Figure 8 in The search finds an end: the morphologically chimeric hysterocinetids belong to the subclass Hymenostomatia (Ciliophora: Oligohymenophorea)

Figure 8. Phylogenetic tree based on the nuclear 18S rRNA gene and mitochondrial COI sequences, showing the phylogenetic position of hysterocinetids within the subclass Hymenostomatia. Ichthyophthirius multifiliis was used as an outgroup, following Zhang and Vďačný (2022). Posterior probabilities for Bayesian inference conducted in MrBayes and bootstrap values for maximum likelihood conducted in IQ-Tree were mapped onto the 50%-majority rule Bayesian consensus tree. Fully statistically supported nodes are marked with red solid circles. The scale bar denotes two substitutions per 10 nucleotide positions. The oral apparatus of tetrahymenids is morphologically plastic (right inset). Most species have maintained the plesiomorphic condition, while some have completely lost the oral apparatus (Clausilocola) or have evolved a highly complex, peritrich-like oral ciliature that was displaced posteriorly (hysterocinetids). Diagrams of Tetrahymena and Clausilocola in the right inset are from Zhang and Vďačný (2022, 2023).