Avatea is a deity of Cook Islands Mythology. They display a mixture of human and piscine traits:

They have two heads, the left one like a fish and the right one like a man. Their body is half fish and half human, with a left side like a fish and the right side like a human. They have a pectoral and pelvic fin on the left of their chest, alongside a dorsal fin on their back. On the right is a human arm. They have half a pelvis, to which their single human leg can attach; on the other side is a complete fish tail, by which they can swim about

How could such a being fit together internally?

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    $\begingroup$ VTC for not following the rules: "the ACS is now limited to questions about documented myths and legends of Humanity and creatures thoroughly designed (other than lacking anatomical fulfillment) for a fictional world of the OP's own creation." (You can thank ITM_Coder for my change of heart. It's time to start hard-lining the ACS rules.) There isn't enough behavioral information about this creature to answer the question. $\endgroup$
    – JBH
    Commented Jul 30, 2022 at 6:13
  • $\begingroup$ @JBH Why do we need to explain a creature's behaviour to ask about its anatomy? Would you ask how an animal acts before trying to deduce its phylum? $\endgroup$ Commented Jul 30, 2022 at 10:05
  • $\begingroup$ @IchtysKing Because behaviours (ie range of actions done) and anatomy are linked. Asking about anatomy without giving some traits they can do is like asking what ingredients you need for a cake without ever telling if it's a salty or sugary one. Without regarding details, it's probably not enough focused on a specific issue you're having. $\endgroup$ Commented Jul 30, 2022 at 13:10
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    $\begingroup$ I note the closed question says "This question does not appear to be about worldbuilding, within the scope defined in the help center." "Help center" there links directly to a page that gives "anatomically correct phoenix" as a specific example of something you CAN ask about on Worldbuilding. $\endgroup$ Commented Jul 30, 2022 at 14:14
  • $\begingroup$ @Tortliena You don't need to know whether a cake is salty or sugary to know that you shouldn't add pitchblende to it. Similarly, there are some things you can say about anatomy that will apply to pretty much all reasonable behaviours that a creature could have $\endgroup$ Commented Jul 30, 2022 at 15:04

2 Answers 2



This isn't much of an issue for this being: There are many examples of people, animals, and fish born with 2 heads on 1 body. This sort of anatomy could easily be copied onto Avatea


It is not entirely possible to combine fish and human torsos side by side perfectly. This is due to the proportions of the meat between tetrapods and most fish: Fish tend to have large amounts of muscle behind the back, with the spine in the middle of the body. On the other hand, tetrapods like humans have the spine in the back of the torso, with little flesh behind it. The only solution here would be to have a fish-type back on both sides. Other than that, there shouldn't be many issues within the torso


The lower anatomy, with the legs and tail, could be managed in a quite regular way: Having a single hip detached from the spine, to which the leg attaches, could simply capture the anatomy of Avatea. This hip would need the same muscular and osseous bulk to match the right side, and the tail will also have to be offset to sit on the left side


How could such a being fit together internally?

By magic, it's not possible otherwise.

Many Polynesian deities are purposely meant to be impossible because it creates a big contrast between spirit and reality. Especially the older and important ones which may have undergone several evolutions in their descriptions over time and place.

Trying to describe them in realistic terms defeats the purpose and is an assault on their sacredness.

When depicted in carvings there is no attempt to make them into something that might actually work. Because there is no need for it. It's just an outward form.


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