Bryozoans

Bryzoans are small animals easily preserved in the fossil record due to their shells being composed of calcium carbonate. They are not found in rocks older than Ordovician age but are known to occur into the modern Quaternary period. They generally prefer warm, tropical waters but are known to occur, even today, throughout global waters. Though generally a nuisance to humans they must be revered for having survived for so many millions of years in a dynamic and ever-changing world.