Analysis of primary structure loops from Hairpins 35 and 48 of the Nematoda SSU rRNA gene provides further evidence that the genera Tripylina Brzeski, 1963, Trischistoma Cobb, 1913 and Rhabdolaimus de Man, 1880 are members of Enoplida

A comparison of small subunit (SSU) rDNA sequences has revealed that a rare nucleotide transition A→G and a trans-version G→Y occurred simultaneously in the evolutionarily conserved loops of Hairpins 35 and 48 of the SSU rRNA geneof Tripylina Brzeski 1963, Trischistoma Cobb 1913 and Rhabdolaimus de Man 1880. The same pair of substitutions oc-curred in all Enoplida analysed but not in other nematodes. This evidence from the primary structure of Hairpins 35 and48 indicates that Tripylina, Trischistoma and Rhabdolaimus are members of Enoplida, supporting previous phylogenetic analyses.