Xenosmilus

''Xenosmilus hodsonae'' (from Greek, , ''xenos'', "strange" + , ''smilē'', " chisel" ) is an extinct species of the Machairodontinae, or saber-toothed cats.

Description

The species name ''hodsonae'' originates from Debra Hodson, the wife of a researcher. 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. The fossils were of Irvingtonian age (1.8 to 0.3 Ma). Because the skeletons were found beside each other, some suspect ''Xenosmilus'' was a social mammal. Found alongside the two skeletons were dozens of peccary bones. It seems likely, with their muscular builds, that ''X. hodsonae'' preyed upon peccaries.


Physically, the cat reached around long with a highly muscular body and weighed around , making it similar in size to the fellow machairodonts '' Machairodus horribilis'' and '' Adeilosmilus kabir''. Only ''Smilodon populator'' was noticeably larger amongst the saber-toothed cats. , its 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. The skull of Xenosmilus was in length, slighty smaller than Amphimachairodus giganteus which was 14 inches in length, although xenosmilus is noted to have a proportionally shorter skull.

Classification

''Xenosmilus'' is in the tribe Homotherini in the subfamily Machairodontinae of the cat family. A 2022 paper that reviewed the phylogeny of machairodonts in relation to a newly-described genus proposed that ''Xenosmilus'' was among the more derived members of the clade.

''Xenosmilus'' is classified as a member of the Homotherini (sometimes referred to as Homotheriina), a tribe or subtribe of machairodonts. According to the 2022 study that suggests the subtribe hypothesis is correct while describing the transitional genus '' Taowu'', ''Xenosmilus'' stands as a derived member of this subtribe, which is proposed to be nestled in the Machairodontini. This same study also suggests an increasing trend of robustness in more derived scimitar-toothed machairodonts, which may be a result of hunting slower, larger, and stronger types of prey.

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. Unlike most other saber-toothed cats, all of ''Xenosmilus'''s teeth were serrated, not just its fangs and incisors. The way its top teeth were lined up also allowed ''Xenosmilus'' to concentrate its bite force on two teeth at a time.

''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''". 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.Domínguez-Rodrigo, M., Egeland, C.P., Cobo-Sánchez, L. et al. Sabertooth carcass consumption behavior and the dynamics of Pleistocene large carnivoran guilds. Sci Rep 12, 6045 (2022). https://doi.org/10.1038/s41598-022-09480-7

References

Homotherini
Pleistocene genus extinctions
Prehistoric carnivoran genera
Pleistocene mammals of North America
Fossil taxa described in 2000

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