Salamanders can regenerate almost anything: limbs, entire tails, and internal organs. Once considered particular to the sometimes-aqueous amphibians, paleontologists now say such capabilities were likely a feature of all four-legged vertebrates—but jettisoned at some point in the evolutionary process.

Salamanders can regenerate almost anything: limbs, entire tails, internal organs—and can do so over and over again. 
Once considered particular to the sometimes-aqueous amphibians, paleontologists now say such capabilities were likely a feature of all four-legged vertebrates—but jettisoned at some point in the evolutionary process. 
Guiding their research was another unique feature of salamanders—their limbs grow in reverse order from all other known tetrapods.