The widespread Leodamas chevalieri (Annelida, Orbiniidae) revealed as a species complex, with descriptions of a new species and a new record for the Arabian region.

Leodamas chevalieri, the only Leodamas species reported in the Arabian region, was originally described from Senegal, western Africa. In this work, the morphological and genetic (COI and ITS2) variation of several populations of Leodamas from different localities in Kuwait, Oman, and western Africa were analyzed. The type material of L. chevalieri is described, and molecular data provided for specimens collected close to the type locality. Based on the molecular analysis, at least twelve lineages were recognized in the studied area (eight in the Arabian region and four in the western Africa), with L. chevalieri being a species complex composed of at least eleven lineages. The species name Leodamas chevalieri is assigned to the lineage found close to the type locality, restricting the species distribution to the coastal areas of Senegal. One lineage from off Kuwait was described as a new species, Leodamas edgari sp. nov., differing from L. chevalieri in fine chaetal characters. Another lineage was identified as Leodamas gracilis, originally described from Sri Lanka, representing a new record of this species for the Arabian region. Further investigation is needed to describe or to name the other lineages belonging to the L. chevalieri species complex. With the description of L. edgari sp. nov., the genus comprises 31 species worldwide. However, the number of discovered genetic lineages in this study indicates a high proportion of undescribed species diversity in the genus.