Griffin Christopher T, Stocker Michelle R, Colleary Caitlin, Stefanic Candice M, Lessner Emily J, Riegler Mitchell, Formoso Kiersten, Koeller Krista, Nesbitt Sterling J
Department of Geosciences, Virginia Tech, 926 West Campus Drive, Blacksburg, VA, 24061, U.S.A.
Department of Vertebrate Paleontology, Cleveland Museum of Natural History, 1 Wade Oval Drive, Cleveland, OH, 44106, U.S.A.
Biol Rev Camb Philos Soc. 2020 Dec 2. doi: 10.1111/brv.12666.
Morphology forms the most fundamental level of data in vertebrate palaeontology because it is through interpretations of morphology that taxa are identified, creating the basis for broad evolutionary and palaeobiological hypotheses. Assessing maturity is one of the most basic aspects of morphological interpretation and provides the means to study the evolution of ontogenetic changes, population structure and palaeoecology, life-history strategies, and heterochrony along evolutionary lineages that would otherwise be lost to time. Saurian reptiles (the least-inclusive clade containing Lepidosauria and Archosauria) have remained an incredibly diverse, numerous, and disparate clade through their ~260-million-year history. Because of the great disparity in this group, assessing maturity of saurian reptiles is difficult, fraught with methodological and terminological ambiguity. We compiled a novel database of literature, assembling >900 individual instances of saurian maturity assessment, to examine critically how saurian maturity has been diagnosed. We review the often inexact and inconsistent terminology used in saurian maturity assessment (e.g. 'juvenile', 'mature') and provide routes for better clarity and cross-study coherence. We describe the various methods that have been used to assess maturity in every major saurian group, integrating data from both extant and extinct taxa to give a full account of the current state of the field and providing method-specific pitfalls, best practices, and fruitful directions for future research. We recommend that a new standard subsection, 'Ontogenetic Assessment', be added to the Systematic Palaeontology portions of descriptive studies to provide explicit ontogenetic diagnoses with clear criteria. Because the utility of different ontogenetic criteria is highly subclade dependent among saurians, even for widely used methods (e.g. neurocentral suture fusion), we recommend that phylogenetic context, preferably in the form of a phylogenetic bracket, be used to justify the use of a maturity assessment method. Different methods should be used in conjunction as independent lines of evidence when assessing maturity, instead of an ontogenetic diagnosis resting entirely on a single criterion, which is common in the literature. Critically, there is a need for data from extant taxa with well-represented growth series to be integrated with the fossil record to ground maturity assessments of extinct taxa in well-constrained, empirically tested methods.
形态学构成了脊椎动物古生物学中最基本的数据层面，因为正是通过对形态的解读来识别分类单元，从而为广泛的进化和古生物学假设奠定基础。评估成熟度是形态学解释最基本的方面之一，它为研究个体发育变化、种群结构和古生态学、生活史策略以及进化谱系中的异时性进化提供了途径，否则这些信息将会随时间流逝而消失。蜥形纲爬行动物（包含鳞龙超目和主龙形下纲的最小分支）在其约2.6亿年的历史中一直是一个极其多样、数量众多且差异巨大的分支。由于该类群差异极大，评估蜥形纲爬行动物的成熟度很困难，充满了方法和术语上的模糊性。我们编纂了一个全新的文献数据库，收集了900多个蜥形纲成熟度评估的个体实例，以批判性地审视蜥形纲成熟度是如何被诊断的。我们回顾了蜥形纲成熟度评估中常用的往往不准确且不一致的术语（如“幼年”“成熟”），并提供了提高清晰度和跨研究一致性的途径。我们描述了用于评估每个主要蜥形纲类群成熟度的各种方法，整合了来自现存和已灭绝分类单元的数据，以全面阐述该领域的当前状况，并提供特定方法的陷阱、最佳实践以及未来研究的富有成效的方向。我们建议在描述性研究的系统古生物学部分添加一个新的标准子部分“个体发育评估”，以提供具有明确标准的明确个体发育诊断。由于不同个体发育标准的效用在蜥形纲中高度依赖于亚分支，即使对于广泛使用的方法（如神经中央缝融合）也是如此，我们建议使用系统发育背景，最好是以系统发育括号的形式，来证明成熟度评估方法的合理性。在评估成熟度时，不同的方法应作为独立的证据线结合使用，而不是像文献中常见的那样完全基于单一标准进行个体发育诊断。至关重要的是，需要将具有代表性生长序列的现存分类单元的数据与化石记录相结合，以便用经过充分约束和实证检验的方法来确定已灭绝分类单元的成熟度评估。
