攻撃的Aggressive if approached
The Eurypterid moves silently along the floor of the ocean, slowly undulating its body to move through the waterways. Since they spawn in clusters of two to four, there will often be many in a single area, often around coral and seaweed in the depths. When a player approaches the area to hunt for Silica Pearl clams or for the Eurypterids themselves, the Eurypterids will swim towards the invader and attack. They can envenom the survivor, knocking them out before dispatching the paralyzed body. In Genesis Part 2, they can be found in shallow waters or even on shorelines. It is unclear if this is intended or not
Superficially resembles a Pulmonoscorpius with adaptations to fit an aquatic lifestyle. The entire animal is armored with a Chitinous exoskeleton. The body is made up of the front "head", or the prosoma, and the segmented body and tail, or the mesosoma and metasoma respectively which together make up the opisthosoma. Its rearmost 4th pair of legs are flattened into flippers and its tail moves in an up and down motion, being propelled by a tail fluke. The end of the tail bears a scorpion-like venomous stinger. The 3rd pair of legs are long and skinny, followed by the thick, highly segmented 2nd pair of legs. The 1st pair of forelimbs are large and strong, armed with formidable spines which can close as a vice to trap and shred prey. 2 arm-like chelicerae rest at the front of the animal, which manipulate food to the mouth. 2 small, beady compound eyes are also present on the head. Range of coloration is currently unknown.
This section describes how to fight against the Eurypterid.
Eurypterids will spawn quite rarely along the ocean floor in small clusters of 2-4. They are rather small, but they can still pack a punch, as their attacks are fairly strong and rapidly raise Torpidity!
The first step is locating a Eurypterid. They remain relatively hidden in the coral and seaweed underwater, so they are quite hard to find. Once found, construct a plan on how to attack without subjecting any players to the deadly poison they employ in their attacks, which can drain stamina and induce high amounts of torpor. Sea mounts can be used to stay safe during killing, but large creatures cause a heavy knockback on the Eurypterids, so the area of effect loses efficiency and damage stops are enforced. The Ichthyosaurus surprisingly can be used to farm the Eurypterids, because it is immune to Torpor and has no knockback, which effectively increases the damage against the Eurypterids since they will never try to flee and stay in range. Keep in mind that the Eurypterids will still deal normal damage to the Ichthy+the Tusoteuthis is also immune to torpor so it can farm it on a great rate.
A strategy that's only recommended for players with the SCUBA Gear:
Swim down to the bottom of the ocean where the Eurypterids hide, then once you find some, swim upwards. These creatures can not leave the ocean floor, so you can safely float above them and shoot them down with a crossbow. Once you've killed them, swim down and safely collect their corpses with a Metal Hatchet. If one desires their rare Black Pearls, be sure to collect their bodies with a Metal Pick.
Employ any weaponry that, in use, will keep a player out of range of the tranquilizing attacks they deal. A Pike can be used by more alert, daring survivors who have powerful melee damage. Otherwise, mounts and ranged weapons like the Crossbow or Harpoon Launcher are your best shot.
Eurypterids are small enough to be easily hidden in the ocean's many plants and reefs. Use caution when collecting pearls, as their venom causes extreme amounts of Torpor, while their actual damage is low, they can even render larger creatures unconscious easily. This can turn a simple collection mission on its head quickly.You might also aggro more powerful aquatic dinos such as Megalodon or Mantas
Eurypterids float barely above the seafloor, but cannot freely swim in the open water. They also have low Health, so bringing a large sea mount guarantees their death.
- Harvestable Resources: The Eurypterid can not be tamed and due to their rarity they cannot be brought together in large enough numbers to cause harm to other tribes. However, they do provide a bountiful amount of resources when gathered, including fairly valuable ones like Silica Pearls, Chitin, and Oil as well as rare Black Pearls needed for high-tech equipment. The Trilobite also yields such items albeit at a much lower amount of Pearls and Oil.
- River Access: Despite the Eurypterid being a deep creature and being untamable a survivor can lure one or a few onto shallow water due to their small size. Because they are smaller than the other animals found in the sea Eurypterid follow survivors up rivers and used to attack enemies. Unlike other aquatic creatures shallow waters don't limit where Eurypterid can go.
- The Eurypterid was first revealed by Drake on 09/08/2015 
- The Dossier was revealed on 9/10/15 on Steam.
- Although it is difficult and there is no purpose for doing so, Eurypterids can be lured to shore where they will strangely swim — almost hovering — in the air. This is most likely a bug.
- In The Ragnarok map they are known to swim out of the waters of Viking Bay, which is quite shallow and near the shore, and tranquilize and eat survivors.
- Eurypterids can be observed doing this naturally along the forest floor in many of the Ocean Biome's Terrariums in Genesis: Part 1. Interestingly, they are the only creature, hostile or otherwise, that spawn inside the Terrariums at all.
- Most real life Eurypterids did not bear stingers as the dossier depicts. Most had tails ending in blade-like shapes, although some had flattened 'flukes' to help propel themselves through water. However, some members of the superfamily, Carcinomatosa, did have stingers used to inject venom into prey.
- Eurypterids were once thought to have been most closely related to horseshoe crabs, as opposed to Arachnids like scorpions. However, this taxonomy has been challenged, with some scientists proposing the close grouping of eurypterids and horseshoe crabs as paraphyletic and thus unnatural and that the Eurypterids are more closely related to arachnids; others still argue that the original grouping is correct. Despite this classification debacle, all 3 creatures were still fairly closely related to one another, with all of them belonging to Prosomapoda, which is a clade within Arachnomorpha, which in turn is a clade within Arthropoda.
- Eurypterids are a broad group with many members. According to the dossier, Ark's Eurypterids are from the genus Jaekelopterus - in real life, these were the largest arthropods ever known to evolve, at 2.5 m (~8 feet) in length.
- The genus Jaekelopterus was the largest genus of Eurypterid, but in ARK, the species is called Jaekelopterus eurypterus, which isn't actually a real species that existed. Jaekelopterus was a genus of eurypterid in the family Pterygotidae, whereas the genus Eurypterus (not a species) was a part of the family Eurypteridae.
- Even though the ARK eurypterid is said to be a part of the Jaekelopterus genus, it seems to combine physical traits from the genera Megalograptus and Mixopterus. Jaekelopterus had far less appendages and had two appendages on the prosoma (upper-most segment on the body) with claws similar to modern crustaceans such as lobsters. The eurypterids in ARK, however, even though they are similar in size to Jaekelopterus, have long appendages on the prosoma covered in large spines with many other appendages such as paddles used for locomotion which is far more similar to the genus Megalograptus, who possessed these features. The genus Mixopterus had similar spined appendages and also the scorpion-like 'stinger' found on the ARK Eurypterids.
|238.0||Eurypterid is added to the game.|
|238.2||Increased spawn frequency by 60%.|
|254.5||Can no longer receive buffs or debuffs.|
|260.0||Increased spawn numbers by 50%.|
|262.0||More Eurypterids are now present in the underwater overworld.|