A few years ago, the professor of ecology and evolutionary biology at Brown University Christine Janis had an intuition to see in a museum the skeleton of a estenurino, an extinct subfamily of giant kangaroos. Janis, an expert on prehistoric other Australian marsupial species like the wolf, thought to see inflexible features of this animal that may not move as current kangaroos. That was the starting point for an investigation in which the scientist at the University of Malaga Borja Figueirido involved and just published in the journal PLoS ONE. Janis's thesis is that those not jumping kangaroos, but walked with his two legs. "Those animals may have had behaviors and lifestyles different from their modern relatives, and bone anatomy provides great tracks," says Janis.I
The estenurinos, also called giant short-faced kangaroos His face is similar to the actuales- rabbits, weighing up to 240 kg -three times more than today, and most likely were bipedal walkers. The experts did a statistical and biomechanical analysis of the bones of a specimen of Sthenurinea kangaroos and wallabies and other past and present to reach this conclusion. From a biomechanical point of view, the estenurinos of any size would be bad jumpers because of their anatomy, the researchers said. In addition, especially for individuals giants, a jump could represent an additional barrier. So Janis believed to be as large had necessarily to walk.I
Current kangaroos jump at high speed and move on all fours when they want to move more slowly. Or, as confirmed by a recent study, more leg drive with the tail. This requires a flexible spine and a strong tail, as well as some top tips that can support your body weight. But individuals Sthenurinea not seem to have any of those attributes. They found many evidence that were more suited to kangaroos today to support your weight on one foot at a time, a prerequisite for walking. "The only current kangaroos able to, anecdotally, are arboreal species," says Janis.I
Moreover, by comparison, the lower end of the tibia of horses and dogs has a lip which wraps over the back of the joint, which provides additional stability to withstand more weight on each ankle and so power running and jumping. Current kangaroos, which distribute their weight evenly on both feet, lack this edge, but they had estenurinos itself. In addition, these extinct animals had the hip joints and knee proportionally larger. The shape of the pelvis is also different, as it was wide and flared, and the muscles of his buttocks were proportionately much larger than those of other kangaroos.I
Those muscles have allowed them to balance the weight on one leg at a time, as humans do to walk.
Therefore, "if they could not, in terms of biomechanics, jump-they were very very slow speeds them heavy and not easy for them to move on all fours, then, since they had to move in some way, what was left to them? "researcher asks. The conclusion, in light of its anatomy, is that these kangaroos were specialized for walking, not for jumping. It remains to clarify why became extinct in the late Pleistocene, about 30,000 years ago. "I might have problems to elude human hunters, or could not migrate far enough to find food when the climate became more arid," says Janis.