Thylacosmilus had long, sabre-like upper canines and short, blunt, peg-like lower canines. The incisors were missing altogether and the other teeth were severely reduced, but, as distinct from machairodonts, their number was complete.[2][clarification needed] It is estimated to have weighed around 150 kilograms (330 lb).[3] Besides Proborhyaena, Thylacosmilus and the similarly sized marsupial lion were the largest carnivorous metatherians. The canines of Thylacosmilus, unlike those of true saber-toothed felines, kept growing throughout its life, and when the mouth was closed, 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.[2] 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.[4][5] Thylacosmilus went extinct during the Pliocene, a timeframe closely corresponding to the arrival of the sabre-toothed cat Smilodon from North America in the Great American Interchange. Out-competition from the anatomically similar Smilodon appears to have driven the extinction, though this is not typical of other South American extinctions during the period.[6]
Posted on: Fri, 09 Aug 2013 23:09:14 +0000