View source for Xenosmilus

{{Short description|Extinct genus of sabertooth cat}}
{{Use dmy dates|date=September 2023}}
{{Lead too short|date=April 2023}}
{{Automatic taxobox
| fossil_range = [[Early Pleistocene]] ([[Blancan]] to [[Irvingtonian]])
~{{Fossil range|2|1}}
Possible [[Middle Pleistocene]] records
| image = Xenosmilus hodsonae.jpg
| image_caption = ''X. hodsonae'', Florida Museum of Natural History Fossil Hall at the University of Florida
| taxon = Xenosmilus
| authority = [[Larry Martin|Martin]] ''et al.'', 2000
| type_species = †'''''Xenosmilus hodsonae'''''
| type_species_authority = [[Larry Martin|Martin]] ''et al.'', 2000
| subdivision_ranks = Other species
| subdivision = *''X. venezuelensis?'' {{small|Rincón et al., 2011}}
}}

'''''Xenosmilus''''' is an extinct genus of [[Homotherini|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''''' (formerly ''Homotherium 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 ==

=== Discovery and Naming ===
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|Alachua County]], [[Florida]].<ref name="wired">{{Cite magazine |title=Cookie-Cutter Cat Not as Cute as the Name Sounds |url=https://www.wired.com/2011/10/cookie-cutter-cat-not-as-cute-the-name-sounds/ |archive-url=https://web.archive.org/web/20211101063625/https://www.wired.com/2011/10/cookie-cutter-cat-not-as-cute-the-name-sounds/ |archive-date=2021-11-01 |access-date=2021-07-04 |magazine=Wired |language=en-US |issn=1059-1028}}</ref> 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.<ref name="Martin2000">{{Cite journal|doi=10.1007/s001140050007 |title=Three Ways to be a Saber-Toothed Cat |date=2000 |last1=Martin |first1=L. D. |last2=Babiarz |first2=J. P. |last3=Naples |first3=V. L. |last4=Hearst |first4=J. |journal=Naturwissenschaften |volume=87 |issue=1 |pages=41–44 |pmid=10663132 |bibcode=2000NW.....87...41M |s2cid=1216481 |url=https://www.researchgate.net/publication/12652111 }}</ref> A radius similar to ''X. hodsonae'' was found in Blacan rocks of Arizona, this represents the earliest record of the genus outside of Florida.<ref>{{Cite journal |last=White |first=Richard S. |last2=Morgan |first2=Gary S. |date=2005 |title=Arizona Blancan Vertebrate Faunas in Region Perspective |url=https://www.academia.edu/1626955/Arizona_Blancan_Vertebrate_Faunas_in_Region_Perspective |journal=Vertebrate Paleontolgy of Arizona, Mesa Southwest Museum Bulletin |pages=117-138}}</ref>

The genus name ''Xenosmilus'' was derived from the [[Greek language|Greek]] {{lang|grc|ξένος}}/{{transliteration|grc|xenos}} meaning "strange", and {{lang|grc|σμίλη}}/{{transliteration|grc|smilē}} meaning "knife". The species name ''hodsonae'' honors Debra Hodson, the wife of a researcher.<ref name="Martin2000"/><ref name=":0">{{Cite web |date=2019-12-19 |title=Xenosmilus is the grittier name for "cookie-cutter panda cat" |url=https://coffeeandcreatures.co.uk/2019/12/19/xenosmilus-facts/ |archive-url=https://web.archive.org/web/20211109092624/https://coffeeandcreatures.co.uk/2019/12/19/xenosmilus-facts/ |archive-date=9 November 2021 |access-date=2020-06-27 |website=Coffee and Creatures |language=en}}</ref>

=== Classification ===
''Xenosmilus'' is in the tribe [[Homotherini]] in the subfamily [[Machairodontinae]] of the [[Felidae|cat family]].<ref name="Martin2000" /> 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.''<ref name=":1">{{Cite journal |last1=Jiangzuo |first1=Qigao |last2=Werdelin |first2=Lars |last3=Sun |first3=Yuanlin |date=2022-05-15 |title=A dwarf sabertooth cat (Felidae: Machairodontinae) from Shanxi, China, and the phylogeny of the sabertooth tribe Machairodontini |url=https://www.sciencedirect.com/science/article/pii/S0277379122001482 |journal=Quaternary Science Reviews |language=en |volume=284 |pages=107517 |bibcode=2022QSRv..28407517J |doi=10.1016/j.quascirev.2022.107517 |issn=0277-3791|url-access=subscription }}</ref> The 2022 study found that ''Xenosmilus'' was nested within ''Homotherium'' as traditionally defined, making ''Homotherium'' without including the species in ''Xenosmilus'' [[paraphyletic]].<ref name=":1" /> A 2024 paper argued that remains of a homotherin from Uruguay should also be assigned to the genus.<ref name=":2">{{Cite journal |last=Manzuetti |first=Aldo |last2=Jones |first2=Washington |last3=Rinderknecht |first3=Andrés |last4=Ubilla |first4=Martín |last5=Perea |first5=Daniel |date=December 2024 |title=Body mass of a large-sized Homotheriini (Felidae, Machairodontinae) from the Late Pliocene-Middle Pleistocene in Southern Uruguay: Paleoecological implications |url=https://linkinghub.elsevier.com/retrieve/pii/S089598112400453X |journal=Journal of South American Earth Sciences |language=en |volume=149 |pages=105231 |doi=10.1016/j.jsames.2024.105231|url-access=subscription }}</ref>

==Description==
The skull of ''Xenosmilus'' was {{convert|33|cm|inches}} in length.<ref>{{cite journal |last1=Rincón |first1=Ascanio |last2=Prevosti |first2=Francisco Juan |last3=Parra |first3=Gilberto E |date=2011 |title=New Saber-Toothed Cat Records (Felidae: Machairodontinae) for the Pleistocene of Venezuela, and the Great American Biotic Interchange |url=https://www.researchgate.net/figure/Upper-tooth-row-and-cranial-measurement-comparisons-among-Homotheriini-in-mm_tbl1_254314670 |journal=Journal of Vertebrate Paleontology |volume=31 |issue=2 |pages=468–478 |bibcode=2011JVPal..31..468R |doi=10.1080/02724634.2011.550366 |s2cid=129693331 |hdl-access=free |hdl=11336/69016}}</ref> 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.<ref name="Martin2000" />  
[[File:Paleo Hall at HMNS Xenosmilus and Glyptodon.jpg|thumb|left|''Xenosmilus'' and ''[[Glyptodon]]'']] 
[[File:Xenosmilus with concealed canine.jpg|thumb|Life restoration by [[Mauricio Antón]]]]
Physically, the cat reached around {{convert|1|m|ft|abbr=on}} tall at the shoulder,<ref>{{cite book |last=Antón |first=M. |year=2013 |chapter=Who's Who of Sabertoothed Predators|title=Sabertooth |edition=1st |publisher=Indiana University Press |location=Bloomington |isbn=978-0-253-01042-1 |oclc=857070029 |url=https://books.google.com/books?id=dVcqAAAAQBAJ|page=138}}</ref> and is estimated about the same size or larger than ''[[Smilodon|Smilodon fatalis]]'', though the body mass estimates of the holotype is around {{convert|118|kg|lb}}.<ref>{{cite journal|first1=L.D.|last1=Martin|first2=J.P.|last2=Babiarz|first3=V.L.|last3=Naples|first4=J.|last4=Hearst|title=Three Ways To Be a Saber-Toothed Cat|journal=Naturwissenschaften|volume=87|pages=41–44|url=https://link.springer.com/content/pdf/10.1007/s001140050007.pdf|doi=10.1007/s001140050007}}</ref><ref>{{cite journal |author1=Torregrosa, V. |author2=Petrucci, M. |author3=Pérez-Claros, J. A. |author4=Palmqvist, P. |name-list-style=amp |year=2010 |title=Nasal aperture area and body mass in felids: Ecophysiological implications and paleobiological inferences |journal=Geobios |volume=43 |issue=6 |pages=653–661 |doi=10.1016/j.geobios.2010.05.001|bibcode=2010Geobi..43..653T }}</ref> A 2019 book suggested a body mass range of {{convert|300|-|350|kg|lb}}.<ref>{{cite book|isbn=9780128172773 |url=https://books.google.com/books?id=xK2wDwAAQBAJ |title=Felines of the World. Discoveries in Taxonomic Classification and History |publisher=Elsevier Science |date=2019 |access-date=19 September 2022 |pages=30–31 |author=Giovanni G. Bellani}}</ref> In 2024,  Manzuetti and colleagues estimated cf. ''Xenosmilus'' sp. could have weighed {{convert|347|-|410|kg|lb}}.<ref name=":2" />

==Paleobiology==
Before the discovery of ''Xenosmilus'', all known saber-toothed cats fell into two general categories. [[Smilodontini|Dirk toothed cats]] had long upper [[canine tooth|canines]] and stout legs. [[Homotherini|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.<ref>{{Cite web|archive-url=https://web.archive.org/web/20220317014600/https://www.sciencenews.org/article/more-fearsome-saber-toothed-cat |title=A more fearsome saber-toothed cat |website=ScienceNews |date=October 20, 2008|url=https://www.sciencenews.org/article/more-fearsome-saber-toothed-cat |archive-date=2022-03-17 }}</ref> Unlike most other saber-toothed cats, all of ''Xenosmilus''{{'}}s teeth were [[Serration|serrated]], not just its [[fang]]s and [[incisor]]s. ''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 [[Premolar|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.<ref name=":0" />

''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".<ref>{{cite book|last=Anton|first=Mauricio|title=Sabertooth|date=2013|authorlink=Mauricio Anton}}</ref><ref name=wired/>  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.<ref name="Martin2000" />

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.<ref>{{Cite journal |doi=10.1038/s41598-022-09480-7 |title=Sabertooth carcass consumption behavior and the dynamics of Pleistocene large carnivoran guilds |date=2022 |last1=Domínguez-Rodrigo |first1=Manuel |last2=Egeland |first2=Charles P. |last3=Cobo-Sánchez |first3=Lucía |last4=Baquedano |first4=Enrique |last5=Hulbert |first5=Richard C. |journal=Scientific Reports |volume=12 |issue=1 |page=6045 |pmid=35501323 |pmc=9061710 |bibcode=2022NatSR..12.6045D }}</ref>

Because the skeletons were found beside each other, some suspect ''Xenosmilus'' was a [[Sociality|social mammal]].<ref name=":0" /> According to Martin and colleagues, the cave deposit the specimens were found in may be evidence of denning behavior.<ref name="Martin2000" />

== Paleoenvironment ==
The holotype and paratype fossils of ''X. hodsonae'' were of [[Irvingtonian]] age (1.8 to 0.3 Ma).<ref>{{Paleodb|taxon|176103|Xenosmilus}}</ref> 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.<ref>{{cite web |last1=Hulbert |first1=Richard C |date=January 2010 |title=A new early Pleistocene tapir (Mammalia: Perissodactyla) from Florida, with a review of Blancan tapirs from the state |url=https://www.researchgate.net/publication/228401554 |accessdate=2022-11-10 |website=researchgate.net}}</ref> Others than ''Platygonus'', it coexisted with other herbivores such as ''[[Megalonyx]]'', ''[[Paramylodon]]'', ''[[Hemiauchenia]]'', and  ''[[Cuvieronius]]''. It also coexisted with ''[[Titanis]]'', one of the last [[Phorusrhacidae|phorusrhacids]], and carnivorans such as the fellow machairodont ''[[Smilodon|Smilodon gracilis]]'', ''[[Canis edwardii]]'', and [[Arctodus|''Arctodus pristinus'']].

Potential species ''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 homotherins in South America may suggest that they lived in low population densities.<ref>{{Cite journal |last1=Rincón |first1=Ascanio D. |last2=Prevosti |first2=Francisco J. |last3=Parra |first3=Gilberto E. |date=2011 |title=New Saber-Toothed Cat Records (Felidae: Machairodontinae) for the Pleistocene of Venezuela, and the Great American Biotic Interchange |journal=Journal of Vertebrate Paleontology |volume=31 |issue=2 |pages=468–478 |bibcode=2011JVPal..31..468R |doi=10.1080/02724634.2011.550366 |jstor=25835839 |s2cid=129693331 |hdl-access=free |hdl=11336/69016}}</ref>

==References==
{{Reflist}}
*{{Cite journal|last1=Martin |first1=L. |last2=Naples |first2=V. |last3=Babiarz |first3=J. |date=2008 |title=COOKIE-CUTTER CATS: ANOTHER SABER-TOOTHED Morphotype |journal=Journal of Vertebrate Paleontology |volume=28 |issue=3 |pages=112A}}
*{{Cite journal|doi=10.1111/j.1096-3642.2010.00675.x |title=A dynamic model for the evolution of sabrecat predatory bite mechanics |date=2011 |last1=Christiansen |first1=Per |journal=Zoological Journal of the Linnean Society |volume=162 |pages=220–242 |doi-access=free }}
*{{Cite journal |journal=Comunicaciones Paleontologicas |url=https://www.mna.gub.uy/innovaportal/file/25910/1/cp35.pdf |title=The First South American Homotheriini}}

{{Wikispecies}}
{{Machairodontinae}}
{{Taxonbar|from1=Q141533|from2=Q20719562}}

[[Category:Homotherini]]
[[Category:Pleistocene genus extinctions]]
[[Category:Monotypic prehistoric carnivoran genera]]
[[Category:Pleistocene mammals of North America]]
[[Category:Fossil taxa described in 2000]]