Population level measures of skeletal pathologies in Mesozoic marine reptiles (Ichthyosauria)

古病理学是研究化石生物体的疾病和损伤的学科。它最引人注目的应用可以说是推断中生代脊椎动物的古生态、行为和营养关系。在种群水平上，化石硬组织中创伤修饰的频率可以揭示关于古代生态系统动态的重要信息，尽管创伤的最终原因往往很难识别。关键的是，缺乏足够的定量测试使得化石记录中骨骼病理的总体流行情况变得不清楚，并导致缺乏明确的假设。我们目前的项目首次对鱼龙的古病理学进行了定量评估，鱼龙是一组类似海豚的次生海洋爬行动物，在德国西南部的早侏罗世PosidoniensHeefer地层中有著名的记录。我们汇编了五个鱼龙属在这个地层限制的区间内的骨骼病理的基线数据集，以测试病理发生和分布的变异性。我们在波西多尼亚页岩鱼龙动物群中观察到了广泛的病理变化，尤其是头骨、肋骨、胃部和前肢的损伤。在所有物种中都观察到了病理骨骼改变。我们测试了一生中骨骼损伤与身体大小和个体发育状态(青少年与成人)的关系。结果表明，这种疾病在成人中比在青少年中更常见，在较大的物种中相对比在较小的物种中更常见。然而，这些初步观察结果与已发表的鱼龙骨骼病理记录并不完全一致。例如，波西多尼亚页岩鱼龙动物群的关节疾病频率比其他地质单位低得多，肋骨创伤的发生率似乎要高得多。为了更严格地评估这些数据，并在空间和时间上相互关联，我们建议调查从中三叠世到早白垩世的可比鱼龙动物群中骨病理学的频率。我们假设，病理的相对频率将在连续的时间段保持恒定，并且可能更本质地受到身体大小和个体发育的影响。该项目的扩展将建立一种新的范例，用于从保存下来的脊椎动物化石损伤和疾病的痕迹中推断古生物学。

Paleopathology is the study of illness and injury in fossil organisms. Its most spectacular application has arguably been to infer paleoecology, behaviour and trophic relationships in Mesozoic vertebrates. The frequency of traumatic modification in fossilized hard tissues at the population level can reveal important information about ancient ecosystem dynamics, although the ultimate cause of the trauma is often difficult to identify. Critically, a lack of adequate quantitative testing has rendered the overall prevalence of skeletal pathologies in the fossil record unclear, and has led to a dearth of explicit hypotheses. Our current project has undertaken the first quantitative assessment of paleopathologies in ichthyosaurs, a group of dolphin-like secondarily marine reptiles famously documented from the Early Jurassic Posidonienschiefer Formation of southwestern Germany. We compiled a baseline data set of skeletal pathologies from five ichthyosaurian genera over this stratigraphically restricted interval to test for variability in the rate of pathological occurrence and distribution. We observed a broad range of pathologies in the Posidonia Shale ichthyosaur fauna, with injuries to the skull, ribs, gastralia, and forelimb being particularly prevalent. Pathological skeletal modifications were observed in all species. We tested the relationship of skeletal damage during life with body size and ontogenetic status (juvenile vs. adult). Results show that pathologies are more frequent in adults than in juveniles, and are relatively more frequent in larger than in smaller species. However, these preliminary observations are not entirely consistent with the published record of ichthyosaur skeletal pathologies. For instance, the frequency of articular disease is much lower in the Posidonia Shale ichthyosaur fauna than in other geological units, and the incidence of traumatic injuries to the ribs appears to be much higher. In order to evaluate this data more rigorously, and correlate through both space and time, we propose to survey the frequency of osteopathologies in comparable ichthyosaur faunas, ranging from the Middle Triassic through to Early Cretaceous. We hypothesize that the relative frequency of pathologies will remain constant across successive time bins, and is likely more intrinsically influenced by body size and ontogeny. This project extension will establish a novel paradigm for inferring paleobiology from preserved traces of injury and disease in fossil vertebrates.