Аннотация:Here we describe fine structure of the syzygy partner in Selenidium pennatum Simdyanov 1992 (Sporozoa, Archigregarinida - as proposed by Grasse and Schrevel). The presence of an apical complex (conoid and rhoptries) and the absence of nucleus are the most interesting properties of this object. Long-term presence of the apical complex during the life cycle is a plesiomorph character for Apicomplexa. Among other things, it distinguishes archigregarines from other sporozoans and confirms the suggestion that this group is the most close to the ancestor of gregarines and sporozoans in general. Diagnosis of Archigregarinida is given. URL: http://protistology.ifmo.ru/num2_3/kuvardina.htm