All the other bijuu are modeled after other animals either real (or combinations of real animals) or folklore. For instance the "Fox" is really modeled after the Kitsune, which is like a fox with many tails from Japanese lore. Hachibi is like a mix of an Ox and an Octopus. Other Bijuu are based on cats, turtles, apes/monkeys, tanuki (japanese racoon-dog, a real creature), A horse with a dolphin's head, a slug, and a beetle.

Here's the question: What is the Juubi supposed to be? I had assumed, based on the silhouette that we've seen from earlier in the manga and the fact that the Gedo Mazo (supposedly the body of the beast) is human-shaped that the Juubi would also be more or less human-shaped (or "demon-shaped"). However, that's clearly not the case. The Juubi has no apparent human features at all. It looks sort of like a one-eyed toad creature with that weird spire on it's back.

Is the Juubi modeled after some kind of animal that I don't recognize? Is this weird form because the Juubi is incomplete/imperfect, or is that what it's supposed to look like?