Echinocephalus persicus n. sp. (Nematoda: Spirurida: Gnathostomatidae) from Two Batoid Hosts, Pastinachus sephen and Urogymnus asperrimus, off Southern Iran

Adult nematodes of the genus <i>Echinocephalus</i> were recovered from the intestines of two batoid species-<i>Pastinachus sephen</i>, collected from both the Persian Gulf and the Gulf of Oman, and <i>Urogymnus asperrimus</i>, collected from the Persian Gulf. Detailed morphological analyses were conducted using light and scanning electron microscopy. Based on the number, arrangement, and size of caudal papillae, along with other morphological and quantitative traits, the specimens were clearly distinguishable from previously described congeners. Consequently, <i>Echinocephalus persicus</i> n. sp. is formally described and added to the genus. With this addition, the total number of valid <i>Echinocephalus</i> species rises to 13, four of which are known from the Indian Ocean, restricted to the coastal waters of India, Sri Lanka, and Iran. Notably, <i>Urogymnus asperrimus</i> hosts four of the four known <i>Echinocephalus</i> species from the Indian Ocean-including three from Sri Lankan waters and one from southern Iran-suggesting that this batoid may represent a species complex and thus warrants further taxonomic reassessment. In addition, the external anatomy of the amphid was discussed across the genus. Observations of fixed specimens of <i>E</i>. <i>persicus</i> n. sp. indicate that intraindividual comparisons of cervical sac length should be made with caution due to potential variability among the four sacs.