Muchlinski Magdalena N, Kirk E Christopher
Center for Anatomical Sciences, University of North Texas, Health Science Center, USA.
Department of Anthropology, University of Texas at Austin, USA; Jackson School Museum of Earth History, University of Texas at Austin, USA.
J Hum Evol. 2017 Apr;105:57-68. doi: 10.1016/j.jhevol.2017.01.017. Epub 2017 Mar 18.
The size of the infraorbital foramen (IOF) is correlated with the size of the infraorbital nerve and number of mystacial vibrissae in mammals. Accordingly, IOF cross-sectional area has been used to infer both the rostral mechanoreceptive acuity and phylogenetic relationships of extinct crown primates and plesiadapiforms. Among living mammals, extant primates, scandentians, and dermopterans (Euarchonta) exhibit smaller IOF cross-sectional areas than most other mammals. Here we assess whether fossil adapoids, omomyoids, and plesiadapiforms show a reduction in relative IOF area similar to that characterizing extant euarchontans. The IOFs of 12 adapoid, 7 omomyoid, 15 plesiadapiform, and 3 fossil gliran species were measured and compared to a diverse extant mammalian sample. These data demonstrate that adapoids and omomyoids have IOFs that are similar in relative size to those of extant euarchontans. Conversely, IOFs of plesiadapiforms are on average about twice as large as those of extant euarchontans and are more comparable in size to those of extant non-euarchontan mammals. These results indicate that crown primates share a derived reduction in relative IOF size with treeshrews and colugos. Accordingly, a decreased reliance on the muzzle and an increased reliance on the hands for environmental exploration may have first evolved in the euarchontan stem lineage. However, the relatively large IOFs of plesiadapiforms imply a continued reliance on the muzzle for close exploration of objects. This finding may indicate that either parallel evolutionary decreases in IOF size occurred within Euarchonta or that plesiadapiforms lie outside the euarchontan crown group.
眶下孔（IOF）的大小与哺乳动物眶下神经的大小和口鼻触须的数量相关。因此，眶下孔横截面积已被用于推断已灭绝的冠类灵长目动物和近猴类动物的吻端机械感受敏锐度以及系统发育关系。在现存哺乳动物中，现存的灵长目动物、树鼩目动物和皮翼目动物（真灵长大目）的眶下孔横截面积比大多数其他哺乳动物小。在此，我们评估化石类跗猴型灵长目动物、始镜猴类动物和近猴类动物的眶下孔相对面积是否呈现出类似于现存真灵长大目动物的减小情况。我们测量了12种类跗猴型灵长目动物、7种始镜猴类动物、15种近猴类动物和3种化石类兔猴类动物的眶下孔，并与多样的现存哺乳动物样本进行比较。这些数据表明，类跗猴型灵长目动物和始镜猴类动物的眶下孔相对大小与现存真灵长大目动物的相似。相反，近猴类动物的眶下孔平均大小约为现存真灵长大目动物的两倍，其大小更接近于现存非真灵长大目哺乳动物的眶下孔。这些结果表明，冠类灵长目动物与树鼩和鼯猴在眶下孔相对大小上具有共同的衍生减小特征。因此，在真灵长大目动物的干群谱系中，可能首先出现了对口鼻依赖的减少以及对双手进行环境探索依赖的增加。然而，近猴类动物相对较大的眶下孔意味着它们仍持续依赖口鼻进行物体的近距离探索。这一发现可能表明，要么在真灵长大目动物内部发生了眶下孔大小的平行进化减小，要么近猴类动物位于真灵长大目动物冠群之外。
