Panthera spelaea

Panthera spelaea, also known as the cave lion or steppe lion, is an extinct Panthera species native to Eurasia and northwest North America during the Pleistocene epoch. Genetic analysis of ancient DNA has revealed that while closely related, it was a distinct species genetically isolated from the modern lion (Panthera leo), with the genetic divergence between the two species estimated at around 500,000 years ago. The earliest fossils of the P. spelaea lineage (either regarded as the separate species Panthera fossilis or the subspecies P. spelaea fossilis) in Eurasia date to around 700,000 years ago (with possible late Early Pleistocene records). It is closely related and probably ancestral to the American lion (Panthera atrox). The species ranged from Western Europe to eastern Beringia in North America, and was a prominent member of the mammoth steppe fauna, and an important apex predator across its range. It became extinct about 13,000 years ago. It closely resembled living lions with a coat of yellowish fur, though unlike living lions males appear to have lacked manes.

Panthera spelaea interacted with both Neanderthals and modern humans, who used their pelts and in the case of the latter, depicted them in artistic works.

Taxonomy
Felis spelaea was the scientific name used by Georg August Goldfuss in 1810 for a fossil lion skull that was excavated in a cave in southern Germany. It possibly dates to the Würm glaciation.

Several authors regarded Panthera spelaea as a subspecies of the modern lion, and therefore as Panthera leo spelaea. One author considered the cave lion to be more closely related to the tiger based on a comparison of skull shapes, and proposed the scientific name Panthera tigris spelaea. Some authors regard the larger Middle Pleisto

Results from morphological studies showed that it is distinct in cranial and dental anatomy to justify the specific status of Panthera spelaea. Results of phylogenetic studies also support this assessment.

In 2001, the subspecies Panthera spelaea vereshchagini was proposed for seven specimens found in Siberia and Yukon, which have smaller skulls and teeth than the average P. spelaea. Before 2020, genetic analysis using ancient DNA provided no evidence for their distinct subspecific status; DNA signatures from P. spelaea from Europe and Alaska were indistinguishable, suggesting one large panmictic population. However, analysis of mitochondrial genome sequences from 31 cave lions showed that they fall into two monophyletic clades. One lived across western Europe and the other was restricted to Beringia during the Pleistocene. For this reason, the Beringian population is considered a distinct subspecies, P. s. vereshchagini.

Evolution
Lion-like pantherine felids first appeared in the Tanzanian Olduvai Gorge about. These cats dispersed to Europe from East Africa in the first half of the Middle Pleistocene, giving rise to Panthera fossilis. The oldest widely accepted fossils of P. fossilis in Europe date to around 700,000 years ago. Different authors considered Panthera fossils as either a distinct species ancestral to P. spelaea, or as a subspecies of P. spelaea. Recent nuclear genomic evidence suggest that interbreeding between modern lions and all Eurasian fossil lions took place up until 500,000 years ago, but by 470,000 years ago, no subsequent interbreeding between the two lineages occurred.

The following cladogram shows the genetic relationship between P. spelaea and other pantherine cats. Specimens intermediate between P. fossilis and Late Pleistocene P. spelaea are referred to as the subspecies P. s. intermedia. The transition from P. fossilis to Late Pleistocene P. spelaea involved significant changes in skull and tooth morphology. Mitochondrial DNA sequence data from fossil lion remains show that the American lion represents a sister group of Late Pleistocene P. spelaea, and likely arose when an early P. spelaea population became isolated south of the Cordilleran Ice Sheet. Initially this was suggested to be around 340,000 years ago, but later studies suggested that the split between the two species was probably younger, around 165,000 years ago, consistent with the late first appearance of P. spelaea in Eastern Beringia (now Alaska and adjacent regions) during the Illinoian (around 190-130,000 years ago).

Characteristics
Carvings and cave paintings of cave lions, which were discovered in the Lascaux and Chauvet Caves in France, were dated to 15,000 to 17,000 years old. A drawing in the Chauvet cave depicts two cave lions walking together. The one in the foreground is slightly smaller than the one in the background, which has been drawn with a scrotum and without a mane. Such cave paintings suggest that male cave lions completely lacked manes, or at most had very small manes. P. spelaea is also known from the Löwenmensch figurine found in Vogelherd cave in the Swabian Alb, southwest Germany, which dates to the Aurignacian culture. These archaeological artifacts indicate that it may have been featured in Paleolithic religious rituals.

P. spelaea was thought to have been one of the largest lion species. The skeleton of an adult male found in 1985 near Siegsdorf in Germany had a shoulder height of around 1.2 m and a head-body length of 2 m without the tail, similar in size to large modern lions. The size of this male was exceeded by other specimens, with another male reaching 2.5 m long without the tail. Similarly, footprints attributed to a male cave lion measured  15 cm across. The heaviest Panthera spelaea was estimated to weigh 339 kg.

This shows that P. spelaea would have been up to or over 12% larger than modern lions, but still smaller than the earlier Panthera fossilis or the American lion (P. atrox). P. spelaea had a relatively longer and narrower muzzle compared to that of the extant lion. Despite this, the two species do not exhibit major differences in morphology. Like modern lions, females were smaller than males.

In 2016, hair found near the Maly Anyuy River was identified as cave lion hair through DNA analysis. Comparison with hair of a modern lion revealed that cave lion hair was probably similar in colour as that of the modern lion, though slightly lighter. In addition, the cave lion is thought to have had a very thick and dense undercoat comprising closed and compressed yellowish-to-white wavy downy hair with a smaller mass of darker-coloured guard hairs, possibly an adaptation to the Ice Age climate.

Distribution and habitat
P. spelaea formed a contiguous population from western Europe to the Yukon over the Bering land bridge, across the range of the mammoth steppe. It was widely distributed in the Iberian Peninsula, Italian Peninsula, Southeast Europe, Great Britain, Central Europe,  the East European Plain, the Ural Mountains, and across most of northern Eurasia into Alaska and Yukon. The cave lion had a wide elevation range as well; in Slovakia, skull, femur and pelvis remains were excavated in ten Karst caves in hilly and montane areas at elevations from 240 to 1133 m.

The oldest known fossils dated with radiocarbon dating were excavated in northeastern Russia and were radiocarbon dated at 62,400 years old. Phalanx bones excavated in Spain's La Garma cave complex were radiocarbon dated to 14,300–14,000 years old. The youngest known fossils are dated 11,925 years old and originated near Fairbanks, Alaska. In Western Europe, however, P. spelaea may have survived into the Early Holocene.

In 2008, a well-preserved mature cave lion specimen was unearthed near the Maly Anyuy River in Chukotka Autonomous Okrug, which still retained some clumps of hair. In the Sakha Republic's Khayrgas Cave, bones of P. spelaea were found together with remains of humans, wolf, reindeer, Pleistocene horse and fish in a layer dated 13,200–21,500 years old.

The cave lion probably inhabited predominantly open habitats such as steppe and grasslands although it would have also have occurred in open woodlands as well. It also lived in mountainous regions, likely because it sought out hibernating bears in montane caves as a food source during the winter. While during the Last Glacial Period it was often associated with cold environments, the species also inhabited temperate environments, such as in Europe during the Last Interglacial/Eemian.

Discoveries
In 2015, two frozen cave lion cubs, estimated to be between 25,000 and 55,000 years old, were discovered close to the Uyandina River in Yakutia, Siberia in permafrost. Research results indicate that the cubs were likely barely a week old at the time of their deaths, as their milk teeth had not fully erupted. Further evidence suggests the cubs were hidden at a den site until they were strong enough to follow their mother back to the pride, as with modern lions. Researchers believe that the cubs were trapped and killed by a landslide, and that the absence of oxygen underground hindered their decomposition and allowed the cubs to be preserved in such good condition. A second expedition to the site where the cubs were found was planned for 2016, in hopes of finding either the remains of a third cub or possibly the cubs' mother.

In 2017, another frozen specimen, thought to be a lion cub, was found in Yakutia on the banks of the Tirekhtyakh River (Тирехтях), a tributary of the Indigirka River. This male cub was thought to be slightly older than the 2015 cubs at the time of its death; it is estimated to have been around one and a half to two months. In 2018, another preserved carcass of a cub was found in a location 15 m away. It was considered to be around a month old when it died approximately 50,000 years ago, and presumed to be a sibling of the male cub. However, carbon dating showed them to have lived about 15,000 years apart, with the female estimated to have lived 28,000 years ago, and the male 43,448 years ago. Both cubs were well preserved, albeit with a few damages, with the female possibly being the "best preserved" animal discovered from the Ice age.

Paleobiology
P. spelaea inhabited colder environments such as mammoth steppe and boreal forest. It was one of the keystone species of the mammoth steppe, being one of the main apex predators alongside the gray wolf, cave hyena and brown bear. Large amounts of bones belonging to P. spelaea were excavated in caves, where bones of cave hyena, cave bear and Paleolithic artefacts were also found. Some of these accumulations of cave lion bones have been attributed to hoarding of meat from cave lion carcasses by cave hyenas in caves occupied by the latter. It is unclear whether P. spelaea was social like the modern lion; some evidence indicates that it may have been solitary.

Isotopic analyses of bone collagen samples extracted from fossils indicate that cave bear cubs, reindeer and other cervids (deer) were prominent in the diet of cave lions. Later cave lions seem to have preyed foremost on reindeer, up to the brink of local extinction or extirpation of both species. Other possible prey species were giant deer, red deer, wild horse, muskox, aurochs, wisent, steppe bison, young woolly rhino, and young woolly mammoth. It likely competed for prey with the European Ice Age leopard, cave hyenas, brown bears and grey wolves in Eurasia, along with short-faced bears, Homotherium, and Beringian wolves in Beringia.

Relationship with humans
There is direct evidence of hunting of cave lions and exploitation of their pelts in Europe by both Neanderthals during the Middle Paleolithic, as well as modern humans during Upper Paleolithic (as evidenced by the Magdalenian aged La Garma site in Spain). Modern humans also drew cave paintings of cave lions, engraved their likeness on bones and created sculptures of them, including the famous anthropomorphic lion man figure from Germany dating to around 41-35,000 years ago with the body of a human and the head of a lion. Cave lion canines with perforated holes may have been worn as personal oraments.

Extinction
Radiocarbon dating suggests that the species went extinct approximately simultaneously across its range during the last few thousand years of the Late Pleistocene, around 14-15,000 years ago, possibly surviving around 1000 years later in the far east Beringian portion of its range. This timing roughly corresponds to the onset of the Bølling–Allerød Interstadial warm period and the consequent collapse of the mammoth steppe ecosystem. The precise cause of its extinction is unclear, but possibly involved environmental change from open habitats to closed forests, changes in prey abundance, as well as human impact, though it is difficult to distentangle the precise causes of its extinction.