Houée Guillaume, Goudemand Nicolas, Germain Damien, Bardin Jérémie
UMR 7207 Centre de recherche en paléontologie - Paris (CR2P), Sorbonne Université, Muséum national d'Histoire naturelle, CNRS, 43 rue Buffon, Paris, 75005, France.
UMR 5242 Institut de Génomique Fonctionnelle de Lyon (IGFL), ENS de Lyon, 46 All. d'Italie, Lyon, 69007, France.
Biol Rev Camb Philos Soc. 2025 Jun;100(3):1047-1066. doi: 10.1111/brv.13173. Epub 2024 Dec 18.
Understanding the origin and evolution of the mineralized skeleton is crucial for unravelling vertebrate history. However, several limitations hamper our progress. The first obstacle is the lack of uniformity and clarity in the literature for the definition of the tissues of concern, especially of enameloid(s) and enamel(s), resulting in ambiguous terminology and inconsistencies among studies. Moreover, the identification criteria currently employed to characterize hypermineralized tissues in extinct taxa, such as the presence or absence of tubules for enameloids, may lead to unsupported conclusions. We suggest that comparative developmental studies may be key to unambiguous terminology, truly diagnostic identification criteria and developmentally informed evolutionary hypotheses. We exemplify this approach by: (i) introducing a new conceptual framework for enameloid(s) and enamel(s), with clear terminologies, definitions and interactions between concepts; (ii) suggesting more rigorous ways to identify tissues, based on the observation of defining or additional properties, as well as on the comparison of developmental scenarios when possible; (iii) constructing a clear phylogenetic framework to discuss their homologies and highlighting possible transitions between these tissues; and by (iv) proposing developmental models that explain both enamel and enameloid formation, and suggest possible transitions between them.
了解矿化骨骼的起源和演化对于揭示脊椎动物的历史至关重要。然而，一些限制因素阻碍了我们的进展。第一个障碍是文献中对于相关组织的定义缺乏统一性和清晰度，尤其是釉质样组织和釉质，这导致术语模糊且研究之间存在不一致性。此外，目前用于鉴定已灭绝类群中高矿化组织的标准，例如釉质样组织中是否存在小管，可能会得出无根据的结论。我们认为，比较发育研究可能是实现明确术语、真正具有诊断性的鉴定标准以及基于发育知识的进化假说的关键。我们通过以下方式举例说明这种方法：（i）为釉质样组织和釉质引入一个新的概念框架，包括清晰的术语、定义以及概念之间的相互关系；（ii）基于对定义性或附加属性的观察以及在可能情况下对发育过程的比较，提出更严格的组织鉴定方法；（iii）构建一个清晰的系统发育框架来讨论它们的同源性，并突出这些组织之间可能的转变；以及（iv）提出能够解释釉质和釉质样组织形成过程并表明它们之间可能转变的发育模型。
