Megantereon

, Paris.The type species of Megantereon, M. cultridens was described by Georges Cuvier in 1824, as Ursus cultridens, based on two teeth collected from Pliocene sediments in the Valdarno region of Tuscany, Italy, erroneously considering them to belong to a bear. In addition to the two teeth of Megantereon, Cuvier included another, much older tooth from the late Miocene of Eppelsheim in Germany in the species, which is now known to belong to the unrelated sabertooth cat Machairodus aphanistus. This decision would result in much later taxonomic confusion. In 1824, a fossil mandible of Megantereon from the Les Etouaires site in France was described by Croizet and Jobert as the new felid species Felis megantereon. As scientists were unfamiliar with the concept of sabertooths at the time, they did not realise that a large upper canine from the site belonged to the same species, instead attributing it to Cuvier's Ursus cultridens. In 1828, French paleontologist M. Bravard described a skull with preserved sabers from the Mont Perrier site in France as the species Megantereon megantereon. He suggested that Ursus cultridens should be renamed Machairodus cultridens and should be restricted to cats with serrated saberteeth (as is the case with the Eppelseim tooth, but not the unserrated teeth from Valdarno). However, in an 1890 review of sabertooth cat remains from Tuscany, Fabrini used the species name Machairodus (Meganthereon) cultridens to refer to cats which had unserrated canine saber teeth like those from Valdarno. There was much taxonomic confusion regarding the issue until 1979 when another review of sabertooth cats from Tuscany was carried out by G. Ficcarelli, who found that Megantereon crenatidens was the valid species according to nomenclatural rules for those sabertooths with unserrated sabers. The number of species of Megantereon is highly controversial, with the number of valid species differing between authors. Historically some authors argued that there was just one species. M. cultridens, but all recent authors agree that there were at least two species, also including the African M. whitei, with some authors arguing for 6 or 7 valid species. Below are a list of named Megantereon species, almost certainly not all of which are valid: • Megantereon cultridens (Cuvier, 1824) (type species) • Megantereon megantereon • Megantereon adroveri Pons Moya, 1987 • Megantereon ekidoit Werdelin & Lewis, 2000 • Megantereon nihowanensis • Megantereon inexpectatus • Megantereon lantianensis • Megantereon macroscelis • Megantereon falconeri Pomel, 1853 • Megantereon hesperus (Gazin, 1933) • Megantereon microta Zhu et al., 2015 • Megantereon vakhshensis Sarapov, 1986 • Megantereon whitei Broom, 1937 • Megantereon gracile • Megantereon eurynodon Remains of Megantereon have been found in eastern and southern Africa, and across Eurasia. Some authors have proposed that the North American M. hesperus is the ancestor of all later Megantereon species, first appearing during the early Pliocene, and dispersing over the Bering Land Bridge around 3.5-3.0 million years ago. Other authors have considered this species, whose holotype specimen is a fragmentary lower jaw, indeterminate remains of Smilodontini, and therefore suggest that Megantereon is only unambiguously known from Afro-Eurasia. In Europe, the oldest remains are known from Les Etouaries (France), a site which is now dated to 2.78 million years ago, which represent among the oldest records of the genus in Euriasia. Ficcarelli (1979), Turner (1987) and Sardella (1998) considered all European remains of the species to belong to the species M. cultridens, though most modern authors distinguish between an earlier M. cultridens, and a later, more advanced form of Megantereon in Europe of disputed classification. The species Megantereon nihowanensis was proposed in 1930 based on remains found in the Nihewan Basin in Hebei, northern China. In 2020, additional remains were assigned to this species from Sabretooth Cave, Chongzuo in southernmost Guanxi, China, near the border with Vietnam. Megantereon lantianensis was named for remains from Lantian, Shaanxi, central north China. Some authors have considered M. lantianensis as chonologically later than Machairodus nihowanensis in northern China, while others have considered M. lantianensis to be a synonym of Megantereon inexpectatus. Some authors have proposed that Megantereon inexpectatus is more closely related to the African M. whitei than to earlier Chinese Megantereon'' species. In Africa, while most remains are attributed to M. whitei, some authors have attributed the earliest known remains of the genus on the continent (dating to around 3.58–3.2 million years ago) from the Turkwel locality in Kenya to the separate species Megantereon ekidoit, based on dental differences from later remains assigned to M. whitei. ==Description==

(bottom/C) in side-on view. Illustration by Mauricio Anton.The skull of Megantereon is very similar in morphology and proportion to that of the closely related Smilodon, with both cats exhibiting very long upper canine teeth. A notable difference exists, however, in the presence of a pronounced mandibular flange in the former, projecting downwards near the front of the mandibles. This flange is shared with other, unrelated sabertooths, such as Barbourofelis and Eusmilus, but is notably absent in Smilodon. Other differences include the lack of serrations on the posterior edge of the upper canines in Megantereon (present in Smilodon)Species of Megantereon were comparable in size to living leopards or jaguars. A 1996 study based on the size of the cross-section of the humerus, suggested a body weight of about for a specimen of Megantereon from the Early Pleistocene of Greece (attributed in the paper to M. whitei). A 2007 study estimated a body mass of a large specimen of Megantereon cultridens (SE311 from Senéze, France) as , with a body length of . Mauricio Anton's reconstruction in The Big Cats and their Fossil Relatives depicts the full specimen found at at the shoulder. ==Palaeobiology and paleoecology==

Predatory behavior and major blood vessels. Artwork by Mauricio Anton.Megantereon is thought to have been an ambush predator. It is thought to have used its powerful forelimbs to restrain prey In a study from 2007, Christiansen estimated that a M. cultridens of may have had a bite force of at the canines. Megantereon also had relatively small carnassial teeth, indicating that once making a kill, it would have eaten its prey at a leisurely pace, either hidden deep in bushes or in a tree away from potential rivals. This indicates a similarity to modern leopards and their lifestyle in that it was probably solitary. Other experts dispute that Megantereon would have been unable to climb proficiently due to its heavy build, and argue that its relatively small claws, stocky limbs and short tail argue against regular climbing. In this case Megantereon would have been unlike the earlier Promegantereon (thought to be its ancestor), but similar to the later Smilodon, which is believed to have spent its time on the ground. Some experts argue even if Megantereon was scansorial, its large, laterally flattened canines would've prevented it from dragging kills long distances or tree caching as seen with leopards. Neuroanatomy of M. cultridens suggests this species of Megantereon was probably scansorial or developed mobility in three dimensions due to morphology and size of the cerebellum. Experts have argued that Megantereon consumed exclusively soft tissues and would've left a significant amount of carrion to other predators much like modern cheetahs, with the felid's leftovers probably being frequently being scavenged by both hominins and hyaenids. The abundance of carcasses generated by Megantereon has been proposed as a facilitator of early hominin expansion out of Africa. Ecology Isotopic analysis of Megantereon (assigned in these studies to M. whitei) from the Venta Micena locality in southeast Spain dating to the Early Pleistocene, around 1.6 million years ago, suggests that at this locality Megantereon hunted large, mainly forest-associated ungulates, including the equine Equus altidens, the muskox-relative Soergelia, and the giant deer Praemegaceros, probably ambushing prey at the border between forest and savannah. It overlapped in diet somewhat with the "European jaguar" Panthera gombaszogensis with which shared its forested habitat, while the larger sabertooth Homotherium latidens and the pack hunting canine Xenocyon lycaonoides are thought to have inhabited more open habitats. Other animals found at the site include the "southern mammoth" Mammuthus meridionalis, and the large hippo Hippopotamus antiquus. Within the Senéze locality of France, M. cultridens coexisted with primates such as Paradolichopithecus arvernensis and Macaca sylvanus, the proboscidean Mammuthus meridionalis, the equine Equus and the large rhino Stephanorhinus etruscus, the suid Sus strozzii, cervids such as Croizetoceros ramosus, Metacervocerus philisi, Eucladoceros ctenoides, and Libralces gallicus, bovids such as Gazellospira torticornis, Megalovis latifrons, Gallogoral meneghinii, Pliotragus ardeus, and Leptobos furtivus, and carnivorans present included felids such as Acinonyx pardinensis and Homotherium, canids such as Canis senezensis, Vulpes alopecoides, Nyctereutes megamastoides, hyenas such as Pliocrocuta perrieri and Chasmaporthetes lunenesis, and the ursid Ursus etruscus. Within the Djurab desert in northern Chad, Megantereon coexisted with machairodonts such as Amphimachairodus kabir, Lokotunjailurus, Tchadailurus and Dinofelis. Additional animals included crocodiles, three-toed horses, fish, monkeys, hippos, aardvarks, turtles, rodents, giraffes, snakes, antelopes, pigs, mongooses, foxes, hyenas, otters, honey badgers and the hominid Sahelanthropus. Based on the available fossils, it is theorized that the Djurab was once the shore of a lake, generally forested close to the shore with savannah-like areas some distance away. The number of felids suggests the Djurab desert had a diverse of habitats that was filled with diverse herbivores. Examinations of the reconstructed brain of Megantereon cultridens published in 2026 suggest behavioral and ecological plasticity comparable to the extant cougar and jaguar. This same study likewise vindicates evidence of Megantereon being scansorial. These adaptations would have been necessary to the animal's ability to survive in habitats with high degrees of intraguild competition and high diversity of medium to large felids, including other machairodonts. Although a skull of Homo erectus georgicus (D2280) from Dmanisi in Georgia has been suggested to display bite marks by Megantereon, other authors have suggested that the bite marks cannot be attributed with certainty to Megantereon, and that the giant hyena Pachycrocuta or a member of the big cat genus Panthera are more likely culprits. A 2000 isotope study of remains from the Early Pleistocene Swartkrans cave in South Africa suggests that at this locality Megantereon preyed on hominins, including Paranthropus robustus and early Homo, as well as baboons. M. nihowanensis was a member of the "Gigantopithecus fauna" of southern China. Contemporary fauna includes the giant ape Gigantopithecus, and extinct species of orangutang (Pongo), proboscideans such as Sinomastodon and Stegodon, rhinoceroses of the genus Rhinoceros, and tapirs (Tapirus). Its rarity in southern China suggests M. nihowensis was not well adapted for closed forests compared to contemporary Panthera, instead open forests or steppe with shrubs are far more ideal environments. == Extinction ==

Megantereon became extinct in East Africa probably no later than around 1.4 Ma, having become extinct in Africa by 1.3 Ma. Additionally, recent analysis found stone damaged bones may have been already widespread around 3-2.58 Ma. Palmqvist et al. 2021 argued that Megantereon likely persisted longer in Eurasia due to the later development of Acheulean tools. The youngest remains of the genus in Europe date to around 1 Ma, becoming extinct in the region during the mid-Pleistocene transition possibly to climatic change, which made the region more arid and increased open grassland habitat at the expense of forest. ==References==