近日,，北卡羅來納州國家進化綜合研究中心的Julie Meachen-Samuels在Paleobiology雜志上發(fā)表論文"Morphological convergence of the prey-killing arsenal of sabertooth predators"稱,，史前貓科動物牙齒越長胳膊越粗壯,。
劍齒虎以及其他具強力牙齒的猛獸可能曾經(jīng)還擁有強健有力的胳膊來幫助它們狩獵,。如此強健的胳膊不僅能輕易捕獲獵物，還能對它們看起來很兇猛,、實際卻極易斷裂的牙齒起到保護作用,。
在劍齒虎進化之前就有許多史前具兇猛牙齒的肉食動物身上也能獲得類似的發(fā)現(xiàn)，比如生活于4200～700萬年前的獵貓（假劍齒虎,，nimravids）,，以及2000～500萬年前的巴博劍齒虎（barbourofelids），巴博劍齒虎是貓科動物的姐妹群,。Julie Meachen-Samuels說,，這些古動物雖然看起來與貓科動物非常相似，但實際上,，貓科動物是在它們幾百年后才出現(xiàn)的,。
獵貓和巴博劍齒虎并沒有現(xiàn)生的后裔，不過化石證據(jù)顯示它們牙齒的形狀和尺寸變化極大,，一些短而圓,，一些長而平，還有一些甚至像切牛排的小刀一樣具鋸齒,。劍齒虎的牙齒看上去令人生畏,，但實際上卻比現(xiàn)生貓科動物的牙齒脆弱得多，它們非常容易破碎,。Meachen-Samuels說,，現(xiàn)生貓科動物的牙齒橫切面短而圓，能夠承受較大的力量,，在獵物掙扎時也不易損壞,，因此對狩獵極為有利。
在之前的研究中,，Meachen-Samuels發(fā)現(xiàn)加州劍齒虎（Smilodon fatalis）擁有比現(xiàn)今任何貓科動物都要強壯的前肢,。她猜測，強壯的前肢能幫助猛獸按住掙扎的獵物,，并保護咬入獵物體內(nèi)的牙齒不被折斷,。通過分析發(fā)現(xiàn)，Meachen-Samuels認為其他諸多具齒猛獸都具有強壯的前肢,。
Meachen-Samuels測量了數(shù)百件博物館收藏的已滅絕貓科動物,、獵貓、巴博劍齒虎以及13種現(xiàn)生貓科動物（包括考慮）的上犬齒和肢骨,。通過對比,，并結(jié)合現(xiàn)今生物個頭越大骨骼越大的事實，她發(fā)現(xiàn)一個明顯的趨勢,，就是牙齒越長,，胳膊越粗壯。這一規(guī)律對肉食動物捕食有明顯的好處。Meachen-Samuels說,，猛獸在咬斷獵物咽喉前都需要將其撲倒,，這一捕食方式在不同譜系的肉食動物中各自趨同進化出來，甚至一些有袋類動物也有這種捕食方式,。（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.
