remain unresolved. Extinction hypotheses have advanced climate or human-driven scenarios, in spite of over three quarters of Sahul lacking reliable biogeographic or chronologic data. Here we present new megafauna from north-eastern Australia that suffered extinction sometime after 40,100 (±1700) years ago. Megafauna fossils preserved alongside leaves, seeds, pollen and insects, indicate a sclerophyllous forest with heathy understorey that was home to aquatic and terrestrial carnivorous reptiles and megaherbivores, including the world’s largest kangaroo. Megafauna species diversity is greater compared to southern sites of similar age, which is contrary to expectations if extinctions followed proposed migration routes for people across Sahul. Our results do not support rapid or synchronous human-mediated continental-wide extinction, or the proposed timing of peak extinction events. Instead, megafauna extinctions coincide with regionally staggered spatio-temporal deterioration in hydroclimate coupled with sustained environmental change.
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| Fig. 2: Summary of field sites and diversity of fossil remains from South Walker Creek (QML1420). a Aerial map of main South Walker Creek fossil sites SW9, SWJ and SW3 with downstream site SWCC indicated by arrow. Megafauna taxa recovered from each site indicated by numbered silhouette: 1. Pallimnarchus sp. 2. ‘Quinkana’ sp., 3. Crocodylus sp. cf. C. porosus, 4. Varanus priscus, 5. Varanus sp. (large), 6. Dromaius sp., 7. Diprotodon optatum, 8. Phascolonus gigas, 9. Sedophascolomys sp. cf. S. medius, 10. Thylacoleo sp., 11. Palorchestes sp., 12. Macropus sp. (giant), 13. Protemnodon sp., 14. Notamacropus sp. (giant), 15. Osphranter sp. cf. O. rufus, 16. sthenurine. b Stratigraphic section A–Aʹ crossing through SW9, SWJ and SW3 (indicated by dashed line in (a)). Quaternary (Qa) alluvial sediment overlies dipping basement Permo-Triassic Rewan Group (Rw) bedrock (vertical exaggeration 5×). Fossil deposit surface expression at SW9 (c), SW3 (d) and SWCC (e). Summary of the diverse fossil remains recovered from SWC sites. ... |
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| Fig. 2: Summary of field sites and diversity of fossil remains from South Walker Creek (QML1420). Fossil deposit surface expression at SW9 (c), SW3 (d) and SWCC (e). Summary of the diverse fossil remains recovered from SWC sites (see Supplementary Note 1 for detailed descriptions): f leaves and bivalves in situ at SW9; g Goodeniaceae seed; h Velesunio wilsoni bivalve; i insect elytron (?Curculionidae); j Pallimnarchus sp. osteoderm; k Crocodylus sp. cf. C. porosus osteoderm; isolated crocodile teeth from l Pallimnarchus, m Crocodylus sp. and n ‘Quinkana’; o Varanus priscus tooth; p Macropus sp. (giant) tibia in situ at SW9; q Varanus priscus dorsal vertebra; associated appendicular elements from Thylacoleo sp., r metacarpal, s phalange and t fibula; u Diprotodon optatum right dentary; v Macropus sp. (giant) humerus with crocodile puncture marks (indicated by arrows); w Articulated pelvis and caudal vertebrae of Phascolonus gigas from SW9; x associated hind limb of juvenile Protemnodon sp. from SW9.
Scale bars equal 1 mm in (g, i); 5 mm in (h, j–t, v, x); 10 mm in (u); and 50 mm in (w).
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| Life and Death in Tropical Australia, 40,000 years ago. Pallimnarchus stalks the world’s largest kangaroo at the edge of a drying billabong. Two Megalania fight over the carcass of Diprotodon optatum whilst another giant kangaroo, standing at 3m tall, reaches for the freshest leaves to eat. In the distance, the sun beats down on the Mt. Britton range, a silent witness to the extinctions yet to unfold.
Illustration: Ryan Bargiel, Vlad Konstantinov, Andrey Atuchin & Scott Hocknull © Queensland Museum (2020).
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Scott A. Hocknull, Richard Lewis, Lee J. Arnold, Tim Pietsch, Renaud Joannes-Boyau, Gilbert J. Price, Patrick Moss, Rachel Wood, Anthony Dosseto, Julien Louys, Jon Olley and Rochelle A. Lawrence. 2020. Extinction of eastern Sahul Megafauna coincides with Sustained Environmental Deterioration. Nature Communications. 11, 2250. DOI: 10.1038/s41467-020-15785-w
Life and death in tropical Australia, 40,000 years ago. natureecoevocommunity.nature.com/users/366107-scott-hocknull/posts/61740-megafauna-extinction
