For a 100 million years or more, amphibians were the dominant animals on land but they still needed water in their environment so they could breathe or respire through their skin and lay their eggs. About 260 million years ago, reptiles had arrived and managed to become less dependent on water. Their shelled eggs were protected from drying out, their skin stayed moist under their hard scales and they moved into habitats previously uninhabited by land vertebrates. These reptiles became the rulers of the earth. They dominated every nook and cranny of it for 160 million years until their downfall.
Scientists do no know why they disappeared although their are many theories.
Today, reptiles and amphibians still occupy many habitats but are much smaller, in fact, most amphibians are less than 6 inches long. Iowa s frogs and toads live anywhere it is wet, at least for part of the year. One of the first signs of spring is the call of the western chorus frog, less than an inch long. It sings from partially submerged grass flooded by spring runoff. It sounds much like the sound of running your fingernail across the teeth of a comb, only much louder.