Diastylis fabrizioi, a new species and brief redescription of D. planifrons Calman, 1912 (Crustacea: Cumacea: Diastylidae) from South America

摘要

A new cumacean from the southwestern Atlantic, Diastylis fabrizioi, is fully described. This species is closely allied to Diastylis planifrons Calman, 1912, whose description is also completed. D. fabrizioi n. sp. can be easily distinguished from D. planifrons by having: (1) a wide pentagonal figure on the posterior part of the female carapace (a narrower pentagonal figure in D. planifrons), (2) a uniformly arched outline of the plateau when the carapace is seen from above (interrupted by two prominent blunt projections in D. planifrons), and (3) a telson with two divergent cuspidate setae distally (in close apposition in D. planifrons). Specimens housing nicothoid copepods inside their branchial chambers were observed in both species herein studied. One of these infested branchial chambers also contained two cryptoniscus larvae (Isopoda, Epicaridea).