Abstract Deladenus longicaudatus n. sp. was recovered from decaying wood of a broad-leaf forest tree in the forests of Javaherdeh, Mazandaran province, northern Iran, and is herein described and illustrated based upon morphological, morphometric, and molecular characters. The new species is mainly characterized by its small to medium body size of free-living mycetophagous females (523–682 µm long) with an elongate conical tail (c = 9.3–11.0 and c′ = 3.9–5.3), a relatively anterior vulval position (V = 84.5–89.0%), the pharyngo-intestinal junction at the level of the nerve ring, the secretory–excretory pore (S–E pore) posterior to the nerve ring, and at the same level as the hemizonid. It is further characterized by seven incisures in the lateral fields, a short stylet (5.0–6.5 µm), small lateral vulval flaps, and absence of a postvulval uterine sac (PUS). By having similarities in tail shape, c′ ratio greater than 3, posterior position of the S–E pore and hemizonid to the nerve ring, and lack of PUS, the new species is comparable to four known species of the genus, namely, D. gilanica , D. hyrcanus , D. zyzyphus , and D. parvus . It is furthermore typologically comparable to mycetophagous phase of Hexatylus vigissi . In molecular phylogenetic analyses using partial small and large subunit (SSU and LSU D2-D3) rDNA sequences, the SSU sequences of the new species formed a moderately supported clade with sequences of Howardula spp. In LSU phylogeny, the newly generated sequences of the new species formed a clade with corresponding sequence of D. hyrcanus .
Salemi et al. (Thu,) studied this question.