OWENIIDAE, RIOJA, 1917

Capa, Maria, Parapar, Julio & Hutchings, Pat, 2012, Phylogeny of Oweniidae (Polychaeta) based on morphological data and taxonomic revision of Australian fauna, Zoological Journal of the Linnean Society 166 (2), pp. 236-278 : 267

POSITION OF OWENIIDAE

The relationships of Oweniidae with other polychaetes have been debated for some decades with conflicting points of view ( Liwanow & Porfirjewa, 1967; Bubko, 1973; Rieger, 1976, 1988; Smith et al., 1987; Minichev & Bubko, 1992; Westheide, 1997; Eeckhaut et al., 2000; Rousset et al., 2004; Struck et al., 2007, 2008; Zrzavý et al., 2009). Morphological data suggest that the presence of monociliated cells ( Gardiner, 1978) and the nephridial type in the mitraria larvae ( Smith et al., 1987) are plesiomorphic conditions ( Rieger, 1976; Smith et al., 1987) and are indicative of the basal position of the oweniids within the annelid tree ( Rieger, 1986; Smith et al., 1987; Westheide, 1997). These conclusions are also supported by some molecular studies ( Struck et al., 2008; Zrzavý et al., 2009). Nevertheless, other authors advocate a close relationship of Oweniidae and Siboglinidae , a more derived group of Annelida, based on the presence of the intra-epidermal nerve cord ( Rousset et al., 2004; Struck et al., 2007; Capa et al., 2011) and the type of hooks ( Meyer & Bartolomaeus, 1996). In the present analyses, based only on morphological data, a close relationship of Oweniidae and Magelonidae is suggested (with low support) based on the absence of nuchal organs, fusion of prostomium and peristomium, presence of ventral buccal organ, and monociliated epidermal cells. These results should however be taken with caution. The absence of nuchal organs could well be interpreted as a secondary loss that has also occurred in some other polychaetes ( Purschke, 1997, 2005). The fusion of prostomium and peristomium in Magelona , being limited to the lips ( Rouse & Fauchald, 1997), needs further investigation ( Rouse & Pleijel, 2001) as there are some opposing argu-