Re-growing limbs may not work as thought 13 (UPI) -- A lizard's regenerated tail is not a perfect replica of the original, a finding that may weaken hopes of re-growing human limbs, U.S. researchers say. Researchers at the University of Arizona said they discovered key anatomical differences when they looked at original and fully regenerated tails in the green anole lizard, which can "drop" its tail when caught by a predator and later grow another. They found the regenerated tail was supported by a long tube of cartilage rather than the chain of true vertebrae found in the original, and there were differences in the muscles also, NewScientist.com reported. Both differences suggest that the regenerated tail would be less flexible, Arizona researcher Rebecca Fisher said, and functionally not up to the level of the original tail. The findings could reduce hopes of eventually regenerating human limbs, scientists said. "Even in a context that we think of as a 'good' example of regeneration, the regenerated structure is not perfect and functioning as well as the original," Jason Pomerantz, a regenerative medicine researcher at the University of California, San Francisco, said, noting the findings highlight the challenge of regenerating a complicated structure.