Mirelurk

Mirelurks, Swamplurks, Mirelurk Kings and Swamplurk Queens are an ancient and advanced civilization with a very organized monarchical politics, vast scientific knowledge and significant advancements in the fields of philosophy and literature. But are also known as retarded fish crab men. They, however, prefer to hide their knowledge to humans by acting as brainless monsters, so the secrets of their civilization aren´t uncovered. Their scientific classification, Kingdom: Phylum: Arthropodia Subphylum: Crustacea/Chelicerata Class: Merostomata/Malacostraca, was indeed coined by themselves and not by the Brotherhood of Steel. Mirelurks also have strong religious beliefs related with bubbling castles, so Mirelurk Priests expend great parts of their lives circling them, which is part of a ceremonial ritual. Some prefer to be called "Meta-Crabs" instead of Mirelurks.

Politics
The Mirelurk political system is a monarchy. Mirelurk Kings and Swamplurk Queens, also known among themselves as "Meta-Turtles", are considered the noble caste and are the only allowed to be rulers, primarly because they have 255 and 480 (respectively) more hit points than the average Mirelurk, and the fact that they have sonic attacks than can heavily damage heads and acid spitting habilities (respectively), so no Mirelurk dares to question their leadership, specially when they remember the face head is their weak point (physically talking).

Military
Mirelurk Hunters are the militar units of the Mirelurk Kingdom. Nobody, except maybe themselves, know why in the world they grow extra limbs. Chris Avellone says its due to F.E.V.. The extra limbs appear to be useless, at least for combat, since they are never seen using them.

Religious
As discovered by The Lone Asshole, Mirelurks have strong religious beliefs and appear to worship little bubbling castles, or perhaps use them as idols to worship another deity. Mirelurk Priests spend great part of the day spinning around said castles, some even most of their lives. Their religious leaders are Mirelurk Popes.