aAll depths listed are from same vertical profile.Values are midpoints of 3-centimeter depth ranges. bDiscrepancy with Y-1163B perhaps due to organic preservative. For more Cueva del Milodon dates, see Markgraf 1985.
aAll depths listed are from same vertical profile.Values are midpoints of 3-centimeter depth ranges. bDiscrepancy with Y-1163B perhaps due to organic preservative. For more Cueva del Milodon dates, see Markgraf 1985.
of Mormon tea (Ephedra) twig in one of Shutler's surface samples. The specimen was submitted to Thomas W. Stafford's Laboratory for Accelerator Radiocarbon Research, then in the Institute of Arctic and Alpine Research at the University of Colorado at Boulder. In a letter dated May 15, 1995, we received the following result from Stafford: "14C AGE— 10,940 ± 60 (CAMS-19997)." This meant there was a 95 percent chance that the age of the specimen fell between 10,820 and 11,060 radiocarbon years before the present, within the range of surface dates obtained in our second round (Long and Martin 1974). Possibly the original date (L-473A; see table 5) had incorporated a mixture of materials, with a small amount of postextinction packrat debris contaminating the youngest sloth dung.
The oldest of our 1969 results also suggested that the sloths first entered Rampart Cave more than 40,000 years ago. For some unknown reason, possibly high water in the Colorado River, they left around 32,000 years ago, abandoning the cave to packrats, marmots, mountain goats, and ring-tailed cats. Twenty thousand years later, the sloths returned. Then, judging by the rate of dung deposition between 13,000 and 11,000 radiocarbon years ago, they flourished right up to the time when deposition ceased. About 10,000 to 11,000 radiocarbon years ago, the Shasta ground sloth seems to have died out, not only at Rampart Cave and adjacent Muav Cave, but throughout its range, which included populations separated both geographically (Nevada to West Texas) and ecologically (the Mojave Desert to spruce woodland) (Martin, Thompson, and Long 1985).
One evening I perched at the mouth of Rampart Cave in a meditative mood. Over 12,000 years ago a Shasta ground sloth might have done the same. The sun sank behind canyon walls, enhancing a sense of sanctity. Shadows lengthened. Breezes of the day died down. In the stillness, the cool air of an early winter evening settled into hollows. I imagine myself as a ground sloth at the moment of arrival of the first people. I am lounging at the mouth of my cave. I have never seen these strange, two-legged creatures before and I have no knowledge of the danger they pose. To avoid cactus they lift their feet high as they stride along, like great blue herons stalking frogs. Now they see me, having discovered my spoor at the bottom of the slope. They raise their arms; every hand holds a rock or a club. I am defenseless against them, and this is the last thing I see.
We also used the Rampart Cave dung samples to further elucidate the ground sloth's diet, which soon became the best-known aspect of its ecology. (Extinct parasites were also found in the dung; Schmidt, Duszynski, and Martin 1992.) Shutler's samples had contained not only globe mallow and juniper pollen (see chapter 3), but also large amounts of pollen from Asteraceae (plants in the sunflower family). Eames (1930) had reported Asteraceae fragments in ground sloth dung at Aden Crater, New Mexico (see Aden Crater dates in table 5). But we wanted more detail. It was Norrie (Eleanora) Robbins, a Desert Lab student working on the diet of the extinct goat, who told me about Dick (Richard M.) Hansen and his composition analysis lab at Colorado State University. Dick investigated the composition of rumen or dung samples from cattle, bison, and other large herbivores, an excellent index to their diet. His method of particle analysis was an elegant technique for determining the forage consumption of living large herbivores. His laboratory maintained reference collections of native forage plants of the western region. He had trained staff who could identify fragments from the digestive tract or excreta of wild or domestic herbivores. Dick agreed to try his method on a sample of ground sloth dung. To our delight, we learned that the dung samples contained well-preserved and identifiable plant parts. We joined forces.
At Rampart Cave Dick collected 514 dung samples from appropriate units in the walls of the trench dug by Kellogg. Back in his lab he supervised microscopic analysis of plant parts recovered from samples of various ages. The lab confirmed that although the ground sloths might have ingested pollen of wind-pollinated species such as juniper, flower heads of creosote bush, and flowers or pollen of Asteraceae, they did not ingest much foliage of juniper or other oily plants (Hansen 1978). However, ground sloth dung collected at over 6,000 feet in the Guadalupe Mountains of West Texas (Van Devender and others 1977; Spaulding and Martin 1979) revealed, somewhat to my surprise, a diet of conifer needles (Douglas fir, genus Pseudotsuga). So did samples, potentially of ground sloth dung, from Cowboy Cave in Utah. These records suggest a wider range of foraging than those at Rampart Cave. They also demonstrate the glacial-age elevational descent of Douglas fir, which at present does not grow in the immediate vicinity of either Cowboy Cave or the sloth caves in the Guadalupe Mountains.
Further confirming our earlier fossil pollen analysis (Martin, Sabels, and Shutler 1961), Dick found that desert globe mallow (Sphaeralcea laxa) leaves or stem fragments made up on average half of the plant parts found in ground sloth dung at Rampart Cave (Hansen 1978). In addition, composition analysis indicated an average diet of 18 percent Mormon tea (Ephedra), with its distinctive, many-furrowed pollen grains; 7 percent saltbush (Atriplex); 6 percent catclaw acacia (Acacia greggii); 5 percent common reed (a tall aquatic grass, Phragmites); 2 percent yucca (Yucca sp.); and lesser amounts of other succulents, including cacti. Dick's laboratory also identified 65 other plant genera, presumably minor dietary items from "accidental bites." Except for Phragmites, Dick found no more than traces of grasses in the dung; these could have been "accidentals" (Hansen 1978).
Data from Rampart Cave and its environs subsequently generated more information on the ground sloth's diet and possible behavior. More generally, it expanded our understanding of the ecology of the region in glacial times. For example, from fossil midden contents, Art Phillips (1984) confirmed that the ground sloths relied heavily on globe mallow.
From contemporary packrat middens he also discovered that when ground sloths roamed the western end of the canyon, cool-adapted plant species were more numerous than at present. For example, juniper and single-leaf ash (Fraxinus anomala) are common plant fossils in packrat middens, indicating that junipers and ash trees or shrubs once grew near the cave mouth. Now juniper and ash grow at higher elevations or in wetter sites, and near the mouth of the cave one finds only the shrubs and cacti of Mojave desertscrub.
Recent work on a ground sloth dung ball from Gypsum Cave by Hendrik Poinar and other members of Svante Paabo's team in Leipzig, Germany, yielded not only Shasta ground sloth DNA but also DNA from plant remains incorporated in its diet (Poinar and others 1998). Their findings indicated that the ground sloths foraged not only in drier sites but also in riparian communities supporting wild grape (Vitis) and very likely the large mustard Stanleya.
These results raise interesting questions as to the time of year the ground sloths spent in the cave. From eastern California to West Texas, ground sloth bones, unlike those of mammoths, camels, and extinct bison, are found more often in caves than in midvalley floodplain alluvium or lake deposits. Despite their rich fossil record in caves, however, I doubt that the sloths spent much time in Rampart, or they soon would have filled it with dung. We estimated that the average annual rate of deposition in the upper part of the deposit was slightly more than a cubic foot a year, an amount that probably represented less than a week's elimination from one healthy adult ground sloth. The presence of embryonic sloth bones suggests that females may have used Rampart Cave as a nursery. Bones of a baby ground sloth the size of a cat found in Gypsum Cave (Harrington 1933, 78) point to a similar conclusion there. This makes particularly good sense if the infant sloths, like many mammals, were born in the spring. I believe late winter or spring following a wet winter would have been the best time for the ground sloths to find forage at low elevations in a xeric habitat such as that surrounding Rampart Cave.
As spring ended and globe mallows and other forage plants dried and shriveled, I expect the ground sloths left the inner gorge for greener pastures at higher and cooler elevations. The nearest place to summer above 5,000 feet in a tolerable climate would be in the Grapevine Mountains and the Garnet Mountains of the Grand Wash Cliffs, within about 40 miles of Rampart Cave. Projecting from late-glacial plant displacements recorded elsewhere (see chapter 3), I would expect that above the juniper-single-leaf ash woodland at Rampart Cave, the sloths would have penetrated a pinyon-pine woodland and perhaps even reached a few limber pine or Douglas fir trees, with sagebrush (Artemisia tridentata) on the flats. Because of the glacial age climate, the vegetation gradient not only from the Grand Wash Cliffs to Rampart Cave but throughout the West would have been less arid and more productive in plant dry matter from forage plants than it is now.
At a very leisurely sloth travel rate averaging one to two miles per day, the vertical migration I propose from canyon bottom past Mead View and up into the Grand Wash Cliffs need have taken no more than a month or two. In the fall, as the weather turned chilly, the ground sloths would slowly have found their way back down again to lower and warmer elevations, perhaps drawn by plants growing along the Colorado during the winter season of low water. In short, I am betting that the ground sloths of the Quaternary, like modern-day elk and mule deer, took advantage of eleva-tional gradients to benefit from seasonal changes in availability of forage.
Finally, the dietary data from ground sloth dung help refute the argument that its extinction around Clovis time resulted from climate change. The ground sloth's favorite food plants—in the Rampart and Muav cave areas, Nevada's Gypsum Cave, the sloth caves of the Guadalupe Mountains of West Texas, and New Mexico's Aden Crater—remain important components in the vegetation of arid regions in North America.
Thanks especially to the remarkable stratified record from Rampart Cave, we know that for thousands of years the Shasta ground sloth browsed on a variety of desertscrub and woodland shrubs and forbs, including species presently favored by wild desert bighorn sheep and feral burros. Even the fossils indicating that the ground sloth once lived in what is now Sonoran Desert—archaeologists have excavated its bones from Ventana Cave on the O'odham reservation west of Tucson—appear to coincide in time with the invasion of many Mojave desertscrub species preserved in the fossil packrat middens at Organ Pipe Cactus National Monument. Most of the plants identified in Rampart Cave sloth dung (Hansen 1978) remain important in the natural vegetation within the seasonal range of the Grand Canyon ground sloths. It is therefore not obvious how one might account for the Shasta ground sloth's extinction by invoking a loss of food supply resulting from climate change. Single-leaf ash and juniper continued to grow near Rampart Cave for at least 2,000 years after the ground sloths disappeared (Phillips 1984). Though these species were not food sources for the sloths, their persistence confirms that no major climate change is likely to have disrupted the animals' food supply (Martin 1986, 122).
Not dreaming what the future would bring, in 1973 Austin Long and I guided author James Michener through the cave, and he wrote about it in Reader's Digest (see plate 6). Michener understood that this was one of only a dozen caves known to contain fossil sloth dung, and that it held the best-preserved and deepest deposit of stratified sloth dung that has been found in North America. It deserved nomination as one of the wonders of the paleontological world, along with the frozen mammoths of Siberia, the thousands of tar-impregnated saber-toothed cats and dire wolf bones of Rancho La Brea, and the fifty young male mammoths and the giant short-faced bear in a sinkhole at Hot Springs, South Dakota.
In July 1976, Austin and I got a call from Roy Johnson at Grand Canyon National Park. The news was bad. He reported that smoke was coming from the mouth of Rampart Cave. We chartered a plane and flew to the canyon, where we joined a Park Service fire crew and rode by heli-
copter to the cave. Heavy smoke creeping along at ground level poured slowly out of its mouth. The crew began to douse the fire. Then a large rock dropped from the low ceiling, perhaps loosened by the heat. More cautious measures were adopted. Eventually the cave ceiling was shored up with massive posts in an effort to make it safe for firefighters to enter. (Perhaps inevitably, a columnist in the Chicago Sun-Times ridiculed the National Park Service for spending tens of thousands of dollars in an unsuccessful effort at saving ancient dung. Even renowned TV anchorman Walter Cronkite could not resist closing an interview with me on this paleontological disaster with a quip about "endangered feces.")
The dung smoldered for months, defeating all efforts at extinguishment. Although there was no real blaze—no visible flames—the insidious combustion slowly and inexorably reduced to ash the magnificent 5-foot-thick blanket of dung east of Kellogg's trench, the very area we had found so valuable in our research. While part of the deposit remains, the main portion, shown in figure 11 and plate 3, is gone. Too late, I regretted that our sampling had not been more intensive. Before more than a few intriguing studies had been completed, the fire all but closed a precious window into the late-Quaternary ecology of the Grand Canyon ground sloths. In its own way, the Rampart Cave fire was as destructive
of information as the long-lamented conflagration of the ancient library in Alexandria, Egypt. Had we given the cave too much publicity? Whatever the explanation, I continue to mourn the loss.
For more information on the extinction of ground sloths throughout their hemispheric range, we needed to look beyond the Southwest, and indeed beyond North America. I had a chance to do just that in 1972, thanks to a sabbatical from the University of Arizona, an NSF grant to cover research costs, and the interest of Ike and Jean Russell, adventurous friends in Tucson who let me fly with them in their Cessna through Central and South America. We headed for southern Chile and the famous Cueva del Milodon (Mylodon Cave, also known as Eberhardt Cave).
At Seno Ultima Esperanza (Last Hope Sound), an arm of the sea behind Andean glaciers near Puerto Natales, settlers over a century ago had learned of this grotto, 400 feet wide, 100 feet high, and 660 feet from front to back. It was the first cave found to contain ground sloth dung— along with hair and, most remarkably, a piece of hide 3 feet in diameter, patched with hair and embedded with dermal bones. Despite its youthful appearance, radiocarbon dates obtained from this prize specimen are approximately 13,000 years old (A-1390, R-4299).
Based in part on dung from this cave, the famous Argentinean paleontologist Florentino Ameghino described what he imagined was a new genus and species of living ground sloth, Neomylodon listai. Other authorities called it Grypotherium domesticum (Hauthal, Roth, and Lehmann-Nitsche 1899). Their work was consistent with contemporaneous travelers' belief that ground sloths still lived in southern Chile. There were legends of a strange animal known not only to the Indians but also to European explorers. One hundred years ago a London newspaper financed an expedition to search Patagonia for living ground sloths. The scientific world was ablaze with curiosity. Alas, the search failed.
Although disturbed by various excavations, Cueva del Milodón still contains an unrivaled deposit of sloth dung along with fossil remains of extinct horses (Hippidium, Onohippidium) (Latorre 1998; see Sutcliffe 1985 for a splendid illustration of the cave). On our 1972 trip we collected surface or shallowly buried, and therefore potentially the youngest, samples of what we took to be ground sloth dung for radiocarbon dating. Possibly some of the samples came from extinct horses, not from mylodons. Judging from the content of their enormous dung balls, in some cases larger than a circus elephant's, ground sloths from Cueva del Milodón ate mainly grasses.
To top off the trip, we visited another cave yielding not only sloth dung but also archaeological remains. Called La Gruta del Indio (Indian Cave) and located on the Río Atuel, outside the small city of San Rafael at the foot of the Andes in Argentina, it had recently been reported by Tito (Humberto) Lagiglia, director of San Rafael's Museum of Natural History. Tito and his family made us most welcome in San Rafael, and he escorted us to the cave (as well as accompanying us to Cueva del Milodón).
La Gruta del Indio is at a latitude equivalent to that of Las Vegas and is surrounded by similar habitat. Although lacking Joshua trees, the vegetation resembles in structure, height, density, and spacing of dry land shrubs the desertscrub near Rampart Cave and in other parts of the Mo-jave Desert. Lush mountain grasslands occupy higher elevations, with alpine plants in the Andes. The cave itself, actually a rock shelter beneath a basalt ledge, is smaller and much more exposed than Rampart Cave. Like Rampart, it harbors middens of some plant-gathering, packrat-like mammal. Unlike Rampart, La Gruta del Indio is an archaeological site, with charcoal deposited immediately above the layers harboring the youngest dung balls (Long, Martin, and Lagiglia 1998) and with late-prehistoric artifacts.
La Gruta del Indio offered very few bones to help with species identi fication. The discovery of one megatheriid tooth and of dermal ossicles embedded in patches of hide (the mark of a mylodon) suggested that both mylodons and megatheriids had been present. The ground sloth dung balls at La Gruta del Indio (see plate 8) were two to four times smaller than those found in Rampart. (I was intrigued to learn from the study of Hector d'Antoni  that the Argentinean ground sloths ate mesquite pods, which we had not found in the dung of the Shasta ground sloth.)
A core question for me throughout this trip was whether the youngest ground sloth dung deposits in South America were the same age as those in North America. An answer could help us ascertain whether the two groups of megafauna had gone extinct at the same time. One previously published radiocarbon date on hide from the Groningen Laboratory, 9,560 ± 60 (GrN-5772), was decidedly younger than any dates that Austin Long and I had obtained on the Shasta ground sloth. Could ground sloths in southern South America have lasted 1,000 to 2,000 years longer than those in North America?
Almost all the ground sloth bonegas (dung balls) from La Gruta del Indio (Long, Martin, and Lagiglia 1998) and Cueva del Milodon (Markgraf 1985) (see table 5) are over 10,000 radiocarbon years old. Those from Cueva del Milodon are no older than 14,000 radiocarbon years. Alejandro Garcia and Tito Lagiglia (1999) recovered much older dates at La Gruta del Indio. With the exception of an early University of Chicago date on mylodon dung that I believe is in error and should be discarded, the youngest dates on the samples from La Gruta del Indio and those Lagiglia and I collected from Cueva del Milodon are quite similar. More than that, they are similar to the surface dates on the Shasta ground sloth dung from Arizona. Based on these dates, if the First Americans caused the extinctions of ground sloths, they spread very rapidly from Arizona to southern South America, so rapidly that some archaeologists question whether it was possible.
A more recent series of six radiocarbon dates from La Gruta del Indio, however (Garcia and Lagiglia 1999; Garcia 2003), includes one that matches the earlier Groningen date. Both are younger than any reported in Long, Martin, and Lagiglia 1998, and in fact any radiocarbon dates on ground sloth dung and other samples of high quality reported in recent years. Thus the question of whether ground sloth extinction in southern South America significantly postdated extinctions in North America is still open.
Though younger age estimates appear from time to time (see Sutcliffe 1985 on work by Saxon in Cueva del Milodon), no ground sloth remains
in North America have been discovered in reliably dated geologic deposits of the last 10,000 years. With the crucial exception of the West Indies, ground sloth remains are absent from numerous Holocene fossil deposits, as are the rest of the near-time extinct megafauna of North and South America. Continental deposits give no hint of a later survival. So matters stood until dating results came in from Cuba and Haiti. There dwarf ground sloths persisted until about 5,000 radiocarbon years ago, approximately the time of settlement (Steadman n.d.).
The South American ground sloth investigations continue. Recently Michael Hofreiter and others (2003) reported a sloth dung cave at the foot of the Andes at 38.5 degrees south. A particle accelerator yielded an age of 14,665 ± 150. The investigators had the benefit of mitochondrial DNA analysis. This technique for analyzing cave earth, cave copro-lite, and subarctic frozen ground is a recent advance in detecting the presence, the identity, and even the diet of extinct animals (Poinar and others 1998, 2003). On the basis of mitochondrial DNA, Hofreiter and others conclude that an undescribed small species of ground sloth lived during the late glacial in the lower parts of the eastern Andes. It may be the same species that left the dung deposit at La Gruta del Indio.
One more cave dry enough to preserve fossil ground sloth dung deserves mention here. I would not have imagined such a find in the Brazilian tropics. Nevertheless, from Gruta de Brejoes in Bahia, one of the drier parts of Brazil, Nick Czaplewski and Castor Cartelle (1998) obtained a date of 12,200 ± 120 (Rafter Radiocarbon Laboratory, NZA-6984) on dung associated with a skeleton of the small ground sloth Nothrotherium maquínense. In addition, Czaplewski (letter of December 19, 2000) called my attention to a study of plant remains in coprolite of an extinct Brazilian llama, Paleolama. These finds give us reason to hope that the caves of Bahia will also yield ample bone collagen suitable for reliable radiocarbon dates and DNA determination. This would constitute a major advance in refining the near-time extinction chronology of the New World tropics, rarely thought of as a suitable environment for preservation of perishable material.
Ground sloths also inhabited the West Indies, but here their story was very different. Zoogeographers dispute whether they got to the islands by swimming (living tree sloths are good swimmers) or by walking over dry-land connections with the mainland sometime during the Tertiary (Iturralde-Vinent and MacPhee 1999). In any event, in the Quaternary the West Indies harbored nine poorly known endemic genera: seven in Cuba, two in Hispaniola (one shared with Cuba), one in Puerto Rico (shared with Cuba), and one in Curacao. All were in the family Mega-lonychidae. As one would expect of an ancient oceanic island fauna, many were severely dwarfed in comparison with their continental ancestors: with one exception all weighed less than 45 kilograms (100 pounds). Until their extinction they appear to have been the predominant mammalian herbivores, the largest plant eaters in the Greater Antilles, despite their dwarf size among the ground sloths.
Most interestingly from my perspective, robust fossil evidence suggests that the ground sloths survived into the Holocene in Cuba and Hispan-iola. From a cave in Cuba, Ross MacPhee and others report a date of 6,250 ± 50 on the largest of the extinct dwarf West Indian ground sloths, Megalocnus rodens (MacPhee, Flemming, and Lunde 1999). A second date, presumably from the same locality, is 6,330 ± 50 (Beta-115697). A third, recently received from the accelerator lab of the University of Arizona, is even younger, 4,486 ± 39 (AA-58430). MacPhee's youngest date on another dwarf ground sloth species, Parocnus brownii, is 4,960 ± 280 (AA-35290) . Although we lack direct radiocarbon dates on all 16 genera of extinct ground sloths from North and South America, or on all eight under 45 kilograms from the West Indies, the early returns indicate that West Indian ground sloths lasted at least 3,000 years longer than the continental ground sloths. The results support an anthropogenic extinction model.
CRYPTOZOOLOGY, GROUND SLOTHS, AND MAPINGUARI NATIONAL PARK
Most zoologists suppress any dreams they may have of the survival of late-Quaternary extinct beasts, such as ground sloths living in some remote corner of Brazil. Such healthy skepticism has not deterred cryptozoologists ("cryptos") from organizing and funding searches, some well supplied with advanced technological equipment, for animals that paleontologists say are extinct or (in the case of Sasquatch and the Loch Ness monster) never existed. Press releases from these expeditions make great copy, and their leaders are likely to appear on television. Like the public at large, cryptos are drawn to charismatic megafauna much more than to small creatures such as arthropods. At least I have yet to hear of enthusiastic searches for bizarre and entirely imaginary invertebrates like flying millipeds or singing earthworms.
David Oren, a Harvard-trained ornithologist now with the Emilio Goeldi Museum in Belem, Brazil, has claimed to have evidence of living ground sloths (Oren 1993). The original reports of these creatures, known to Indians and local hunters as mapinguari, came from the Amazon Basin on the Tapajos River. Whether or not Oren knew about the search for living ground sloths a century earlier in Tierra del Fuego, history was repeating itself. Along with paleontologist and ground sloth expert Greg McDonald of the U.S. National Park Service, Oren appeared on the Discovery Channel on the proper tributary of the upper Amazon, the alleged habitat of the mapinguari. What would they find?
Oren did his best to lure a mapinguari by imitating what its call was supposed to sound like. There was no response. An Amazonian Indian guide found a dung sample suspected to be from the mapinguari. According to McDonald, its DNA, extracted in Svante Paabo's lab in Germany, matched that of Tamandua, the living arboreal anteater of tropical America.
My astute cryptozoological friend Richard Greenwell, who is properly concerned with scientific methodology, says that a scientist cannot exclude chance, whether one in ten or one in a million or one in a number approaching infinity. If the only evidence is negative, there has to be a possibility, however small, that mapinguari are still living. Richard likes to remind me that the coelacanth Latimeria, unknown in the fossil record since the Cretaceous, turned up alive in the haul of fishermen in the Indian Ocean near Madagascar in 1938. And in the 1990s, Laotian and Vietnamese zoologists (not cryptos) described two genera of previously unknown and unexpected large animals from west-central Vietnam and Laos: Pseudoryx, a bovid, and Megamuntiacus, a cervid, each weighing about 100 kilograms (220 pounds). Nevertheless, while the world would be thrilled at the fabulous discovery of living ground sloths, I do not give their seekers a chance.
Would I love to be proved wrong? Yes, indeed! One side of me is wholeheartedly rooting for David Oren. What a thrill it would be for me to see a living, breathing ground sloth in the flesh. More than that, their discovery in the Amazon would fuel the initiative needed to set aside one or more large reserves in the world's largest rain forest (Holloway 1999). The ongoing global destruction of rain forests is one of the unspeakable tragedies of our time.
As wonderful as it would be to find ground sloths alive, however, the sad fact is that these amazing animals have been absent from the fossil record for thousands of years. The mantra of paleontologists, "The absence of evidence is not evidence of absence," is popular among cryptozoologists. Nevertheless, only in the West Indies have ground sloths been found in the fossil record of the Holocene, and they surely are extinct. Thousands of years of absence from the fossil record of North and South America of an animal as obvious as a ground sloth, not a crossopterygean fish lurking in the depths of the sea, is a big step in the direction of incredibility. So many late-Holocene fossil deposits— thousands, if not tens of thousands—have been sampled or excavated in continental North and South America without yielding ground sloth remains, or those of any other large extinct Quaternary mammal, that it seems impossible that West Indies ground sloths are still alive. Alas, David Oren and others hunting for the mapinguari started their quest thousands of years too late. That should not detract from the goal of establishing a vast mapinguari tropical forest reserve to represent the likely habitat of extinct ground sloths, gomphotheres, and glyptodonts.
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