Endo Hideki, Taru Hajime, Yamamoto Masako, Arishima Kazuyoshi, Sasaki Motoki
Department of Zoology, National Science Museum, Tokyo, 3-23-1, Hyakunin-cho, Shinjuku-ku, Tokyo 169-0073, Japan.
Ann Anat. 2003 Jun;185(3):287-92. doi: 10.1016/S0940-9602(03)80043-2.
The morphological differences in the muscles of mastication between the giant panda (Ailuropoda melanoleuca) and the Asiatic black bear (Ursus thibetanus) were sought to confirm the adaptational strategy of these muscles in the giant panda. We measured some skull characteristics and weighed the muscles of mastication, and macroscopically observed the muscles of mastication in the two species. The noticeable differences between the two species are classified as follows: (1) The size ratio of the zygomatic width was much larger in the giant panda than in the Asiatic black bear. (2) The weight ratio of the two pterygoid muscles was also much larger in the giant panda than in the Asiatic black bear. (3) The lateral slips of the temporal muscles are thicker and stronger in the Asiatic black bear than in the giant panda. (4) The deep layer of the masseter muscle was rostrocaudally divided, and a complicated running of tendons is observed in the giant panda. (5) The two pterygoid muscles were much larger and well-developed in the giant panda than in the Asiatic black bear. The points (1) and (4) may be related to the generation of the force necessary to chew the bamboo in the giant panda. We thought that the large mass of the masseter and temporal muscles are needed in this species. In the points of (2) and (5), the two pterygoid muscles were obviously different in form and weight ratio between the two species. We suggest that the two pterygoid muscles may act as an additional force generator to dorsoventrally press and crush bamboo stems.
研究大熊猫（Ailuropoda melanoleuca）和亚洲黑熊（Ursus thibetanus）咀嚼肌的形态差异，以证实这些肌肉在大熊猫中的适应策略。我们测量了一些头骨特征并对咀嚼肌进行称重，并对这两个物种的咀嚼肌进行了宏观观察。这两个物种之间的显著差异分类如下：（1）大熊猫的颧宽尺寸比远大于亚洲黑熊。（2）大熊猫两块翼状肌的重量比也远大于亚洲黑熊。（3）亚洲黑熊颞肌的外侧肌束比大熊猫更厚更强壮。（4）咬肌深层在前后方向上被分开，在大熊猫中观察到肌腱的复杂走行。（5）大熊猫的两块翼状肌比亚洲黑熊更大且发育良好。要点（1）和（4）可能与大熊猫咀嚼竹子所需力量的产生有关。我们认为该物种需要大量的咬肌和颞肌。在要点（2）和（5）中，两个物种的两块翼状肌在形态和重量比上明显不同。我们认为这两块翼状肌可能作为额外的力量发生器，从背腹方向挤压和碾碎竹茎。
