First discovery of a primitive coelacanth fin fills a major gap in the evolution of lobed fins and limbs
First discovery of a primitive coelacanth fin fills a major gap in the evolution of lobed fins and limbs
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DOI：
10.1111/j.1525-142x.2007.00169.x
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发表时间：
2007-07-01
影响因子：
2.9
通讯作者：
Anderson, Philip
中科院分区：
文献类型：
--
作者：
Friedman, Matt;Coates, Michael I.;Anderson, Philip
化石记录为裂片鳍的原始形态提供了独特的线索，裂片鳍是指肢的前身。这些信息对于理解从鱼鳍到四足动物四肢的进化转变是至关重要的，它指导了研究这一事件背后的发育变化的模型系统的选择。然而，四足动物四肢进化的前提条件仍不清楚。这种不确定性源于我们对早期裂片鳍的认识上的一个显著差距：没有化石数据记录腔棘鱼的原始胸鳍状况，腔棘鱼是三大类鳍类（裂片鳍）鱼类之一。来自怀俄明州泥盆纪中晚期的新化石保存了第一个也是唯一一个原始腔棘鱼胸鳍内骨骼的例子。这种鳍的强烈不对称骨架证实了这是原始肉鳍动物模式的假设，这种模式在陆地脊椎动物最接近的鱼类亲属中持续存在。新材料揭示了现代腔棘鱼和活肺鱼成对鳍的专门化。因此，这些可能用于研究脊椎动物鳍和四肢之间进化和发育关系的背景发生了变化。我们的数据表明，对于寻求了解四足动物四肢起源的发育研究来说，原始的放动翼类鱼类，而不是现存的肢类鱼类及其衍生的附属物，是最有信息的比较物。
The fossil record provides unique clues about the primitive pattern of lobed fins, the precursors of digit-bearing limbs. Such information is vital for understanding the evolutionary transition from fish fins to tetrapod limbs, and it guides the choice of model systems for investigating the developmental changes underpinning this event. However, the evolutionary preconditions for tetrapod limbs remain unclear. This uncertainty arises from an outstanding gap in our knowledge of early lobed fins: there are no fossil data that record primitive pectoral fin conditions in coelacanths, one of the three major groups of sarcopterygian (lobe-finned) fishes. A new fossil from the Middle-Late Devonian of Wyoming preserves the first and only example of a primitive coelacanth pectoral fin endoskeleton. The strongly asymmetrical skeleton of this fin corroborates the hypothesis that this is the primitive sarcopterygian pattern, and that this pattern persisted in the closest fish-like relatives of land vertebrates. The new material reveals the specializations of paired fins in the modern coelacanth, as well as in living lungfishes. Consequently, the context in which these might be used to investigate evolutionary and developmental relationships between vertebrate fins and limbs is changed. Our data suggest that primitive actinopterygians, rather than living sarcopterygian fishes and their derived appendages, are the most informative comparators for developmental studies seeking to understand the origin of tetrapod limbs.