INTRODUCTION

For the greatest part of the Cenozoic (the last 65 million years), South America has been an isolated continent, home to a peculiar endemic fauna that consisted mostly of marsupials, xenarthrans (armadillos, glyptodonts, anteaters, and sloths), and several groups of the now extinct native "ungulates" (Simpson 1980). This "splendid isolation" ended about three million years ago with the formation of the Panamanian land bridge that now connects South and North America (Stehli and Webb 1985). This resulted in a mixing of the faunas of both continents that reached its peak diversity after the beginning of the Great American Biotic Interchange (GABI), but before the late Pleistocene megafaunal extinctions 10-15,000 years ago.

Recent discoveries of new cave faunas in the Andes of central Perú provide rare opportunities to sample mammals from this post-GABI / pre-megafaunal extinction period (Salas and Stucchi 2005; Anonymous 2006; Shockey et al. 2007; Figure 1). Their location is particularly fortuitous because these caves preserve samples of Pleistocene mammals from low latitudes (from 9° to just over 12° South), whereas much of the knowledge of Pleistocene South America comes from high latitude localities in Argentina (>30°). The drier conditions and cooler temperatures at high elevation negated the usual disadvantage of low latitude Pleistocene fossils—the destruction of organic molecules in warm and humid environments (Austin et al. 1997; Wayne et al. 1999). Also, the location of the fossils within the ground provided some protection against damaging ultraviolet radiation.

Most Pleistocene fossils known from the Andes of Perú have come from caves (Pujos and Salas 2004; Salas and Stucchi 2005). Gervais (1855) reported fossils from Sansón-Machay near Cerro de Pasco in the central Andes, and Nordenskiöld (1908) reported and described remains of various taxa from Casa del Diablo Cave located on the Altiplano of southern Perú at 3,819 m. Other Peruvian Andean cave faunas include Santa Rosa, near Celdín, in northern Perú (Pujos 2002); Huargo Cave in the Departamento de Huánuco, central Perú (Cardich 1973); Tres Ventanas in the Departamento de Lima at about 4,000 m, and Pikimachay cave in the Ayacucho Valley at 2,800 m (see Pujos and Salas 2004 for a summary of these and other Andean faunas of Perú). Of these, only a few have been radiometrically dated. These include Tres Ventanas, with a ¹⁴C age estimated to be greater than 40,000 BP (Engel 1970); Huargo, cave bed 8, with a ¹⁴C age of 13,490 ± 700 BP (Cardich 1973); and Pikimachay with ¹⁴C age estimates of 14,150 ± 180 and 19,620 ± 3,000 BP (McNeish et al. 1970). As far as we know, no previous radiocarbon analyses of Andean faunas of Perú were accomplished using accelerator mass spectrometry (AMS).

The purpose of this work is to summarize the results of our field studies of the three caves that contain Pleistocene faunas (a fourth cave that contained remains of a mid-Holocene spectacled bear, Tremarctos ornatus, is documented elsewhere [Stucchi et al. 2009]). This summary includes the basic locality data for the caves, a faunal list of taxa recovered with figures of some of the more instructive specimens, results of radiocarbon dating from bone samples from two of the caves, and a list of plant taxa of which pollen or spores were found in sediment or fecal samples. We also provide previews of recently completed and pending ancient DNA studies.

Limitations of the present study include the permitting constraints that allowed only surface collections and our desire to avoid disturbing any archaeological material. Detailed analyses regarding particular taxa are deferred for forthcoming studies that involve other investigators.