The American lion (Panthera atrox), also known as the North American lion, was a large, extinct cat that lived in North America during the Late Pleistocene, from about 129,000 to 13,100 years ago. Its scientific name means "savage" or "cruel." Genetic studies show that the American lion is most closely related to the modern lion (Panthera leo). It is believed to have separated from the Eurasian cave lion (Panthera spelaea) around 165,000 years ago. Fossils of the American lion have been found across North America, from Canada to Mexico.
The American lion was about 25% larger than the modern lion, making it one of the largest known cats in history. It was a top predator in North American ecosystems, living alongside other large carnivores like the sabertooth cats Smilodon and Homotherium. Some scientists think the American lion may have lived in groups, like modern lions, but this is not certain. Unlike modern lions, which are mostly active at night, the American lion may have been active during the day.
The American lion became extinct during the end-Pleistocene extinction event, which caused the disappearance of many large animals in the Americas. This extinction occurred after humans arrived in the region. Possible reasons for its extinction include climate change, which reduced suitable habitats, and human hunting of herbivores, which disrupted the balance of the ecosystem.
History and taxonomy
The first fossil now called Panthera atrox was found in the 1830s by William Henry Huntington. He shared his discovery with the American Philosophical Society on April 1, 1836, and placed it with other fossils in the Academy of Natural Sciences in Philadelphia. The fossil came from ravines in Natchez, Mississippi, and was dated to the Pleistocene era. It included only part of a left jaw with three molars and a partial canine tooth. The fossils were not properly described until 1853, when Joseph Leidy named the incomplete specimen Felis atrox, meaning "savage cat." In 1873, Leidy also named another species, Felis imperialis, based on a jaw fragment from Livermore Valley, California. However, Felis imperialis is now considered the same as Panthera atrox. A replica of the jaw from the first American lion fossil discovered is displayed in the hand of a statue of Joseph Leidy, which stands outside the Academy of Natural Sciences in Philadelphia.
Few more fossils were found until 1907, when the American Museum of Natural History and College of Alaska collected several Panthera atrox skulls from a location first discovered in 1803 by gold miners in Kotzebue, Alaska. In 1930, these skulls were classified as a new subspecies, Felis atrox "alaskensis." However, this name is now considered invalid and is grouped with Panthera atrox. Further south, in Rancho La Brea, California, a large cat skull was found and described in 1909 by John C. Merriam. He named it Felis atrox bebbi, a subspecies of Felis atrox. This subspecies is now considered the same as Panthera atrox.
From the early to mid-1900s, many fossils of Panthera atrox were found at La Brea, including bones and full skeletons. Merriam and Stock described these fossils in detail in 1932, grouping many previously named species with Felis atrox. At least 80 individuals from La Brea Tar Pits are known, and these fossils define the subspecies, providing a complete picture of the taxon. In 1941, George Simpson moved Felis atrox to Panthera, believing it was a subspecies of the jaguar. Simpson also grouped fossils from central Mexico, Chiapas, Nebraska, and other western U.S. regions with Panthera atrox. In 1971, fragmentary remains from Alberta, Canada, were described, expanding Panthera atrox’s range north. In 2009, a fossil site in Natural Trap Cave, Wyoming, was briefly studied. It is the second most productive site for Panthera atrox fossils and contains well-preserved mitochondrial DNA from many partial skeletons.
In the 1890s, fossil collector Rodolfo Hauthal found a partial skeleton of a large cat in the "Cueva del Milodon" in southern Chile. He sent it to Santiago Roth, who named it "Iemish listai" in 1899. However, this name is now considered invalid. In 1904, Roth renamed it Felis listai and grouped other fossils, including mandibles and a partial skull, with this species. In 1934, Angel Cabrera named Felis onca mesembrina based on a partial skull from "Cueva del Milodon." The skull was later lost, but Cabrera illustrated it. Additional fossils, including feces and mandibles, from Tierra del Fuego, Argentina, and other southern sites in Chile were also referred to Felis onca mesembrina.
In 2016, a genetic study classified Felis onca mesembrina as a subspecies of the jaguar. In 2017, another study grouped Felis onca mesembrina with Panthera atrox due to similar features, though this is not widely accepted.
The American lion was first named Panthera atrox, meaning "cruel" or "fearsome panther" in Latin. Some scientists believed it was a distinct species, while others thought it was closely related to the modern lion (Panthera leo) or the extinct Eurasian cave lion (Panthera leo spelaea). Later, it was classified as a subspecies of Panthera leo (P. leo atrox). Recently, both P. spelaea and P. atrox have been treated as full species.
Studies using physical features have not clearly determined the American lion’s place in the evolutionary tree. One study suggested it was closely related to tigers based on skull comparisons, particularly the braincase. Another study proposed it and the Eurasian cave lion were early branches of a lineage leading to modern leopards and lions. A more recent study concluded the American lion was a distinct species, not a lion. It may have evolved from pantherines that migrated to North America during the mid-Pleistocene, leading to American lions and jaguars. Another study grouped the American lion with modern lions and tigers, suggesting similarities with jaguars were due to evolution, not shared ancestry. Genetic studies show modern lions are the closest living relatives of Panthera atrox and P. spelaea.
Lion-like cats first appeared in Tanzania’s Olduvai Gorge about 1.7 to 1.2 million years ago. These cats spread to Eurasia from East Africa around the end of the Early Pleistocene, leading to Panthera (spelea) fossilis. The oldest accepted fossils of P. fossilis in Europe are about 700,000 to 600,000 years old, such as those found in Pakefield, England. Older fossils may exist in Western Siberia and Spain, dating to about 1 million years ago. Genetic analysis suggests Eurasian cave lions and modern lions split about 1.85 million years ago. Nuclear DNA studies indicate cave lions and American lions diverged from modern lions around 500,000 years ago, though this conflicts with fossil evidence.
Mitochondrial DNA from fossils shows the American lion (P. atrox) is closely related to late Pleistocene Eurasian cave lions (P. spelaea). It likely evolved when an early cave lion population became isolated south of the North American ice sheet. Early studies suggested the split between American and Eurasian cave lions occurred about 340,000 years ago, but later studies placed it around 165,000 years ago, matching the earliest cave lion fossils in eastern Beringia (now Alaska) during the Illinoian period (190,000
Description
The American lion is estimated to have measured 1.6 to 2.5 meters (5 feet 3 inches to 8 feet 2 inches) from the tip of the nose to the base of the tail and stood 1.2 meters (3.9 feet) tall at the shoulder. Panthera atrox, the scientific name for the American lion, showed differences in size between males and females. DeSantis et al. (2012) estimated that male American lions may have weighed between 235–523 kilograms (518–1,153 pounds), while females likely weighed between 175–365 kilograms (386–805 pounds). Wheeler and Jefferson (2009) found that American lions had greater differences in size between males and females compared to modern lions. American lion males were 1.4 times larger than females, while modern lion males are only 1.26 times larger. Their study estimated that average male American lions may have weighed 247 kilograms (545 pounds), with the largest male in their sample weighing 457 kilograms (1,008 pounds). Female American lions averaged 177 kilograms (390 pounds), with the largest female weighing 262 kilograms (578 pounds). Sorkin (2008) suggested that the American lion could have weighed up to 420 kilograms (930 pounds). Christiansen and Harris (2009) estimated that male American lions averaged 256 kilograms (564 pounds), while the largest specimen they studied weighed 351 kilograms (774 pounds).
About 80 American lion remains have been found at the La Brea Tar Pits in Los Angeles, giving scientists detailed knowledge of their physical features. These lions closely resembled modern lions but were much larger, similar to Panthera spelaea (the cave lion) and the Pleistocene Natodomeri lion of eastern Africa. Panthera atrox had stronger limb bones than modern African lions, with strength similar to that of a brown bear. Their limbs were also 10% longer than those of modern African lions relative to skull length. Studies showed that both P. spelaea and P. atrox had stronger limb bones than the large saber-toothed cat Nimravides. The strength of their upper arm bones likely resulted from being part of a group of cats with naturally stronger bones than other similarly sized cats.
Some preserved skin remains found with bones in caves in Patagonia, South America, are thought by some scientists to belong to the American lion. These skins were reddish in color. However, many scientists disagree about whether these remains belong to P. atrox. Preserved fur from closely related P. spelaea in Siberia suggests that P. spelaea had a coat similar to modern lions but slightly lighter. It likely had a thick, dense undercoat made of soft, wavy yellowish-to-white hair, along with a smaller layer of darker guard hairs. Boeskorov et al. (2021) proposed that juvenile P. spelaea had yellowish fur, while adult individuals may have had grey fur. It is unclear whether American lions had manes or not. Cave art of P. spelaea suggests that male cave lions likely had no manes or only very small ones. Manes may have evolved only in the modern lion lineage after the split between cave lions and modern lions, likely around 320,000 to 190,000 years ago. This idea suggests that manes did not develop in the cave lion lineage.
Paleobiology
Phylogenetic analysis shows American lions may have hunted during the day, unlike modern lions, which hunt at night. The shape of their limbs suggests they were ambush predators. The structure of their jaws clearly indicates they were specialized to hunt large animals. American lions likely preyed on mammoths, deer, horses, camels, tapirs, American bison, and other large hoofed mammals. Evidence from Natural Trap Cave in Wyoming, including nitrogen and carbon isotopes, shows that pronghorns were an important food source for American lions. This may have been due to direct hunting or stealing food from Miracinonyx, a predator sometimes called the "American cheetah." Other than pronghorns, their diet appears to have been evenly split among horses, bison, and sheep. In San Luis Potosí, carbon isotopes suggest American lions hunted in open forests, targeting prey such as bison, pronghorns, horses, and mammoths. Strontium isotopes indicate they likely did not travel far to find food, instead staying near water sources. At La Brea Tar Pits, isotopic analysis of bone collagen shows American lions had similar values to Smilodon fatalis and dire wolves, suggesting competition among these large predators. However, more recent isotopic analysis of tooth enamel found dire wolves had much higher carbon values than American lions and Smilodon, with little overlap. Dire wolves likely focused on open environments, while American lions preferred forested areas, similar to Smilodon. The availability of prey in the Rancho La Brea area was likely similar to modern East Africa.
Dental microwear patterns suggest American lions avoided bones, like modern cheetahs, more than Smilodon. Panthera atrox, a related species, had the most broken canines in La Brea, indicating a preference for larger prey than other carnivores. Microwear also shows that carcass use by Panthera atrox declined over time (about 30,000 to 11,000 radiocarbon years ago). A gray wolf femur from La Brea shows signs of a severe bite, possibly amputating the leg. Researchers believe Panthera atrox, with its strong bite force and ability to shear bones, may have caused the injury. Based on skull width, a 347 kg (765 lb) American lion likely had a bite force of 2,830 newtons.
Like most Panthera species, American lions may have been able to roar, based on the structure of their hyoid bones. Whether they lived in groups like modern lions or were solitary like tigers is unknown. Some scientists argue that American lions and Panthera spelaea (another species) were social because of similar sexual dimorphism to modern lions, which may have evolved early in their lineage. However, other scientists caution that sexual dimorphism alone is not a reliable indicator of social behavior, as leopards have similar traits but are solitary. Fossil and isotopic evidence suggest Panthera spelaea was likely solitary. In 2009, Christiansen and Harris proposed American lions were not part of the lion lineage and were solitary. However, genetic studies challenge this, and differences in remains suggest behavioral differences between the two species.
Some scientists suggest that if American lions were social, they might have had larger brains relative to their body size compared to solitary predators at La Brea. However, studies show no direct link between brain size and social behavior in big cats. American lion remains are less common than those of Smilodon fatalis or dire wolves at La Brea, which may indicate they were better at avoiding traps, possibly due to higher intelligence. However, the presence of many dire wolves, also considered intelligent, challenges this idea.
Despite their rarity, the high number of juvenile American lion remains at La Brea suggests possible social behavior, as seen in modern lions. However, their low numbers may also indicate they were more solitary than Smilodon or dire wolves, or lived in small groups like African wild dogs. Some researchers, such as Wheeler and Jefferson, argue American lions likely lived in prides like modern lions, based on the presence of many young males and few young females at La Brea. They suggest female American lions may have stayed in prides more often, avoiding traps. However, the small number of remains before 14,000 years ago does not confirm or deny this theory.
Distribution
The earliest American lions found in the Americas south of Alaska lived during the Sangamonian Stage, a time period similar to the global Last Interglacial, which occurred about 130,000 to 115,000 years ago. During this time, American lions spread quickly across North America. Their range included areas from Canada to southern Mexico and from California to the Atlantic coast. They usually did not live in the same areas as jaguars, which preferred forests over open spaces. American lions were not found in eastern Canada or the northeastern United States, possibly because dense boreal forests covered those regions. Fossils of the American lion have been found in Extinction Cave in Belize. It was once thought that American lions reached northwestern South America as part of the Great American Interchange, when animals moved between North and South America. However, fossils found in tar pits in Talara, Peru, were later identified as belonging to a very large jaguar, not an American lion. In southern Chile and Argentina, some scientists have suggested that fossils from the late Pleistocene, traditionally thought to be a rare type of jaguar, might actually belong to the American lion. However, this idea is debated, and many scientists still believe the fossils are from jaguars. The American lion likely lived in savannas and grasslands, similar to modern lions. Studies of their bones suggest they also lived in forests and areas with few trees, showing they adapted to a variety of environments.
Extinction
The American lion became extinct during the end-Pleistocene extinctions, which happened around 13,000 to 12,000 years ago. This extinction occurred at the same time as many large mammals across the Americas. Early research suggested that the most recent fossil of the American lion, found in Edmonton, Canada, was about 12,877 years old. This fossil was 400 years younger than the youngest cave lion fossil found in Alaska. However, newer studies indicate that the American lion may have gone extinct slightly earlier, with the most recent reliable evidence dating to about 13,100 years ago. These extinctions happened after humans arrived in the Americas. Scientists have debated the causes of these extinctions, with many suggesting that climate change, human activity, or a combination of both were responsible.
Arias-Alzate et al. (2017) proposed that the American lion’s habitat in North America shrank significantly during the Last Glacial Period, making it harder for the species to survive. Valkenburgh and Hertz (1993) noted that higher rates of tooth fractures in American lion fossils suggest that prey was scarce at times, leading to increased competition for food among large carnivores. However, DeSantis et al. (2012) questioned this idea, arguing that larger carnivores have weaker teeth and that the high rates of tooth breakage in American lions and Smilodon may have been caused by eating large prey. Additionally, evidence shows that American lions used carcasses less frequently in later periods, which contradicts the idea that conditions were worsening during the La Brea era.
Ripple and Valkenburgh (2010) suggested that the extinction of the American lion, along with other large carnivores like dire wolves and Smilodon, may have been caused by trophic cascade effects. These effects could have resulted from early humans hunting herbivores, which disrupted the balance of ecosystems. These researchers believed that herbivores were already at low population levels before humans arrived because their numbers were limited by predators, not by the availability of food. Humans, with their flexible diets, may have survived better than other predators as herbivore populations declined. The extinction of the American lion happened before the Younger Dryas and during the Bølling-Allerød warming period. During this time, temperatures rose, and habitats opened up, which coincided with a decline in herbivore populations. This period also saw an increase in wildfires, likely caused by human activity.