Abstract: Despite the identification of several species within the Xenocriconemella macrodora species complex in recent years, it is likely that even greater species diversity exists within this group. In the present study, a population of ring nematodes was collected from forested regions in northern Iran, exhibiting a high degree of morphological similarity to X. macrodora and related taxa. Morphological, morphometric, and molecular analyses, conducted using an integrative taxonomic approach, confirmed the presence of a novel species: Xenocriconemella persica sp. nov. Only females were observed, suggesting parthenogenetic reproduction. The species is characterised by a bare body measuring 234–316 μm in length. The lip region comprises two annuli that are continuous with the body contour, with the second annulus enclosed by the first. The stylet is slender and flexible, measuring 83–103 μm, and constitutes 28.4–37.0% of the total body length. The excretory pore is situated 1–9 annuli anterior to the stylet knobs, at a distance of 83–100 μm from the lip region. The female reproductive system is monodelphic and prodelphic, occupying 30.2–46.1% of the body length, with the vagina slightly curved ventrally. The anus is located 6–9 annuli from the tail terminus, and the tail is short, conoid, and bluntly rounded. Ribosomal and mitochondrial markers (D2-D3 expansion domains of 28S, ITS, partial 18S rRNA, and COI), together with phylogenetic analyses, revealed that this species occupies a distinct evolutionary position relative to other members of the X. macrodora complex. The findings indicate the presence of a cryptic species within this group, which, despite morphological resemblance, exhibits clear genetic divergence from closely related taxa. This study contributes to our understanding of hidden diversity in morphostatic taxa and underscores the significance of molecular data in species delimitation.
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