NORTH-AMERICAN SPECIES OF NEOMAMERSINAE LUNDBLAD (ACARI, HYDRACHNIDA,LIMNESIIDAE)

Morphological, distributional, and habitat data are presented for Nort h American species of the three genera of the subfamily Neomamersinae, Neomamersa Lundblad, 1953, Arizonacarus gen.nov., and Meramecia Cook, 1963. Neomamersa lundbladi lundbladi Cook, N. lundbladi paucipora Coo k, and N. hexapora Cook are redescribed based on examination of types and newly collected specimens, and six new species of Neomamersa from the United States are described, namely N. boultoni sp.nov., N. psammi cola sp.nov., N. californica sp.nov., N. chihuahua sp.nov., N. neomexi cana sp.nov., and N. cramerae sp.nov. Arizonacarus chiricahuensis gen. nov., sp.nov. is described from the southwestern United States. Merame cia (Meramecia) anisitsipalpis (Cook), M. (Meramecia) perplexa (Cook), and M. (Meramecia) ocularis (Cook) are redescribed based on study of types and newly collected specimens, and M. (Meramecia) occidentalis s p.nov. is described from the western United States. Meramecia (Paramer amecia) multipora subgen.nov., sp.nov. is also described from the sout hwestern United States. Revised diagnoses, keys, and distribution maps are presented for all North American taxa. Phylogenetic relationships of Neomamersinae are discussed, leading to the conclusion that compre hensive reassessment of the families Limnesiidae and Anisitsiellidae i s warranted. Consideration of available phylogenetic and distributiona l data suggests that Neomamersinae originated in Gondwanaland before t he separation of India from the rest of the southern supercontinent. S ubsequently, the clade evolved and diversified extensively in South Am erica. Neomamersinae apparently first entered North America either by crossing a ''filter bridge'' during late Cretaceous, Paleocene, or Mio cene times or by traversing the corridor established with the formatio n of the Panamanian Isthmus during the late Pliocene. The group exhibi ts considerable taxonomic diversity in hyporheic and groundwater habit ats in the United States, and the various species represent potentiall y useful indicators of water quality and the impact of environmental c hanges on freshwater communities.