论文摘要
How can we make the skeletal reconstructions of extinct animals as accurate as possible? The forelimb posture is especially problematic, because it involves determining the positions of the scapule in relation to the ribcage that are not directly connected with each other, and also involves determination of the limb joint angle in the support phase into the limited range, although they usually have a wider range of motion.These problems are due to our poor knowledge on the relationship between the skeletal morphology and the limb postures even among the extant taxa.Accordingly, the forelimbs of many extinct taxa, such as ceratopsian dinosaurs, have been reconstructed in various postures, but with an insufficient scientific basis.Here I introduce some recent studies that tackled these problems using the moment arms of anti-gravity muscles.In the support phase of quadrupedal tetrapod, the ribcage is suspended between the scapulae via serratus and rhomboid muscles against the gravity.Three-dimensional muscle moment analyses on extant quadrupedal taxa revealed that roll, yaw, and pitch moments of the trunk caused by the contraction of these muscles and the gravity are minimized if the scapula in support is located in the median, dorsal, and anterior portion on the ribcage.This scapular position is shared among all the extant tetrapods that facultatively/obligately support their body on the forelimbs.Muscle moment arm analyses using 300< extant quadrupedal taxa found that the extant tetrapods in sagittal, creeping, and sprawling postures emphasize moment arms of the each anti-gravity muscles of the elbow joint—the elbow extensor, flexor, and adductor muscles, respectively.Another study found that extant tetrapods keep the elbow joint angle where the moment arm of the anti-gravity muscle is maximized.According to the above-mentioned interpretations, the forelimb postures were indicated to be different among the ceratopsians.Among the ceratopsians, ceratopsids and protoceratopsids likely employed sagittal and sprawling forelimb postures, respectively.However, both families shared the scapular positions at along the median plane.The forelimb postures indicated for these taxa are consistent with the preservation of articulated specimens, the manus anatomy, and the ichnological evidence.
论文目录
文章来源
类型: 国际会议
作者: Shin-ichi FUJIWARA
来源: 第一届亚洲古生物学大会—暨中国古生物学会成立90周年纪念 2019-11-17
年度: 2019
分类: 基础科学
专业: 生物学,地质学
单位: Nagoya University Museum
分类号: Q915
页码: 179
总页数: 1
文件大小: 177k
下载量: 2