|photo by Mokele|
The fact that females lack the "tail" that this species is named for should give you a hint that this protuberance is not really a tail after all. The male tailed frog is the only amphibian in the Northern Hemisphere that has an external copulatory organ.
A frog sporting something akin to a penis seems strange until you consider the habitat of the tailed frog. You won't find them lazing about in some backwater pond or lake here in the Pacific Northwest. No, they inhabit rushing mountain streams, where the usual froggy fertilization technique of sperm released over a cluster of eggs would be swiftly washed away. This species' method of mating may be unorthodox for amphibians, but a tailed frog's gotta do what a tailed frog's gotta do.
Internal fertilization isn't the only lifestyle difference found in tailed frogs. They have no vocal sacs (maybe because they'd be unable to outcompete the singing of their rivers) and, correspondingly, no eardrums (the round membranes on either side fo the head, obvious in many frog species).
The tailed frog belongs to what is considered the most primitive of frog families, and you'd have to tramp around New Zealand streams to find its closest relatives. Which, by the way, I would totally love to do.
How about you?