Temporal range: Middle - Late Pleistocene, 0.34–0.011Ma
|Skeleton from the La Brea tar pits at the George C. Page Museum|
|Species:||Disputed; P. leo or †P. atrox|
|Subspecies:||Disputed; †P. l. atrox or none|
|Panthera leo atrox
The American lion (Panthera leo atrox or P. atrox) — also known as the North American lion, Naegele’s giant jaguar or American cave lion — is an extinct lion of the family Felidae, endemic to North America and northwestern South America during the Pleistocene epoch (0.34 mya to 11,000 years ago), existing for approximately . It has been shown by genetic analysis to be a sister lineage to the Eurasian cave lion (Panthera leo spelaea or P. spelaea).
The American lion is one of the largest types of cat ever to have existed, slightly larger than the Early Middle Pleistocene primitive cave lion, P. leo fossilis and about 25% larger than the modern African lion.
The American lion is an extinct animal that originated in North America and is believed to have colonized northwestern South America as part of the Great American Interchange. (However, it has been suggested that the fossil remains found in Peru may actually correspond to large jaguars.) The head-body length of the American lion is estimated to have been 1.6–2.5 m (5 ft 3 in–8 ft 2 in) and it would have stood 1.2 metres (4 ft) at the shoulder. Thus it was smaller than its contemporary competitor for prey, the giant short-faced bear, which was the largest carnivoran of North America at the time. The American lion was not as heavily built as the saber-toothed cat Smilodon populator, which may have weighed up to 360 kilograms (790 lb). Sorkin (2008) estimated the American lion to weigh roughly 420 kilograms (930 lb), but a more recent study showed an average weight for males of 256 kg (560 lb) and 351 kg (770 lb) for the largest specimen analyzed.
Approximately one hundred specimens of American lions have been recovered from the La Brea Tar Pits, in Los Angeles, so their body structure is well known. The features and teeth of the extinct American lion strongly resemble modern lions, but they were considerably larger. The American lion is believed to be the largest subspecies of lion.
The American lion was initially considered a distinct species of Pantherinae, with the scientific name Panthera atrox (pron.: / /), which means "cruel" or "fearsome panther" in Latin. Overall, the skull of the extinct cat was most like that of the jaguar (P. onca). Some later authors accepted this view, but other experts considered the American lion most closely related to the African lion (P. leo) and its extinct Eurasian relative, the cave lion (P. leo spelaea or P. spelaea). Later paleontologists assigned the extinct American cat as a subspecies of P. leo (P. leo atrox) rather than as a separate species.
Cladistic studies using morphological characteristics have been unable to resolve the phylogenetic position of the American lion. At least one authority considers the American lion (along with the cave lion), to be more closely related to the tiger, P. tigris, citing a comparison of skull shapes; the braincase, in particular, appears to be especially similar to the braincase of a tiger. It has also been suggested that the American lion and Eurasian cave lion were successive offshoots of a lineage leading to an extant lion-leopard clade. A more recent study that compared the skull, jaw, and teeth of the American lion with other pantherines concluded it was not a lion and was distinct from all extant species. The authors suggested that it may have arisen from pantherines that migrated into North America in the mid-Pleistocene epoch and also gave rise to jaguars.
However, mitochondrial DNA sequence data from remains of the American lion from Wyoming and Alberta show that it is a sister lineage to the cave lion, and likely arose when an early cave lion population became isolated south of the North American continental ice sheet. The most recent common ancestor of the two populations apparently lived about 340,000 (194,000–489,000) years ago. The most recent common ancestor of the atrox lineage is estimated to have lived about 200,000 (118,000–246,000) years ago. The dates imply that genetic isolation from spelaea had begun by the time of the Illinoian glaciation, ~300,000–130,000 years ago (a spelaea population is known to have been present in eastern Beringia by that period, where it persisted until at least 11,925 ± 70 years ago). This separation was maintained during the Sangamon interglacial, ~130,000–110,000 years ago, as well as during later interstadials of the earlier glaciation and those of the following Wisconsinan glaciation, ~110,000–10,000 years ago. It has been suggested that boreal forest may have contributed to the separation during warmer intervals; alternatively, a species barrier may have existed. The study also indicated that the present-day lion is the closest extant relative of atrox and spelaea. (In the same study, Eurasian and Beringian cave lions were found to be genetically indistinguishable.)
The earliest lions known in the Americas south of Alaska are from the Sangamonian Stage (the last interglacial). After that, the American lion spread widely from Alberta to Maryland to Peru. In North America, it has been found in more locations in the west than in the east; and as far south as Chiapas, Mexico. It was generally not present in the same areas as the jaguar, as the latter favored forests, while American lions preferred open habitats. Like many other large mammals, it went extinct at the end of the Pleistocene. The most recent fossil, from Edmonton, dates to 11,355 ± 55 years ago. By then, the American lion was one of the abundant Pleistocene megafauna, a wide variety of very large mammals that lived during the Pleistocene. The most abundant remains have come from the La Brea Tar Pits.
In some areas of its range, the American lion lived under cold climatic conditions. They probably used caves or fissures for shelter from the cold weather. They may have lined their dens with grass or leaves, as the Siberian tiger does, another great cat that currently lives in the north.
There are fewer American lions in the La Brea tar pits than other predators such as saber-toothed cats (Smilodon fatalis) or dire wolves (Canis dirus), which suggests they may have been smart enough to avoid the hazard. American lions likely preyed on deer, North American horses (now extinct), North American camels, North American tapirs, American bison, mammoths, and other large, herbivorous animals. This species disappeared about the same time as other megafaunal species during the Quaternary extinction event, which wiped out many of the species that the American lion would have preyed on. Lion bones have been found in the trash heaps of Paleolithic American Indians, suggesting human predation may have contributed to its extinction.
A replica of the jaw of the first specimen of American lion discovered can be seen in the hand of a statue of paleontologist Joseph Leidy, which is currently standing outside the Academy of Natural Sciences in Philadelphia.
See also 
- Panthera leo vereshchagini, the East Siberian or Beringian cave lion
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|Wikispecies has information related to: Panthera leo atrox|
- Prehistoric cats and prehistoric cat-like creatures, from the Messybeast Cat Resource Archive
- Panthera atrox in cryptozoology