http://en.wikipedia.org/wiki/Mammal
The evolution of erect limbs in mammals is incomplete — living and fossil monotremes have sprawling limbs. The parasagittal (nonsprawling) limb posture appeared sometime in the Early Cretaceous or latest Jurassic; it is found in the eutherian Eomaia and the metatherian Sinodelphys, both dated 125 million years ago.
The evolution of erect limbs in mammals is incomplete — living and fossil monotremes have sprawling limbs. The parasagittal (nonsprawling) limb posture appeared sometime in the Early Cretaceous or latest Jurassic; it is found in the eutherian Eomaia and the metatherian Sinodelphys, both dated 125 million years ago.
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