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Reconstructing pectoral appendicular muscle anatomy in fossil fish and tetrapods over the fins-to-limbs transition
Biological Reviews ( IF 10.0 ) Pub Date : 2017-11-10 , DOI: 10.1111/brv.12386
Julia L. Molnar 1 , Rui Diogo 2 , John R. Hutchinson 3 , Stephanie E. Pierce 4
Affiliation  

The question of how tetrapod limbs evolved from fins is one of the great puzzles of evolutionary biology. While palaeontologists, developmental biologists, and geneticists have made great strides in explaining the origin and early evolution of limb skeletal structures, that of the muscles remains largely unknown. The main reason is the lack of consensus about appendicular muscle homology between the closest living relatives of early tetrapods: lobe‐finned fish and crown tetrapods. In the light of a recent study of these homologies, we re‐examined osteological correlates of muscle attachment in the pectoral girdle, humerus, radius, and ulna of early tetrapods and their close relatives. Twenty‐nine extinct and six extant sarcopterygians were included in a meta‐analysis using information from the literature and from original specimens, when possible. We analysed these osteological correlates using parsimony‐based character optimization in order to reconstruct muscle anatomy in ancestral lobe‐finned fish, tetrapodomorph fish, stem tetrapods, and crown tetrapods. Our synthesis revealed that many tetrapod shoulder muscles probably were already present in tetrapodomorph fish, while most of the more‐distal appendicular muscles either arose later from largely undifferentiated dorsal and ventral muscle masses or did not leave clear correlates of attachment in these taxa. Based on this review and meta‐analysis, we postulate a stepwise sequence of specific appendicular muscle acquisitions, splits, and fusions that led from the ancestral sarcopterygian pectoral fin to the ancestral tetrapod forelimb. This sequence largely agrees with previous hypotheses based on palaeontological and comparative work, but it is much more comprehensive in terms of both muscles and taxa. Combined with existing information about the skeletal system, our new synthesis helps to illuminate the genetic, developmental, morphological, functional, and ecological changes that were key components of the fins‐to‐limbs transition.

中文翻译:

在鳍到四肢的过渡上重建化石鱼类和四足动物的胸附肌解剖

四足动物的四肢如何从鳍进化而来的问题是进化生物学的一大难题。虽然古生物学家、发育生物学家和遗传学家在解释肢体骨骼结构的起源和早期进化方面取得了长足的进步,但肌肉的起源和早期进化在很大程度上仍然未知。主要原因是对早期四足动物的近亲:叶鳍鱼和冠四足动物之间的附肢肌肉同源性缺乏共识。根据最近对这些同源性的研究,我们重新检查了早期四足动物及其近亲的胸带、肱骨、桡骨和尺骨肌肉附着的骨学相关性。在可能的情况下,使用文献和原始标本的信息将 29 种已灭绝和 6 种现存的肉翅目动物纳入荟萃分析。我们使用基于简约的特征优化分析了这些骨学相关性,以重建祖先叶鳍鱼、四足鱼、茎四足动物和冠四足动物的肌肉解剖结构。我们的综合表明,四足动物的肩部肌肉可能已经存在于四足动物中,而大多数更远侧的附肢肌肉要么是后来从很大程度上未分化的背侧和腹侧肌肉群中产生的,要么没有在这些分类群中留下明确的附着物。基于这篇综述和荟萃分析,我们假设从祖先的肌翅目胸鳍到祖先的四足动物前肢,特定的附肢肌肉获得、分裂和融合的逐步序列。这个序列与之前基于古生物学和比较工作的假设基本一致,但它在肌肉和分类群方面要全面得多。结合有关骨骼系统的现有信息,我们的新合成有助于阐明作为鳍到四肢过渡的关键组成部分的遗传、发育、形态、功能和生态变化。
更新日期:2017-11-10
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