A new species of alpheid shrimp tentatively assigned to Salmoneus Holthuis, 1955 (Decapoda: Caridea) from the Ryukyu Islands, Japan

A new alpheid shrimp species, provisionally assigned to the genus Salmoneus Holthuis, 1955, is described and illustrated on the basis of three specimens extracted from intertidal soft sediments on seagrass beds at Iriomote Island, southern Ryukyu Islands, Japan. Salmoneus singularis n. sp. is highly distinctive within the genus in having a pair of postorbital spines on the carapace, otherwise showing some affinities to the species of the S. gracilipes Miya, 1972 group. The possession of paired spines on the dorsolateral surface of the carapace is shared with several members of Triacanthoneus Anker, 2010, which is undoubtedly closely related to Salmoneus. However, the new species cannot be placed in Triacanthoneus because of the absence of a mid-dorsal spine on the carapace.