Liropus tenebris, a new species of caprellid (Crustacea: Amphipoda) from the middle mesophotic zone of Bahía de Banderas, Mexican Pacific.

A new species of the genus Liropus Mayer (Caprellidae) is described based on material collected from the middle mesophotic zone of southern Bahía de Banderas, Jalisco, Mexico. Specimens were found associated with gorgonians and sponges from a vertical rocky wall at 60-70 m depth. The new species, Liropus tenebris sp. nov., can be distinguished from all its congeners mainly by a head without projections; eyes present but not clearly distinguishable; antenna 1 flagellum five-articulate; antenna 2 flagellum two-articulate; body dorsally smooth; pereonite 2 with a pair of anterolateral projections in males; gnathopod 2 basis slightly curved, smooth as long as pereonite 2; pereopods 3 and 4 one-articulate; pereopod 5 two-articulate; abdomen without appendages in males. This is the fourth species of Liropus recorded in the Mexican Pacific and the Eastern Pacific.