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Three-Million-Year-Old Kangaroo Teeth Illuminate Ancient Australian Climate

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In Pliocene-era Australia about 3 million years ago, massive marsupials, including giant wallabies weighing up to 250 pounds and rhino-sized grazing herbivores (diprotodontids), walked—or sometimes hopped—the land.

Protemnodon sp. illustration

In Pliocene-era Australia, many now-extinct marsupial species, including giant wallabies (Protemnodon sp.), walked the land. What led to their extinction? A new study led by a Museum researcher may help answer the question. 

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Today, those “megafauna” are extinct, many species having disappeared around the time humans arrived in Australia, perhaps 40,000 to 50,000 years ago. Researchers have long wondered whether humans led to the animals’ disappearance—or whether climate change could be the cause.

A new study analyzing the teeth of extinct plant-eating kangaroos and other marsupials in southeastern Australia during the Pliocene era (about 5.3 to 2.6 million years ago) adds information that could help answer the question. The study was led by Dr. Shaena Montanari, a comparative biologist and a recent graduate of the Museum’s Richard Gilder Graduate School, and was published last month in the open access journal PLOS ONE.  

The chemical analysis of 3-million-year old fossil teeth from southeastern Queensland reveal that the climate there was likely not as arid as previously thought.

The enamel of animals’ teeth holds a chemical record of what they ate: while trees and shrubs have a certain carbon isotope ratio (due to C3 photosynthesis), grasses have a different one (C4 photosynthesis). In the study, the fossil-teeth studied indicated the animals ate a mixture of both types but mainly C3 plants, which indicate a wetter, “subtropical,” environment, says Montanari.

"It is vital for us to understand what types of environments Australian megafauna thrived in during the Pliocene,” adds Montanari, who is currently a visiting postdoctoral scholar at the Museum’s Sackler Institute for Comparative Genomics and has just begun a 3-year research and lecturer position in Frontiers of Science at Columbia University. “Obtaining detailed environmental records from this time can help us find the drivers of the subsequent extinctions of many of these large marsupials."

Read the full study here.

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