New insights into the morphology of the Carboniferous tetrapod Crassigyrinus scoticus from computed tomography
New insights into the morphology of the Carboniferous tetrapod Crassigyrinus scoticus from computed tomography
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DOI：
10.1017/s1755691018000804
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发表时间：
2019-03-01
影响因子：
1.2
通讯作者：
Hutchinson, John R.
中科院分区：
文献类型：
--
作者：
Herbst, Eva C.;Hutchinson, John R.
石炭纪四足动物 Crassigyrinus Scoticus 就其形态和系统发育位置而言是一种神秘的动物。 Crassigyrinus 的前肢极度萎缩，其次可能是水生动物。最近的系统发育分析暂时将 Crassigyrinus 置于与 Whatcheeriids 接近的位置。许多石炭纪四足动物表现出与陆地运动相关的多种特征，许多研究都集中在这种新颖的运动模式是如何进化的。然而，为了估计脊椎动物进化中这一重要时期的选择压力和限制，研究早期四足动物（例如仍然是水生的或后来变成水生的Crassigyrinus）也很重要。我们使用计算机断层扫描来搜索有关 Crassigyrinus 骨骼形态的更多数据，并发现了一些先前被矩阵隐藏的元素。这些元素包括更多的肋骨、另一个神经弓、耻骨骨化的潜在证据以及可能的胸膜中心。我们还发现了几个额外的跖骨，具有有趣的不对称形态，可能具有功能意义。最后，我们将之前被认为是左骶骨的肋骨重新分类为左腓骨，并显示了之前未知的桡骨形态。这些发现在功能和系统发育背景下进行了检查。
The Carboniferous tetrapod Crassigyrinus scoticus is an enigmatic animal in terms of its morphology and its phylogenetic position. Crassigyrinus had extremely reduced forelimbs, and was aquatic, perhaps secondarily. Recent phylogenetic analyses tentatively place Crassigyrinus close to the whatcheeriids. Many Carboniferous tetrapods exhibit several characteristics associated with terrestrial locomotion, and much research has focused on how this novel locomotor mode evolved. However, to estimate the selective pressures and constraints during this important time in vertebrate evolution, it is also important to study early tetrapods like Crassigyrinus that either remained aquatic or secondarily became aquatic. We used computed tomographic scanning to search for more data about the skeletal morphology of Crassigyrinus and discovered several elements previously hidden by the matrix. These elements include more ribs, another neural arch, potential evidence of an ossified pubis and maybe of pleurocentra. We also discovered several additional metatarsals with interesting asymmetrical morphology that may have functional implications. Finally, we reclassify what was previously thought to be a left sacral rib as a left fibula and show previously unknown aspects of the morphology of the radius. These discoveries are examined in functional and phylogenetic contexts.