Megantereon Model

''Megantereon'' is an extinct genus of prehistoric machairodontine saber-toothed cat that lived in Eurasia, Africa and possibly North America from the late Pliocene. It is a member of the tribe Smilodontini, and closely related to and possibly the ancestor of the famous American sabertooth ''Smilodon''. In comparison to ''Smilodon'' it was somewhat smaller, around the size of a jaguar, though it is thought to have had a similar hunting strategy as an ambush predator.

Taxonomy and evolution

The type species of ''Meganteron'', ''M. cultridens'' was described by Georges Cuvier in 1824, as '' Ursus cultridens'', based on two teeth collected from Pliocene 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 (which true ''Megantereon'' lacked). 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 true ''Megantereon''. 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 true 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.Werdelin L, Flink T: The phylogenetic context of ''Smilodon''.In ''Smilodon: The Iconic Sabertooth'', L. Werdelin, H. G. McDonald, and C. A. and Shaw, eds. (Baltimore: Johns Hopkins University Press),2018;14–29.

The true number of species may be less than the full list of described species reproduced below:
* ''Megantereon cultridens'' (Cuvier, 1824) (type species)
* ''Megantereon adroveri'' Pons Moya, 1987
* ''Megantereon ekidoit'' Werdelin & Lewis, 2000
* ''Megantereon falconeri'' Pomel, 1853
* ''Megantereon hesperus'' (Gazin, 1933)
* ''Megantereon microta'' Zhu ''et al.'', 2015
* ''Megantereon vakhshensis'' Sarapov, 1986
* ''Megantereon whitei'' Broom, 1937
Remains of ''Megantereon'' have been found in eastern and southern Africa, and across Eurasia. The origin of ''Megantereon'' is uncertain. 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. Some authors have hypothesised that an early lineage of ''Megantereon'' was ancestral to ''Smilodon,'' though this has been disputed by others, who considered ''Smilodon'' and ''Megantereon'' to be sister groups. The oldest confirmed samples of ''Megantereon'' are known from Africa from the South Turkwel site in Kenya, dated to about 3–3.5 million years ago, though possible older records are known in Africa dating to 4.4 million years ago. 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.

Remains from the Siwalik Hills in the northern Indian subcontinent dating to the Early Pleistocene have been attributed to the species ''M. falconeri.'' Some authors have attributed all remains of ''Megantereon'' in Asia to ''M. falconeri'', but others consider the species confined to the Indian subcontinent. Remains from Tajikistan in Central Asia were originally assigned to the species ''M. vakhscensis'' but this species is widely regarded as invalid and they are generally either considered either as ''M. cultridens'' or conspecific with the Indian species.

Canine teeth reportedly from the island of Java in Indonesia of Pleistocene age have been attributed to ''Megantereon'', but their provenance is uncertain. 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.'''' According to Martínez-Navarro, 1992, Martínez-Navarro and Palmqvist, 1995, Martínez-Navarro and Palmqvist, 1996, Palmqvist et al. (2007), and Li and Sun (2022), ''M. cultridens'' was replaced in Europe by the African ''M. whitei'' during the Early Pleistocene, around 1.8-2 million years ago, while others, including Werdelin and Flink (2018), and Lavrov et al. (2022) suggest that the advanced later European ''Megantereon'' instead represents a distinct species ''M. adroveri'' derived from ''M. cultridens.''

In China, Early Pleistocene remains from Renzidong Caves in Anhui, eastern China, have been attributed to the species ''Megantereon megantereon'' (a species widely considered to be a synonym of ''M. cultridens'' by European authors), though others have considered them indeterminate to the genus. Remains from Yanliang Cave, Guangxi, southern China, have also been attributed to this species, but also to the separate species ''Megantereon microta'' or also considered indeterminate within the genus. The species ''Megantereon inexpectatus'' was named for remains found in Zhoukoudian cave near Beijing. 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''.

''Megantereon'' became extinct in East Africa probably no later than around 1.4 million years ago, having become extinct in Africa by 1.3 million years ago. The youngest remains of the genus in Europe date to around 1 million years ago, 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. The youngest remains in East Asia (which are the youngest records of the genus globally) date to the Middle Pleistocene sometime between 780,000 and 350,000 years ago, and are attributed to the species ''Megantereon inexpectatus''.

Description

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'') and a less exaggerated development of the mastoid process, among other relatively subtle differences in morphology. According to a 2024 study by Antón and colleagues, ''Megantereon's'' upper canines were most likely exposed in life, as suggested also for ''Smilodon''.Species of ''Megantereon'' were comparable in size to living leopards or jaguars.'''' Their body proportions were relatively similar to those of jaguars, but with a shorter tail, a longer neck, proportionally larger vertebrae and a reduced number of vertebrae in the lumbar region, resulting in a proportionally shorter back than in feline cats. The forelimbs and shoulder of ''Megantereon'' were powerfully built with a proportionally large scapulae, while the hindlimbs were relatively more gracile and around 10% longer than the forelimbs. The limbs were relatively short, particularly the lower (distal) parts.

The largest species within the genus was ''M. falconeri'','''' with a 1995 study estimating body weight of for Siwalik ''Megantereon'' with an average body weight of . The North American species, ''M. hesperus'', was estimated to have weighed between , with an average body weight of in the same study. The African ''M. whitei'' was estimated to have a body weight of while specimens of ''Megantereon'' from the Early Pleistocene of Spain, attributed to ''Megantereon cultridens adroveri'' were estimated to have had a body mass of . These estimates were based on the size of the lower carnassial tooth. 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

''Megantereon'' is thought to have been an ambush predator. It is thought to have used its powerful forelimbs to restrain prey to deliver a fatal "canine-shear" throat bite, severing most of the victim's major nerves and blood vessels. To this end, it is thought to have used its powerful neck muscles to rotate the skull downward, forcing its saber teeth into the victim's neck, while the lower jaw served as an anchor. While the teeth would still risk damage, the prey animal would be killed quickly enough that any struggling would be feeble at best. 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. Whether and to what extent ''Megantereon'' would have been scansorial and therefore able to climb trees is debated. Arguments in favor rest upon comparisons to modern leopards, and their avoidance of larger predators by the caching of kills in trees. For ''Megantereon'', likely competitors would have included the fellow machairodont ''Homotherium'' and the hyena ''Pachycrocuta''. ''Homotherium'' is often thought to have dominated ''Megantereon'', thanks to its generally larger size and putative social lifestyle. This picture is somewhat reversed, however, at Zhoukoudian, China, where unusually small ''Homotherium'' specimens apparently coexisted with particularly large ''Megantereon'' specimens. Given that the latter was considerably stockier, this may have reversed the normal dominance relationship. 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.

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. However, this interpretation has been called into question as dental microwear suggests ''M. whitei'', which is known for its specialized dentition, has durophagy on more similar to felids such as lions than cheetahs.

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 gombaszoegensis'' 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''.

A 2023 isotope study of fossils found in the Turkana Basin in Kenya, suggested that ''M. whitei'' preyed on animals with a mean mass of ; this would have likely included the antelopes '' Aepyceros'', ''Antidorcas recki'', ''Megalotragus'', '' Kobus sigmoidalis'' and ''Tragelaphus'', the swines ''Kolpochoerus limnetes'' and '' Metridiochoerus andrewsi'', and the three-toed equine ''Eurygnathohippus ethiopicum''. Its diet was suggested to have overlapped with that of the contemporary hyena ''Crocuta ultra''.

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'', 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.

References

Further reading

* Augustí, Jordi. ''Mammoths, Sabertooths and Hominids: 65 Million Years of Mammalian Evolution in Europe''. New York: Columbia University Press, 2002, .
* Mol, Dick, Wilrie van Logchem, Kees van Hooijdonk and Remie Bakker. ''The Saber-Toothed Cat of the North Sea''. Uitgeverij DrukWare, Norg 2008, .
* Turner, Alan. ''The Big Cats and Their Fossil Relatives: An Illustrated Guide to their Evolution and Natural History''. Illustrations by Mauricio Anton. New York: Columbia University Press, 1997, .

External links

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Smilodontini
Pliocene carnivorans
Pleistocene carnivorans
Messinian genus first appearances
Pleistocene genus extinctions
Miocene mammals of Africa
Pliocene mammals of Asia
Pliocene mammals of Europe
Pliocene mammals of Africa
Pliocene mammals of North America
Pleistocene mammals of Asia
Pleistocene mammals of Europe
Pleistocene mammals of Africa
Pleistocene mammals of North America
Prehistoric carnivoran genera
Fossil taxa described in 1828
Extinct animals of Indonesia