Along with supernumerary bones, sesamoids, defined as any organized intratendinous/intraligamentous structure, including those composed of fibrocartilage, adjacent to an articulation or joint, have been frequently considered as enigmatic structures associated with the joints of the skeletal system of vertebrates. This review allows us to propose a dynamic model to account for part of skeletal phenotypic diversity: during evolution, sesamoids can become displaced, attaching to and detaching from the long bone epiphyses and diaphysis. Epiphyses, apophyses and detached sesamoids are able to transform into each other, contributing to the phenotypic variability of the tetrapod skeleton. This dynamic model is a new paradigm to delineate the contribution of sesamoids to skeletal diversity. Herein, we first present a historical approach to the study of sesamoids, discussing the genetic versus epigenetic theories of their genesis and growth. Second, we construct a dynamic model. Third, we present a summary of literature on sesamoids of the main groups of tetrapods, including veterinary and human clinical contributions, which are the best‐studied aspects of sesamoids in recent decades. Finally, we discuss the identity of certain structures that have been labelled as sesamoids despite insufficient formal testing of homology. We also propose a new definition to help the identification of sesamoids in general. This review is particularly timely, given the recent increasing interest and research activity into the developmental biology and mechanics of sesamoids. With this updated and integrative discussion, we hope to pave the way to improve the understanding of sesamoid biology and evolution.

中文翻译：

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四足动物中的籽粒：新骨骼形态的起源

与多余的骨头一起，籽骨被定义为任何有组织的腱内/韧带内结构，包括由纤维软骨组成的与关节或关节相邻的结构，经常被认为是与脊椎动物骨骼系统关节相关的神秘结构。这篇综述使我们能够提出一个动态模型来解释骨骼表型多样性的一部分：在进化过程中，籽骨会发生位移，附着在长骨骨骺和骨干上或从骨干上分离。骨骺、骨突和分离的籽骨能够相互转化，导致四足动物骨骼的表型变异。这种动态模型是描述芝麻对骨骼多样性的贡献的新范式。在此处，我们首先提出了一种研究芝麻的历史方法，讨论了它们发生和生长的遗传与表观遗传理论。其次，我们构建了一个动态模型。第三，我们总结了有关四足类主要群体的籽粒的文献，包括兽医和人类临床贡献，这是近几十年来籽粒研究最深入的方面。最后，我们讨论了尽管对同源性的正式测试不足，但仍被标记为芝麻的某些结构的身份。我们还提出了一个新的定义，以帮助识别一般的籽粒。鉴于最近对籽粒发育生物学和力学的兴趣和研究活动日益增加，本综述特别及时。通过这次更新的综合性讨论，