Tailed Frogs: Ascaphidae

The tailed frogs get their name from their "tails," but only the males have them and they are not really tails at all. The tiny nub of a "tail" is really a fleshy structure that the adult male uses to mate with a female. Besides the "tails," the males and females look alike. Both have wide heads and large eyes with vertical, often diamond-shaped pupils. Unlike many other frogs, they have no round patch of an eardrum showing on the sides of the head. The skin of the tailed frog's back is covered with little warts, giving it a grainy look.

The frogs are usually shades of brown or gray, sometimes with a hint of green or red, and have darker markings, including blotches on the back and bands on all four legs. A lighter-colored patch, usually outlined with a thin, dark stripe, stretches between the eyes. Once in a while, a tailed frog may be almost completely black. The underside is pink, sometimes speckled with white. Tailed frogs have slender forelegs with no webbing on the toes and larger hind legs with well-webbed toes. Their toes, especially the outside toe on each foot, are quite wide.

Adult tailed frogs are small, growing only to 1.2 to 2.0 inches (3 to 5 centimeters) long from the tip of the snout to the end of the rump. The females are a bit bigger than the males. The tailed frog tadpole is dark gray and has a large, telltale sucker on the bottom of its broad head. Like other frogs, the tadpole has a long tail. When it begins to change into a frog, the tail shrinks until it disappears altogether. Often, people see an adult male tailed frog and believe that it is just a froglet that still has some of its tadpole tail left. This is not correct. The fleshy nub on an adult male tailed frog is different from a tadpole tail and never disappears.

Two species of tailed frogs exist: the Rocky Mountain tailed frog and the coastal tailed frog. They look so much alike that scientists thought they were the same species until 2001 when they compared the frogs' DNA. DNA, which is inside the cells of all animals, is a chain of chemical molecules that carry the instructions for creating each species and each individual. In other words, DNA is a chemical instruction manual for "building" a frog. The DNA of the Rocky Mountain tailed frog and the coastal tailed frog were just different enough to separate them into two species.

Both of these frog species have very small lungs, compared to most other frogs, and have extra backbones. Only one other living group of frogs, the New Zealand frogs, has the same extra backbones. Scientists have found fossil frogs far in the past that had the extra bones. These date back to the dinosaur age 150 million years ago and are the oldest known frogs.