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The ancestor of modern - 24-hour interval kangaroo , giant marsupials with rabbitlike nerve , may have walked upright on two foot , sans any hopping , a raw bailiwick find .
These enormous creatures , part of the nonextant folk of sthenurine kangaroo , once roamed the Australian outback from about 100,000 to 30,000 years ago . But they were likely bad groundball , said lead investigator Christine Janis , a professor of environmental science and evolutionary biology at Brown University in Rhode Island .
The extinct Sthenurine kangaroo likely didn’t hop, but walked.
" advanced tumid kangaroos are not the ' average ' for kangaroo , " Janis told Live Science . " In fact , they come out to be more like a chetah in equivalence with other large cats — slimly build and streamline for specialised , firm motivity . " [ exposure : See How Kangaroos utilise Their Tails to Walk ]
Janis and her co-worker traveled to about half a XII museum around the world , appraise the bones of 140kangaroos , include sthenurine and wallaby skeleton in the closet .
The largest kangaroo ( Procoptodon goliah ) weighed an estimated 529 pounds ( 240 kilograms ) , or about three times the free weight of today ’s kangaroos . Their enormous size may have prevented them from hop , and analysis show that their bodies were configured otherwise than their modern ancestor .
For example , the anatomy of sthenurines indicate they held their bodies in an erect position , and could support their weight on one leg at a time by using their big hips , knees and stabilise ankle joint joints .
It ’s possible that small sthenurine kangaroos hop sometimes , though " not as fast and graciously as a advanced bad kangaroo , " Janis suppose . " But when go tardily , they would have walk on two leg rather than using the drive that modern kangaroos do , which is to walk on all foursusing the tail as a ' 5th tree branch . ' "
The sthenurines ' ivory structure , the fresh study shows , kept them mostly earthbound .
" Apart from their massive size , unanimous eubstance and comparatively forgetful faces , these extinct kangaroos lacked the specialisation for high - stop number hopping take in in New - solar day kangaroos , such as a flexible spine , proportionately long peg , and large tail , " said Karen Black , an Australian Research Council postdoctoral cuss of fossilology at the University of New South Wales in Australia , who was not involved in the subject area .
" Instead , these guys show adaptations ( such as a more rigid spine , big hips , large knees and a reduced tail ) for a more just posture and bipedal walking ( more like humans ) , " Black said in an email .
She called the discipline about these scant - faced heavyweight " very sound , " even though it ’s tough to imagine " giant kangaroos stride through the bush when most animation kangaroo are effective , superfast hopper , " she said .
Hopping around
The project began when Janis visited a museum in Sydney , Australia , in 2005 . There , she noticed a sthenurine frame , particularly the beast ’s sturdy spikelet . It did n’t look flexible , she state . [ See picture of Kangaroos and Other Cute Marsupials ]
" I thought , ' that looks really weird , ' " Janis state . “I wonder if they hopped like advanced kangaroos do ? "
She and her co-worker then spent year studying the biomechanics of kangaroo skeletons . They were n’t the first to take note differences between sthenurines and innovative red and gray kangaroos . Other researchers have take note thatsthenurines had teethmade for browse leaves on Sir Herbert Beerbohm Tree and shrubs rather than grazing on grasses , as reddened kangaroos do today .
Kangaroos today can hop at immobile speeds , and move on all four — five if you count the bum — for slower speeds . These movements imply a flexible backbone , uncompromising tush and hands that can hold their physical structure weightiness . In contrast , the sthenurines the research worker studied did n’t have any of these qualities .
Yet , kangaroo locomotion is a hotly debated field among paleontologists , tell Natalie Warburton , a senior lector of anatomy at Murdoch University in Australia , who was not postulate in the fresh discipline . It ’s potential that the extinct kangaroo did , in fact , hop , some say , whereas others consider the marsupials ' giant body size would have preclude them from moving like their modern ancestors , Warburton said .
" One of the things that make the question hard to do is that there are many similarities between the frame of life and out kangaroo , and that for the most part , the group we bear on to as Macropodoidea ( kangaroos , wallabies and their relative ) have evolve to [ keep ] bipedal skip locomotion , perhaps more than once , " Warburtonwrote in an email .
The version that gargantuan kangaroos walk , rather than hopped , certainly is novel , Warburton said . " I suspect that the locomotion of sthenurines will continue to be debated , but that is what science is about — propose hypotheses based on the available evidence and then testing them . "
It ’s unreadable whether the sthenurines ' possible reliance on walking led to their quenching , perhaps from human hunters or by being unable to go cursorily enough to hand food as the mood turned more arid , the investigator of the new study say .
" We should appreciatethe diversity of unlike kangaroosalive today , " and verify that modern animals do n’t go the manner of their herald , Janis said .
The report was published today ( Oct. 15 ) inPLOS ONE .
