The genus Stammericaris Jakobi (Copepoda: Harpacticoida: Parastenocarididae) in the Nearctic subregion: description of Stammericaris remotaepatriae sp. nov., proposal of Stammericaris palmerae (Reid 1992) comb. nov., and remarks on other North American Parastenocarididae.

We describe a new harpacticoid, Stammericaris remotaepatriae sp. nov., collected from the hyporheic habitat of a stream in Nantucket, MA, USA. The new species is characterized by the size of the caudal rami of both sexes, which are shorter than the anal somite, by the morphology and armature of the P3 and, mainly, by the P4 endopod of males, represented by a curved plate with a strongly bifid tip, the distal proximal outgrowth of the distal margin spiniform and denticled, the proximal outgrowth missing. The study of the new species allowed us to review the systematic position of Parastenocaris palmerae Reid, 1992, which we transferred to Stammericaris Jakobi, 1972 as Stammericaris palmerae (Reid, 1992) comb. nov., based mainly on the structure of the male P4 endopod complex and the setation of the caudal rami. We also discussed the taxonomic position and affinities of Parastenocaris trichelata Reid, 1955, suggesting that this species is related to the two former ones for a set of diagnostic features, but can not be attributed to the genus due to the peculiar morphology of the male P4 endopod complex; P. trichelata is therefore considered species inquirenda. We also discussed Parastenocaris sp. 1 and Parastenocaris sp. 3, two taxa only partially described and drawn in Strayer (1988). In fact, Parastenocaris sp. 1 can be related to Stammericaris and might represent a third species of the genus in the Nearctic region. Remarkably, the structure of the male P4 endopod of Parastenocaris sp. 3 is typical of Proserpinicaris Jakobi, 1972; this hypothetical assignment of the species to Proserpinicaris, if confirmed, would be of relevant taxonomic and biogeographic value. Finally, we provide an updated distribution map of the genus Stammericaris and brief remarks on the faunistic and ecological characteristics of the taxa presented and discussed in this paper.