Polypora spinulifera Bryzoan fossil a.jpg
Polypora spinulifera Bryzoan fossil
Chesterian Zone of the Bangor Limestone Formation in northern Alabama
Mississippian Period c 325,000,000 years ago
Bryozoa (also known as the Polyzoa, Ectoprocta or commonly as moss animals), are a phylum of aquatic invertebrate animals. Typically about 0.5 millimetres (0.020 in) long, they are filter feeders that sieve food particles out of the water using a retractable lophophore, a "crown" of tentacles lined with cilia. Most marine species live in tropical waters, but a few occur in oceanic trenches, and others are found in polar waters. One class lives only in a variety of freshwater environments, and a few members of a mostly marine class prefer brackish water. Over 4,000 living species are known. One genus is solitary and the rest are colonial.