RESULTS

Geographic and Geological Setting. Jatun Uchco (Quechuan for "The Big Hole") is a network of caves that penetrates cliffs overlooking the city of Ambo, Perú in the Departamento de Huánuco (South 10° 07' 55", West 76° 12' 07") at an elevation of 2,150 m (about 7,050 ft above sea level) (Figure 2). Although residents of the region have known of these caves for centuries, the fossils were only discovered in 2001 (personal communication with Iván Solano, Figure 1). This was accomplished largely by Iván Solano Beteta of Ambo, who (with several friends) explored beyond dangerous passageways into the deeper galleries where he found fossils. He reported his findings to local and national authorities, which then lead to our fieldwork.

Prospecting for fossils and mapping (Figure 3) occurred from the lower entrance of Jatun Uchco, which led to the Gran Galería, one of the fossil localities (JU 1). Several narrow passageways extend outward from the Gran Galería. These include Área del Perezoso (JU 2), which leads to a lower fossil-producing area we refer to as Bajo Área del Perezoso (JU 3). Below JU 3 is a hole that produced fossils of a baby sloth. That area is denoted as Wawawasi (Quechuan for nursery) (JU 4). Still lower, in a remote part of the cave reached by Miguel Custodio Martel and our spelunking specialists (P.B. and J.-L. G), is a fossil producing locale we refer to as Sitio Miguel (JU 5). Another large tunnel leads from the Gran Galaría. This hole, named Pozo Hondo, includes the localities Pozo Hondo: Repisa (JU 6), which overlies Pozo Hondo: Zona Principal (JU 7) and Pozo Hondo: Zona Lateral (JU8).

Fauna. The mammal fauna we recovered from Jatun Uchco includes six species of carnivorans (puma [Puma sp. cf. P. concolor], saber cat [Smilodon populator, Figure 5.1-2], a large extinct, unnamed felid allied to jaguar [Panthera onca], Andean fox [Lycalopex sp.], and skunk [Conepatus sp.]), at least three species of bats, and specimens from several individuals of the enigmatic sloth, †Diabolotherium nordenskioldi, including associated partial skeletons of two individuals (Figure 4.1-2) from Área del Perezoso (JU-2). Also, a few bird bones were recovered. These bones include those of an owl and a vulture, Coragyps sp. (See Table 1, Figure 4, Figure 5. and Figure 6, and Discussion.)

Flora. Analysis of pollen and spores suggests that cacti were the most common plant of the region at the time of deposition. (See Table 2.) Amaryllidaceae (flowering monocots that grow from bulbs, like lilies and daffodils) and Thymelaceae (shrubs and trees of fibrous bark) also were present.

Age. We were unable to obtain collagen of appropriate quantity or quality to obtain reliable radiocarbon ages from any of the bones sampled from Jatun Uchco. These included bones from both extinct taxa (e.g., †Diabolotherium, †Smilodon) and extant (e.g., Puma concolor). Thus, we still have no ¹⁴C age to report for the Jatun Uchco fauna. The presence of the extinct taxa suggests that at least some of the fossils from Jatun Uchco are of Pleistocene age.

Cueva Roselló

Geographic and geological setting. Cueva Roselló is located in the Departamento de Junín at South 12° 14' 51'' and West 75° 22' 34'', about 26 km southwest of Huancayo, Perú (but a two hour drive, owing to the terrain) and 5 km southeast of the pueblo of Yanacancha at an elevation of 3,875 m (12,713 ft). The cave was discovered during travertine mining operations when it was fortuitously opened. The general manager of the mine, Gonzalo Roselló, discovered great quantities of fossils scattered about the cave floor (Figure 7) and donated them to the MUSM.

Fauna. The composition of the vertebrate fauna of Cueva Roselló is distinct from that of the other caves discussed in the dominance of ungulates, including vicuña (Vicugna sp.) (Figure 7), an extinct horse (†Onohippidium devillei = Hippidion devillei) (Figure 8), and a couple of deer (cf. Pudu sp. and cf. Hippocamelus). Remains of carnivorans included several partial skulls and jaws of Puma sp., the Andean fox, Lycalopex sp. (e.g., Figure 6), and a jaw of the hognose skunk, Conepatus sp. Sloths were uncommon, but a partial skull and jaws of a juvenile †Scelidodon sp., postcranial elements of a subadult mylodontid, cf. †Scelidodon sp., and fragmentary remains of †Diabolotherium sp. were recovered.

We specifically refer the extinct horse to Onohippidium devillei. The mean length and width of our sample of Onohippidum metatarsals (n=4) of Cueva Roselló was nearly identical to those reported by MacFadden for †Onohippidium devillei from Tarija, Bolivia, the type locality of O. devillei (Gervais 1855, MacFadden 1997). The Roselló horse metatarsals III had a mean length of 191 mm and mean mid-shaft width of 31.7 mm; those from Tarija were 191 mm and 32.4 mm, respectively (MacFadden 1997).

Flora. No pollen was found in sediment samples of the Cueva Roselló. However, spores of the club moss Lycopodium were fairly common (Table 2).

Age. Collagen was extracted from two bone samples from Cueva Roselló and submitted for AMS radiocarbon dating. The bone sample of metcarpal III of †Onohippidium devillei yielded a conventional radiocarbon age of 23,340 ± 120 BP (Table 3). That of a metacarpal of Vicugna sp. yielded a conventional radiocarbon age of 22,220 ± 130 BP (Table 2), which significantly extends the record of vicuña in the Altiplano by over 10,000 years. (Previously, vicuña were thought to have migrated to the Altiplano around 12,000 to 9,000 years ago [Marin et al. 2007 and references within].)

Trigo Jirka

Geographic and geological setting. Trigo Jirka is a large opening of shallow depth in cliffs about 300 meters above the Río Marañón (Figure 9), near Huacaybamba, Departamento de Huánuco, South 9° 7' 36", West 76° 47' 48" at an elevation of 2700 m (8,868 ft). Fossils in this shallow cave were first discovered by Don Magno (Figure 1), who brought these fossils to the attention of R. S.-G.

Fauna. Remains of two extinct sloth species were recovered from Trigo Jirka. These are referable to †Diabolotherium nordenskioldi and †Megatherium sp. Remarkably, a ungula phalanx of Diabolotherium retains the protein keratin covering, despite its relatively great antiquity (see below).

Flora. Over 20 species of plants were identified from pollen and spores recovered from the ancient dung, possibly that of a large sloth (Table 2). Most of the pollen is that of Alnus sp., the Andean alder of the birch family, Betulaceae. There were also many spores of club moss (Lycopodium), ferns, and fungi.

Age. Accelerator mass spectrometry of collagen recovered from a distal phalanx of the sloth †Diabolotherium (Figure 4.3) yielded a conventional radiocarbon age of 29,140 ± 260 BP (Table 3).

Due to the presence of human and other archaeological remains at Trigo Jirka, we limited our field studies to making preliminary superficial examinations of trenches that had already been dug by locals. The profiles of these trenches showed a thin superficial layer of fine sediments that covered a deeper layer that contained plant material, including maize. Underlying the plant layer was a layer of dung that was a half-meter deep in places. Some of this dung retained a form that suggested it came from a very large animal. The vertical nature of the surrounding terrain makes it unlikely that a proboscidian was the source of the half-meter deep layer of defecations (even us less climbing challenged humans had some difficulty getting to the cave), so we suspect that a large sloth may have been the source of the feces.

Excepting those remains that had been previously recovered by locals and left upon the surface, all sloth fossils we encountered were below the level in which the maize was observed. Señor Magno had previously recovered a claw of †Diabolotherium and he indicated that it, too, came from below the archaeological level. Its radiocarbon age of 29,140 ± 260 BP is consistent with Señor Magno's recollection of its level of occurrence.