What is "sabellidae"

Sabellidae (feather duster worms) are sedentary marine polychaete tube worms where the head is mostly concealed by feathery branchiae. They build tubes out of parchment, sand, and bits of shell. Glomerula secretes a tube of calcium carbonate. They tend to be common in the intertidal zones around the world. Their oldest fossils are known from the Early Jurassic.