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While designing my species of trolls I came to the question of how there heads attach to their bodies.

What I've had in mind was that their necks were horizontal rather than vertical so that their heads stick out from their chest (or an area of torso above their chest) instead of sitting on top of their torso. My first thought was that this would be ok because it's how gorilla's necks attach, but gorillas largely walk on all fours and my trolls will stand upright like a human (though they would have slightly longer arms they wouldn't be as long as gorillas).

So what I have in mind is something like the cave troll from the Lord of the Rings movies or perhaps a saurus warrior from Warhammer (head position only, probably a shorter neck) or similar.

The first obvious disadvantage I can see is range of movement in regards to visibility. My trolls presumably can't look over their shoulders to see what's behind them. What else would they not be able to do?

And are there any positives to such a neck position?

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  • $\begingroup$ Gorillas can walk on two legs, as do all great apes. Watch and see that their heads connect with their necks just like ours; moreover, gorillas spend quite a lot of time sitting with their torsos upright. You may have been mislead in judging the position of their heads because their braincases are smaller than ours, their jaws project forward and their neck muscles are very much more developed. $\endgroup$
    – AlexP
    Aug 13, 2020 at 17:40
  • $\begingroup$ @AlexP that's kind of my point, I'd assumed my troll's heads and necks might work like gorillas but on closer inspection they don't. Gorilla's heads do attach at the back but their posture is either quadrupedal or human like, I want a creature who stands upright like a human with their neck projecting forward instead of upwards. $\endgroup$ Aug 13, 2020 at 17:50
  • $\begingroup$ Do you want to have neck opening in the back as well? Or you want to have 2 necks - one for the spine, and one for all other conduits? $\endgroup$
    – Alexander
    Aug 13, 2020 at 18:01
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    $\begingroup$ I'd say this would work for a theropod which has a massive tail for balance (like in your example #2), and not work for an upright tailless humanoid (like in your example #1). $\endgroup$
    – Alexander
    Aug 13, 2020 at 19:57
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    $\begingroup$ Lack of tail can be compensated by posture, but this should make these creatures slow. $\endgroup$
    – Alexander
    Aug 13, 2020 at 20:01

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One of the main issues of a head connected to the back of the skull is that the part of the neck doing most of work to keep it from pending to the ground is the muscles rather than the bones. Because of this arrangement, the skull has a smaller max weight limit than if it relied more on the bones to sustain it (position yourself in a horizontal position leaving your head and neck unassisted, you'll notice how after a while your neck might begin to feel tired if you try to keep your head stable rather than giving in to gravity.

For that reason, one main issue with this arrangement is that it limits how large the head can get and thus it limits how large the brain can grow. We can see this problem regarding growth in how many prehistoric animals reach a point in which the head begins to look smaller in proportion to the body (the largest mammal, indricotherium, for example had a skull smaller than the modern African elephant in proportion to body size). This means that, unless your trolls also have strategies to make their heads lighter (less bone, the presence of holes in the skull, regions with pneumatic bones like seen in certain birds with enormous beaks) the size it can grow to in relation to the body might be limited.

The second thing is that they'll likely have a relatively long neck. For your upright standing troll to have a head seeming to come out of the front of the upper chest region, you'll need them to have a relatively long neck, see as follows:enter image description here

In this rough sketch, we can see how the neck region of the skeleton (drawn in black, highlighted in yellow) needs to be pretty long for the head to located in such a way. A potential advantage of such an arrangement is that harming this being's throat or windpipe will probably be a harder job, depending on how it's positioned, and snapping it's neck will most likely be very hard. As a counter, the top region of the body where the neck lies might be at a higher risk of damage, making it a vulnerable region to weapons such as blades, with a well placed stab with a short sword between the vertebrae by someone who managed to climb these creatures risking severe wounds to the spinal cord and potentially resulting in the troll's death (a heavy Boulder falling in this region might also risk severely damaging the neck and killing the troll as well ).

In addition, since this arrangement seems to limit head articulation as a whole, it wouldn't be surprising if these trolls also had a hard time looking up and even down, which could be highly detrimental with such a potential weak point lying exactly on their large blind spot at the top of their bodies (and also why I'd assume they'd likely be selected to grow larger, since the taller they get, the higher from the ground this weakness will be and the harder to reach it will be for enemies, with the larger trolls with thicker and tougher "neck" regions likely being selected by the environment due to have their weak point more well protected).

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  • $\begingroup$ Interesting, none of those are particularly putting me off the idea other than the intelligence factor. How big could the head be if the trolls were 7 - 8 feet tall and weighed 450 - 600lbs? Might they be able to have a human sized brain? $\endgroup$ Aug 13, 2020 at 20:01
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    $\begingroup$ @adaliabooks I'm no biologist, so I can't give you a 100% answer, but your troll seems a bit too light for a bipedal creature the size of an African elephant (which weights over 13000 pounds). They'd likely have very powerful muscles and thick bones, weight at least 6000 pounds and could have a similarly sized skull (especially since they have no trunk or tusks adding more weight), so I'd say they could probably have an elephant-sized brain and matching intelligence (just watch out for the body, such a creature will need strong muscles and bones to properly be able to grow like that). $\endgroup$ Aug 13, 2020 at 20:17
  • $\begingroup$ Probably, that was just estimated on the weight of gorillas (which are shorter than I want my trolls to be) though I don't really envision them being as big as elephants... I may need to put a bit more effort into working this stuff out. $\endgroup$ Aug 13, 2020 at 20:23
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    $\begingroup$ @adaliabooks unless you rely on magic, just remember the square cube law: the weight of a creature increases faster than their muscle power, so unless we're talking about azhdarchids (pterosaurs as big as giraffes with heavy adaptations to be light), they'll get very heavy the more they grow and will need stronger muscles and bones to sustain this weight. I recommend looking at T-Rex as an example of adaptations for a heavy biped to grow bigger and taller (they could grow up to 20 feet tall ). $\endgroup$ Aug 13, 2020 at 20:30
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    $\begingroup$ To be fair there is a lot of hand waving away of stuff like that due to magic, there are actual giants far bigger than the trolls and flying fire breathing dragons and I'm even going to attempt to explain how they might work, I just want their anatomy to make sense (and to know what they might be capable of or not). Also I'd not heard of azhdarchids before, they are awesome, so thanks for that. $\endgroup$ Aug 13, 2020 at 22:33

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