Ontogenetic variation of the Middle Triassic pseudosuchian Batrachotomus kupferzellensis: Implications for the palaeobiology of early archosaurs

原始龙类的分支由两个主要分支组成，鸟颈龙类（包括现存的鸟类）和伪鳄类（包括现存的鳄类），是四足动物中最成功的分支之一。我们对中生代初龙古生物学的大部分知识（例如种内变异、生长生理学和功能形态学）都是基于鸟龙类（即非鸟类恐龙和翼龙），而对早期伪鳄类的相关知识有限，尽管后者进化出了巨大的分类学和生态多样性，特别是在三叠纪时期。由于可获得几个不同个体发育阶段的标本，巴登符腾堡州中三叠世露头的Batrachotomus kupferzellensis代表了这一时期的陆地顶级捕食者之一，是研究早期伪鳄类古生物学的合适对象。因此，拟议的项目的目的是获得更好的洞察这一主题，使用Batrachotomus kupferzellensis作为模式生物。在这个项目中需要回答的重要问题包括：Batrachotomus kupferzellensis需要多长时间才能生长到成年大小，何时达到性成熟？它的增长受季节性影响的程度有多大？这告诉我们关于这个分类群的生长率的什么？动物在不同的身体区域均匀生长吗？在骨骼学上，Batrachotomus kupferzellensis的主要个体发育变化是什么？牙齿是否有变化（例如锯齿、牙齿形态）？这些数据是否揭示了生态学中的个体发育差异，例如在运动和进食行为方面？如果将这些数据与现存的鳄鱼类、其他基底伪鳄类和基底恐龙的数据进行比较，那么Batrachotomus kupferzellensis的个体发生数据是否提供了任何证据，证明在早期的祖龙进化中发生了异时事件？假设的初龙类祖先的类形个体发育和生长模式是什么？回答这些问题的中心方法将是骨组织学分析，形态测量学，骨骼学的详细研究以及基于MicroCT数据的内部颅骨结构的三维重建。总之，拟议的项目将有助于更多地了解Batrachotomus kupferzellensis和密切相关的物种的古生物学，这也有助于了解它们作为三叠纪陆地生态系统中的顶级捕食者的作用。由于与其他初龙形目进行了更广泛的比较，该项目将对三叠纪伪鳄类和基底初龙类的古生物学有更深入的了解。

The clade of Archosauria consists of two main clades, the Ornithodira (including extant birds) and the Pseudosuchia (including extant crocodylians), and represents one of the most successful clades among tetrapods. Most of our knowledge of the palaeobiology of Mesozoic archosaurs (e.g. intraspecific variation, growth physiology and functional morphology) is based on ornithodirans (i.e. non-avian dinosaurs and pterosaurs), whereas respective knowledge is limited for early pseudosuchians, although the latter evolved a great taxonomic and ecological diversity, especially in the Triassic period. Due the availability of several specimens of different ontogenetic stages the pseudosuchian Batrachotomus kupferzellensis from the Middle Triassic outcrops of Baden Württemberg, which represents one of the terrestrial top predators during this time period, represents an appropriate object to study the palaeobiology of early pseudosuchians. Thus, the aim of the proposed project is to obtain better insights into this topic, using the Batrachotomus kupferzellensis as a model organism. Important questions to be answered during this project include the following: How long did Batrachotomus kupferzellensis take to grow to adult size and when did it reach sexual maturity? How far was its growth subject to seasonality? What does this tell us about growth rates in this taxon? Did the animal growth uniformly within different body regions? What are main ontogenetic changes in the osteology of Batrachotomus kupferzellensis? Are there changes in dentition (e.g. serration, morphology of teeth)? Do these data reveal ontogenetic differences in ecology, e.g. in terms of locomotion and feeding behaviour? If comparing the data with that of extant crocodylians, other basal pseudosuchians and basal dinosaurs, does the ontogenetic data of Batrachotomus kupferzellensis provide any evidence for heterochronic events in early archosaur evolution? What are the plesiomorphic ontogenetic and growth patterns of the hypothetical ancestor of Archosauria? The central methods to answer these questions will be the analysis of bone histology, morphometrics, detailed studies of the osteology as well as three-dimensional reconstructions of internal cranial structures based on MicroCT data. In sum, the proposed project will help to learn more about the palaeobiology of Batrachotomus kupferzellensis and closely related species, which also helps to understand their role as top-predators in the terrestrial ecosystems of the Triassic. Due to a wider comparison with other Archosauriformes, the project will obtain deeper insights in the palaeobiology of Triassic pseudosuchians and basal archosaurs in general.