Graptolites were colonial organisms that first appeared in the Cambrian. In early Ordovician times they migrated from the benthos into the plankton, becoming some of the most significant zooplankton of the Lower Palaeozoic. Planktonic graptolites radiated quickly, reached an acme of variation in the late Ordovician and Silurian, then declined into extinction by the mid-Devonian. The benthic graptolites followed them to extinction in the Carboniferous.

Planktonic graptolites underwent rapid evolution, recorded in their widespread and relatively durable, colonial skeletons. Their evolutionary variation through time affords important biostratigraphical data, but there was also latitudinal or palaeogeographical control on the distribution of...

First Page Preview

First page PDF preview
You do not currently have access to this article.