Palaeoscolecidans represent an extinct class of vermiform organisms with a prominent annulation ranging from the Lower Cambrian to the Upper Silurian. Since the first descriptions in the 1950s, they have been attributed to different groups, but recently they have been linked to the priapulids (Conway Morris, 1997). Palaeoscolecids are mainly considered to represent members of Ecdysozoa. Their position within this clade is still under discussion, but cladistic analyses indicate that they are either close relatives of nematomorphs (Hou and Bergström, 1994) or part of an extinct sister clade to the priapulids (Wills, 1998; Dong...

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