English: Graptoloidea hypothetical restitution. The planktic Graptoloidea lived un-attached in the oceans and were actively moving through the water column, filtering the water column to gather food. Graptolites can be identified as a group of clonal, colonial pterobranchs, secreting a characteristic housing structure: the tubarium. The tubarium can fossilize, but not the pneumatocysta and gonangia which are speculative. Fossil evidence of attachment to seaweeds or other floating materials does not exist. The zooids of the genus Rhabdopleura can be regarded as a general model to reconstruct graptolite zooids, but may not represent precisely the soft-body anatomy of extinct taxa.