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Imagine what the offspring of a koala bear and an orangutan would look like. Now add into the mix a little grizzly bear and maybe a touch of ape. That’s what Nimbadon lavarackorum, a 15-million-year-old Australian marsupial, looked like. Not much was known about the ancestry and living habits of this strange creature until a recent study that analyzed its skeleton and compared it to the bone morphology of other animals.

Nimbadon lavarackorum belongs to the Diprotodontia, an order of marsupial native only to Australia, New Zealand, New Guinea and the islands surrounding those countries. Diprodontia encompasses more than 110 species; many, like Nimbadon, are now extinct. They are grouped together based on their distinctive dental configuration—they have two large incisors protruding from their lower jaw and lack canine teeth, a formation useful for the vegetation that serves as the sole food source for most diprotodonts. Modern diprotodonts include possums, kangaroos, koalas, and wombats. (Read more about diprotodonts at The Tree of Life Web Project.)

Most paleontologists had agreed that Nimbadon moved like most other ancient diprotodonts, that is, it travelled in packs, roaming the land in search of grasses and low-lying shrubs. But this most recent study suggests otherwise. Karen Black from the University of South Wales, who led the study on Nimbadon, examined the skeletons of Nimbadon from a cave in Australia’s Riversleigh World Heritage Area, and compared it alongside the skeletons of a number of other animals in hopes of discovering how this funny creature moved and where it would have lived. The researchers found that Nimbadon’s skeleton had morphology similar to that of today’s koalas rather than ancient diprotodonts. It had characteristics of an animal well suited to climbing trees: very strong forelimbs that ended in huge hands with long, strong digits and large, curved claws. Their hind limbs were short and stout, an adaptation for hanging from tree branches like orangutans. Also conducive to branch-swinging were Nimbadon’s joints– its incredibly flexible and strong shoulders and elbows allowed for extension and rotation of its arms beyond that of other diprotodonts. The conclusion: Nimbadon probably lived high in the treetops, or at least climbed up there frequently. It used its upper body strength and tight—gripping hands and feet (that, surprisingly, had semi-opposbale “thumbs”) to hug tree trunks and hoist itself up into areas where resources would be plentiful and predators would be few.

As exciting as this new information about Nimbadon is, it comes tinged with bad news. It appears the diprotodonts were more diverse than previously thought. Somewhere along the line, the Australian ecosystems became less friendly to diversity and many species, including Nimbadon, became extinct. Scientists are trying to figure out why modern ecosystems such as Nimbadon‘s lack the diversity of ancient ones. Unfortunately, human interference probably plays a big role in the problem. Working on preserving ecosystems is still something humans need to work on, and though Nimbadon is no longer around, perhaps a new array of species will take their places on the stage of life.

Read more at www.sci-news.com.

This study is published in the journal PLoS-ONE.

The Paleontological Research Institution, Ithaca, New York, is pleased to sponsor Paleontology content for This View of Life. Founded in 1932, PRI has outstanding programs in research, collections, and publications, and is a national leader in development of informal Earth science education resources for educators and the general public.

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Published On: February 6, 2013

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