American lion

Few additional discoveries came until 1907, when the American Museum of Natural History and College, Alaska collected several Panthera atrox skulls in a locality originally found in 1803 by gold miners in Kotzebue, Alaska.^[9] The skulls were referred to a new subspecies of Felis (Panthera) atrox in 1930, Felis atrox "alaskensis". Despite this, the species did not get a proper description and is now seen as a nomen nudum synonymous with Panthera atrox.^[7] Further south in Rancho La Brea, California, a large felid skull was excavated and later described in 1909 by John C. Merriam, who referred it to a new subspecies of Felis atrox, Felis atrox bebbi.^[10][9] The subspecies is synonymous with Panthera atrox.^[7]

Throughout the early to mid 1900s, dozens of fossils of Panthera atrox were excavated at La Brea, including many postcranial elements and associated skeletons.^[10] The fossils were described by Merriam & Stock in detail in 1932, who synonymized many previously named taxa with Felis atrox.^[9] At least 80 individuals are known from La Brea Tar Pits and the fossils define the subspecies, giving a comprehensive view of the taxon.^[10] It was not until 1941 that George Simpson moved Felis atrox to Panthera, believing that it was a subspecies of jaguar.^[9] Simpson also referred several fossils from central Mexico,^[11] even as far south as Chiapas, as well as Nebraska and other regions of the western US, to P. atrox.^[9] 1971 witnessed the description of fragmentary remains from Alberta, Canada that extended P. atrox's range north.^[12][11] In 2009, an entrapment site at Natural Trap Cave, Wyoming was briefly described and is the second most productive Panthera atrox-bearing fossil site. It most importantly contains well-preserved mitochondrial DNA of many partial skeletons.

Panthera onca mesembrina and possible South American material

In the 1890s in the "Cueva del Milodon" in southern Chile, fossil collector Rodolfo Hauthal collected a fragmentary postcranial skeleton of a large felid that he sent to Santiago Roth who described them as a new genus and species of felid, "Iemish listai", in 1899,^[13] though the name is considered a nomen nudum.^[13] 5 years later in 1904, Roth reassessed the phylogenetic affinities of "Iemish" and named it Felis listai and referred several cranial and fragmentary postcranial elements to the taxon. Notably, several mandibles, a partial skull, and pieces of skin were some of the specimens referred.^[13] 30 years later in 1934, Felis onca mesembrina was named by Angel Cabrera based on that partial skull from "Cueva del Milodon" and the other material from the site was referred to it.^[13] Unfortunately, the skull (MLP 10-90) was lost, and was only illustrated by Cabrera.^[13] Further material, including feces and mandibles, was referred to as F. onca mesembrina from Tierra del Fuego, Argentina and other southern sites in Chile.^[14]

In 2016, the subspecies was referred to Panthera onca in a genetic study, which supported its identity as a subspecies of jaguar.^[15] Later in 2017, the subspecies was synonymized with Panthera atrox based on morphological similarities of all material, although these similarities are unreliable.^[13]

Evolution

The American lion was initially considered a distinct

The study also indicates that the modern lion is the closest living relative of P. atrox and P. spelaea.[19] The lineages leading to extant lions and atrox/spelaea were thought to have diverged about 1.9 million years ago,^[4] before a whole genome-wide sequence of lions from Africa and Asia by Marc de Manuel et al. showed that the lineage of the cave lion diverged from that of the modern lion around 392,000 – 529,000 years ago.^[20]

Description

The American lion is estimated to have measured 1.6 to 2.5 m (5 ft 3 in to 8 ft 2 in) from the tip of the nose to the base of the tail and stood 1.2 m (3.9 ft) at the shoulder.^[21] Panthera atrox was at least as sexually dimorphic as African lions, with an approximate range of between 235kg to 523 kg (518lbs-1153lbs) in males and 175kg to 365 kg (385lbs-805lbs) for females.^[22] In 2008, the American lion was estimated to weigh up to 420 kg (930 lb).^[23][24] A study in 2009 showed an average weight of 256 kg (564 lb) for males and 351 kg (774 lb) for the largest specimen analyzed.^[3]

Panthera atrox had limb bones more robust than those of an African lion, and comparable in robustness to the bones of a brown bear.^[25]About 80 American lion individuals have been recovered from the La Brea Tar Pits in Los Angeles, so their morphology is well known.^[26] Their features strongly resemble those of modern lions, but they were considerably larger, similar to P. spelaea and the Pleistocene Natodomeri lion of eastern Africa.^[27]

Preserved skin remains found with skeletal material thought by its describers to be from the American lion in caves in the Argentine Patagonia indicate that the animal was reddish in color. Cave paintings from El Ceibo in the Santa Cruz Province of Argentina seem to confirm this, and reduce the possibility of confusion with fossil jaguars, as similar cave paintings accurately depict the jaguar as yellow in color.^[28][14]

Distribution

The earliest lions known in the Americas south of Alaska are from the Sangamonian Stage – the last interglacial period – following which, the American lion spread from Alberta to Maryland, reaching as far south as Chiapas, Mexico.^[11][29] It was generally not found in the same areas as the jaguar, which favored forests over open habitats.^[21] It was absent from eastern Canada and the northeastern United States, perhaps due to the presence of dense boreal forests in the region.^[30][31] Farther south, fossilised remains of the American lion have been discovered in Extinction Cave, Belize.^[32] The American lion was formerly believed to have colonized northwestern South America as part of the Great American Interchange.^[33] However, the fossil remains found in the tar pits of Talara, Peru actually belong to an unusually large jaguar.^[34][35][36] On the other hand, fossils of a large felid from late Pleistocene localities in southern Chile and Argentina traditionally identified as an extinct subspecies of jaguar, Panthera onca mesembrina, have been reported to be remains of the American lion.^[13]

Habitat

The American lion inhabited savannas and grasslands like the modern lion.^[8] In some areas of their range, American lions lived under cold climatic conditions. They probably used caves for shelter from the cold weather in those areas,^{[31][note 1]} and might have lined their dens with grass or leaves, as the modern Siberian tiger does.^[31]

Paleoecology

American lions likely preyed on

The remains of American lions are not as abundant as those of other predators like Smilodon fatalis or dire wolves (Aenocyon dirus) at the La Brea Tar Pits. This suggests that they were better at evading entrapment, possibly due to greater intelligence.^[8] While the ratio of recovered juveniles to adults suggests that Panthera atrox was social, its rarity suggests that it was at least more solitary than Smilodon and Aenocyon, or was social but lived in low densities.^[39]

Analyses of dental microwear suggest that the American lion actively avoided bone just like the modern cheetah (more so than Smilodon). Panthera atrox has the highest proportion of canine breakage in La Brea, suggesting a consistent preference for larger prey than contemporary carnivores. Dental microwear additionally suggests that carcass utilization slightly declined over time (~30,000 BP to 11,000 radiocarbon BP) in Panthera atrox.^[22] The fragment of a femur from a gray wolf from the La Brea Tar Pits shows evidence of a violent bite which possibly amputated the leg. Researchers believe that Panthera atrox is a prime candidate for the injury, due to its bite force and bone shearing ability.^[40]

Extinction

The American lion went extinct along with most of the

Notes

References

Wikimedia Commons has media related to American lion.

Wikispecies has information related to Panthera leo atrox.