Extinct organisms with no close analogs and only distant living relatives are especially difficult subjects for paleobiological interpretation. Graptolites, especially the derived planktic Graptoloidea, are among this group of enigmatic fossils. Although the Pterobranchia are widely regarded as a sister group to graptolites, their entirely benthic, loosely organized colonies provide a poor analog for the mobile, highly integrated graptoloid colonies with their complex geometries. As a consequence, many basic features of zooid form and function are unknown. Under these circumstances, particularly troubling features—that is, features that do not readily fit into our simple models—may provide critical data with which to...

First Page Preview

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