Planarias several times got and lost ability to head regeneration

Unique ability to let grow anew any parts of a body, including the head, is not at all planarias. To understand regeneration evolution, scientists studied a collection of planarias from all over the world. Judging by the turned-out evolutionary tree, the general ancestor of planarias was not able to let grow the new head. In different groups of planarias this ability several times independently appeared and was again lost...