摘要：A new deep-sea species of isopod is described and illustrated. The material was collected in soft substratum in the
Bay of Campeche, SW Gulf of Mexico, at a depth of 2,548 m aboard the research vessel “Justo Sierra” on September 4,
2009. Gracilimesus tzasnae sp. nov. can be distinguished from all other known species by its antennula with 5 articles;
uropod length vs. pleotelson 0.3×; pereonite 7 not reduced; pereopod 7 absent; pleotelson dorsal surface smooth and
not separated in lateral fields. The new species represents the first described Gracilimesus in the Gulf of Mexico. We
present a table with the most important diagnostic characters to separate all the known species of the genus Gracilimesus.
关键词：Bathyal zone; Benthos; Peracarida; Distribution; Morphology; Sediment; Species richness; Taxonomy
