The Burgess Shale animal Oesia is not a chaetognath: A reply to Szaniawski (2005)

The Middle Cambrian Oesia disjuncta, a monospecific genus, is known only from the celebrated Burgess Shale of British Columbia. It has been re−interpreted by Szaniawski (Acta Palaeontologica Polonica 50:1–8; 2005) as a chaetognath, a distinctive phylum whose exact position in the protostomes is still controversial. Unequivocal chaetognaths, that have no similarity to Oesia, are already known to occur in the Cheng− jiang Lagerstätte (Lower Cambrian, S.W. China), and here I describe the first example of a chaetognath from the Burgess Shale itself. Comparisons betweenOesia and chaetognaths fail to find any significant homologies.Whilst the phyletic position of Oesia is very uncertain, a place in the hemichordates may be worth exploring.