We used a comparative morphological approach to define and describe a set of potentially informative characters and determine which are suitable for phylogenetic analysis of 64 species across putative genera. Forty-six structural characters were identified. Those are characters of anterior end including mouth parts, and genital organs of males and females.

Phylogenetic analyses were completed to provide resolution among groups of species. We developed hypotheses for character evolution (through taxonomic and functional outgroup comparisons). A complete morphological phylogeny of horse Strongylidae genera was preceded by analyses of a clade with 38 species, unresolved in molecular phylogenies. We obtained 181 equivocal trees from which a consensus tree was created. On all trees the genera Cyathostomum, Coronocyclus and Cylicocyclus are resolved as separate monophyletic groups. Cylicodontophorus, Tridentoinfundibulum and Cylicostephanus are presented in one common branch. The genus Petrovinema is quite separate from the above genera.