Homotherium

Extinct genus of carnivoresTemplate:SHORTDESC:Extinct genus of carnivores

***Homotherium*** (also known as the **scimitar-toothed cat** or **scimitar cat**) is an extinct genus of machairodontine saber-toothed cats, often termed scimitar-toothed cats, that inhabited North America, South America, Eurasia, and Africa during the Pliocene and Pleistocene epochs (4 mya – 12,000 years ago), existing for approximately 4 million years.

It became extinct in Africa some 1.5 million years ago. The most recent Eurasian remains, recovered from what is now the North Sea, have been dated to around 28,000 years BP. In South America it is only known from a few remains in the northern region (Venezuela), from the mid-Pleistocene.

## Taxonomy and distribution

The name *Homotherium* (Greek: ὁμός (*homos*, 'same') and θηρίον (*therion*, 'beast')) was proposed by Emilio Fabrini (1890), without further explanation, for a new subgenus of *Machairodus*, whose main distinguishing feature was the presence of a large diastema between the two inferior premolars.

The lineage of *Homotherium* is estimated (based on mitochondrial DNA sequences) to have diverged from that of *Smilodon* about 18 million years ago. *Homotherium* probably derived from *Machairodus* and appeared for the first time at the Miocene–Pliocene border, about 4 to 5 million years ago. During the Pleistocene it occurred in vast parts of Eurasia, North America and until the middle Pleistocene (about 1.5 million years ago) even in Africa. A fossil of *H. crenatidens* was inadvertently dredged from the bed of the North Sea, which was a flat, low-lying extent of marshy tundra laced with rivers during the last glacial period. It was thought that *H. latidens* had gone extinct relatively early, nearly 300,000 years ago, but a rogue specimin of *H. latidens* was found in the North Sea of Europe, dated to be from 28,000 years ago. There has also been a discovery of 1.8-million-year-old fossils in Venezuela, indicating that scimitar-toothed cats were able to invade South America along with *Smilodon* during the Great American Interchange. These remains form the holotype of *Homotherium venezuelensis*. How long they lasted in South America is not yet evident. *Homotherium* survived in Eurasia until about 28,000 years ago.

Several Eurasian species have been recognized based mainly on differences in the size and shape of the upper canines and body size: *H. latidens*, *H. nestianus*, *H. sainzelli*, *H. crenatidens*, *H. nihowanensis*, and *H. ultimum*. However, given the range of sizes found in extant large cats, it is likely that they represent a single species, *Homotherium latidens*.

Two species described from early Pleistocene Africa, *H. ethiopicum* and *H. hadarensis—*also hardly differ from the Eurasian forms. On the African continent the genus disappeared about 1.5 million years ago. In North America a very similar species, *H. serum*, occurred from the late Pliocene until the late Pleistocene. However, both morphological and genetic data suggest that all late Pleistocene *Homotherium* individuals worldwide should probably be regarded as members of *H. latidens*. Remains have been found at various sites between Alaska and Texas. In the southern parts of its range the American *Homotherium* co-existed with *Smilodon*; in the northern parts it was the only species of saber-toothed cat. The American *Homotherium* was originally described by the name *Dinobastis*.

Despite *Homotherium*'s vast range and the large quantity of fossil remains from Eurasia, Africa and North America, complete skeletons of this cat are relatively rare. One of the most famous sites of *Homotherium* remains is Friesenhahn cave in Texas, where 30 *Homotherium* skeletons were found, along with hundreds of juvenile mammoths and several dire wolves.

The genus *Dinobastis* was originally named by Cope (1893). Its type is *Dinobastis serus*. It was synonymized subjectively with *Smilodon* by Matthew (1910) and later with *Homotherium* by Churcher (1966), Schultz *et al.* (1970), Waldrop (1974), Kurtén and Anderson (1980), Churcher (1984) and Dalquest [fi] and Carpenter (1988).

## Description

*Homotherium* reached 1.1 m (3 ft 7 in) at the shoulder and weighed an estimated 190 kg (420 lb) and was therefore about the size of a male African lion. Compared to more familiar machairodonts, like *Smilodon* or *Megantereon*, *Homotherium* had comparatively shorter upper canines, but these flat, serrated teeth were still longer than those of any living cat. *Homotherium'*s incisors and lower canines formed a powerful puncturing and gripping device. The skull was longer than in *Smilodon* and had a well-developed crest, where muscles were attached to power the lower jaw. This jaw had down-turned forward flanges to protect the scimitars. Its large canine teeth were crenulated and designed for slashing rather than purely stabbing. However, a 2018 study by Figueirido and colleagues found that *Homotherium* possessed a bite adapted to clamp and hold while inflicting damage with its canines that was more similar to a lion's due to the larger amounts of trabecular bone present in the skulls of the genus. This is unlike the canine shear-bite of *Smilodon*, which it has been compared to, and this difference in killing bites provides evidence for distinct ecological adaptations.

*Homotherium* had the general appearance of a cat, but had a number of atypical features for a felid. *Homotherium* had unusual limb proportions, with longer, more robust forelimbs that gave it a hyena-like appearance. Features of the hind limbs indicate that this cat was moderately capable of leaping. The pelvic region, including the sacral vertebrae, was bear-like, as was the short tail composed of 13 vertebrae—about half the number of long-tailed cats'.[*citation needed*]

The unusually large, square nasal opening, similar to that of the cheetah (*Acinonyx jubatus*), presumably allowed faster oxygen intake, which would have aided in rapid or extended running and in cooling the brain. Again similarly to the cheetah, the visual cortex in *Homotherium'*s brain was large and complex, implying that the scimitar cat relied heavily on vision during the hunt.

Based on *Homotherium*'s preference for open habitat such as plains and comparisons with modern cats, it is considered likely by ethologist William Allen *et al* that *Homotherium* would have been plainly colored like lions to better camouflage itself.

## Diet and habitats

The decline of *Homotherium* could be a result of the disappearance of large herbivorous mammals like mammoths in America at the end of the Pleistocene. In North America fossil remains of *Homotherium* are less abundant than those of its contemporary *Smilodon*. For the most part it probably inhabited higher latitudes and altitudes and therefore was likely to be well adapted to the colder conditions of the mammoth steppe environment. The reduced claws, relatively slender limbs, and sloping back all appear to be adaptations for endurance running in open habitats.

Genomic analysis supports the hypothesis that *Homotherium* was social and well-adapted to life as a pursuit predator. Genes revealing high genetic diversity indicate the genus was far more common than previously assumed due to the preservation bias of the fossil record. The study also revealed that this genus of machairodont was most likely diurnal, and would have mainly hunted in daylight.

African *Homotherium* species seem to have hunted early Pleistocene species of *Deinotherium*, likely preferring to target the more vulnerable adolescents or calves in a herd. Due to their saber-teeth, an attack on such thick-skinned prey would have likely been significantly easier and less time-consuming compared to a similar hunt on modern elephants by lions.

At the well known Friesenhahn Cave site in Texas, the remains of almost 400 juvenile mammoths were discovered along with numerous *Homotherium* skeletons of all ages, from elderly specimens to cubs. Based on this fossil site, *Homotherium* was likely a social predator that would have been specialized in hunting young mammoths and that subsequently dragged the kills into secluded caves to eat in relative peace. *Homotherium* also seemed to have retained the excellent nocturnal vision typical of most cats, and hunting at night in the arctic regions where many *Homotherium* have been found would have been a prime hunting method. The sloped back and powerful lumbar section of *Homotherium*'s vertebrae suggest a bear-like build, and thus that these animals could have been capable of pulling formidable loads; further, broken upper canines - a common injury in fossils of other machairodonts such as *Machairodus* and *Smilodon* that would have resulted from struggling with their prey - is not seen in *Homotherium*, perhaps because their social groups would completely restrain prey items before any of the cats attempted to kill the target with their saber teeth. Moreover, the bones of the young mammoths found in Friesenhahn Cave show distinctive marks matching the incisors of *Homotherium*, indicating that they could efficiently process most of the meat on a carcass and that the mammoths had been deposited in the caves by the cats themselves and not by scavengers. Examination of the bones also indicates that the carcasses of these juvenile mammoths were dismembered after being killed by the cats before being dragged away, suggesting that *Homotherium* would disarticulate their kill to transport it to a safe area such as a hidden lair or den and prevent competitors such as dire wolves and American lions from usurping the carcass.

## References

1. ↑ 1.0 1.1 Antón, Mauricio. Sabertooth. Indiana University Press, 2013.
2. ↑ "American Scimitar Cat". *Yukon Beringia Interpretive Center*. Retrieved 19 February 2018. The scimitar cat was the second largest feline species to live in Yukon during the Ice Age (after the Beringian lion) — weighing in around 200 kilograms.
3. ↑ PaleoBiology Database: *Homotherium*, basic info
4. ↑ 4.0 4.1 Turner, A. (1997). *'The big cats and their fossil relatives*. Columbia University Press.  ISBN 0-231-10229-1
5. ↑ 5.0 5.1 Reumer, Jelle W. F.; Rook, Lorenzo; Van Der Borg, Klaas; Post, Klaas; Mol, Dick; De Vos, John (11 April 2003). "Late Pleistocene survival of the saber-toothed cat Homotherium in northwestern Europe". *Journal of Vertebrate Paleontology*. **23** (1): 260–262. doi:10.1671/0272-4634(2003)23[260:LPSOTS]2.0.CO;2.
6. ↑ 6.0 6.1 6.2 Rincón, Ascanio D.; Prevosti, Francisco J.; Parra, Gilberto E. (17 March 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. doi:10.1080/02724634.2011.550366.
7. ↑ Fabrini, E. (1890). "I Machairodus (Meganthereon) del Val d'Arno superiore". *Bollettino Comitato Geologico d'Italia* (in Italian). **21**: 121–144, 161–177; esp. 176.
8. ↑ R. L. (February 1891). "III.—Dr. E. Fabrini on Machærodus - Machærodus (Meganthereon) del Valdarno Superiore, Memoria del Dott. Emilio Fabrini (Boll. R. Com. Geol. 1890 Nos. 3–6, pp. 43, pls. 3.)". *Geological Magazine*. **8** (2): 82. Bibcode:1891GeoM....8...82R. doi:10.1017/S0016756800185498.
9. ↑ 9.0 9.1 Paijmans, Johanna L.A.; Barnett, Ross; Gilbert, M. Thomas P.; Zepeda-Mendoza, M. Lisandra; Reumer, Jelle W.F.; de Vos, John; Zazula, Grant; Nagel, Doris; Baryshnikov, Gennady F.; Leonard, Jennifer A.; Rohland, Nadin; Westbury, Michael V.; Barlow, Axel; Hofreiter, Michael (November 2017). "Evolutionary History of Saber-Toothed Cats Based on Ancient Mitogenomics". *Current Biology*. **27** (21): 3330–3336.e5. doi:10.1016/j.cub.2017.09.033 . PMID 29056454.
10. ↑ 10.0 10.1 Turner, Alan (1990). "The evolution of the guild of larger terrestrial carnivores during the Plio-Pleistocene in Africa". *Geobios*. **23** (3): 349–368. doi:10.1016/0016-6995(90)80006-2.
11. ↑ Rincon, Paul (18 November 2008). "Big cat fossil found in North Sea". *BBC*. http://news.bbc.co.uk/2/hi/science/nature/7735544.stm.
12. ↑ Meachen, Julie A. (November 2017). "Ancient DNA: Saber-Toothed Cats Are the Same Beasts After All". *Current Biology*. **27** (21): R1165–R1167. doi:10.1016/j.cub.2017.09.024 . PMID 29112870.
13. ↑ Sanchez, Fabiola (2008-08-21). "Saber-toothed Cat Fossils Discovered". Associated Press. Retrieved 2017-10-20.
14. ↑ Orozco, José (2008-08-22). "Sabertooth Cousin Found in Venezuela Tar Pit -- A First". *National Geographic News*. National Geographic Society. Retrieved 2008-08-30.
15. ↑ Rawn-Schatzinger, Viola (1992). *The Scimitar Cat, Homotherium Serum Cope: Osteology, Functional Morphology, and Predatory Behavior*. Illinois State Museum. ISBN 978-0-89792-136-7. OCLC 1028676558.
16. ↑ W. D. Matthew. 1910. Bulletin of the American Museum of Natural History 28
17. ↑ C. B. Schultz et al. 1970. Bulletin of the Nebraska State Museum 9
18. ↑ W. W. Dalquest and R. M. Carpenter. 1988. Occasional Papers, Museum, Texas Tech University 124
19. ↑ Sorkin, Boris (2008). "A biomechanical constraint on body mass in terrestrial mammalian predators". *Lethaia*. **41** (4): 333–347. doi:10.1111/j.1502-3931.2007.00091.x.
20. ↑ Meade, G.E. 1961: The saber-toothed cat *Dinobastis serus*. Bulletin of the Texas Memorial Museum 2(II), 23–60.
21. ↑ Figueirido, Borja; Lautenschlager, Stephan; Pérez-Ramos, Alejandro; Van Valkenburgh, Blaire (October 2018). "Distinct Predatory Behaviors in Scimitar- and Dirk-Toothed Sabertooth Cats". *Current Biology*. **28** (20): 3260–3266.e3. doi:10.1016/j.cub.2018.08.012 . PMID 30293717.
22. ↑ Switek, Brian. "Did Saber Cats Have Spotted and Striped Coats?". *scientificamerican.com*. Retrieved 23 April 2018.
23. ↑ Anton, M; Galobart, A; Turner, A (May 2005). "Co-existence of scimitar-toothed cats, lions and hominins in the European Pleistocene. Implications of the post-cranial anatomy of (Owen) for comparative palaeoecology". *Quaternary Science Reviews*. **24** (10–11): 1287–1301. doi:10.1016/j.quascirev.2004.09.008.
24. ↑ "Social life of extinct sabre-toothed cat revealed by ancient DNA".
25. ↑ Barnett, Ross; Westbury, Michael V.; Sandoval-Velasco, Marcela; Vieira, Filipe Garrett; Jeon, Sungwon; Zazula, Grant; Martin, Michael D.; Ho, Simon Y. W.; Mather, Niklas; Gopalakrishnan, Shyam; Ramos-Madrigal, Jazmín; Manuel, Marc de; Zepeda-Mendoza, M. Lisandra; Antunes, Agostinho; Baez, Aldo Carmona; Cahsan, Binia De; Larson, Greger; O’Brien, Stephen J.; Eizirik, Eduardo; Johnson, Warren E.; Koepfli, Klaus-Peter; Wilting, Andreas; Fickel, Jörns; Dalén, Love; Lorenzen, Eline D.; Marques-Bonet, Tomas; Hansen, Anders J.; Zhang, Guojie; Bhak, Jong; Yamaguchi, Nobuyuki; Gilbert, M. Thomas P. (21 December 2020). "Genomic Adaptations and Evolutionary History of the Extinct Scimitar-Toothed Cat, Homotherium latidens". *Current Biology*. **30** (24): 5018–5025.e5. doi:10.1016/j.cub.2020.09.051. PMC 7762822  Check `|pmc=` value (help). PMID 33065008 Check `|pmid=` value (help).
26. ↑ "Deinotheres for lunch? A sabertooth's tough-skinned diet". 2017-03-23.
27. ↑ Metcalfe, Jessica (2011). *Late Pleistocene climate and proboscidean paleoecology in North America: Insights from stable isotope compositions of skeletal remains* (Thesis).
28. ↑ "The Diet of Saber-Toothed Cats". 2008-03-07.
29. ↑ Antón, Mauricio (2013). *Sabertooth*. Bloomington, Indiana: University of Indiana Press. pp. 227–228. ISBN 978-0-253-01042-1.

## External links

* The saber-toothed cat of the North Sea, 2008, accessed 10/28/2019
* American Scimitar Cat
* Saber-toothed cat jaw
* South America gets two more sabercats