Analysis of the genus Gymnodampia (Acari: Oribatida), with redescription of G. setata and description of two new species from North America

Morphology, distribution, and habitat data are presented for three species of the oribatid mite genus Gymnodampia Jacot occurring in North America. A revised generic diagnosis is given and the type species Gymnodampia setata (Berlese) is redescribed based on topotypic material from Missouri. Immatures of G. setata are described and aspects of their biology are presented. Two new species from North America, G. jacotisp. nov. and G. lindquistisp. nov., are proposed and described on the basis of adults, and a key is given for North American species of Gymnodampia. The ameroid genera Cristamerus Hammer, from Pakistan and China, and Defectamerus Aoki, from Japan, Korea, and China, are considered junior synonyms of Gymnodampia, and G. conformis (Fujikawa) is considered a junior synonym of G. fusca (Fujikawa). Immatures of G. setata are apheredermous, but with a circular line of dehiscence, whereas known immatures of the superfamily Ameroidea are eupheredermous. Nonetheless, without convincing apomorphic traits linking Gymnodampia to any known apheredermous family of Brachypylina, we hypothesize that Gymnodampia has lost the eupheredermy characteristic of Ameroidea, and we place it in the family Ameridae on the basis of adult similarities.