This result corroborates the assumption that sabellids evolved an elastic, rapidly secreted tube the animals can easily migrate from and thus were able to colonize instable environments. Increase of the manubrial length of thoracic uncini evolved in the stem lineage of the Sabellidae. A comparison within the Sabellida leads to the assumption that reduction of the rostrum in abdominal uncini occured in the stem lineage of the Fabriciinae, because Sabellinae, Caobangia and Serpulidae retain the plesiomorphic uncinal design with rostrum, capitium and a short manubrium. Their characteristic curvature also results from re-orientation of the microvilli during chaetogenesis. The narrow coastal plain in the Knysna area has a. At the begining of their chaetogenesis several individual microvilli form the spines of the capitium. protected valleys throughout the region nurture patches of evergreen forest or thicket vegetation. During chaetogenesis re-orientation of the microvilli causes curvation of the rostrum and capitial spines. A group of microvilli preforms the rostrum, while individual microvilli give rise to each spine of the capitium.

The chaetae are formed at the dorsal edge of the neuropodial rim, close to the notopodial group of capillary chaetae. Rostrum and capitium are bent towards the manubrium. stellaris consist of a large rostrum, which is surmounted by several spines of the capitium. In order to compare both kinds of chaetae and to find hypotheses on the chaetation in the ground pattern of the Sabellidae, structure and development of thoracic and abdominal uncini of the small sabellid Fabricia stellaris were studied ultrastructurally and compared with SEM studies of the sabellids Branchiomma bombyx, Euchone analis and Sabella spallanzani, and the serpulids Protula tubularia and Pomatoceros triqueter. In several sabellid species the shaft (manubrium) of thoracic neurochaetae is much longer than that of abdominal notochaetae. Within the Sabellida, Serpulidae and Sabellidae are sister groups and possess uncini, which are aligned in a transverse row inside the neuropodial rim of the thorax and the notopodial rim of the abdomen.

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