Xenosmilus

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. 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. A radius similar to X. hodsonae was found in Blacan rocks of Arizona, this represents the earliest record of the genus outside of Florida. The genus name Xenosmilus was derived from the Greek / meaning "strange", and / meaning "knife". The species name hodsonae honors Debra Hodson, the wife of a researcher. Classification Xenosmilus is in the tribe Homotherini in the subfamily Machairodontinae of the cat family. The 2022 study found that Xenosmilus was nested within Homotherium as traditionally defined, making Homotherium without including the species in Xenosmilus paraphyletic. ==Description==

by Mauricio Antón The skull of Xenosmilus was in length. 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. and is estimated about the same size or larger than Smilodon fatalis, though the body mass estimates of the holotype is around . A 2019 book suggested a body mass range of . In 2024, Manzuetti and colleagues estimated cf. Xenosmilus sp. could have weighed . ==Paleobiology==

'', Houston Museum of Natural Science 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 Xenosmiluss 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. Because the skeletons were found beside each other, some suspect Xenosmilus was a social mammal. According to Martin and colleagues, the cave deposit the specimens were found in may be evidence of denning behavior. == Paleoenvironment ==

The holotype and paratype fossils of X. hodsonae were of Irvingtonian age (1.8 to 0.3 Ma). 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. Inglis 1a was previously thought to have been a longleaf pine flatwoods and pine-oak scrub are known to have occupied the area, similar to the modern flora. However, more recent interpretations suggest that the environment of Pliocene-Pleistocene Florida was a mosaic of different communities (i.e. a mixture of forests, savannas, wetlands, etc.). Skull morphology and short limbs suggests Xenosmilus lived in forested environments. 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. ==References==