Phylogenetic relationship of Oxyspirura petrowi within the Spirurida nematodes as determined by Bayesian inference (BI) and maximum likelihood (ML) methods based on 18S rRNA sequences from Spirurida and Ascaridida (112 taxa with 1,544 positions) (A) and from species more closely related to Thelazioidea (35 taxa with 1,599 positions) (B). In both approaches, the general time reversal (GTR) nucleotide substitution model was used with the consideration of fraction of invariance and 4-rate of discrete gamma (i.e., GTR + F
). Numbers at the nodes indicate posterior probability (BI) and bootstrap proportion (ML) supporting values. Nodes highlighted by dots were supported by >95% in both BI and ML bootstrapping analyses. Letter “x” indicates nodes supported by <50% in either BI or ML analysis.