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Show The best- dated, best- stratified, and richest small mammal assemblage now available from the Great Basin comes from Homestead Cave, located on a northern spur of the Lakeside Mountains not far west of the Great Salt Lake and adjacent to the playa of Pleistocene Lake Bonneville. The deposits within this cave began accumulating about 11,300 years ago; the sequence as a whole covers the latest Pleistocene and virtually the entire Holocene. Although work on the mammals provided by this sequence is still underway, some 170,000 specimens have been identified to at least the genus level, with excellent coverage now available through the Middle Holocene and for the latest Holocene. As a whole, the Homestead Cave fauna provides a detailed account of changes in the local mammalian community, both in terms of taxonomic arrivals and extinctions, and in terms of changing relative abundances of mammals through time. The latest Pleistocene and earliest Holocene record from Homestead Cave documents that during this period of time ( ca 11,300 to 8,300 yr BP), marmots ( Marmota flaviventris), bushy- tailed woodrats ( Neotoma cinerea), pygmy rabbits ( Brachylagus idahoensis), Great Basin pocket mice ( Perognathus parvus), and Ord's kangaroo rats ( Dipodomys ordii) were common in the Homestead Cave area, though more common toward the beginning of this period than toward the end ( see figures) . All of these taxa became locally extinct, or nearly so, during the Middle Holocene. Taken as a group, these animals document the local presence of habitats dominated by big sagebrush ( Artemisia tridentata), on which pygmy rabbits, for instance, are dependent. In addition, they strongly suggest a climatic regime that was both moist ( as the models suggest) and cool ( as the models do not) . The local extinction, or near extinction, of each of these species suggests both the loss of sagebrush habitat ( as witnessed, for instance, by the near replacement of Ord's kangaroo rat by the chisel- toothed kangaroo rat, Dipodomys microps) and increasing aridity as the Middle Holocene is approached. In general, the earliest Holocene mammal assemblages from Homestead Cave strongly suggest, and are certainly fully consistent with, a cool and moist climatic regime. Homestead Cave thus joins other Early Holocene small mammal sequences from the Great Basin, including those that document the presence of pikas ( Ochotona princeps) in low elevation settings at this time, in suggesting that Early Holocene climates in at least the more northern parts of the Great Basin were cool and moist. If the models suggesting otherwise are correct, the challenge becomes explaining how mammals that today tend to be found either at far higher elevations within the Great Basin or at comparable elevations to the north could have existed at low elevations under temperature conditions warmer than modern. Ecological work from other desert contexts demonstrates a correlation between species richness and available moisture: the wetter an arid setting, the more species of mammals supported by that setting. Given that both the models and the mammalian data suggest that the latest Pleistocene and Early Holocene of the Great Basin was wetter than what came later, it follows that Great Basin mammal faunas from this period of time should also |