Evolutionary stasis (long-term stability of morphology in an evolving lineage) is a pattern for which explanations are usually elusive. The Triassic tetrapod Gerrothorax pulcherrimus, a gill-bearing temnospondyl, survived for 35 million years in the Germanic Basin of Central Europe persisting throughout the dinosaur-dominated Late Triassic period. This evolutionary stasis coincides with the occurrence of this species in a wide range of habitats and environmental conditions. By the combination of palaeoecological and palaeohistological analyses, we found great ecological flexibility in G. pulcherrimus and present substantial evidence of developmental and metabolic plasticity despite the morphological stasis. We conclude that G. pulcherrimus could show the capacity to settle in water bodies too harsh or unpredictable for most other tetrapods. This would have been made possible by a unique life history strategy that involved a wide reaction norm, permitting adjustment to fluctuating conditions such as salinity and level of nutrients. Growth rate, duration of juvenile period, age at maturity, and life span were all subject to broad variation within specimens of G. pulcherrimus in one single lake and in between different lakes. In addition to providing a better understanding of fossil ecosystems, this study shows the potential of such a methodology to encourage palaeobiologists and evolutionary biologists to consider the mechanisms of variation in extant and fossil organisms by using a similar time-scope reference.

中文翻译：

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骨组织学揭示了高环境和代谢可塑性作为长寿稳态三叠纪 Temnospondyl 的成功进化策略。

进化停滞（进化谱系中形态的长期稳定性）是一种通常难以解释的模式。三叠纪四足动物Gerrothorax pulcherrimus是一种带鳃的 temnospondyl，在中欧的日耳曼盆地存活了 3500 万年，一直存在于以恐龙为主的晚三叠纪时期。这种进化停滞与该物种在广泛的栖息地和环境条件中的出现相吻合。通过结合古生态学和古组织学分析，我们发现G. pulcherrimus具有很大的生态灵活性，尽管形态停滞，但仍提供了发育和代谢可塑性的大量证据。我们得出结论，G. pulcherrimus可能显示出在对大多数其他四足动物来说过于严酷或不可预测的水体中定居的能力。这本可以通过独特的生活史策略实现，该策略涉及广泛的反应规范，允许对盐度和营养水平等波动条件进行调整。G. pulcherrimus标本在一个湖泊和不同湖泊之间的生长速度、幼鱼期持续时间、成熟年龄和寿命都存在很大差异。除了更好地了解化石生态系统之外，这项研究还展示了这种方法论的潜力，可以鼓励古生物学家和进化生物学家通过使用类似的时间范围参考来考虑现存生物和化石生物的变异机制。