DOD Bestiary: Eurypterid

Common Name: Eurypterid (Sea scorpion)
Pronounced: (You-rip-terr-id)
Classification: Eurypterida / various sp.
SGOC Rank: Mesofauna / Fauna / Megafauna

Length: up to 24 feet
Height: up to 15 inches (ground level)
Legspan: up to 7 feet
Weight: up to 1800 lbs.
Diet: Carnivore / Omnivore
Social Structure: Solitary, Group (5-100 members)
Home Planet: Earth
Distribution: Oceans worldwide, large coastal rivers; the World Below
IUCN Status: Least Concern

Description:

Eurypterids, or more commonly “sea scorpions”, are an order of aquatic arthropods that first evolved in the Ordovician period nearly 460 MYA, and have been surviving in the World Below caverns ever since. These invertebrates are famous for their size and scorpion-like appearance and range in diversity from half-inch scavengers to twenty-foot-plus monsters of the deep. They are one of the longest-lived and most successful animal groups in Earth’s history.

Most post-Cycle eurypterid species are of the same line as the ancient Eurypterus, a prehistoric sea scorpion and arguably the most successful genus this order ever produced; this means that most of today’s eurypterids have two large paddle-like legs for swimming. A few others have long spider-like legs and tiptoe around on the seafloor like giant arachnids, occasionally crawling out onto dry land to find washed-up carrion and attack seabirds. All sea scorpions have bad eyesight and rely more on smell and vibrations to detect prey; many burrow into the sand and wait for food to pass their way, while others are active swimmers that chase down fast-moving fish and cephalopods.

Most fresh/brackish-water eurypterids are less than a foot in length, but those living in the prey-rich shallow seas can grow to frightening sizes: the largest of all is the riptide (Aestarachne monstrosus, “Monstrous Tide-spider”), a twenty-foot monster that inhabits the shallows off the coast of western Australia, hauls itself out to bask like a crocodile, and has been known to maim swimmers when on their annual migrations inland to lay their eggs. The most common and commercially viable species is the scuttlebug, a meager two-footer that lives off the west African coast and is now a seafood staple all across post-Cycle Earth.

The most unusual eurypterids by far are a fully terrestrial group known as golems, which are endemic to the World Below caverns. They cling to the rocky ceiling of the great caverns, feeding on the abundant bacteria as well as each other, and are known from isopod-like scuttlers, spidery creepers, and more than three dozen sedentary species that mimic rocks, stalactites, and even crystal formations.

Eurypterids are pretty easy to catch via crab traps. They make up a good part of peoples’ diets in many parts of the world, and the Tylobans and Skrag view them as a delicacy. Eurypterids large and small are also quite popular in public aquariums. Some predatory species can pose a risk to swimmers, but attacks are rare and have been attributed mainly to people stepping on or antagonizing the animals.