Craniofacial Development in Eutherian and Metatherian Mammals

真兽类(胎盘类)和变态类(有袋类)哺乳动物之间最显著的区别在于它们的繁殖和发育模式。与真兽类相比，变态动物出生时处于早产状态，并在依附于乳头、哺乳的过程中完全发育。这些变色论和真心学策略的进化后果、优缺点构成了大量文献的基础。然而，关于形态发育差异的大多数细节尚不清楚。这项拟议的研究将研究变态动物和真兽类动物头面部特征的发育，旨在形成哺乳动物头面部发育长期研究的第一部分。这一具体项目的重点是详细比较两个物种的头面部发育情况，这两个物种是家养斑点藻科(Didelphidae，Marsupialia)和金黄地鼠(Mescricus Auratus)(啮齿目)。这些被认为是这两个组的代表性分类群。将收集两个物种的发育速度、分化顺序和发育事件协调的数据。重点将放在头部的骨骼、肌肉和神经上。然后，这些数据将被初步应用于系统发育比较，以评估在这些代表性类群中观察到的模式的共性，并形成关于适当特征的假设，以便进一步研究胎盘和有袋哺乳动物的发育事件的极性。

The most significant differences between eutherian (placental) and metatherian (marsupial) mammals involve their modes of reproduction and development. Metatherians are born at a premature state relative to eutherians, and complete development while attached to the teat, nursing. The evolutionary consequences, advantages and disadvantages of these metatherian and eutherian strategies form the basis of an extensive literature. Yet, most details on the differences in morphological development are unknown. The proposed study will examine development of craniofacial features in metatherians and eutherians and is intended to form the first part of a long term study of craniofacial development in mammals. The focus of this specific project is on a detailed comparison of craniofacial development in two species, Monodelphis domestica (Didelphidae, Marsupialia), and Meoscricetus auratus (Rodentia). These are hypothesized as representative taxa for the two groups. Data on rate of development, on sequence of differentiation, and on coordination of developmental events will be collected for both species. Focus will be on the bones, muscles and nerves of the head. These data will then be applied in a preliminary manner in phylogenetic comparisons in order to assess the generality of patterns observed in these representative taxa and to form hypotheses on appropriate characters for further examination of the polarity of developmental events in placental and marsupial mammals.