Xenosmilus

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Xenosmilus
Temporal range: Early to Middle Pleistocene
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Xenosmilus hodsonae.jpg
X. hodsonae, Florida Museum of Natural History Fossil Hall at the University of Florida
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
Genus:† Xenosmilus
Martin et al., 2000
Type species
†Xenosmilus hodsonae
Martin et al., 2000

Xenosmilus is an extinct genus of homotherin machairodontine (saber-toothed cat) that was discovered in Florida in 2001. It has one species, Xenosmilus hodsonae.

Discovery and naming

The new genus and species Xenosmilus hodsonae was described in 2001 based on a nearly complete skeleton (BIOPSI 101) from the Florida site Haile 21A, with a second partial skeleton (UF 60,000) as the paratype. Both skeletons came from Early Pleistocene-aged rocks in Florida. [1]

The genus name Xenosmilus was derived from the Greek ξένος/xenos meaning "strange", and σμίλη/smilē meaning "knife". The species name hodsonae honors Debra Hodson, the wife of a researcher. [1] [2]

Description

Two fairly intact specimens were found by amateur fossil hunters in 1983 (1981 by some sources) in the Haile limestone mines in Alachua County, Florida. In 1994, the fossils were examined, and it was decided that the cats were of an entirely new genus. [3] The fossils were of Irvingtonian age (1.8 to 0.3 Ma). [4] Xenosmilus has also been found in quarries dating to the end Blancan such as Inglis 1a and Haile 7g, dating it up to 2 million years ago. [5] The skull of Xenosmilus was 33 centimetres (13 in) in length. [6] Because the skeletons were found beside each other, some suspect Xenosmilus was a social mammal. [2] Found alongside the two skeletons were dozens of peccary bones. It seems likely, with their muscular builds, that X. hodsonae preyed upon peccaries.

Xenosmilus and Glyptodon Paleo Hall at HMNS Xenosmilus and Glyptodon.jpg
Xenosmilus and Glyptodon
Life restoration by Mauricio Anton Xenosmilus with concealed canine.jpg
Life restoration by Mauricio Antón

Physically, the cat reached around 1 m (3.3 ft) tall at the shoulder, [7] and is estimated about the same size or larger than Smilodon fatalis , though the body mass estimates of the holotype is around 118 kilograms (260 lb). [8] [9] A 2019 book suggested a body mass range of 300–350 kilograms (660–770 lb). [10]

Classification

Xenosmilus is in the tribe Homotherini in the subfamily Machairodontinae of the cat family. [1] A paper published in 2022 proposed that Xenosmilus is a more derived member of the tribe Machairodontini (another name for Homotherini), and that Homotherium venezuelensis should be reassigned to Xenosmilus. [11]

Paleobiology

Before the discovery of Xenosmilus, all known saber-toothed cats fell into two general categories. Dirk toothed cats had long upper canines and stout legs. Scimitar toothed cats had only mildly elongated canines, and long legs. Xenosmilus broke these groupings by possessing both stout muscular legs and body, and short broad upper canines. [12] Unlike most other saber-toothed cats, all of Xenosmilus's teeth were serrated, not just its fangs and incisors. Xenosmilus differs from Homotherium and most other cats in the lack of a gap separating the last incisor tooth and the canine, as well as the loss of the p3 tooth. Notably only the later species of Smilodon have also lost the p3 tooth. The way its top teeth were lined up also allowed Xenosmilus to concentrate its bite force on two teeth at a time. [2]

Xenosmilus has also been theorized by some to have hunted via a "bite and retreat" strategy using its teeth to inflict deep wounds because of the way its canines and incisors could operate as a unit during a bite, leading to Xenosmilus bearing the occasional moniker of "cookie-cutter cat". [13] [3] Studies published in 2022 suggest that Xenosmilus and other machairodonts such as Smilodon were also capable of efficiently removing meat from a kill without damaging their teeth, as evidenced by bite marks on the bones of Platygonus. This same study also suggests that machairodonts could consume at least smaller bones when feeding, similar to lions. [14]

Related Research Articles

<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 a genus of felids belonging to the extinct subfamily Machairodontinae. 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. 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 machairodontine scimitar-toothed cat that inhabited North America, South America, Eurasia, and Africa during the Pliocene and Pleistocene epochs from around 4 million to 12,000 years ago. In comparison to Smilodon, the canines of Homotherium were shorter, and it was probably adapted to running down rather than ambushing prey.

<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">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 from the Miocene to the Pleistocene, living from about 16 million until about 10,000 years ago.

<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 Europe and Asia during the Middle and Late Miocene from 15 to 9 Ma. A 2022 phylogenetic analysis suggested that the genus may be polyphyletic.

<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. It is closely related to and possibly the ancestor of Smilodon.

Miomachairodus is an extinct genus of large machairodontine containing only a single species, Miomachairodus pseudailuroides. It is known from Miocene-age fossils in China and Turkey and persisted until the Late Miocene. Fossils of this machairodont have been found in the Vallesian-age Bahe Formation in Shaanxi, China, and Yeni Eskihisar in Anatolia. This Turkish site is of Miocene age and is well known for its pollen studies.

<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.

<span class="mw-page-title-main">Thylacosmilidae</span> Extinct family of mammals

Thylacosmilidae is an extinct family of metatherian predators, related to the modern marsupials, which lived in South America between the Miocene and Pliocene epochs. Like other South American mammalian predators that lived prior to the Great American Biotic Interchange, these animals belonged to the order Sparassodonta, which occupied the ecological niche of many eutherian mammals of the order Carnivora from other continents. The family's most notable feature are the elongated, laterally flattened fangs, which is a remarkable evolutionary convergence with other saber-toothed mammals like Barbourofelis and Smilodon.

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

Homotherini is a tribe of saber-toothed cats of the family Felidae. The tribe is commonly known as scimitar-toothed cats. These saber-toothed cats were endemic to North America, Europe, Asia, Africa, and South America from the Miocene to Pleistocene living from c. 23 Ma until c. 12,000 years ago.

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

Rhizosmilodon is an extinct genus of saber-tooth cat of the subfamily Machairodontinae that lived during the Early Pliocene and was discovered in the U.S. state of Florida. Comparable in size to a medium-sized modern jaguar at about 165 lb. in weight, fossils of Rhizosmilodon are known only from Florida. The best specimens for this species are its lower jaw and teeth, which carry intermediate characteristics between advanced forms such as Smilodon and primitive forms such as Paramachairodus. It was likely an ambush predator, preying on animals such as deer, tapirs and horses.

<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.

Hemimachairodus is an extinct genus of machairodontine (sabre-toothed) cat with only one species, Hemimachairodus zwierzyckii, known from fossils from the Pleistocene of Java.

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

Promegantereon is an extinct genus of machairodont from the Miocene of Europe. It is one of the oldest machairodont cat species in the Smilodontini and is believed to be an ancestor of Megantereon and Smilodon.

Tchadailurus is a genus of machairodontine felid from the late Miocene of Chad, Africa.

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. 1 2 3 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.
  2. 1 2 3 "Xenosmilus is the grittier name for "cookie-cutter panda cat"". Coffee and Creatures. 19 December 2019. Archived from the original on 9 November 2021. Retrieved 27 June 2020.
  3. 1 2 "Cookie-Cutter Cat Not as Cute as the Name Sounds". Wired. ISSN   1059-1028. Archived from the original on 1 November 2021. Retrieved 4 July 2021.
  4. ↑ Xenosmilus in the Paleobiology Database
  5. ↑ Hulbert, Richard C (January 2010). "A new early Pleistocene tapir (Mammalia: Perissodactyla) from Florida, with a review of Blancan tapirs from the state". researchgate.net. Retrieved 10 November 2022.
  6. ↑ Rincón, Ascanio; Prevosti, Francisco Juan; Parra, Gilberto E (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. Bibcode:2011JVPal..31..468R. doi:10.1080/02724634.2011.550366. hdl: 11336/69016 . S2CID   129693331.
  7. ↑ Antón, M. (2013). "Who's Who of Sabertoothed Predators". Sabertooth (1st ed.). Bloomington: Indiana University Press. p. 138. ISBN   978-0-253-01042-1. OCLC   857070029.
  8. ↑ Martin, L.D.; Babiarz, J.P.; Naples, V.L.; Hearst, J. "Three Ways To Be a Saber-Toothed Cat" (PDF). Naturwissenschaften. 87: 41–44. doi:10.1007/s001140050007.
  9. ↑ Torregrosa, V.; Petrucci, M.; Pérez-Claros, J. A. & Palmqvist, P. (2010). "Nasal aperture area and body mass in felids: Ecophysiological implications and paleobiological inferences". Geobios. 43 (6): 653–661. Bibcode:2010Geobi..43..653T. doi:10.1016/j.geobios.2010.05.001.
  10. ↑ Giovanni G. Bellani (2019). Felines of the World. Discoveries in Taxonomic Classification and History. Elsevier Science. pp. 30–31. ISBN   9780128172773 . Retrieved 19 September 2022.
  11. ↑ Jiangzuo, Qigao; Werdelin, Lars; Sun, Yuanlin (15 May 2022). "A dwarf sabertooth cat (Felidae: Machairodontinae) from Shanxi, China, and the phylogeny of the sabertooth tribe Machairodontini". Quaternary Science Reviews. 284: 107517. Bibcode:2022QSRv..28407517J. doi:10.1016/j.quascirev.2022.107517. ISSN   0277-3791.
  12. ↑ "A more fearsome saber-toothed cat". ScienceNews. 20 October 2008. Archived from the original on 17 March 2022.
  13. ↑ Anton, Mauricio (2013). Sabertooth.
  14. ↑ Domínguez-Rodrigo, Manuel; Egeland, Charles P.; Cobo-Sánchez, Lucía; Baquedano, Enrique; Hulbert, Richard C. (2022). "Sabertooth carcass consumption behavior and the dynamics of Pleistocene large carnivoran guilds". Scientific Reports. 12 (1): 6045. Bibcode:2022NatSR..12.6045D. doi:10.1038/s41598-022-09480-7. PMC   9061710 . PMID   35501323.
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