Bryozoans are primarily marine invertebrates common in the fossil record, appearing in the early
Ordovician Period, about 490 million years ago.
The electron micrograph at right shows some of the calcium carbonate skeletons of individuals making up a bryozoan colony. Food
is captured by an individuals lophophore, a ring of ciliated tentacles centered on the mouth, that protrudes from the round
opening in its skeleton. Find out more about bryozoans here.