Based on their relatively large, chisel-like incisors and robust dentaries, species of the Paleocene plesiadapid mammal Chiromyoides have been described as potential ecological analogues of either seed-eating rodents or the unusually specialized lemur Daubentonia madagascariensis. Here, we analyze the most complete dentaries of Chiromyoides currently known in order to illuminate jaw form and function in this taxon. Principal Component Analysis shows that Chiromyoides campanicus and Daubentonia are uniquely similar in select dentary proportions when compared with a sample including seven other fossil plesiadapid taxa as well as 22 extant primates, dermopterans and scandentians. Comparative allometric analyses indicate that in both Daubentonia and Chiromyoides, the unique jaw proportions are likely achieved through hypertrophy of masseteric fossa length and dentary depth, rather than simple reduction of tooth row length. Consistent with these dentary features indicative of powerful gnawing, we show that incisor apex morphology became increasingly chisel-like in certain younger species of Chiromyoides. Importantly, slight reduction in molar area relative to jaw length and body mass appears to characterize all species of Chiromyoides in which molar proportions can be estimated. Notably, this pattern occurs in one of the oldest known specimens of Chiromyoides, an edentulous but relatively complete dentary from the middle Tiffanian of Texas, which differs from other Chiromyoides specimens in having a relatively shallower corpus. Taken together, this evidence suggests that Chiromyoides was a Daubentonia-like extractive forager that evolved from taxa whose diets emphasized exudates.

古新世 plesiadapid 哺乳动物Chiromyoides具有相对较大的凿子状门牙和坚固的牙齿，因此被描述为食种子啮齿动物或异常特化的狐猴Daubentonia madagascariensis 的潜在生态类似物。在这里，我们分析的最完整的dentaries Chiromyoides目前，以便照亮下颚形式和功能在这一类群知。主成分分析表明，Chiromyoides campanicus和Daubentonia与包括 7 种其他化石 plesiadapid 分类群以及 22 种现存灵长类动物、皮翅目动物和斯堪的动物类动物的样本相比，它们在选择的齿类比例上具有独特的相似性。比较异速生长分析表明，在Daubentonia和Chiromyoides 中，独特的下颌比例可能是通过咬肌窝长度和牙齿深度的肥大来实现的，而不是简单地减少牙列长度。与这些指示强大啃咬的齿状特征一致，我们表明在某些年轻的Chiromyoides物种中，门牙顶端形态变得越来越像凿子。重要的是，相对于下颌长度和体重而言，臼齿面积略有减少似乎是所有摇蚊的特征其中摩尔比例可以估计。值得注意的是，这种模式发生在已知最古老的Chiromyoides标本之一中，这是一种来自德克萨斯州中部蒂凡尼阶的无牙但相对完整的牙齿，与其他Chiromyoides标本的不同之处在于其语料库相对较浅。总之，这方面的证据表明，Chiromyoides是Daubentonia样采掘觅食，从类群，其饮食强调分泌物演变。