Research Abstract


The endoskeletal origin of the turtle carapace

2013年7月9日 Nature Communications 4 : 2107 doi: 10.1038/ncomms3107


平沢 達矢1, 長島 寛2 & 倉谷 滋1

  1. 理化学研究所 発生・再生科学総合研究センター 形態進化研究グループ
  2. 新潟大学 医歯学総合研究科 生体機能調節医学専攻 機能再建医学講座 肉眼解剖学分野
The turtle body plan, with its solid shell, deviates radically from those of other tetrapods. The dorsal part of the turtle shell, or the carapace, consists mainly of costal and neural bony plates, which are continuous with the underlying thoracic ribs and vertebrae, respectively. Because of their superficial position, the evolutionary origins of these costo-neural elements have long remained elusive. Here we show, through comparative morphological and embryological analyses, that the major part of the carapace is derived purely from endoskeletal ribs. We examine turtle embryos and find that the costal and neural plates develop not within the dermis, but within deeper connective tissue where the rib and intercostal muscle anlagen develop. We also examine the fossils of an outgroup of turtles to confirm that the structure equivalent to the turtle carapace developed independently of the true osteoderm. Our results highlight the hitherto unravelled evolutionary course of the turtle shell.