Meeting Abstract

30.5  Jan. 5  Feeding Mechanisms in Rodents DRUZINSKY, R.E.; Governors State University r-druzinsky@govst.edu

The Rodentia is a remarkably successful order, comprising roughly half of the extant species of the Mammalia. Rodents share a suite of derived characters of the jaw apparatus. These characters include a single incisor in each quadrant of the dentition, upper and lower diastemata, and the absence of the articular eminence at the anterior end of the glenoid fossa. Together these characters form a biomechanical complex for gnawing. Traditionally the rodents have been divided into three categories – sciuromorphy, hystricomorphy, and myomorphy �based on specialized arrangements of the jaw adductor muscles. Each of the three specializations is an anatomical solution that allows for rostral placement of jaw-closing muscles that have long moment arms, large physiological cross-sections, but relatively short fiber lengths. Numerous authors (e.g., Wood, 1973; Hartenberger, 1980) have suggested that these specializations of the rodent feeding apparatus are associated with chewing in which antero-posterior or �propalinal� movements are emphasized. But mechanical analyses demonstrate that it is more probable that sciuromorphy, hystricomorphy, and myomorphy are parallel evolutionary pathways for building a feeding apparatus for gnawing, and all have evolved more than one time.