The genus Pilumnus covering a large group of bristle crabs, a typical resident of rocky, cobble and coral habitats. Taxonomy of the genus in the Persian Gulf and Gulf of Oman have always been source of disagreement among specialists due to potential taxonomic uncertainty in the genus. We used combined morphological and molecular characteristics to provide an insight into the real diversity within this genus. Partial fragment of two mitochondrial genes (COI and 16S rRNA) and one nuclear gene (H3) were used for molecular analyses. Both Bayesian and Maximum likelihood methods estimated a similar tree topology with highly supported clades. The tree showed the occurrence of two groups including the Atlantic and Indo-West Pacific species. Our result showed that there is a well consistency between morphological and molecular characteristics at interspecific level. Five species were identified from the Persian Gulf and Gulf of Oman, including P. incanus, P. longicornis, P. savignyi, P. persicus n. sp. and P. parvusi n. sp. Pilumnus persicus n. sp. is closely related to P. minutus, which has been already recorded from the region, but it is described here as a new species; according to current morphology and molecular data. Pilumnus parvusi n. sp. differed from the other congeners occurring in the Persian Gulf, whereas it is genetically presented as sister clade to the Atlantic species group.

Pilumnus属覆盖了一大群硬毛蟹，是多岩石，卵石和珊瑚栖息地的典型居民。由于属中潜在的分类学不确定性，波斯湾和阿曼湾的属的分类学一直是专家之间分歧的根源。我们结合了形态和分子特征，以深入了解该属中的真正多样性。使用两个线粒体基因（COI和16S rRNA）和一个核基因（H3）的部分片段进行分子分析。贝叶斯方法和最大似然方法都估计了具有高度支持进化枝的相似树形拓扑。该树显示了包括大西洋和印度西太平洋物种在内的两组物种的发生。我们的结果表明，在种间水平上，形态和分子特性之间具有良好的一致性。P. incanus，P. longicornis，P. savignyi，P. persicus n。sp。和P. parvusi。sp。Pilumnus persicus ñ。sp。与该地区已经有记录的小体育假单胞菌密切相关，但在这里被描述为一个新物种。根据目前的形态学和分子数据。Pilumnus parvusi ñ。sp。与波斯湾的其他同类动物不同，而从基因上讲，它是大西洋物种组的姊妹进化枝。