Department of Genetics, Evolution, and Environment, University College London, 4 Stephenson Way, London NW1 2HE, UK.
Proc Biol Sci. 2011 Jun 22;278(1713):1831-9. doi: 10.1098/rspb.2010.2031. Epub 2010 Nov 24.
Carnivory has evolved independently several times in eutherian (including placental) and metatherian (including marsupial) mammals. We used geometric morphometrics to assess convergences associated with the evolution of carnivory across a broad suite of mammals, including the eutherian clades Carnivora and Creodonta and the metatherian clades Thylacoleonidae, Dasyuromorphia, Didelphidae and Borhyaenoidea. We further quantified cranial disparity across eutherians and metatherians to test the hypothesis that the marsupial mode of reproduction has constrained their morphological evolution. This study, to our knowledge the first to extensively sample pre-Pleistocene taxa, analysed 30 three-dimensional landmarks, focused mainly on the facial region, which were digitized on 130 specimens, including 36 fossil taxa. Data were analysed with principal components (PC) analysis, and three measures of disparity were compared between eutherians and metatherians. PC1 showed a shift from short to long faces and seemed to represent diet and ecology. PC2 was dominated by the unique features of sabre-toothed forms: dramatic expansion of the maxilla at the expense of the frontal bones. PC3, in combination with PC1, distinguished metatherians and eutherians. Metatherians, despite common comparisons with felids, were more similar to caniforms, which was unexpected for taxa such as the sabre-toothed marsupial Thylacosmilus. Contrary to previous studies, metatherian carnivores consistently exhibited disparity which exceeded that of the much more speciose eutherian carnivore radiations, refuting the hypothesis that developmental constraints have limited the morphological evolution of the marsupial cranium.
肉食性在真兽类（包括胎盘类）和有袋类（包括有袋目）哺乳动物中已经独立进化了多次。我们使用几何形态测量学来评估与肉食性进化相关的趋同，涵盖了广泛的哺乳动物类群，包括真兽类的 Carnivora 和 Creodonta 以及有袋类的 Thylacoleonidae、Dasyuromorphia、Didelphidae 和 Borhyaenoidea。我们进一步量化了真兽类和有袋类的颅骨差异，以检验有袋类繁殖方式限制了它们形态进化的假说。这项研究，据我们所知，是第一个广泛采样更新世前分类群的研究，分析了 30 个三维标志点，主要集中在面部区域，这些标志点在 130 个标本上进行了数字化，包括 36 个化石分类群。数据采用主成分（PC）分析进行分析，并比较了真兽类和有袋类之间的三种差异度量。PC1 显示出从短脸到长脸的转变，似乎代表了饮食和生态。PC2 主要由剑齿形式的独特特征主导：上颌骨的急剧扩张，牺牲了额骨。PC3 与 PC1 相结合，区分了有袋类和真兽类。有袋类动物，尽管与猫科动物进行了常见比较，但与犬形目动物更为相似，这对于像剑齿有袋目动物 Thylacosmilus 这样的分类群来说是出乎意料的。与之前的研究相反，有袋类肉食动物的差异始终超过了种类繁多的真兽类肉食动物辐射，驳斥了发育限制限制了有袋类颅骨形态进化的假说。
