近日,，北卡羅來(lái)納州國(guó)家進(jìn)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(dòng)物牙齒越長(zhǎng)胳膊越粗壯。
劍齒虎以及其他具強(qiáng)力牙齒的猛獸可能曾經(jīng)還擁有強(qiáng)健有力的胳膊來(lái)幫助它們狩獵,。如此強(qiáng)健的胳膊不僅能輕易捕獲獵物，還能對(duì)它們看起來(lái)很兇猛,、實(shí)際卻極易斷裂的牙齒起到保護(hù)作用,。
在劍齒虎進(jìn)化之前就有許多史前具兇猛牙齒的肉食動(dòng)物身上也能獲得類似的發(fā)現(xiàn)，比如生活于4200～700萬(wàn)年前的獵貓（假劍齒虎,，nimravids）,，以及2000～500萬(wàn)年前的巴博劍齒虎（barbourofelids），巴博劍齒虎是貓科動(dòng)物的姐妹群,。Julie Meachen-Samuels說(shuō),，這些古動(dòng)物雖然看起來(lái)與貓科動(dòng)物非常相似，但實(shí)際上,，貓科動(dòng)物是在它們幾百年后才出現(xiàn)的,。
獵貓和巴博劍齒虎并沒(méi)有現(xiàn)生的后裔,，不過(guò)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(zhǎng)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(shí)際上卻比現(xiàn)生貓科動(dòng)物的牙齒脆弱得多,，它們非常容易破碎。Meachen-Samuels說(shuō),，現(xiàn)生貓科動(dòng)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(shí)也不易損壞,，因此對(duì)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(dòng)物都要強(qiáng)壯的前肢,。她猜測(cè),，強(qiáng)壯的前肢能幫助猛獸按住掙扎的獵物，并保護(hù)咬入獵物體內(nèi)的牙齒不被折斷,。通過(guò)分析發(fā)現(xiàn),，Meachen-Samuels認(rèn)為其他諸多具齒猛獸都具有強(qiáng)壯的前肢。
Meachen-Samuels測(cè)量了數(shù)百件博物館收藏的已滅絕貓科動(dòng)物,、獵貓,、巴博劍齒虎以及13種現(xiàn)生貓科動(dòng)物（包括考慮）的上犬齒和肢骨。通過(guò)對(duì)比,，并結(jié)合現(xiàn)今生物個(gè)頭越大骨骼越大的事實(shí),，她發(fā)現(xiàn)一個(gè)明顯的趨勢(shì)，就是牙齒越長(zhǎng),，胳膊越粗壯,。這一規(guī)律對(duì)肉食動(dòng)物捕食有明顯的好處。Meachen-Samuels說(shuō),，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(dòng)物中各自趨同進(jìn)化出來(lái)，甚至一些有袋類動(dòng)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.
