Divisional morphogenesis in Bakuella pampinaria nov. spec, and reevaluation of the classification of the urostylids (ciliophora, hypotrichida).

A new hypotrichous ciliare, Bakuella pampinaria nov. spec, colonizing vineleaf and pear-tree litter, is described. Bakuella pampinaria differs from the other species of the genus by having distinct rows of yellowish cortical granules. Several morphogenetic differences separate Bakuella pampinaria from Bakuella edaphoni and other congeners, especially in that the transverse cirri do not participate in the formation of the oral primordium. The type population of Pseudourostyla cristata was reinvestigated. Two frontoterminal cirri are recognizable in dividing specimens indicating that this genus is valid, i.e. different from Urostyla, which very likely lacks such cirri. The urostyline hypotrichs are recognized as a monophyletic taxon by two apomorphies, viz. the midventral cirri and the partial or complete reorganization of the proter's adorai zone of membranelies during cell division. Phylogeny and evolution within the urostylids are much less clear since character states (apomorphies, plesiomorphies, convergencies) are uncertain and morphogenetic data are still too sparse or inaccurate. This is exemplified on a selected set of genera using Hennig's phylogenetic method.