The genus Dolichodorus was discovered from a natural forest in Gilan province, north Iran, in association with an oak tree. The recovered population represents a new species, and was described and illustrated based upon morphological and molecular data, as D. rex n. sp. It is characterized by 2171–3275 μm long females having offset crown-like cephalic region with well sclerotized cephalic framework, raised perioral disc apparently with a small raised oral plate, 118.5, 130.0 μm long stylet, its conus ca. 55% of the total length and three posteriorly sloping knobs, 291–316 μm long pharynx with a short overlap, secretory-excretory pore at slightly variable position (one-two annuli posterior, or four annuli anterior to metacorpus base), vulva sunken in body, at %50 of the body length, vagina heavily sclerotized with two drop-like refractive pieces close to the vulval opening, 78–104 μm long tail with proximal convex conoid, and conical distal part with pointed to blunt tip; and a 2634 μm long male with 108.5 μm long stylet, 291 μm long pharynx, 20 μm long tail and 53 μm long spicules. In molecular phylogenetic analyses using partial sequences of the small, and D2-D3 expansion segments of the large subunit ribosomal DNA, the new species formed a clade with two other currently sequenced species of the genus in both phylogenies.

属Dolichodorus是从天然森林吉兰省，伊朗北部，在伴随橡树发现。回收的种群代表一个新物种，并根据形态和分子数据进行了描述和说明，称为D. rex。sp。它的特征是长2171–3275μm的雌性，具有偏移的冠状头状区域，具有良好的硬化性头颅骨架，显然是口周盘隆起，带有小的隆起的口腔盘，长118.5，长130.0μm，探针圆锥。总长度的55％和三个向后倾斜的结节，咽长291-316μm，重叠短，分泌-排泄的毛孔在稍有变化的位置（后壁1-2个环，或meta骨基底部的前4个环），外阴凹陷身体，在体长的50％处，阴道严重硬化，在靠近外阴开口处有两个液滴状的折射片，尾巴长78-104μm，近端呈凸状圆锥形，圆锥形的远端具尖端钝头。长2634μm的雄性，长108.5μm的探针，291μm的咽，20μm的尾巴和53μm的针头。