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I want to make my unicorns use the horn as their male genital. Is it biologically possible to put the genital on their head? I know there are many strange genital locations for animals, for example, the kangaroo, and i know there are many strange shapes and numbers for animals genitals, but so far I have not found any with genitals located on their heads.

My design is that their genitals are covered with ceratin and spiraled (like pig/duck genital) but more compact to look like narwhal horn. Their testicles are either inside (like dolphin/lizard) together with their brain or covered with another layer of skull in their head. If this is impossible or can damage their brain or something. then I guess I just put it around their neck (think of chicken wattle) or put it in the standard horse location so this testicle hangs more outward like most common mammal testicles organs. But in any case, the genital is still on their head disguised as a horn (or what human think as a horn).

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  • $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$ – Monty Wild Jan 3 at 7:51
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There are all kinds of ways to have sex in the animal kingdom. Spiders, for example, don't have intromissive sex, but instead the males deposit some sperm on a pedipalp and then post it into the female's genital opening (let's ignore the spiders who tear off said pedipalp and offer it to the female to use herself for now, as that probably isn't the sort of courtship you're after). Many cephalopods are similar, with a dedicated arm (the hectocotylus) used for handing over a blob of sperm (or again, to be torn off and handed over).

If your unicorns used a similar approach, the genital plumbing could therefore still be in the regular place, but the male unicorns would need to be flexible enough to reach their horn back and spaff on it, or perhaps make a deposit on some other convenient surface and pick it up with the horn. They can then use the horn to deposit the sperm where they see fit. This avoids the need to take up precious head real estate with various glands and tubes and all the rest of the infrastructure usually associated with sperm production in mammals.

If you were interested in something a bit more gristly, a hard and sharp horn at the front end of a strong animal and backed onto a pretty tough skull might be used for traumatic insemination. This would be a rough proposition for the female, but you'd also have to worry about any animal capable of surviving being run through the abdomen by a big spike. They'd be a bit dangerous to hunt, I'd bet...

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    $\begingroup$ i know that one including anglerfish type of reproduction (after reading a bit of the Equoid), and i know about traumatic insemination hence i even mention male genital fencing in the comment, but iam curious are invertebrate can technically or biologically do the same? how or what kind of modification to make it possible ? (i mean the female to survive or get pregnant) $\endgroup$ – Li Jun Dec 28 '19 at 17:25
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    $\begingroup$ @LiJun in species which have evolved traumatic insemination, the females have specific structures designed to collect and transport sperm but which don't have any other important function. I'm not sure what the mammalian equiavlent would be, but you could look at species like elephant seals where the males have tough fatty layers around their throats to stop tem being killed immediately in a duel. They can take deep slashes and indeed bleed from them but don't sustain fatal damage or even seem to suffer from dangerous infections as a result of their injuries. Might be a useful pattern. $\endgroup$ – Starfish Prime Dec 28 '19 at 17:34
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It's possible...on Snaiad

Is is structurally possible? Sure, why not.

But it it evolutionary plausible? Not likely, at least not on this planet. The vertebrate body plan is pretty solidly set to have the genitals on the back end of the animal, and from fish to mammals, there is no example that breaks this rule. It takes a pretty severe mutation to stick the reproductive system on the head, and the chances of this resulting in both a functional reproductive system and a functional head (both absolutely necessary for reproduction) is basically zero.

There are other animals that have their genitalia in odd places, but these tend to be animals with drastically un-mammalian body plans (like snails, starfish, and squid). The chances of any one of those evolving into something resembling a horse is...very, very low, especially when they have to compete with existing vertebrates.

But on a planet with a completely different evolutionary lineage, it's not out of the question.

Snaiad is a speculative evolution project describing a planet where the dominant animal lineage evolved from a creature not unlike the Earth barnacle, which was mainly sedentary and used its long, extendable genitalia to seek out mates. Over time, the genitals developed more advanced sensory organs, essentially turning into the creatures' heads. Descendants of these creatures eventually grew mobile and became animals analogous to vertebrates, while retaining the a body plan that placed the genitals and the sensory organs on the same appendage.

Your unicorns would fit perfectly well on a planet like that.

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    $\begingroup$ so outside of the evolutionary/natural selection thing, are theres no complication against all my proposed genital organs or anatomy ? $\endgroup$ – Li Jun Dec 29 '19 at 9:07
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    $\begingroup$ Structurally it's fine - glands can be pretty much anywhere as long as they have a blood supply, and the brain can be any shape you need to make room for them (squids have a ring-shaped brain and their esophagus passes through it). $\endgroup$ – IndigoFenix Dec 29 '19 at 10:53
  • $\begingroup$ oh thanks for the information, and to be honest the squid brain is actually what inspired me to put the glands there, but iam curious does that mean it possible for horse or other creature to have ring brain or other weird shape brain ? $\endgroup$ – Li Jun Dec 29 '19 at 15:07
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    $\begingroup$ In general, the more advanced or complex an organism is, the harder it is to make significant anatomical changes. The vertebrate brain is extremely complex so it's very unlikely for an existing mammal like a horse to develop a ring-shaped brain. But a simpler animal could evolve a different body plan and then through convergent evolution wind up looking roughly horse-like after millions of years. $\endgroup$ – IndigoFenix Dec 30 '19 at 7:40
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Where would the female organs of that species be? Horn-like penis still would work like a penis -it would be supposed to be inserted to do its job. I'd say not into the skull of a female. The closer to female's uterus the better evolution-wise. Also genitals tend to be located in safe places, where they are not endangered by an accidental tear-off. Horns on the other... hand are usually located atop of a very much used head. In case of horse-like creatures they are used to bash each other brains off. You'd just make all the manly unicorn jousts... gay. Well, they ARE unicorns...

I really think what Starfish Prime said about just making it a pipette would be the best way of handling it. I only am afraid that it could make the older males unable to reproduce due to having more used horns. I mean they would obviously use it for things other than semen-handing. It'd be located on their main environmental probe. They'd scrape bark off the trees, dig holes, use in mating season fights. Maybe the species would just mutate faster without the old specimens handing out the same set of DNA over and over till they are too weak to stand.

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    $\begingroup$ i originally just think the female genital organs in common horse location, and i actually want to turning it into hermaphrodite, and fighting whos gonna be the one bearing the children by fencing using their genital horn (reason why it covered with ceratin) like flatworm do with genital fencing. $\endgroup$ – Li Jun Dec 28 '19 at 17:35
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    $\begingroup$ +1. The question is what an 'orn' looks like before a Y chromosome turns it into a 'horn'. Making something phallic into a penis is the easy part.... $\endgroup$ – Mazura Dec 28 '19 at 23:52
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First off, it's good that you are exploring different concepts, so definitely keep it up.

That being said, I think you might get benefits from trying to answer some questions when you're tackling the idea of cranial-genitalia unicorns (heretofore referred to as CGUs). Maybe just think about this stuff in your notes outside of the main content — otherwise you might run into some problems later when writing story details:

Consider These Questions to Answer for Yourself and Make Your Writing Process Easier

  • Why did the CGU evolve to have its genitals on its head? If it was a random mutation, then why did it succeed while the other unicorns died out? Are there lots of fossils with unicorns that would have side genitalia?
  • Is the sex organ still made of keratin (the horn/fingernail/hoof/hair protein)? If so, why not hoof genitals or some other form?
  • Are there "traditional" unicorns in the same universe, and do they ever encounter the CGUs? If so, can your characters tell the difference or does it not matter?
  • Is there an additional hole in the skull to let the veins, vesicles, and other stuff (ask a reproductive biologist) pass through?
  • Does making the horn a genital change how people in the universe use or relate the horn in lore-based or practical terms). For instance, some Earth humans kill endangered animals to use their horns as aphrodisiacs. Would your characters do this, or would that be too on-the-nose?
  • A CGU gets in an accident where its horn breaks off. Does it grow back like deer antlers do? Can it still produce offspring?

Finally, and this is the most important question: How do CGUs add to the story that you want to tell? If it's just there as a sort of random detail, then it might seem out of place. I think you should go for whatever you want, but you still maybe ought to consider how your reader or audiences will receive it within the surrounding context that you've built.

One good way to troubleshoot tough story details is to imagine yourself talking (as the author, local deity, another character, or whoever) to the character you're considering. For instance, if a CGU could talk (some fantasy unicorns have that ability) what do you think it would have to say about where its genitals were? Would it complain about them or have special problems?

By answering these kinds questions, you can hopefully build a rich story environment, although it definitely seems like you're well on the way already. Have fun.

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  • $\begingroup$ 1 i was actually thinking the traumatic insemination breeding way like make it fast to force breed the female or the loser like flatworm do, although at that time i though that direct piercing the body probably wont work for mammal (starfish say otherwise) so they do the normal insertion reproduction.2 i dont know, putting it on the hoof mean it getting contact a lot with pressure and probably awkward for walking and i think thats more dangerous than putting it on their head3 no CGU is the only unicorn.4 yes i guess would help for correction though. $\endgroup$ – Li Jun Dec 29 '19 at 2:50
  • $\begingroup$ 5 no and thats also the reason its aphrodisiac..... 6 no but it hard enough to not easily break, unless it hit by a truck. even their fencing is not bashing each other head but more like sword fencing and chasing each other rear to determine whose stronger and faster. $\endgroup$ – Li Jun Dec 29 '19 at 2:55
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Have the horn be an additional method of impregnation, rather than replacing the current method

As others have pointed out, yes it would be possible, but the horn would be very exposed and, if they are also used for defence or duelling, then they are put in a lot of unnecessary danger.

What i propose is to make the horn more of an additional form of impregnation, rather than the sole method. Many animals, such as sharks and snakes, have two sets of “equipment” (though normally these are located next to each other, there is no reason they couldn’t be in different places). A unicorn would probably have similar equipment to a horse - though likely smaller if the horn is meant as the primary method of impregnation. Im not sure how feasible this is but having a secondary reproductive system as a back up seems logical - especially if the primary system is at risk of damage.


The horn might be like a snail’s love dart

Alternatively, the horn may be akin to a snail’s love dart in that it is used prior to insemination, inserting hormones into the female unicorn to create more favourable conditions to increase the chances of successful impregnation. If this were the case, I feel it would make a lot more sense for several reasons:

Firstly, although the horn is used in reproduction, much like a snail’s love dart, it is not strictly necessary - it simply increases the chance of insemination being successful. This means that having the horn exposed and using it for duelling is not as risky as they are not fighting with an organ that is necessary for their survival.

Secondly, it means that the horn can be far stronger as it does not need as much soft tissue inside of it. All it would need is a channel through the middle of it to allow fluids to pass through, much like the teeth of venomous snakes. So, if the horn is stronger, it further reduces the risk of damage and also reduces the need for it to be protected (allowing it to be very exposed on their heads).

Thirdly, because the horn is now just for inserting hormone-filled fluids, it shouldn’t need to take up as much space inside the unicorn’s head. Also, there is some real life precedent for this as the venom tubes for snakes runs through their head:

the anatomy of a snake’s head, showing how the venom gland is located in its head and the tubes run under its brain Source:https://thebrainbank.scienceblog.com/2014/12/01/why-is-snake-venom-so-variable/

Imagine if, instead of a snake, this was a unicorn. And instead of the ducts running under the brain and through the snake’s teeth, they instead ran upwards through the inside of a unicorn’s horn.

Now proportionately, the gland would be far smaller compared to the brain of a unicorn (which would likely be similar to a horse or zebra), and it would contain hormone-filled fluid rather than venom, but it would function in a similar way nonetheless.

In regards to how insemination would actually work, the unicorn would first inject the hormones into it’s mate’s reproductive system, before continuing to mate like a horse would.

(Or, if you felt so inclined, you could have the horn be like an injection - it pierces the female’s skin to inject the hormones into her bloodstream.)

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