for National Geographic News
A giant, wombat-like marsupial that roamed Ice Age Australia, may have been much bigger than experts previously believed.
The beast, known as Diprotodon optatum, may have been larger than all but the biggest hippopotamus or rhinoceros, according to the first rigorous experimental estimate of its bulk by scientists in Sydney, Australia.
Experts now believe that Diprotodon weighed in at a whopping 6,142 pounds (2,786 kilograms), or nearly 32 times as heavy as the largest marsupial alive today, the red kangaroo (Macropus rufus). Red kangaroos rarely weigh more than 187 pounds (85 kilograms).
Diprotodon has been known in the fossil record to scientists since the 1830s. Previous estimates suggested Diprotodon was slightly bigger than a large cow.
The animal lived during the Ice Ages of the Pleistocene Periodthe era from two million to 10,000 years ago. The beast went extinct sometime between 45,000 to 35,000 years ago, soon after human colonization of Australia.
Diprotodon survived by browsing on huge quantities of low-quality foliage, similar to today's koala. While not strictly related, the ancient animal appeared "basically [like] a cross between a wombat and a hippopotamus," said University of Sydney paleontologist Stephen Wroe, lead researcher behind the new study.
Diprotodon led a "life of incredible boredom, punctuated by the odd moment of panic when a whopping great marsupial lion crept up on it," Wroe said.
Scientists have long squabbled as to the reason for the pouched giant's demise. Human hunter-gatherers and their burning practices, along with the diseases and pest species that accompanied them, have been implicated in many large-animal declines. Another possible explanation is the drier climate ushered in at the end of the last Ice Age.
A generation of students has been taught that Australian habitats have been too dry, barren, and nutrient-poor to support the kind of large mammals that punctuate the ancient natural history of other continents. But the new body size estimate for Diprotodon, detailed online last month in the science journal Biology Letters, may challenge that theory.
"The [earlier] smaller body mass estimate for Diprotodon, propped up the notion that Australia was a biologically stunted land, unable to support large mammals," said Wroe. "Our work obviously undermines this interpretation."
Tipping the Scales
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