Form and mode of life of Dicellograptus (Graptolithina)

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Abstract
The majority of Dicellograptus species have stipes which spiralled to a greater or lesser extent; this explains continuous variation of axial angle found in several species and many anomalous features of flattened or partially flattened specimens. The effects of variation in thecal style along the stipe are distinguished from those produced by variable orientation of the rhabdosome during flattening and by later tectonic distortion. It is concluded that Dicellograptus probably lived with stipes pointing upward and that the rhabdosome rotated in a horizontal plane due to eddies created by the non-directional ciliary activity of radially dispersed zooids in order to improve feeding efficiency.