The American lion (Panthera leo atrox) – also known as the North American cave lion – is an extinct subspecies of lion that lived in North America during the Pleistocene epoch (340,000 to 11,000 years ago). Genetic analysis has revealed that it was the sister lineage to the Eurasian cave lion. It was part of the Pleistocene megafauna, a wide variety of large mammals that lived at the time. The majority of American lion fossils have come from the La Brea Tar Pits.
The American lion was about 25% larger than the modern African lion, making it one of the largest known felids.
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. Thus, it was smaller than its contemporary competitor, the giant short-faced bear, which was the largest carnivoran of North America at the time, and arguably the saber-toothed cat, Smilodon populator, which may have weighed up to 400 kg (880 lb). In 2008, the American lion was estimated to weigh up to 420 kg (930 lb). 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. A study in 2012 estimated a range of 235–523 kg (518–1,153 pounds) for males and 175–365 kg (386–805 pounds) for females, which suggests that the lion was heavier than Smilodon.
About 80 American lion individuals have been recovered from the La Brea Tar Pits in Los Angeles, so their morphology is well known. Their features strongly resemble those of modern lions, but they were considerably larger, and are believed to have been the largest subspecies of lion.
Preserved skin remains found with skeletal material thought to be from the American lion in caves in Argentina indicate that the animal was reddish in color. Cave paintings from in El Ceibo in the province of Santa Cruz seem to confirm this, and reduce the possibility of confusion with fossil jaguars, as similar cave paintings show the latter cat accurately as being yellow in color.
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. It was generally not found in the same areas as the jaguar, which favored forests over open habitats. It was absent from eastern Canada and the northeastern United States, perhaps due to the presence of dense boreal forests in the region. The American lion was formerly believed to have colonized northwestern South America as part of the Great American Interchange. However, the fossil remains found in the tar pits of Talara, Peru actually belong to an unusually large jaguar. 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.