[Taxacom] Branchiobdellida (leeches?, oligochaetes?, or stem annelids?)

[Kenneth Kinman]

Dear All,         
       There seems to be some controversy over whether Order
Branchiobdellida is:  (1) a primitive oligochaete taxon, (2) a primitive
hirudinean (leech) taxon, or (3) something which split off before either
of these main clitellate annelid taxa.  Is there any recent literature
which might clearly point which of these three possibilities is the most
likely?
           ---------Thanks,
                              Ken Kinman