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Figure 2. The geologic time scale. Note that Near Time comprises a tiny and recent portion of the Earth's history, underscoring how close to our own time was the world populated by an array of large mammals. "mya" = million years ago; NA = North America; f = mass extinction. Adapted from McKenna and Bell 1997 (© Columbia University Press); Museum of Paleontology, University of California, Berkeley; Merriam-Webster's Collegiate Dictionary, 11th ed.

rats (Rattus exulens) may have been the agents of over a hundred extinctions of ground-nesting birds in New Zealand and of endemic land snails on thousands of Pacific islands.

Significantly, no avian extinctions have been detected in the Galapagos, where fossil cave faunas sampled by David Steadman (Steadman and Zousmer 1988) on various islands are made up entirely of living species, including species of Darwin's Finches. Extinction of the endemic Galapagos rat, Megaoryzomys, coincides with historic human contact. On a visit to the island of Santa Fe, Dave and his field assistants searched for Pleistocene sediments and fossils without success. They found a rich fossil record in caves on Floreana, but it was apparently not old enough to include extinct species.

While not the first to be intrigued by these patterns, I was among the first to compare near-time extinctions between continents and continental extinctions with those on oceanic islands. Radiocarbon dating made such comparisons possible. Moreover, vertebrate paleontologists have greatly improved and refined the fossil records of mammals, large and small. After a false start early in the twentieth century by paleontologists such as O. P. Hay, who thought that numerous extinctions of mammals took place early in the Quaternary, paleontologists and geologists came to recognize that megafaunal extinctions in America happened mainly around the end of the last glacial episode, at the end of the Quaternary. This was about 13,000 years ago or less. The extinctions were not only of species and genera, but also of higher taxonomic categories, such as families and occasionally an order. The evolution of a family of mammals normally takes tens of millions of years. Some paleontologists argued fatalistically that the late-Quaternary extinctions were inevitable; their time had come. But so many, so suddenly, in so many corners of the world, and involving established lineages of large mammals on continents? Something strange had happened. What was it?

"Blighted" is the right word for the animal kingdoms of America and Australia after the near-time extinctions ran their course. Globally, extinction was the fate of about half of the genera of large terrestrial mammals known to have existed on the continents at the time. They were soon followed by thousands of species or taxa (taxonomic categories, in this case distinct populations) of island birds and land snails. Prehistoric extinctions swept the remote corners of the Pacific, including Hawaii, the Marquesas, Rapanui (Easter Island), and New Zealand.

In near time, North America lost more genera than it had in the preceding 1.8 million years. Table 1 lists the living and extinct large mammals

TABLE 1 Late Quaternary Extinct and Living Species of Large (>45 Kilograms) Land Mammals, Western North America and Northern Mexico

Classification

Common name

Xenarthra

tGlyptotherium floridanum

glyptodont

tParamylodon harlani

big-tongued ground sloth

tMegalonyx jeffersonii

Jefferson's ground sloth

tNothrotheriops shastensis

Shasta ground sloth

Carnivora

Canis *dirus

dire wolf

Canis lupus

gray wolf

Ursus americanus

black bear

Ursus arctos

brown (grizzly) bear

f Arctodus simus

giant short-faced bear

fSmilodon fatalis

saber-toothed cat

Panthera leo *atrox

American lion

Panthera onca

jaguar

fMiracinonyx trumani

American cheetah

Puma concolor

mountain lion

Proboscidea

tMammut americanum

American mastodon

tMammuthus columbi

Columbian mammoth

tMammuthus exilis

dwarf mammoth

tMammuthus primigenius

woolly mammoth

Perissodactyla

Equus *conversidens

Mexican horse

Equus *occidentalis

western horse

Equus *spp.

extinct horses or asses

Tapirus *californicus

tapir

Artiodactyla

fCamelops hesternus

western camel

fHemiauchenia macrocephala

long-legged llama

*Mylohyus nasutus

long-nosed peccary

*Platygonus compressus

flat-headed peccary

Odocoileus hemionus

mule deer

Odocoileus virginianus

white-tailed deer

*Navahoceros fricki

mountain deer

Rangifer tarandus

woodland caribou

Alces alces

moose, moose deer

Cervus elaphus

wapiti, elk

TABLE l continued

Classification

Common name

Antilocapra americana

pronghorn

Oreamnos * harringtoni

Harrington's mountain goat

Oreamnos americanus

mountain goat

Ovis canadensis

bighorn

*Euceratherium collinum

shrub ox

*Bootherium bombifrons

bonnet-headed musk ox

Bison bison

bison

Bison *spp.

extinct bison

source: After Martin and Szuter 1999. Courtesy Blackwell Publishing. fExtinct genus.

*Extinct species. The more common taxa have terminal radiocarbon dates around 13,000 calendar years ago (Stuart 1991).

source: After Martin and Szuter 1999. Courtesy Blackwell Publishing. fExtinct genus.

*Extinct species. The more common taxa have terminal radiocarbon dates around 13,000 calendar years ago (Stuart 1991).

known in western North America and northern Mexico in near time. Table 2 lists the large mammals of North America north of Mexico over the last two million years and shows the concentration of extinctions in the late Quaternary, with its distinctive Rancholabrean fauna. Table 3 lists all living and extinct large land mammals of near time found throughout the world.

It is well worth examining in more detail the kinds of animals that went extinct in the late Quaternary and the geographic regions that were affected. The following sketch treats some of the more common large animals eliminated by extinctions in the last 50,000 years. (For more details and illustrations see E. Anderson 1984; Hulbert 2001; Kurten 1988; Kurten and Anderson 1980; Lange 2002; MacPhee 1999; Martin and Klein 1984; Murray 1991; Steadman n.d.; and Sutcliffe 1985.)

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