- any of several salamanders of the genus Ambystoma that inhabit lakes and ponds of Mexico and remain in the larval stage as sexually mature adults.
- any of several aquatic salamanders of the North American genus Ambystoma, esp A. mexicanum (Mexican axolotl), in which the larval form (including external gills) is retained throughout life under natural conditions (see neoteny): family Ambystomidae
- any of various other North American salamanders in which neoteny occurs or is induced
