Vol. 21, No. 4 Internal. J. Acarol. 253 PALEOZERCON CAVERNICOLUS, N.GEN., N.SP., FOSSIL MITE FROM A CAVE IN THE SOUTHWESTERN U.S.A. (ACARI, GAMASIDA: ZERCONIDAE), WITH A KEY TO NEARCTIC GENERA OF ZERCONIDAE Czeslaw Blaszak , James C. Cokendolpher , and Victor J. Polyak 7. Department of Animal Morphology, A. Mickiewicz University, Szamarzewskiego 91A, 60-569 Poznan, Poland (e- mail: Blaszak%plpuaml l@plearn.edu.pl). 2. Department of Biology, Midwestern State University, Wichita Falls, Texas 76308, U.S.A. (e-mail: jccoke@aol.com). 3. Department of Geosciences, Box 41053, Texas Tech University, Lubbock, Texas 79409-1053, U.S.A. (e-mail: aqvjp@ttuvml.ttu.edu). ABSTRACT - A new genus and species of zerconid mite, Paleozercon cavernicolus, is described from a cave in southeastern New Mexico, U.S.A. The mites were preserved (probably during the late Pleistocene) after being entrapped in mineralized waters and coated by calcium carbonate on the surface of an active stalagmite. This is the first record of a fossil zerconid as well as the first record of the family from a cave in the New World. A taxonomic key (based primarily on females) to the genera of Zerconidae from the Nearctic Region is provided. INTRODUCTION Among fossil material recovered by digesting car- bonate speleothems by Polyak and Cokendolpher (1993) were six zerconid mites. Although each specimen is im- perfect, there is no doubt that they represent the same undescribed species. All features necessary for recogni- tion of a new genus are also present. Our purpose is to name these taxa and to provide a taxonomic key to the zerconid genera (based primarily on females) of the Nearctic Region. MATERIALS AND METHODS The mites were digested from a calcium carbonate stalagmite with 5% hydrochloric acid and mounted on microscopic slides with CMC-10 medium as outlined by Polyak and Cokendolpher (1993). The description is based on a composite of the six available specimens. The holotype was drawn and the missing setae and pores were added from the other speci- mens. Setal and gland numbering are illustrated in Blaszak, 1974, 1981b. Measurements are given in mi- crometers (u.m). SYSTEMATICS Paleozercon, gen. nov. Type-species - Paleozercon cavernicolus, sp. nov. Diagnosis - Peritremal shield with posterolateral ends extending beyond bases of setae R5. Peritremal shields with two smooth setae, pi short, p2 twice as long as seta pi. Aggenital glands gv2 present. Lateral margins of opisthonotum with eight pairs of setae (Rl -R8). Ante- rior margin of ventroanal shield with one pair of setae. Etymology - The generic name is from the Greek Paleo, meaning ancient, and the generic name Zercon. It is masculine in gender. Systematic position - Paleozercon belongs to the group of the genera with aggenital glands gv2 and with peritremal shields with posterolateral ends which extend beyond bases of setae R3. Xenozercon Blaszak, 1976b, differs from the new genus by having a deep incision in the peritremal shield which reaches to the level of seta r6, and two pairs of setae on anterior margin of the ven- troanal shield. The new genus lacks the incision and only