Park A W, Nowosielski-Slepowron B J
Acta Anat (Basel). 1976;94(3):356-68.
A survey of skull development of the rice rat (Oryzomys palustris natator) covering a period of 21 days to 16 months involving equal numbers of males and females (108) was undertaken using various skull parameters. Sexual dimorphism in relation to body weight and length emerged before that of the skull which was only clearly marked by 2 months. A number of the skull parameters by virtue of their individual growth potential did not show sexual differences in size for a long time, whereas others were clearly marked. Once the differences between the sexes had been established they were maintained. One parameter - lenght of cranium - represents those parameters which show changes and it was found that the male rat continued to show a steady linear increase in length up to 16 months, whereas the female cranial length shows a deceleration with termination around 12 months. The skull differences are mirrored in the weight and length findings and it suggested that the earlier sexual maturity of the females is compensated by an earlier cessation of growth compared to the males which mature later and have a correspondingly later cessation.
对稻鼠（Oryzomys palustris natator）头骨发育进行了一项调查，涵盖21天至16个月的时间段，涉及数量相等的雄性和雌性（各108只），采用了各种头骨参数。与体重和体长相关的两性异形在头骨的两性异形出现之前就已出现，头骨的两性异形直到2个月时才明显显现。一些头骨参数由于其个体生长潜力，在很长一段时间内没有显示出大小上的性别差异，而其他参数则有明显差异。一旦两性之间的差异确立，它们就会保持下去。一个参数——颅长——代表了那些显示出变化的参数，研究发现，雄性大鼠的颅长在16个月前持续呈稳定的线性增长，而雌性颅长则在12个月左右出现减速并停止增长。头骨差异反映在体重和体长的研究结果中，这表明雌性较早的性成熟通过与雄性相比更早停止生长来得到补偿，雄性成熟较晚，相应地停止生长也较晚。
