Crinoids attached to coral These delicate animals are all armiture. Their arms are loaded with fine, feather-like projections that function to filter food particles from the water, and then move the tiny morsels to the digestive chamber located at the base of the inner side of the arms. The sprout-like projection below the arms are used to anchor the animal to a surface, in this case a coral. Crinoids have a long fossil record dating back hundreds of millions of years.