Postdoctoral Fellowship: EAR-PF: Geochemical taphonomy of a rare dicynodont bonebed and its paleobiological implications of social behavior in the stem-mammalian lineage

佐伊·T Kulik已被授予NSF博士后奖学金，以调查一个罕见的化石丰富的骨床的沉积历史，该骨床保存了100多个与哺乳动物血统有关的双齿兽物种化石，称为Dolichuranus。从这个骨床的见解可以提供一个潜在的快照是什么样的生活，这些灭绝的哺乳动物亲属从~ 2.4亿年前。例如，利用周围寄主岩石的地质学，可以做出解释来确认或反驳这个化石组合是否代表一个单一的种群。此外，从骨组织组成的微观细节的见解可以用来重建骨骼和组织学的变化，这个物种（也许人口）在生长和发育过程中经历了大的身体尺寸。事实上，硬组织组织学--研究牙齿和骨骼组织的微观结构和组成--提供了了解化石记录中生长速率的唯一见解。为此，该项目的目标是描述骨床的沉积历史，以便将可以从那里恢复的化石遗骸中理解的古生物学解释结合起来，这可以提供有关哺乳动物深层进化史中的社会行为，大型体型进化和人口年龄结构的新信息。这项工作的更广泛的影响包括：（1）与菲尔德自然历史博物馆合作，通过在格兰杰科学中心的临时展览向广大观众传播成果，（2）指导洛约拉大学芝加哥的本科生和研究生，以及（3）马卡莱斯特学院为大学生开发一门课程，重点是地球化学埋藏学和骨组织学。该项目旨在调查沉积利用传统和地球化学埋藏学方法研究以二齿象为主的骨床的历史。该骨床是坦桑尼亚利富阿段化石地点地层序列中最低的一处，将用于评估河流和洪泛平原沉积物中脊椎动物遗骸的时空改造程度。此外，该项目旨在测试大型双齿兽物种的形态、大小和年龄是否相关，由于混合年龄双齿兽组合的稀缺性，尚未完成新的工作。初步的地球化学和传统的埋藏结果表明，双犬齿骨床保留了一个单一的，快速埋葬反映均匀的埋藏历史，但需要更大的样本来验证，这个骨床是一个单一的人口的快照。通过独立的证据线，包括沉积学，岩相学，生物碎屑保存，微量元素分析，并通过硬组织组织学的尺寸-年龄评估，该项目将重建生活史和双齿齿兽从这个骨床从微观结构到组合的全尺度的进化史。这种新颖的方法组合将在长期研究的哺乳动物社会行为问题上建立一条新的研究路线，也将填补我们对二叠纪-三叠纪干层最丰富的群体的生长和发育的理解的关键空白。该奖项反映了NSF的法定使命，并被认为是值得支持的，使用基金会的知识价值和更广泛的影响审查标准进行评估。

Zoe T. Kulik has been awarded an NSF EAR Postdoctoral Fellowship to investigate the depositional history of a rare fossil-rich bonebed that preserves over 100 fossils of a dicynodont species allied with the mammalian lineage called Dolichuranus. Insights from this bonebed can provide a potential snapshot of what life was like for these extinct mammal-relatives from ~240 million years ago. For example, using the geology of the surrounding host rock, interpretations can be made to confirm or refute if this fossil assemblage represents a single population. Furthermore, insights from the microscopic details of fossilized bone tissue composition can be used to reconstruct the skeletal and histological changes that this species (and perhaps population) experienced during growth and development to large body size. Indeed, hard tissue histology- the study of dental and bone tissue microstructure and composition- provide the only insights to understand growth rates in the fossil record. To this end, the project goals are to characterize the depositional history of the bonebed in order to contextualize palaeobiological interpretations that can be understood from the fossilized remains that were recovered there, which can provide new information on social behavior, evolution of large body size, and population age structures in the deep evolutionary history of mammals. Broader impacts of this work include (1) working with the Field Museum of Natural History to disseminate results to a broad audience through a temporary exhibit in the Grainger Science Hub, (2) mentoring undergraduate and graduate students at Loyola University Chicago, and (3) developing a curriculum for college students focused on geochemical taphonomy and bone histology at Macalester College.This project aims to investigate the depositional history of a dicynodont-dominated bonebed using traditional and geochemical taphonomic approaches. This bonebed is the lowermost occurrence in a stratigraphic succession of fossil localities in the Lifua Member of Tanzania that will be used to assess the degree of temporal and spatial reworking of vertebrate remains in fluvial and floodplain deposits. In addition, this project aims to test whether morphology, size, and age are correlated in the large dicynodont species, novel work that has not yet been done due to the scarcity of mix-aged dicynodont assemblages. Preliminary geochemical and traditional taphonomic results suggest that the dicynodont bonebed preserves a homogenous taphonomic history reflective of a single, rapid burial, but a larger sample is needed to validate that this bonebed is a snapshot of a single population. Through independent lines of evidence including sedimentology, petrography, bioclast preservation, trace-element analysis, and size-age assessment through hard tissue histology, this project will reconstruct the life history and preservational history of dicynodonts from this bonebed from microstructural to assemblage-wide scales. This novel combination of methods will establish a new line of inquiry in the long- studied question of mammalian social behavior and will also fill critical gaps in our understanding of growth and development in the most abundant group of Permo-Triassic stem-mammals to provide valuable comparative data to identify ontogenetic stages in dicynodonts more broadly.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.