Eickhoff S
Abteilung Morphologie des Zentrums Anatomie der Universität Göttingen.
Gegenbaurs Morphol Jahrb. 1990;136(6):827-43.
The therian scapula was until now thought to show very primitive features during early morphogenesis, as are found in the scapula of adult monotremes (elevated position of the scapula, lack of a spina and a fossa supraspinata, laterally directed cavitas glenoidalis). A morphogenetic study of the scapula of Tupaia belangeri has proved some of these assumptions to be wrong. The scapula undergoes a tilting which shifts its angulus articularis cranially, but no descent of the scapula could be found. The supraspinous fossa, which was supposed to develop very late in ontogeny from the anterior border of the scapula (Lewis 1902, Cheng 1955), is present in Tapaiai from the start. Part of it ossifies in membrane. The scapular spine does not develop as a cartilaginous outgrowth from the anterior border, but is formed mainly as an appositional bone along the lateral surface of the scapula. The glenoid cavity and the humerus are initially directed laterally. They attain their definitive form after the heart has migrated downward and the arms have been adducted. This represents a true plesiomorphous character state in therian ontogeny.
直到现在，兽类肩胛骨在早期形态发生过程中一直被认为具有非常原始的特征，就像成年单孔类动物的肩胛骨那样（肩胛骨位置较高，没有肩胛冈和冈上窝，关节盂侧向）。对树鼩肩胛骨的形态发生学研究证明，其中一些假设是错误的。肩胛骨会发生倾斜，使其关节角向头侧移动，但未发现肩胛骨下降。原本认为在个体发育过程中很晚才从肩胛骨前缘发育而来的冈上窝（Lewis，1902年；Cheng，1955年），在树鼩中从一开始就存在。它的一部分在膜内骨化。肩胛冈不是从肩胛骨前缘以软骨突出的形式发育而来，而是主要沿着肩胛骨外侧表面以附加骨的形式形成。关节盂和肱骨最初是侧向的。在心脏向下迁移且手臂内收后，它们才达到最终形态。这在兽类个体发育中代表一种真正的近裔性状状态。
