The Evolution of the Maxillary Canal in Probainognathia (Cynodontia, Synapsida): Reassessment of the Homology of the Infraorbital Foramen in Mammalian Ancestors
The Evolution of the Maxillary Canal in Probainognathia (Cynodontia, Synapsida): Reassessment of the Homology of the Infraorbital Foramen in Mammalian Ancestors
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DOI：
10.1007/s10914-019-09467-8
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发表时间：
2020-09-01
影响因子：
1.9
通讯作者：
Rubidge, Bruce S.
中科院分区：
文献类型：
--
作者：
Benoit, Julien;Ruf, Irina;Rubidge, Bruce S.
在哺乳动物中，眶下管为三叉神经的上颌分支的眶下支提供通道。眶下神经确保上牙和眼睛与上唇之间的面部的触觉敏感性，更重要的是，神经支配的mystyrus vibrissae（胡须）。相比之下，大多数非哺乳动物的突触体显示出更“爬行动物样”的祖先条件，其中一个长而分叉的上颌管完全封闭眶下神经沿着与三叉神经的其他分支。从祖先的“爬行类”到衍生的“哺乳类”条件的系统发育过渡已被假设发生在Probainognathia分支的基础上。使用μ CT和同步辐射扫描，这项研究的目的是详细记录这种转变，专注于非哺乳动物的probainognathian犬齿象和早期的cardialiforms的样本。我们发现哺乳动物的情况是由于上颌管逐渐缩短，使眶下神经在面部软组织内分叉。移动的胡须只有在哺乳动物的眶下神经进化之后才成为可能，这表明这些结构出现在原颌兽和更衍生的犬齿兽中。最后，位于泪骨腹侧边缘的孔，通常与衍生的Probainognathia和早期哺乳动物目的眶下孔同源，最有可能与哺乳动物的颧面孔同源。
In mammals, the infraorbital canal provides a passage for the infraorbital ramus of the maxillary branch of the trigeminal nerve. The infraorbital nerve ensures tactile sensitivity of the upper teeth and face between the eye and upper lip and, more significantly, the innervation of mystacial vibrissae (whiskers). In contrast, most non-mammalian synapsids display a more "reptilian-like" ancestral condition in which a long and ramified maxillary canal completely enclosed the infraorbital nerve along with other branches of the trigeminal nerve. The phylogenetic transition from the ancestral "reptilian-like" to the derived "mammal-like" condition has been hypothesized to occur at the base of the Probainognathia clade. Using mu CT and synchrotron scanning, this study aims to document this transition in detail by focusing on a sample of non-mammalian probainognathian cynodonts and early mammaliaforms. We find that the mammalian condition is the result of a gradual shortening of the maxillary canal, which enabled the infraorbital nerve to ramify within the soft tissues of the face. Mobile whiskers became possible only after the mammalian infraorbital nerve had evolved, which suggest that these structures appeared inProbainognathusand more derived cynodonts. Finally a foramen located on the ventral margin of the lacrimal bone, which has been often homologized with the infraorbital foramen of derived Probainognathia and early Mammaliaformes, is most probably homologous to the mammalian zygomaticofacial foramen.