近日，北卡罗来纳州国家进化综合研究中心的Julie Meachen-Samuels在Paleobiology杂志上发表论文"Morphological convergence of the prey-killing arsenal of sabertooth predators"称，史前猫科动物牙齿越长胳膊越粗壮。
剑齿虎以及其他具强力牙齿的猛兽可能曾经还拥有强健有力的胳膊来帮助它们狩猎。如此强健的胳膊不仅能轻易捕获猎物，还能对它们看起来很凶猛、实际却极易断裂的牙齿起到保护作用。
在剑齿虎进化之前就有许多史前具凶猛牙齿的肉食动物身上也能获得类似的发现，比如生活于4200～700万年前的猎猫（假剑齿虎，nimravids），以及2000～500万年前的巴博剑齿虎（barbourofelids），巴博剑齿虎是猫科动物的姐妹群。Julie Meachen-Samuels说，这些古动物虽然看起来与猫科动物非常相似，但实际上，猫科动物是在它们几百年后才出现的。
猎猫和巴博剑齿虎并没有现生的后裔，不过化石证据显示它们牙齿的形状和尺寸变化极大，一些短而圆，一些长而平，还有一些甚至像切牛排的小刀一样具锯齿。剑齿虎的牙齿看上去令人生畏，但实际上却比现生猫科动物的牙齿脆弱得多，它们非常容易破碎。Meachen-Samuels说，现生猫科动物的牙齿横切面短而圆，能够承受较大的力量，在猎物挣扎时也不易损坏，因此对狩猎极为有利。
在之前的研究中，Meachen-Samuels发现加州剑齿虎（Smilodon fatalis）拥有比现今任何猫科动物都要强壮的前肢。她猜测，强壮的前肢能帮助猛兽按住挣扎的猎物，并保护咬入猎物体内的牙齿不被折断。通过分析发现，Meachen-Samuels认为其他诸多具齿猛兽都具有强壮的前肢。
Meachen-Samuels测量了数百件博物馆收藏的已灭绝猫科动物、猎猫、巴博剑齿虎以及13种现生猫科动物（包括考虑）的上犬齿和肢骨。通过对比，并结合现今生物个头越大骨骼越大的事实，她发现一个明显的趋势，就是牙齿越长，胳膊越粗壮。这一规律对肉食动物捕食有明显的好处。Meachen-Samuels说，猛兽在咬断猎物咽喉前都需要将其扑倒，这一捕食方式在不同谱系的肉食动物中各自趋同进化出来，甚至一些有袋类动物也有这种捕食方式。（生物谷bioon.com）
doi:10.1666/10036.1
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Morphological convergence of the prey-killing arsenal of sabertooth predators
Julie A. Meachen-Samuels
Sabertooth members of the Felidae, Nimravidae, and Barbourofelidae are well-known for their elongated saber-shaped canines. However, within these groups, there is a wide range of independently derived tooth shapes and lengths, including dirk-tooth and scimitar-tooth morphs. In conjunction with the saberteeth, forelimbs were also used to subdue prey. Thus, there may be a functional link between canine shape and forelimb morphology. Because there are no living sabertooth forms for comparison, extant felids make a good proxy for examining the morphology of these extinct organisms. Here, I examine the forelimb morphology of different sabertooth groups from across North America; I address whether forelimb morphologies are associated with tooth morphologies, and whether these associated tooth and forelimb morphologies are convergent among different families. To answer these questions, I analyzed six functional indices of the forelimbs and two canine characters for 13 species of sabertooth predators and 15 extant felid species. Results indicate that sabertooth morphs with longer, thinner canines show more robust limb proportions. These patterns were convergent among sabertooth felids, nimravids, and barbourofelids, and indicate a positive functional relationship between saber elongation and increased forelimb robustness. This suggests that sabertooth carnivorans demonstrated niche partitioning of predation strategies according to canine shape and corresponding forelimb morphology.
