Squat lobsters are much smaller than commercially-harvested true lobsters. For example, Munida rugosa has a maximum body length of 4 in with abdomen extended, and the striated squat lobster Galathea australiensis has a carapace that reaches 6 in in length.
The body of a squat lobster is usually flattened, the abdomen is typically folded under itself, and the first pereiopods (front legs) are greatly elongated and armed with long chelae (claws). The fifth pair of pereiopods is usually hidden within the gill chamber, under the carapace, giving squat lobsters the appearance of having only eight pereiopods.
It was long assumed that squat lobsters hide in crevices and catch prey with their long claws. However, recent observations showed the animals to wait on the tops of Lophelia coral reefs and catch fish swimming past.
Munidopsis andamanica is a deep sea species that is specialized to feed only on sunken wood, including trees washed out to sea and timber from ship wrecks.