>>28679829The larval phase and associated metamorphosis is characteristic of amphibians, but not a defining feature, just like laying eggs is characteristic of fish but a few bear live young.
In the case of amphibians there's generally a life cycle that involves two environments: aquatic and terrestrial. A few, such as lungless salamanders, some toads, and a few frogs, only live in one environment, and as a result have developed past this need. To be more accurate, what would be the larval phase passes rapidly and is spent inside the egg, so it isn't observed.
