Morphological and phylogenetic analyses of Stephanurus dentatus reveal close relationships with the Chabertiidae family and new insights into Strongyloidea phylogeny.

The parasitic nematode Stephanurus dentatus has been documented in Brazil and other tropical regions, where it has been linked to significant economic losses in pig and wild boar populations. Despite its evident relevance, detailed morphological descriptions are scarce, and its current classification within the Syngamidae family has recently been called into question by mitochondrial data. This study takes an integrative taxonomic approach, combining morphological characterisation using light and scanning electron microscopy with a phylogenetic analysis based on concatenated 18S and ITS sequences from 45 Strongylida species. We describe in detail the morphology of this parasite, including distinct features in copulatory structures and tail morphology. Our results support the positioning of S. dentatus in the Chabertiidae, reinforcing the paraphyly of Strongyloidea.