Temporal range: late Miocene–late Pliocene
|Thylacosmilus atrox and Glyptodon|
Thylacosmilus ("pouch sabre") was a genus of sabre-toothed metatherian predators that first appeared during the Miocene. Remains of the animal have been found in parts of South America, primarily Argentina. Though Thylacosmilus is one of several predatory mammal genera typically called "sabre-toothed cats", it was not a felid but a sparassodont, a group closely related to marsupials, and only superficially resembled other sabre-toothed mammals due to convergent evolution.
The most notable feature of Thylacosmilus are its canines, which are saber-like and grew throughout the animal’s life, like the incisor teeth of rodents. When the mouth was closed, these teeth were protected by a pair of elongated, scabbard-like flanges growing from the lower jaw. Its cervical vertebrae were very strong and to some extent resembled the vertebrae of machairodonts. Recent comparative biomechanical analysis have estimated the bite force of T. atrox starting at maximum gape at 38 newtons (8.5 lbf), several times weaker than that of a leopard, suggesting that its jaw muscles had an insignificant role on the dispatch of prey. Its skull was similar to that of Smilodon in that it was much better adapted to withstand loads applied by the neck musculature, which, along with evidence for powerful and flexible forelimb musculature and other skeleton adaptations for stability, support the hypothesis that its killing method consisted on immobilization of its prey followed by precisely directed deep bites into the soft tissue driven by powerful neck muscles.
Body mass estimates of Thylacosmilus suggest that this animal weighed between 80 and 120 kg (170 to 260 lbs), about the same size as a modern jaguar or leopard. This would make it one of the largest known carnivorous metatherians.
Although older references have often stated that Thylacosmilus went extinct due to competition with the “more competitive” saber-toothed cat Smilodon during the Great American Biotic Interchange, newer studies have shown this is not the case. Thylacosmilus died out during the late Pliocene, whereas saber-toothed cats are not known from South America until the middle Pleistocene epoch. As a result, the last appearance of Thylacosmilus is separated from the first appearance of Smilodon by over one and a half million years.
Thylacosmilus atrox skull cast: Original is P 14531 in the collections of the Field Museum of Natural History.
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- Hogenboom, M. (2013-07-02). "Sabretooth killing power depended on thick neck". BBC. Retrieved 2013-08-03.
- Wroe, S; Chamoli, U; Parr, WCH; Clausen, P; Ridgely, R (2013-06-26). "Comparative Biomechanical Modeling of Metatherian and Placental Saber-Tooths: A Different Kind of Bite for an Extreme Pouched Predator". PLoS ONE 8 (6). doi:10.1371/journal.pone.0066888.
- Ercoli, Marcos D.; Francisco J. Prevosti (2011). "Estimacion de masa de las especies de Sparassodonta (Mammalia, Metatheria) de edad Santacrucense (Mioceno Temprano) a partir del tamano del centroide de los elementos apendiculares: inferencias paleoecologicas". Ameghiniana 48: 462–479.
- Evolution of the Earth by Donald R. Prothero, Jr., Robert H. Dott, Donald Prothero, and Jr., Robert Dott
- The Earth Through Time by Harold L. Levin
- Bringing Fossils To Life: An Introduction To Paleobiology by Donald R. Prothero
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