哺乳动物鳞鼹鼱的双下颌关节结构

Two Pairs of Particular Structures of Mandibular Joints of Mammalian Sorex

作者对10只鳞鼹鼱的下颌关节进行了研究,发现下颌关节共两对:一对在后、外、上方,暂名外侧下颌关节;另一对在颅底,位于外侧下颌关节的前、内、下方,暂名颅底下颌关节。关节窝均由鳞骨组成。4个关节独立,均具有各自的关节窝、髁状突、关节盘及关节囊,外侧下颌关节上腔宽松。适应于大张口运动,颅底下颌关节腔窄小,适应于铰链运动,起支持下颌运动的作用。此双下额关节结构的发现,是形态与功能相适应的又一例证。

The mandibular joints ofChinese Anouroserex squamipes.spuamipes,MILNE-EDWARDS were examined by grossand microscopic studies. We discovered thatthere were two pairs of joints in theseanimals. The upper pair of joints, namedlateral mandibular joints, were placed onboth sides under the parietal bone. Thelower pair of joints. named skull-basemandibular joints,were placed on both sidesof the skull-base. These two pairs of jointscould not be observed simultaneously inthe same plane either sagittally or frontally.The lateral fossa and condyle were obli-quely from outward, backward and upwardto inward, forward and downward on bothsides; the fossa looked like a groove concavedownward, and the head of the condylesappeared in a cylindrical form. Thelower fossae and condyles were transverselyforward and inward from the lateral man-dibular joints; the fossa lcoked like a shal-low spoon concave upward, and the condyleappeared in a flat surface to fit the upwardfossa. The sorex likes to dig holes on theground.to live in and search for insects inthe soil to eat. The skull-base mandibularjoints will support the jaw to counteractthe digging force and protect the lateralmandibular joints from injury. This studyhas suggested that the morphology of themandibular joints is adapted to their func-tional requirements during evolution.