Abstract
During a survey on the members of the family Neotylenchidae in northern Iran, a population of Deladenus was recovered, which, based on the morphology and molecular characters, identified as a new species. Deladenus hyrcanus sp. n., was isolated from dead wood of Acer velutinum in Balaband forests, Mazandaran Province. Morphologically, the new species is characterized by the moderate body length of the mycetophagous females (718-806 μm) with c = 10.2-12.6, c' = 3.5-4.4 and V = 86-87, stylet length 7.5-10 μm with three small knobs inclined backward, the lateral field with 7-8 incisures, position of excretory pore at level of hemizonid or slightly posterior to it, lacking a post-uterine sac, elongate-conoid tail (58-72 μm), with rounded to pointed terminus and males not observed. According to similarities in general morphology, D. hyrcanus sp. n., resembles D. gilanica and D. zyzyphus; however, the new species is distinguished from them in body length, lateral field incisures, and tail length. It was furthermore compared with D. aridus, D. bonabensis and D. brevis, by similarities in the position of the excretory pore and hemizonid, posterior to the nerve ring, lack of a median chamber, and a conoid tail narrowing to a rounded to pointed terminus. Molecular phylogenetic analysis based on D2-D3 expansion domain of 28S rDNA placed the new species close to D. gilanica in a clade with 1.00 posterior probability. The measurements, line illustration, and LM photographs are provided for the new species.