Abstract

The progressive loss of stipes through the Ordovician and the appearance of uniserial forms in the Silurian mark obvious changes in graptoloid morphology through time. However, several features of graptoloids are shown here to have remained remarkably constant. The feeding areas of graptoloids, and the intensities with which they fed have been measured, assuming that graptoloids rotated as they moved through the water. The mean and range of feeding intensity remained constant through time although the total number of zooids changed. It is postulated that graptoloids with low feeding intensities lived in areas of low food availability. High intensity feeders would have lived where food was more abundant. -from Author