Departments of Occupational Therapy, Governors State University, University Park, IL 60484, USA. r-druzinsky @ govst.edu
Cells Tissues Organs. 2010;192(1):50-63. doi: 10.1159/000284930. Epub 2010 Feb 16.
The protrogomorph condition of the rodent masticatory apparatus is thought to be present in only one living species, the mountain beaver Aplodontia rufa. The major anatomical difference between protrogomorphs and sciuromorphs is that the relative size of one part of the masseter muscle, the anterior lateral masseter, is much greater in sciuromorphs than in protrogomorphs. The mechanics of force production at the incisors were compared in A. rufa and six sciuromorph rodents. Is the sciuroid masticatory apparatus more effective for production of forces at the incisors during biting than the primitive, protrogomorph condition? To answer this question, three measures of mechanical ability were employed and three hypotheses were tested: (1) the mechanical advantage of the adductor musculature is greater in sciuromorphs than in A. rufa; (2) the relative force produced at the incisors is greater in sciuromorphs than in A. rufa, and (3) the relative amount of force produced that can be used to drive the incisors into an object, is greater in sciuromorphs than in A. rufa. The results demonstrated that the protrogomorph, A. rufa, is not as efficient at generating bite forces at the incisors as the sciuromorphs.
啮齿动物咀嚼器官的原兽形状态据认为仅存在于一个现存物种，即山貛 Aplodontia rufa。原兽形类和松鼠形类之间的主要解剖学差异在于，咀嚼肌的一部分——前外侧咀嚼肌在松鼠形类中的相对大小比在原兽形类中要大得多。比较了 A. rufa 和六种松鼠形啮齿动物的门齿处的力产生力学。在咬噬时，松鼠形的咀嚼器官在产生门齿力方面是否比原始的原兽形状态更有效？为了回答这个问题，采用了三种力学能力的衡量标准，并检验了三个假设：（1） 松鼠形类的内收肌力学优势大于 A. rufa；（2） 松鼠形类在门齿处产生的相对力大于 A. rufa，以及（3） 可以用来驱动门齿进入物体的相对力产生量在松鼠形类中大于 A. rufa。结果表明，原兽形类的 A. rufa 在产生门齿咬合力方面的效率不如松鼠形类。
