The graptolites: strange plankton of the past

The graptolites are one of the most puzzling groups of fossils. They formed marine colonies so closely integrated that they can fairly be described as superindividuals and their elaborately sculptured skeletal remains are widely distributed. Yet their affinity with the rest of the animal kingdom remains obscure. While they are often regarded as having an affinity with the hemichordates, there are nevertheless objections to this theory. They still remain creatures in search of relatives.