Redescription of Atopospira galeata (Kahl, 1927) nov. comb. and A. violacea (Kahl, 1926) nov. comb. with redefinition of Atopospira Jankowski, 1964 nov. stat. and Brachonella Jankowski, 1964 (Ciliophora, Armophorida).

The taxonomy of the Metopidae (Ciliophora, Armophorida) remains poorly understood since most of its members have not been studied by modern morphologic and molecular methods. Recent molecular investigations have indicated that the two most species-rich genera, Metopus and Brachonella, are likely nonmonophyletic with at least one well-supported 18S rDNA clade comprised of a species from each of these genera (Brachonella galeata and Metopus violaceus). We investigated these two species with silver impregnation and scanning electron microscopy. Both taxa share important morphologic characteristics not described in other species of Metopus or Brachonella. These synapomorphies include: (1) a diplostichomonad paroral membrane, (2) a bipartite adoral zone with a short buccal part composed of ordinary membranelles and a longer distal part composed of much smaller membranelles bearing a single cilium or none and extending the same length as the perzonal ciliary stripe. We transfer Brachonella galeata (Kahl, 1927) Jankowski, 1964 and Metopus violaceus Kahl, 1926 to genus Atopospira Jankowski, 1964 nov. stat. Pending detailed morphologic and molecular characterization, Brachonella campanula, B. cydonia and B. pyriforma, B. intercedens, and B. lemani remain in Brachonella Jankowski 1964.