The American Lion (Panthera atrox)

Taxonomy

Panthera atrox, more commonly known as ‘the American lion’ is a species belonging to cat family, felidae. It’s relationship to other big cats (Panthera spp.) has been contentious, affinities to the cave lion (Panthera spalea), jaguar (Panthera onca), lion (Panthera leo) and tiger (Panthera tigris) have all been suggested at various times (4, 8). In the light of recent DNA discoveries, it has been established that the name ‘American lion’ is well deserved as it is most closely related to the Cave lion, and the closest living relative is the modern lion (Panthera leo) (1). This has also been corroborated by a recent morphological analysis (5), though other morphological analyses have produced alternative results (4). There is no consensus on whether the three lions should be treated as separate species or subspecies of Panthera leo. The American Lion diverged from the cave lion about 340,000 years ago (1) and the modern lion around 550,000 years ago (1), though some studies place this divergence at 1.85-1.89 million years ago (9, 10). Gene flow between the species appears negligible (1). The recent divergence date from the cave lion indicates that the American lion is derived from a population of cave lions which colonised North America from Eastern Beringia but became isolated by the presence of the North American glaciers and speciated into the American Lion (1).

Distribution and Age

The earliest remains date of the American lion date to the Illinoian stage around 200kya (8), placing it significantly later than the suggested origin time (1). The youngest directly dated remains of the American lion are about 11,355 years old, datings which are based on associated charcoal extend this to 10,370ya but are dubious (1), the American lion is therefore certainly a part of the megafaunal extinctions in the Americas at the end of the Pleistocene. The distribution of the American lion was quite extensive, ranging from Central Alberta to Southern Mexico (2). Fossils appear most common along the western part of North America, but a few have been retrieved from the Eastern seaboard (2).

Specimens from Southern Chile assigned to the extinct subspecies of Jaguar Panthera onca mesembrina have been suggested by a few authors to belong to the American lion (3). One such specimen is from an individual estimated at 230kg, more than twice that of an average Jaguar and significantly more than any known extinct Jaguar (3). Teeth-mark attributable to Panthera on very large megafauna, also indicates the presence of large species (3). The material does show some affinities to the American lion but is fragmented, thus further findings and analysis will be required before a definite assignment to the American lion can be established. If correct it would expand the range of the American lion to almost the entirety of the Americas. Recent DNA evidence has however reaffirmed the identity of the giant pantherid as a subspecies of large jaguar (12).

Morphology and Ecology

The American lion is a very large felid, eclipsing all extant cat species in body mass. Depending on the morphology analysed a large range of estimates can be extracted, with liberal estimates placing the largest individuals around 450kg, but a weighted estimate of 332kg may be closer to the mark (8). Additionally, the species is highly sexually dimorphic with males 40% larger than females, females averaged 178kg and males 251kg at La Brea Tar Pits but this may not be indicative of the whole population (8). Much like in modern lions the American lion likely lived in prides and performed co-operative hunting, cave paintings have clearly shown this behaviour in the cave lion, implying the behaviour to be a shared feature of the lion lineage (8). Evidence of prides and group hunting in the American lion is difficult to come by, though disproportionately high mortality in young males at La Brea Tar Pits has been observed, which would make sense as young males are expelled from lion prides in Africa and may be both inexperienced and reckless (8).

As one might expect the morphology of the American lion  is most reminiscent of the cave lion, though differences can be noted in the dental morphology, the skull also shares similarities with both the lion, tiger, and jaguar (4, 8). An Interesting characteristic is the high length of the limbs of the American lion even more so than in modern lions, this is probably an adaptation to pursuit hunting in open spaces (8). Otherwise, the American lion is rather typical in build for a large pantherine.

The American lion appears to have been most at home in an open landscape, as can be noted from the presence of plains species such as the American cheetah (Miracionyx trumani) and pronghorn (Antilocapra americana) at sites where the American lion is common. This is further backed up by the rarity of the species when in the presence of Smilodon fatalis which is a well-established ambush predator, suggesting a niche partitioning between the two species with the American lion dominating where ambush predation is less effective (8).

A study conducted by Van Valkenburgh et al estimated that if American lions were indeed group hunters they were probably capable of taking prey as large as 6,700kg which would include all megafauna on the continent, except for large male proboscideans (7). The typical prey would range between 200 and 900kg (Van 7) and inhabit the open plains of North America. The most common prey species would have varied considerably across the range of the American lion but may have included camelids (Hemiauchenia and Camelops), horses (Equus ferus and Haringtonhippus francisci), bovids (Bootherium bombifrons and Bison spp.) and deer (Cervus canadensis and Rangifer tarandus)(2, 6, 8). Many large predators may well have competed with the American lion for prey. Chief amongst them would be the other large felids Homotherium latidens, Smilodon fatalis and jaguar (Panthera onca). Additionally, both the Grey Wolf (Canis lupus) and Dire wolf (Aenocyon dirus), as well as the Short-faced bear (Arctodus simus), would have prey overlap.

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References

1.      Barnett, R., Shapiro, B., Barnes, I., Ho, S. Y. W., Burger, J., Yamaguchi, N., Higham, T. F. G., Wheeler, H. T., Rosendahl, W., Sher, A. V., Sotnikova, M., Kuznetsova, T., Baryshnikov, G. F., Martin, L. D., Harington, R., Burns, J. A., Cooper, A.. (2009). Phylogeography of lions (Panthera leo ssp.) reveals three distinct taxa and a late Pleistocene reduction in genetic diversity. Molecular Ecology 18, 1668-1677.

2.      Bravo-Cuevas, V. M., Priego-Vargas, J., Cabral-Perdomo, M. A., Maldonado, M. A. P.. (2016). First occurrence of Panthera atrox (Felidae, Pantherinae) in the Mexican state of Hidalgo and a review of the record of felids from the Pleistocene of Mexico. Fossil Record 19, 131-141.

3.      Chimento, N. R., Agnolin, F. L.. (2017). The fossil American lion (Panthera atrox) in South America: Palaeobiogeographical implications. Comptes Rendus Palevol 16. 850-864.

4.      Christiansen, P., Harris, J. M.. Craniomandibular morphology and phylogenetic affinities of Panthera atrox: implications for the evolution and paleobiology of the lion lineage

5.      King, L. M., Wallace, S. C.. (2014). Phylogenetics of Panthera, including Panthera atrox, based on craniodental characters, Historical Biology 26(6), 827-833.

6.      Kohn, M. J., McKay, M. P.. (2012). Paleocology of late Pleistocene-Holocene faunas of eastern and central Wyoming, USA, with implications for LGM climate models. Palaeogeography, Palaeoclimatology, Palaeoecology 326-328, 42-53.

7.      Van Valkenburgh, B., Hayward, M. W., Ripple, W. J., Meloro, C., Roth, V. L.. (2016). The impact of large terrestrial carnivores on Pleistocene ecosystems. PNAS 113(4). 862-867.

8.      Wheeler, H. T., Jefferson, G. T.. (2009). Panthera Atrox: Body proportions, size, sexual dimorphism, and behaviour of the cursorial lion of the North American Plains.

9. Barnett, R., Mendoza, M. L. Z., Soares, A. E. R., Ho, S. Y. W., Zazula, G., Yamaguchi, N., Shapiro, B., Kirillova, I. V., Larson, G., Gilbert, M. T. P..(2016). Mitogenomics of the Extinct Cave Lion, Panthera spelaea (Goldfuss, 1810), Resolve its Position within the Panthera Cats. Open Quaternary, 2 (4), 1–11

10. Stanton, D. W. G., Alberti, F., Plotnikov, V., Androsov, S., Grigoriev, S., Fedorov, S., Kosintsev, P., Nagel, D., Vartanyan, S., Barnes, I., Barnett, R., Ersmark, E., Doppes, D., Germonpre, M., Hofreiter, M., Rosendahl, W., Skoglund, P., Dalen, L.. (2020). Scientific Reports 19, 12621

11. Faurby, S., Pedersen, R. Ø., Davis, M., Schowanek, S. D., Jarvie, S., Antonelli, A., & Svenning, J.C. (2020). PHYLACINE 1.2.1: An update to the Phylogenetic Atlas of Mammal Macroecology. doi:10.5281/zenodo.3690867

12. Metcalf, J. L., Turney, C., Barnett, R., Martin, F., Bray, S. C., Vilstrup, J. T., Orlando, L., Salas-Gismondi, R., Loponte, D., Medina, M., De Nigris, M., Civalero, T., Fernandez, P. M., Gasco, A., Duran, V., Seymour, K. L., Otaola, C., Gil, A., Paunero, R., Prevosti, F. J., Bradshaw, C. J. A., Wheeler, J. C., Borrero, L., Austin, J. J., Cooper, A.. (2016). Synergistic roles of climate warming and human occupation in Patagonian megafaunal extinctions during the Last Deglaciation. Science Advances 2 (6)