Any member of an extinct group of small, aquatic colonial invertebrates that first became apparent during the Cambrian Period and persisted into the Early Carboniferous Period (354–323 million years ago).
Graptolites were floating animals that had tentacles and a hard outer covering. They most often have been preserved as impressions on black shales. Graptolite fossils show a gradual development through time, and evolutionary relationships between different graptolite groups have been discovered and analyzed.