The newly discovered fossilized teeth of an extinct kangaroo species — as well as a variety of new fossils from other extinct marsupials — are helping to shed new light on the climate of the Australian Pliocene — revealing that the region of Australia where they were found was much less arid than was previously thought.
The fossils were discovered in southeastern Queensland, and date back to around 2.5-5-million-years ago. Based on the new research, this region was apparently a ‘mosaic’ of wetlands, forests, and grasslands — considerably wetter than was previously thought. The new findings are the result of the chemical analysis of tooth enamel taken from the fossils.
The chemical analysis of the tooth enamel has revealed distinctive carbon isotope ratios, ones which strongly imply that the extinct kangaroo species ate plants similar to those eaten by extant kangaroos living in temperate and tropical regions — as opposed to the plants that currently grow in the region. “The fossils examined also suggest that different animals in the area occupied specialized dietary niches and did not rely on identical sources of food.”
The researchers provide some context: “This period, the Pliocene, is critical to understand the origins and evolution of Australia’s unique modern animals. It is during this time that the Australian fauna first began to take on its modern appearance and distinctiveness, with many modern Australian marsupials, such as the agile wallaby Macropus gracilis, first appearing in Pliocene fossil deposits.”
Shaena Montanari, from the American Museum of Natural History, says: “It is vital for us to understand what types of environments Australian megafauna thrived in during the Pliocene. Obtaining detailed environmental records from this time can help us find the drivers of the subsequent extinctions of many of these large marsupials.”
The discovery isn’t that surprising — new species typically emerge within very-productive habitats, very often tropical or temperate forests, or wetlands. The species which live in marginal regions — deserts, cold environments, drylands, etc — typically emerge in habitats such as tropical/temperate forests or wetlands, before then expanding their range opportunistically, and losing the traits/qualities which are maladaptive in the new regions.
The new research was just published in the open access journal PLOS ONE.