Jump to content

Xenosmilus

From Wikipedia, the free encyclopedia
(Redirected from Xenosmilus hodsonae)

Xenosmilus
Temporal range: Early Pleistocene (Blancan to Irvingtonian) ~2–1 Ma
↓
 Possible Middle Pleistocene records
X. hodsonae, Florida Museum of Natural History Fossil Hall at the University of Florida
Scientific classification Edit this classification
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
Other species
  • X. venezuelensis? Rincón et al., 2011

Xenosmilus is an extinct genus of homotherin machairodontine (saber-toothed cat) that roamed the North America from the Early Pleistocene. The type species of the genus, X. hodsonae, is known from Early Pleistocene deposits in Florida.

Over the recent years, scientists have proposed X. venezuelensis (Synonymous with H. venezuelensis) could be a valid species within the genus, in addition to a possible third unnamed species, cf. Xenosmilus sp., from Uruguay. If valid, both species would extend the genus’ range into the Middle Pleistocene and South America.

Taxonomy

[edit]

Discovery and Naming

[edit]

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.[1] The genus and type 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.[2]

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.[2][3]

Classification

[edit]

Xenosmilus is in the tribe Homotherini in the subfamily Machairodontinae of the cat family.[2] 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.[4] With 2024 paper arguing that remains of a Homotherini from Uruguay should also be assigned to the genus.[5] The 2022 study found that Xenosmilus was nested within Homotherium as traditionally defined, making Homotherium without including the species in Xenosmilus paraphyletic.[4]

Description

[edit]

The skull of Xenosmilus was 33 centimetres (13 in) in length.[6] Compared to other machairodonts, Xenosmilus skull was relatively small, however, the occipital condyles was unusually large for the skull size. Overall, it had a more bearlike than catlike appearance.[2]

Xenosmilus and Glyptodon
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] In 2024, Manzuetti and colleagues estimated cf. Xenosmilus sp. could’ve weighed 347–410 kilograms (765–904 lb).[5]

Paleobiology

[edit]

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.[11] 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.[3]

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".[12][1] It seems likely, with their muscular builds, that X. hodsonae preyed upon peccaries, due to the large numbers of peccaries found within the same site.[2]

A study published in 2022 suggests 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. The same study also suggests that machairodonts could consume at least smaller bones when feeding, similar to lions.[13]

Because the skeletons were found beside each other, some suspect Xenosmilus was a social mammal.[3] According to Martin and colleagues, the cave deposit the specimens were found in, may be evidence of denning behavior.[2]

Paleoenvironment

[edit]

The holotype and paratype fossils of X. hodsonae were of Irvingtonian age (1.8 to 0.3 Ma).[14] However, it has also been found in quarries dating to the late Blancan such as Inglis 1a and Haile 7g, dating it up to at least 2 million years ago.[15] Others than Platygonus, it coexisted with other herbivores such as Megalonyx, Paramylodon, Hemiauchenia, and Cuvieronius. It also coexisted with the one of the last phorusrhacids Titanis, and carnivorans such as the fellow machairodont Smilodon gracilis, Canis edwardii, and Arctodus pristinus.

X. venezuelensis was found in El Breal de Orocual of the Mesa Formation in Venezuela, which may have been a similar environment to modern day Llanos. The rarity and scarcity of homotherini in South America may suggest that they lived in low population densities.[16]

References

[edit]
  1. ^ a b "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.
  2. ^ a b c d e f 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.
  3. ^ a b c "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.
  4. ^ a b 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.
  5. ^ a b Manzuetti, Aldo; Jones, Washington; Rinderknecht, Andrés; Ubilla, Martín; Perea, Daniel (December 2024). "Body mass of a large-sized Homotheriini (Felidae, Machairodontinae) from the Late Pliocene-Middle Pleistocene in Southern Uruguay: Paleoecological implications". Journal of South American Earth Sciences. 149: 105231. doi:10.1016/j.jsames.2024.105231.
  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. ^ "A more fearsome saber-toothed cat". ScienceNews. 20 October 2008. Archived from the original on 17 March 2022.
  12. ^ Anton, Mauricio (2013). Sabertooth.
  13. ^ 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.
  14. ^ Xenosmilus in the Paleobiology Database
  15. ^ 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.
  16. ^ Rincón, Ascanio D.; Prevosti, Francisco J.; 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. JSTOR 25835839. S2CID 129693331.
Wikispecies has information related to Xenosmilus.
Retrieved from "https://en.wikipedia.org/w/index.php?title=Xenosmilus&oldid=1282304001"