Infraclass ACANTHOBDELLIDA Livanow, 1905
Introduction
This small group of annelids have a fixed number of body segments with 29 postoral segments, chaetae restricted to the anterior portions of the body and have a posterior sucker. Of the two known species, one has an anterior sucker, the mouth is not located within this sucker.
Diagnosis
Tweny-nine postoral body segments, chaetae restricted to the anterior portions of the animal (typically five rows), reduced coelom with septa only found in the anterior portions of the body.