I'd like to ask some questions about a type of animal with a very complex anatomy. Due to the complexity and uniqueness, it'd be hard to list out all the characteristics on every question about them, so I'd like to ask if we have a name for these animals

The traits of this animal are:

  • Their skull is solid and made of many bones, as in tetrapods. The primordial arrangement of the main bones is shown in this tetrapod, but many species have fewer. They also, like the tetrapods, have some number of mandible-bones, which sit in two pairs that are often fused at the tip, and an extra ring of bones around the back of the skull, where the spinal cord enters
  • Like tetrapods, they have a brain that exists as two hemispheres, and is found in the skull. Often the hemispheres are connected by nerves somewhere across the inner halves. Each half of the brain is divided into a large cerebrum for processing, and a cerebellum for coordinating motion, much like the divisions found in tetrapods
  • Their mouth is made of two jaws which, like tetrapods, have one below and one above. It also has enamel teeth, a lot like a tetrapod
  • For sensory organs: they have a pair of tetrapodal nares at the tip of the snout, which go into a pair of nasal cavities just above (and open to) the mouth; A pair of simple eyes like a tetrapod; A tympanum or eardrum behind the eyes with the reverse connected to the mouth, a lot like in tetrapods; A tongue, anchored to a very tetrapod-like bone in the throat, which sits in the mouth and is also used to manipulate food, and sometimes to speak
  • They have a throat at a variable position within the head/neck, which is made of the tongue bone and 2 other cartilages, a lot like a tetrapod
  • They have a neck between the head and the torso, very much like the setup in tetrapods
  • They have a tetrapodal spine, made of many vertebrae, which is divided into 5 segments: neck-part, chest part (sometimes split further into a true chest-part and an abdomen-part), hip-part, and tail-part, very much like the split arranged in tetrapods
  • They have ribs on the chest part of the spine, which divide the body like in tetrapods
  • They have limbs, structured very similarly to tetrapods, with an upper part with one bone, a middle part with two parallel bones, and a final part, acting as a foot, with many bones in multiple segmented lines
  • These limbs have 2 quite tetrapodal ways of attaching: The anterior limbs attach to a large, 'floating' limb girdle, like the tetrapod's scapula, which often has other rather tetrapodal bones supporting it. The posterior limbs are attached with a single fused block of bones, akin to the tetrapodal pelvis, which also is fused to the hip-part of the spine
  • In its chest it has a tetrapodal heart made of two parts, one to pump blood around the body, and another to pump blood to the lungs, which are large and spongy like in tetrapods
  • Its intestines, like in tetrapods, are divided into a large and small section, and have a tetrapodal biliary tract with a liver and gallbladder. They also often have multiple pancreata
  • Their excretory and reproductive systems are bundled together under the tail, as in tetrapods, though they can sometimes form distinct but nearby structures

Is there a name that refers to such animals on Worldbuilding? And if so, what is it?

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    $\begingroup$ Fictional animals, won't it do? $\endgroup$
    – L.Dutch Mod
    Commented Oct 23, 2021 at 12:19
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    $\begingroup$ What L. Dutch means is the animal you're asking about is fictional. Just put the tag "creature design" on your question and we'll take it from there. I think I said once before, and it bears repeating: you're overthinking this problem! You really don't need a specific word to call this. Just give enough description in the question to address the specific problem you're trying to solve! For example, if you're asking about the animal's limb arrangement, we don't really care about its skull or its lungs or how many livers it's got. $\endgroup$
    – elemtilas
    Commented Oct 23, 2021 at 16:54
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    $\begingroup$ Upvoted +1 for asking on meta. The effort of improving oneself alone is worth at least that! $\endgroup$ Commented Oct 23, 2021 at 18:00

2 Answers 2


The term for such a creature is "this critter I made up with a laundry list of traits described below."

Most made up creatures don't have such obsessively described internals. This is because unless I'm creating a picture book called "The anatomy of critters I've made up" or a game called "Surgeon Simulator: fantastic made up critters edition" this level of will never be seen. Even in such examples you will be able to get away with little more in the way of detail than "the x bone is connected to the y bone by a joint" and "this blobby flesh organ bit is how it does impossible thing z".

Most worldbuilding, smartly, ignores the details because they don't matter to the reader and explaining will detract from the story.

And low the angle of the lord was upon them. And they beheld a ring of flaming eyes. And the eyes didn't burn because the angles naturally excrete an asbestos layer which insulated them from the heat, and the asbestos is produced because angels eat silicate mostly sand, well not actually the sand, they filter feed through the sand to eat, sand bugs, which totally make sense in my world because.... many hours later... and the angel said "Be not afraid".

It seems to me that you want to have a magic term that lets you skip the work of asking clear and precise questions. There isn't such a term. It is your responsibility to ask questions that are detailed and specific enough that people are able to give you the answers you are looking for.

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    $\begingroup$ ichthys king --- I like the obsessively described internals --- but you really need to learn how to focus on only those obsessively described internals that are specific to the question you're asking. $\endgroup$
    – elemtilas
    Commented Oct 23, 2021 at 16:55
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    $\begingroup$ sphennings --- also if you are the author of Sector General. I wouldn't say it's "smart worldbuilding" to ignore those details. Some of us enjoy working on the anatomy and physiology of the creatures in our worlds. And some of us go into great detail! $\endgroup$
    – elemtilas
    Commented Oct 23, 2021 at 16:57
  • $\begingroup$ sphennings --- That said: I do concur, following from your example text, that writers need to be careful how much worldbuilding detail to give in their stories, and how they go about informing the reader. $\endgroup$
    – elemtilas
    Commented Oct 23, 2021 at 23:19
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    $\begingroup$ I mean sure, if you're just thinking about things for fun, do whatever you want, but if you're trying to use that world as the setting for a work of fiction, unnecessary explanation and info dumps will quickly detract from the work. If you want an unknowable horror sthat watches from the strange angles, explaining the evolutionary pressures that lead to it's unknowableness, is just making the fantastic and horrible mundane. Thanks @elemtilas I now have a discussion topic the next time I can meet up with friend. :) $\endgroup$
    – sphennings
    Commented Oct 23, 2021 at 23:38


I read through the list, and I don't see any key factor on the list that I don't share with my cat. I was expecting to see something strange on that list, but all of those things have been fundamental to the vertebrate body plan for hundreds of millions of years.

To address your specific question, the word "vertebrate" should suffice. "Tetrapod" would also work. If the specific animal you're asking about has more than four limbs, then "hexapod" or "decapod" would also work. You don't need to define "vertebrate" every time you ask about it.

  • $\begingroup$ Are these key factors just as common in sharks or lampreys? Those are vertebrates too, and a lot closer to the first ones than you or your cat $\endgroup$ Commented Oct 24, 2021 at 14:28
  • $\begingroup$ Enough of them. Certainly not everyone has lungs per se, but they do have analogous structures. If the question focuses on a fishlike creature for example that lacks lungs, you'd simply make note of the variances. The point being: "vertebrate" is a word that covers everything on your list. And then some. $\endgroup$
    – elemtilas
    Commented Oct 24, 2021 at 16:15

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