Homotherini

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Homotherini
Temporal range: 23–0.012  Ma
Homotheriumtex1.JPG
Skeleton of Homotherium serum from Friesenhahn cave, Texas Memorial Museum, University of Texas at Austin, Austin, Texas
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Suborder: Feliformia
Family: Felidae
Subfamily:† Machairodontinae
Tribe:† Homotherini
Fabrini, 1890
Genera

Homotherini (Machairodontini) is a tribe (or subtribe) [1] of saber-toothed cats of the family Felidae (true cats). The tribe is commonly known as scimitar-toothed cats. These saber-toothed cats were endemic to North America, Europe, Asia, Africa, and South America [2] from the Miocene to Pleistocene living from c. 23 Ma until c. 12,000 years ago. [3] The evolutionary relationship between the tribes Homotherini and Machairodontini cause paleontologists to classify Homotherini either as a subtribe of Machairodontini, or the same tribe often using either name interchangeably.

Contents

Description

Compared to the usually massively built dirk-toothed phenotype, apparent in Smilodon , Megantereon and the feliform Barbourofelis (just to list a few), their upper canines were smaller than those of equally sized cats of that phenotype, but they had serrated edges. [4] [5] The scimitar-toothed phenotype has also evolved independently in other mammal families. [6]

The subtribe Homotherini evolved towards a body style more fit for running, with lighter builds and long legs seen in the genera Lokotunjailurus and Homotherium [7] as well as larger noses for better respiration during pursuit.

The subtribe Machairodontini retained features more similar to extant pantherines, with shorter legs and longer tails than Homotherins, while maintaining saber tooth features such as a longer neck and upper canine teeth that were larger and bladed. [8] Machairodontins had heavier bodies with some species in the genus Machairodus almost reaching the size of Smilodon populator. [9]

Evolution

Based on mitochondrial DNA sequences extracted from fossils, the lineage of Homotherium is estimated to have diverged from that of Smilodon about 18 Ma ago. [10]

The scimitar tooth form was used to assist in the hunting of herbivorous megafauna. With its hyper sharp and serrated form it was perfect for ripping flesh off of downed prey. However, if this tooth would come into contact with bone it could get caught, serrations worn off, or even completely broken thus leaving the organism without a food source, leading to starvation and death. [11] [12]

There is a debate about how both the scimitar-tooth and the dirk-tooth evolved in felines and other mammals. the two sides of the debate revolve around whether it was derived from a sexual dimorphic trait or if it was completely natural selection that drove the creation of these phenotypes. The argument for sexual dimorphic origins stems from the fact that in mammals sexual dimorphic traits manifest as tools for males to compete for females. It is believed that the scimitar-tooth and the dirk-tooth were originally only in males for use in competition but then with the rise of mega-herbivores it became favorable for females to take up the trait as well. [13] The natural selection side of the debate argues that the scimitar and dirk-tooth both evolved because of the unfilled niche of predation of megaherbivores so the trait evolved to take advantage of said niche. [14]

Classification

Tribe †Homotherini
TribeGenusSpeciesImage
†Homotherini
† Homotherium Fabrini, 1890
  • †H. ischyrus
  • †H. latidens
  • †H. serum
  • †H. venezuelensis
 Homotherium serum.jpg
† Xenosmilus Martin et al., 2000
  • †X. hodsonae
 Xenosmilus.jpg
† Lokotunjailurus Werdelin 2003
  • †L. emageritus
  • †L. fanonei
  • †L. chinsamyae
† Amphimachairodus Kretzoi, 1929
  • †A. alvarezi
  • †A. coloradensis
  • †A. giganteus
  • †A. kurteni
  • †A. hezhengensis
 Machairodus giganteus 1.jpg
† Nimravides Kitts 1958
  • †N. catacopsis
  • †N. galiani
  • †N. hibbardi
  • †N. pedionomus
  • †N. thinobates
 Nimravides catacopis.JPG
Tribe †Machairodontini
†Machairodontini
† Machairodus Kaup, 1833
  • †M. alberdiae
  • †M. aphanistus
  • †M. horribilis
  • †M. laskerevi
  • †M. robinsoni
  • †M. lahayishpup
 Machairodus aphanistus - Cerro de los Batallones - Museo Arqueologico Regional CAM.JPG
† Hemimachairodus Koenigswald, 1974
  • †H. zwierzyckii
† Longchuansmilus Jiangzuo et al 2022
  • †L. xingyongi
† Adeilosmilus Jiangzuo, Werdelin, Sun et al 2022
  • †A. kabir
† Taowu Jiangzuo, Werdelin, Sun et al 2022
  • †T. liui
† Miomachairodus Schmidt-Kittler 1976
  • †M. pseudaeluroides

Phylogeny

The phylogenetic relationships of Homotherini are shown in the following cladogram: [15] [16] [17] [18] [19]

 †Homotherini 
 † Amphimachairodus  

†Amphimachairodus kurteni

†Amphimachairodus alvarezi

†Amphimachairodus coloradensis

†Amphimachairodus giganteus

 † Nimravides  

†Nimravides catacopsis

†Nimravides galiani

†Nimravides hibbardi

†Nimravides pedionomus

†Nimravides thinobates

 † Lokotunjailurus  

†Lokotunjailurus emageritus

†Lokotunjailurus fanonei

 † Xenosmilus  

†Xenosmilus hodsonae

†Xenosmilus venezuelensis

 † Homotherium  

†Homotherium ischyrus

†Homotherium latidens

†Homotherium crenatidens

†Homotherium serum

Related Research Articles

<span class="mw-page-title-main">Felidae</span> Family of mammals

Felidae is the family of mammals in the order Carnivora colloquially referred to as cats. A member of this family is also called a felid.

<i>Machairodus</i> Extinct genus of carnivores

Machairodus is a genus of large machairodont or ''saber-toothed cat'' that lived in Africa, Eurasia and North America during the late Miocene. It is the animal from which the subfamily Machairodontinae gets its name and has since become a wastebasket taxon over the years as many genera of sabertooth cat have been and are still occasionally lumped into it.

<i>Dinofelis</i> Extinct genus of carnivores

Dinofelis is an extinct genus of machairodontine, usually classified in the tribe Metailurini. It was widespread in Europe, Asia, Africa and North America from 5 million to about 1.2 million years ago. Fossils very similar to Dinofelis from Lothagam range back to around 8 million years ago, in the Late Miocene.

<i>Smilodon</i> Extinct genus of saber-toothed cat

Smilodon is an extinct genus of felids. It is one of the best known saber-toothed predators and prehistoric mammals. Although commonly known as the saber-toothed tiger, it was not closely related to the tiger or other modern cats, belonging to the extinct subfamily Machairodontinae, with an estimated date of divergence from the ancestor of living cats around 20 million years ago. Smilodon was one of the last surviving machairodonts alongside the distantly related Homotherium. Smilodon lived in the Americas during the Pleistocene epoch. The genus was named in 1842 based on fossils from Brazil; the generic name means "scalpel" or "two-edged knife" combined with "tooth". Three species are recognized today: S. gracilis, S. fatalis, and S. populator. The two latter species were probably descended from S. gracilis, which itself probably evolved from Megantereon. The hundreds of specimens obtained from the La Brea Tar Pits in Los Angeles constitute the largest collection of Smilodon fossils.

<i>Homotherium</i> Extinct genus of carnivores

Homotherium is an extinct genus of scimitar-toothed cat belonging to the extinct subfamily Machairodontinae that inhabited North America, Eurasia, and Africa during the Pliocene and Pleistocene epochs from around 4 million to 12,000 years ago. It was one of the last surviving members of the subfamily alongside the more famous sabertooth Smilodon, to which it was distantly related. It was a large cat, comparable in size to a lion, functioning as an apex predator in the ecosystems it inhabited. In comparison to Smilodon, the canines of Homotherium were shorter, and it is suggested to have a different ecology from Smilodon as pursuit predator adapted to running down large prey in open habitats, with species of the genus also proposed to have engaged in cooperative hunting.

<span class="mw-page-title-main">Dire wolf</span> Extinct species of canine mammal

The dire wolf is an extinct canine. The dire wolf lived in the Americas during the Late Pleistocene and Early Holocene epochs. The species was named in 1858, four years after the first specimen had been found. Two subspecies are recognized: Aenocyon dirus guildayi and Aenocyon dirus dirus. The largest collection of its fossils has been obtained from the Rancho La Brea Tar Pits in Los Angeles.

<span class="mw-page-title-main">Saber-toothed predator</span> Group of extinct animals

A saber-tooth is any member of various extinct groups of predatory therapsids, predominantly carnivoran mammals, that are characterized by long, curved saber-shaped canine teeth which protruded from the mouth when closed. Saber-toothed mammals have been found almost worldwide from the Eocene epoch to the end of the Pleistocene epoch.

<span class="mw-page-title-main">Nimravidae</span> Extinct family of mammals in the order Carnivora

Nimravidae is an extinct family of carnivorans, sometimes known as false saber-toothed cats, whose fossils are found in North America and Eurasia. Not considered to belong to the true cats, the nimravids are generally considered closely related and classified as a distinct family in the suborder Feliformia. Fossils have been dated from the Middle Eocene through the Late Miocene epochs, spanning about 33.2 million years.

<span class="mw-page-title-main">Machairodontinae</span> Extinct subfamily of carnivores

Machairodontinae is an extinct subfamily of carnivoran mammals of the family Felidae. They were found in Asia, Africa, North America, South America, and Europe, with the earliest species known from the Middle Miocene, with the last surviving species becoming extinct around Late Pleistocene-Holocene transition.

Metailurini is an extinct taxonomic tribe of large saber-toothed cats that lived in Africa, Asia, Europe, and North America from the Miocene to the Pleistocene.

<span class="mw-page-title-main">Smilodontini</span> Extinct tribe of carnivores

Smilodontini is an extinct tribe within the Machairodontinae or "saber-toothed cat" subfamily of the Felidae. The tribe is also known as the "dirk-toothed cats". They were endemic to South America, North America, Europe, Asia, and Africa during the Miocene to Pleistocene, from 10.3 mya—11,000 years ago, existing for approximately 10.3 million years.

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.

<i>Xenosmilus</i> Extinct genus of carnivores

Xenosmilus is an extinct genus of homotherin machairodontine that was discovered in Florida in 2001. It has one species, Xenosmilus hodsonae.

<i>Thylacosmilus</i> Extinct genus of mammals

Thylacosmilus is an extinct genus of saber-toothed metatherian mammals that inhabited South America from the Late Miocene to Pliocene epochs. Though Thylacosmilus looks similar to the "saber-toothed cats", it was not a felid, like the well-known North American Smilodon, but a sparassodont, a group closely related to marsupials, and only superficially resembled other saber-toothed mammals due to convergent evolution. A 2005 study found that the bite forces of Thylacosmilus and Smilodon were low, which indicates the killing-techniques of saber-toothed animals differed from those of extant species. Remains of Thylacosmilus have been found primarily in Catamarca, Entre Ríos, and La Pampa Provinces in northern Argentina.

<i>Megantereon</i> Extinct genus of saber-toothed cat from North America, Eurasia and Africa

Megantereon is an extinct genus of prehistoric machairodontine saber-toothed cat that lived in North America, Eurasia, and Africa from the late Pliocene to the Middle Pleistocene. 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.

<span class="mw-page-title-main">Barbourofelidae</span> Extinct family of feliform carnivorans

Barbourofelidae is an extinct family of carnivorans of the suborder Feliformia, sometimes known as false saber-toothed cats, that lived in North America, Eurasia and Africa during the Miocene epoch and existed for about 7.9 million years. Thought to be an independent lineage from the Nimravidae and Machairodontinae, which had all attained elongated canines, recent research argues that it may be a subfamily of the Nimravidae, extending its biochronological range into the Miocene, although this issue is not yet fully resolved.

<i>Nimravides</i> Extinct genus of carnivores

Nimravides is a genus of extinct saber-toothed cats that lived in North America during the Late Miocene, between 10.3 and 5.332 Ma. Despite its scientific name, Nimravides does not belong to the Nimravidae, but is a true cat belonging to the family Felidae.

<i>Lokotunjailurus</i> Extinct genus of carnivores

Lokotunjailurus is an extinct genus of saber-toothed cats (Machairodontinae) which existed during the late Miocene and earliest Pliocene epoch and is known from localities in northern, central, eastern and southern Africa. A big cat, it was more slender than comparable recent species and its build suggests cursoriality. It is grouped among a group of similar-looking saber-toothed cats known as the scimitar-tooths.

<i>Amphimachairodus</i> Extinct genus of carnivores

Amphimachairodus is an extinct genus of large machairodonts. It is also a member of the tribe Homotherini within Machairodontinae and is most closely related to such species as Xenosmilus, Homotherium itself, and Nimravides. It inhabited Eurasia, Northern Africa and North America during the late Miocene epoch.

Taowu is an extinct genus of machairodonts, a type of saber-toothed cat. It lived during the Early Pleistocene about 2.5 million years ago in East Asia. So far, only one skull is known, found in northern China. Based on this, a relatively small representative of the saber-toothed cats can be reconstructed, which only reached the size of a present-day leopard. In its dentition characteristics, it mediates between phylogenetic older forms such as Amphimachairodus and younger members such as Homotherium. The genus was scientifically described in 2022, but the find material was recovered as early as the 1930s.

References

  1. ↑ Jiangzuo, Q.; Werdelin, L.; Sun, Y. (2022). "A dwarf sabertooth cat (Felidae: Machairodontinae) from Shanxi, China, and the phylogeny of the sabertooth tribe Machairodontini". Quaternary Science Reviews. 284: Article 107517. Bibcode:2022QSRv..28407517J. doi:10.1016/j.quascirev.2022.107517.
  2. ↑ Rincon, A.; Prevosti, F.; Parra, G. (2011). "New saber-toothed cat records (Felidae: Machairodontinae) for the Pleistocene of Venezuela, and the Great American Biotic Interchange". Journal of Vertebrate Paleontology. 31 (2): 468–478. doi:10.1080/02724634.2011.550366. hdl: 11336/69016 . S2CID   129693331.
  3. ↑ Paleobiology Database: Homotherini Basic info.
  4. ↑ Martin, L.D. (1989). "Fossil history of the terrestrial Carnivora". In Gittleman, J.L. (ed.). Carnivore behaviour, ecology, and evolution. Vol. 1. Ithaca, IL: Cornell University Press. pp. 536–568.
  5. ↑ Van Valkenburgh, B (2007). "Deja vu: the evolution of feeding morphologies in the Carnivora". Integrative and Comparative Biology. 47 (1): 147–163. doi: 10.1093/icb/icm016 . PMID   21672827.
  6. ↑ Meloro, C.; Slater, G. J. (2012). "Covariation in the skull modules of cats: the challenge of growing saber-like canines". Journal of Vertebrate Paleontology. 32 (3): 677–685. doi:10.1080/02724634.2012.649328. S2CID   55862923.
  7. ↑ Antón, Mauricio (2013). Sabertooth. Bloomington: Indiana University Press. pp. 118–138. ISBN   9780253010421.
  8. ↑ Antón, Mauricio (2013). Sabertooth. Bloomington: Indiana University Press. pp. 118–138. ISBN   9780253010421.
  9. ↑ Bellani, Giovanni G. (2020). Felines of the world: discoveries in taxonomic classification and history. London; San Diego, CA: Academic Press is an imprint of Elsevier. ISBN   9780128172773.
  10. ↑ Paijmans, J. L. A.; Barnett, R.; Gilbert, M. T. P.; Zepeda-Mendoza, M. L.; Reumer, J. W. F.; de Vos, J.; Zazula, G.; Nagel, D.; Baryshnikov, G. F.; Leonard, J. A.; Rohland, N.; Westbury, M. V.; Barlow, A.; Hofreiter, M. (2017-10-19). "Evolutionary History of Saber-Toothed Cats Based on Ancient Mitogenomics". Current Biology. 27 (21): 3330–3336.e5. doi: 10.1016/j.cub.2017.09.033 . PMID   29056454.
  11. ↑ Van Valkenburgh, B (2007). "Deja vu: the evolution of feeding morphologies in the Carnivora". Integrative and Comparative Biology. 47 (1): 147–163. doi: 10.1093/icb/icm016 . PMID   21672827.
  12. ↑ Slater, G. J.; Valkenburgh, B. Van (2008). "Long in the tooth: evolution of sabertooth cat cranial shape". Paleobiology. 34 (3): 403–419. doi:10.1666/07061.1. S2CID   85353590.
  13. ↑ Randau, Marcela; Carbone, Chris; Turvey, Samuel T. (August 8, 2013). Evans, Alistair Robert (ed.). "Canine Evolution in Sabretoothed Carnivores: Natural Selection or Sexual Selection?". PLOS ONE. 8 (8). Public Library of Science (PLoS): e72868. Bibcode:2013PLoSO...872868R. doi: 10.1371/journal.pone.0072868 . ISSN   1932-6203. PMC   3738559 . PMID   23951334.
  14. ↑ Van Valkenburgh, B.; Sacco, T. (2002). "Sexual dimorphism, social behavior, and intrasexual competition in large Pleistocene carnivorans". Journal of Vertebrate Paleontology. 22: 164–169. doi:10.1671/0272-4634(2002)022[0164:sdsbai]2.0.co;2. S2CID   86156959.
  15. ↑ "Paleobiology Database". Archived from the original on 2012-03-25. Retrieved 2011-06-16.
  16. ↑ Turner, Alan (1990). "The evolution of the guild of larger terrestrial carnivores during the Plio-Pleistocene in Africa". Geobios. 23 (3): 349–368. doi:10.1016/0016-6995(90)80006-2.
  17. ↑ Martin, L. D.; Babiarz, J. P.; Naples, V. L.; Hearst, J. (2000). "Three Ways To Be a Saber-Toothed Cat". Naturwissenschaften. 87 (1): 41–44. Bibcode:2000NW.....87...41M. doi:10.1007/s001140050007. PMID   10663132. S2CID   1216481.
  18. ↑ Turner, Alan (1997). The Big Cats and their fossil relatives. New York: Columbia University Press. p. 60. ISBN   978-0-231-10228-5.
  19. ↑ Wallace, S. C.; Hulbert, R. C. (2013). Larson, Greger (ed.). "A New Machairodont from the Palmetto Fauna (Early Pliocene) of Florida, with Comments on the Origin of the Smilodontini (Mammalia, Carnivora, Felidae)". PLOS ONE. 8 (3): e56173. Bibcode:2013PLoSO...856173W. doi: 10.1371/journal.pone.0056173 . PMC   3596359 . PMID   23516394.
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