Paramachairodus

''Paramachaerodus'' is an extinct genus of saber-tooth cat of the subfamily Machairodontinae, which was endemic to Eurasia during the Middle and Late Miocene from 15 to 9 Ma. A 2022 phylogenetic analysis suggested that the genus may be polyphyletic.

''Paramacherodus'' is one of the earliest known true saber-toothed cats. Many fossils were discovered in Cerro de los Batallones, a Late Miocene fossil site near Madrid, Spain. One leopard-sized species is known, ''Paramachaerodus orientalis'' from the Turolian. A second species, ''Paramacharodus maximiliani'', has been considered a synonym of ''Paramachaerodus orientalis'' by some authors, but was considered a valid species in the most recent systematic revision. That revision, based on an extensive morphological analysis, also determined that the species ''P. ogygia'' exhibited less derived sabertooth features than the other ''Paramachaerodus'' species and should be assigned to a separate genus, '' Promegantereon''.

Description

The animals were about high at the shoulder, similar to a leopard, but with a more supple body. The shape of its limbs suggests that it may have been an agile climber, and could have hunted relatively large prey.

History and naming

In 1913, Guy Ellcock Pilgrim named the new genus ''Paramachaerodus'' for the species ''Machaerodus orientalis'', ''Machaerodus schlosseri'', and ''Felis ogygia''; at the time, however, he failed to designate a type species. In 1915 he described more material that he assigned to ''Paramachaerodus'' cf. ''schlosseri'' (two hemimandibles, GSI-140 and GSI-141), though Matthew (1929) noted that both of those specimens did not closely resemble others in the genus. He rectified the lack of a type species in 1931 by designating ''Paramachaerodus orientalis'' the type species, now including ''Paramachaerodus schlosseri'' as a junior synonym.

However, in the intervening span of time, Miklos Kretzoi had proposed another new genus, ''Pontosmilus'', for the species ''P. orientalis'' (also the type species), ''P. schlosseri'', ''P. ogygia'', ''P. hungaricus'', and the new species ''Pontosmilus indicus'' that he described based on GSI-141. He restricted ''Paramachaerodus'' to another new species, ''P. pilgrimi'', that he described based on GSI-140. He also proposed the genus ''Proamphimachairodus'' for the species ''Machairodus maximiliani''.

With Pilgrim's clarification of ''Paramachaerodus'' in 1931, and utter rejection of both ''Pontosmilus'' and ''Proamphimachairodus''-he included ''Machairodus orientalis'', ''Felis ogygia'', and ''Machairodus maximiliani'' as species of ''Paramachaerodus''-''Pontosmilus'' was rendered an invalid genus, for it possessed no valid type species, and both ''Pontosmilus'' and ''Proamphimachairodus'' were designated junior synonyms of ''Paramachaerodus''.

A major review of the genus in 2010 designated ''P. matthewi'', ''P. schlosseri'', ''P. hungaricus'' as junior synonyms of ''P. orientalis'', with ''P. maximiliani'' the only other valid species in ''Paramachaerodus'', and assigning ''P. agygia'' back to ''Promegantereon''. It also noted that ''"Pontosmilus" indicus'' (GSI-141) was a feline, and ''"Pontosmilus" pilgrimi'' (GSI-140) a machairodontine not of ''Paramachaerodus'' or ''Promegantereon'', though the authors offered no alternate genus assignments for either species.

A third species, ''Paramachaerodus transasiaticus'', was described in 2017 based on analysis of new fossil material from the late Miocene localities of Hezheng, Gansu Province, China, and Hadjidimovo, Bulgaria. These specimens had sabertooth characteristics intermediate between those of ''P. ogygia'' and those of ''P. orientalis'' and ''P. maximiliani''.

In 2022, a new species ''Paramachaerodus yingliangi'' was proposed based on fossils from northeastern China; the same paper also proposed separating ''Paramachaerodus schlosseri'' as the new type species and moving ''P. orientalis'' and ''P. maximiliani'' to the resurrected genus ''Pontosmilus''.

Classification

The position of ''Paramachaerodus'' within the Machairodontinae has been subject to much controversy, partially because many names have historically been proposed for it based on only scanty material. While ''Paramachaerodus'' is generally accepted as a close relative and probable forerunner of ''Megantereon'' and therefore an ancestor of ''Smilodon'', the role ''Promegantereon'' played in this is still controversial. While researchers have generally favoured the classification of ''Promegantereon'' as a distinct genus starting in the early 2000's, it was still thought to be a close relative and potential ancestor of ''Paramachaerodus''. Thus, ''Paramachaerodus''' position within the Smilodontini was generally understood as intermediate, with ''Promegantereon'' as the first and ''Smilodon'' as the ultimate representative of that machairodontine tribe.

However, a 2022 phylogenetic analysis by Jiangzuo et al. cast doubt on this, and indeed on the monophyly of ''Paramachaerodus'' itself. While it confirmed ''P. orientalis'' as basal to the ''Megantereon-Smilodon'' clade (the Smilodontini sensu stricto) as proposed earlier, ''P. maxilmiliani'' was instead found to be basal to a clade comprising '' Rhizosmilodon'' and '' Dinofelis''. At the same time, ''Promegantereon'' and ''Paramachaerodus transasiaticus'' were found to group together with '' Metailurus'' and ''Yoshi'', which are usually placed in the separate Metailurini tribe. This would make ''Paramachaerodus'', the Smilodontini and the Metailurini as traditionally definded polyphyletic, and calls for more work regarding machairodontine systematics, suggesting that a major revision of the subfamily may be needed.

Paleobiology

Based on the morphology of its humerus, ''P. orientalis'' is inferred to have been adapted for wooded environments.

Paleoecology

References

External links

Paramachairodus at the bluelion.org

{{Taxonbar, from1=Q2051668, from2=Q122231603, from3=Q122231608, from4=Q122231610, from5=Q122231612

Smilodontini
Miocene felids
Prehistoric carnivoran genera
Fossil taxa described in 1913