Figueirido Borja, Palmqvist Paul, Pérez-Claros Juan A, Dong Wei
Área de Paleontología, Departamento de Ecología y Geología, Facultad de Ciencias, Universidad de Málaga, Campus Universitario de Teatinos, 29071, Málaga, Spain.
Naturwissenschaften. 2011 Feb;98(2):107-16. doi: 10.1007/s00114-010-0748-x. Epub 2010 Dec 4.
In this study, landmark-based methods of geometric morphometrics are used for investigating the main aspects of cranial shape transformation in the evolution of the giant panda, Ailuropoda melanoleuca. Specifically, we explore if the highly derived cranial adaptations for bamboo feeding of the living panda were developed early in the panda's lineage. Results obtained show that the overall cranial morphologies of the oldest known panda, the "pygmy" Ailuropoda microta, and the late Pleistocene Ailuropoda baconi are both very similar to that of their closest living relative, A. melanoleuca, which agrees with a previous proposal based on qualitative criteria. However, we also describe several differences between the crania of A. microta, A. baconi, and A. melanoleuca, including the development of the postorbital process, the orientation of the occipital region, and the expansion of the braincase. As a result, the cranial morphology of A. microta shows a less specialized morphology toward a fibrous and durophagous diet compared to the giant panda. These results are confirmed by a comparative analysis of the dimensions of the upper teeth in bears, which has revealed differences in relative tooth size between A. microta and A. melanoleuca, most probably as a result of mosaic evolution. Therefore, we conclude that cranial shape did not remain essentially uniform in the Ailuropoda lineage, as previously thought, but underwent a number of changes during more than 2 Myr.
在本研究中，基于地标点的几何形态测量方法被用于探究大熊猫（Ailuropoda melanoleuca）进化过程中颅骨形状转变的主要方面。具体而言，我们探讨现存大熊猫高度特化的用于取食竹子的颅骨适应性特征是否在大熊猫谱系的早期就已形成。所获结果表明，已知最古老的大熊猫“侏儒”始熊猫（Ailuropoda microta）和更新世晚期巴氏大熊猫（Ailuropoda baconi）的整体颅骨形态与其现存最近的亲属大熊猫（A. melanoleuca）都非常相似，这与之前基于定性标准提出的观点一致。然而，我们也描述了始熊猫、巴氏大熊猫和大熊猫颅骨之间的一些差异，包括眶后突的发育、枕部区域的方向以及脑壳的扩张。因此，与大熊猫相比，始熊猫的颅骨形态在适应纤维性和硬食性饮食方面表现出较低的特化程度。对熊类上齿尺寸的比较分析证实了这些结果，该分析揭示了始熊猫和大熊猫在相对牙齿大小上的差异，这很可能是镶嵌进化的结果。所以我们得出结论，大熊猫谱系中的颅骨形状并非如之前所认为的那样基本保持一致，而是在超过200万年的时间里经历了许多变化。
