#tailed frog

Coastal Tailed Frog (Ascaphus truei), family Ascaphidae, found in fast flowing freshwater mountain streams in the Pacific NW of the US and Canada

Though the males appear to have a tail, this is a copulatory organ, used to insert sperm into the female’s cloaca during mating.

Other frogs, and indeed most amphibians, do not have penises or other male copulatory organs.

Internal fertilization with a copulatory organ is believed to be an adaptation to deal with mating in fast moving water.

Basically no. The famous 'tailed frog', genus Ascaphus, has a tail-like posterior extension of the cloaca (used for internal fertilisation, very rare in frogs), and not a true tail

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There is a pretty good reason adult frogs cannot really keep a tail. Tails are made of post-sacral vertebrae. The sacrum is the vertebra involved in the hip. A tail is separate from the main trunk of the body. This is achieved by the tail starting behind the cloaca, which is basically where the body ends. In frogs, two things are going on.

Firstly, frogs have extended parts of the hip that articulate (interact) with the sacrum—the ilia. This elongation is responsible for frogs being so good at jumping.

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Because the cloaca is kind of tied to the hip, the cloaca of the frog is shifted dramatically backwards relative to the sacrum. So now, the end of the main trunk of the body is not right behind the sacrum like it is in most tetrapods, but shifted waaay back, all the way to where the hip is.

Secondly, all frogs actually have post-sacral vertebrae. But they are fused into a single rod, called the urostyle, which does not extend outside of the body, but is instead coopted into the funky jumpy hip joint. If frogs were to gain a tail, it would either have to be (a) by breaking the urostyle back into its component vertebrae and separating them out of the main body of the animal—extremely unlikely, because it would compromise the hip joint and require major muscle restructuring, or (b) by adding additional vertebrae behind the urostyle that would be normal—extremely unlikely because there are no known mutants that do anything like that to my knowledge, and it would also probably require some kind of support at the base (a second hip?), which is hard to imagine.

So in a way, frogs actually have tails, they're just on the inside. But it is very, very unlikely that any frog would evolve a tail again, without first rebuilding the whole hip mechanism. Even with the weird-ass stuff that evolution has done to frogs over the millennia, they seem to be pretty canalised on this tailless fate. But, at least they get to have a highly functional tail as tadpoles—at least, in those species that have tadpoles.

Tailed frog

✨Tailed Frog✨

Tailed frogs are part of an ancient suborder of frogs called Archaeobatrachia which dates back to the early Jurassic period. In addition to the tail, they have an extra vertebra, free floating ribs, and no vocal sacs!

BUT the most interesting thing to me is....well...

Well, I'll let Wikipedia explain...

"The "tail" is found only in males, and is actually part of the cloaca, used to insert sperm into the female during mating. This anatomical feature improves breeding success by minimizing loss of sperm in the turbulent, fast-flowing streams inhabited by this species. Thus, the tailed frogs exhibit internal fertilisation, rather than the external fertilisation found in other frogs."

What I'm trying to say here is

DO Y'ALL KNOW ABOUT TAILED FROGS???

Coastal Tailed Frog (Ascaphus truei), family Ascaphidae

The small frogs live in clear fast flowing mountain streams in the Pacific Northwest and upper Rocky Mountains of North America. They reach a maximum length of up to 5 cm.

Though the males appear to have a tail, this is a copulatory organ, used to insert sperm into the female's cloaca during mating. Frogs, and indeed most amphibians, do not have penises or similar copulatory organs. Internal fertilization with a copulatory organ is believed to be an adaptation to deal with mating in fast moving water.

The Rocky Mountain Tailed Frog (A. montanus) is no longer considered to be a separate species, but is now cl;assified as a subspecies, or just a population of the Coastal Tailed Frog.

OMG THIS IS INCREDIBLE!!!

Coastal Tailed Frog (Ascaphus truei), family Ascaphidae

The small frogs live in clear fast flowing mountain streams in the Pacific Northwest of North America. They reach a maximum length of up to 5 cm.

Though the males appear to have a tail, this is a copulatory organ, used to insert sperm into the females cloaca during mating. Frogs, and indeed most amphibians, do not have penises or similar copulatory organs. Internal fertilization with a copulatory organ is believed to be an adaptation to deal with mating in fast moving water. There are only 2 species of frog that reproduce in this way, the Coastal (A. truei) and Rocky Mountain Tailed Frog (A. montanus).