Ever met a cry baby?..This guy will wail if you hit it and will cover you in a type of pheromone gas....causing you to attract every dino, sea or land, to bite your butt. Prepare for war. You only need to survive 80sec.
This section describes how to fight against the Ammonite.
The Ammonite is a non-aggressive animal that will not attack the player on sight.
The shell of the Ammonite is tough and resilient against most weapons. Therefore, players should target the tentacled head, which is vulnerable to damage.
A Pike is the best used for close quarters, as the weak area is quite small and hard to aim with a crossbow or rifle. It is also recommended to kill all wild animals nearby, as these will become hostile when you attack the Ammonites.
The Ammonite itself is not a danger, however, when attacked it will release a green substance into the waters, causing nearby wildlife to become aggressive for a whole minute. An Ammonite hunt can quickly become overwhelmed by masses of normally passive animals. Its rage effect will last for 60 seconds. Also, the underwater caverns and depths Ammonites dwell in have their own dangers, such as mass shoals of Cnidaria, as well as many other terrors of the deep.
The Ammonite will not fight back in any way, making for a rather easy kill so long as there are no other animals nearby.
Guess how I found out there was a 105 Tusoteuthis in the water with me....
Don't hit them. Just... dont't
Ammonite is passive, and when you hit it, you (or your mounted tame) will get the Buff/Debuff "Rage" (depending how you look at it)
With the Buff/Debuff, everything nearby will have a sudden, uncontrollable urge to kill you. Even the Parasaurs!
You can find Ammonite dwelling in the deep ocean, usually alone or in groups of 1-3. They are untameable. They drop Ammonite Bile, used to craft Pheromone Darts. If you get hit with "Rage", Prepare for that Alpha Mosasaur you thought you had outrun or that Tuso to come out and slaughter you. Or just get offed by a Coelacanth. Both is good.
For Those who are wondering what their bile is for, check the wiki. It's the irreplaceable material for crafting pheromone darts, the dart can be used to attract all wildlife around the target to enrage and attack the target for 30 seconds. Useful in pvp but just about useless in singleplayer. So if you're on singleplayer (like me) there's not much to gain by killing ammonites.
Some things that i don't think anyone has mentioned yet:
1. Ammonite rage attracts not just normal wildlife but alphas as well, and as people have said they will not be restricted by their normal limit in water so Look around before hitting an ammonite, especially if u can't kill it in one hit.
2. As Icthyosaurus have a "invisible" glitch/feature that causes creatures to simply ignore it and it's rider most of the time, even when attacked.(shared by all creatures tamed inside tribute caves. To ensure you do not anger any creature u want to kill hit from behind and wait for the creature to calm down before hitting again if it angers.) It might seem perfectly suited to kill ammonites. Wrong. ammonite rage completely nullifies the invisible glitch when it's active, often resulting in a breathtaking sprint away from furious plesios, mosas, and in one occasion an alpha mosa that nearly managed to kill my icthy. So Unless you just want a quick getaway mount, don't bring an icthy to kill ammonites.
3. Aside from their unique bile, they also drop silica pearls, oil, and rarely black pearls. And they're not as rare as some of the other black pearl dropping creatures. So If u can handle anything the ocean throws at u it might be worth your time to find and kill them for the pearls.