From Curini-Galletti et al. (2010) (citation): "C. constricta cluster[s] within the Unguiphora [by complete ssrDNA and partial (D1-D6) lsrDNA sequences], although with poor support.... Albeit scarcely probative, this result may be taken as indicative of a close relationships of Ciliopharyngiella with the Proseriata. A similar result was obtained by Willems et al. (2006), who included a large sample of Rhabdocoela. The similarities of Ciliopharyngiella with Proseriata, based on general topography of female genital structures and brain morphology, were already remarked by the author of the taxon (Ax, 1952a), who ascribed it to the Proseriata, although with some hesitancy. Later, the taxon was removed from the Proseriata for the presence of a bulbous-type pharynx rosulatus (Proseriata have a plicatus-type pharynx) and the structure of the male system, and assigned to the Typhloplanoida (Ehlers 1972). Ciliopharyngiella has received considerable phylogenetic attention, since it was assumed as the earliest derived taxon of the Rhabdocoela (Ehlers 1972; Ax, 1995). Affinities of the taxon on morphological grounds are, however, still a matter of contention. The pharynx rosulatus of Ciliopharyngiella has a unique morphology among the Rhabdocoela (Ax, 1995), and some of its supposed autapomorphies (such as the presence of ciliation both internally and externally) are indeed shared with the Proseriata. Claimed synapomorphies with Rhadocoela and Prolecithophora (see Sopott-Ehlers 2001) are not unequivocal, such as the lack of true lamellated rhabdites, a character assumed to be shared with representatives of the Prolecithophora, but lacking in the Proseriata as well (Sopott-Ehlers, 1985). Indeed, some of the observed characters on which rhabdocoelan affinities were based, ‘might be a convergence’ (Sopott-Ehlers, 2001, p. 163). Furthermore, there are reasonable suspicions that some of the supposed affinities with the Rhabdocoela, and of the very numerous autapomorphies of the taxon (Sopott-Ehlers, 2001), are biased by the overall poor knowledge of the Unguiphora. Bruggemans (1986) pointed at synapomorphies among Ciliopharyngiella and Unguiphora in the development and ultrastructure of the stylet. Unfortunately, the genus Ciliopharyngiella is still poorly known. It includes at present two species: the type species, C. intermedia and C. constricta, which is the only one sequenced."
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