Neotenic Arizona tiger salamander with both external gills and legs, at the onset of metamorphosis Ambystoma tigrinum nebulosum Photographed in captivity From a desert pond in Hidalgo County, New Mexico, USA Photographed under controlled conditio

Neotenic Arizona tiger salamander with both external gills and legs, at the onset of metamorphosis, Ambystoma tigrinum nebulosum, Photographed in captivity, From a desert pond in Hidalgo County, New Mexico, USA, Photographed under controlled conditions Photo on Sept, 16, Metamorphosis photo series over a 3-month period (UNM-0220 - UNM-0290): one 4-legged, gilled aquatic larva through metamorphosis to terrestrial adult, (Photo by Wild Horizons/Universal Images Group via Getty Images)