Capacity to regenerate body parts may be the primitive state for all 4-legged vertebrates

This seems like going backward. Maybe the loss of this capacity was a by-product of defense against cancer? Maybe it was just lost accidentally and those who lost it were not at enough disadvantage for the loss to be removed from the gene pool?

http://www.eurekalert.org/pub_releases/2015-10/bu-ctr102215.php

Public Release: 26-Oct-2015
Capacity to regenerate body parts may be the primitive state for all 4-legged vertebrates
Brown University

A team of paleontologists of the Museum für Naturkunde Berlin, the State University of New York at Oswego and Brown University shows in a new study of fossil amphibians that the extraordinary regenerative capacities of modern salamanders are likely an ancient feature of four-legged vertebrates that was subsequently lost in the course of evolution.

Salamanders are extraordinary among modern four-legged vertebrates in showing an astonishing capacity to regenerate limbs, tails, and internal organs that were injured or lost due to amputation repeatedly and throughout their entire lifespan. The mechanisms controlling this high regenerative capacity are the focus of a large field of research driven by the hope to some day apply the findings to human medicine.

•••••

The regenerative capacities of salamander tails are likewise remarkable.

"As opposed to lizards, which usually can only regenerate their tails once or twice and merely replace the vertebral column in the tail with a cartilaginous rod, salamanders regenerate a genuine tail including vertebral elements, the neural spine, and associated musculature" said Dr. Constanze Bickelmann, co-author on the study.

•••••

Classically the high regenerative capacities of salamanders were considered something special and derived for salamanders. New data from the fossil record offers a new perspective on the evolution of the enormous regenerative capacities of modern salamanders. In their studies the authors investigated different amphibian groups of the Carboniferous and Permian periods (ca. 300 million years ago) and showed that different groups of fossil tetrapods were able to regenerate their legs and tails in a way previously exclusively known from modern salamanders.

"We were able to show salamander-like regenerative capacities in both -- fossil groups that develop their limbs like the majority of modern four-legged vertebrates as well in groups with the reversed pattern of limb development seen in modern salamanders," said Dr. Jennifer Olori of State University of New York at Oswego, co-author on the study.

•••••