Anatomy and relationships of stem group salamanders from the middle jurassic of Mongolia

现代蝾螈提供了解剖学和动物生活方式的最佳活体模型，这些动物在3.65亿年前从古老的鱼类进化成第一批陆地脊椎动物。 大多数从水生卵孵化，在水中度过他们的早期生活，并蜕变为陆地成年人。 不幸的是，我们对已知最古老的现代蝾螈和它们可能的祖先之间的2亿年化石记录的知识存在差距。在过去的15年里，这一差距已经被一系列来自1.65亿年前沉积物的化石所弥补，这些化石位于内蒙古和邻近中国的热河生物群的底部，产生了有羽毛的恐龙，一些最古老的哺乳动物和古代鸟类的化石。 由于它们的身体在反复火山爆发的缺氧沉积物中被迅速掩埋，蝾螈的遗骸被精美地保存下来，包括数十个完整的、有关节的骨骼，从幼虫到成虫的生长阶段，眼睛的印象，外部鳃和肌肉。 在一些蝾螈中，皮肤显示出其原始的纹理、色素分布的模式和肋沟，这些肋沟在陆地蝾螈中将水从地面引导到身体的两侧，以帮助皮肤呼吸。与内蒙古省博物馆合作研究了数十件标本。 在对现代蝾螈的解剖学、生理学、个体发育和行为学有一定了解的研究生、博士后学生和专业同事的帮助下，我们将从道虎皋地区发现至少五个高度分化的谱系，并将其与古代两栖动物、热河序列其他地方的蝾螈和现代蝾螈科中假定的祖先进行详细的说明、描述和比较。 这项研究将大大提高我们对所有蝾螈历史上的关系和进化的理解。

Modern salamanders provide the best living models of the anatomy and way of life of animals that evolved from archaic fish into the first terrestrial vertebrates 365 million years ago. Most hatch from aquatic eggs, spend their early life in the water and metamorphose to terrestrial adults. Unfortunately, there has been a gap in our knowledge of the fossil record of 200 million years between the oldest known modern salamanders and their possible ancestors among ancient amphibians. Within the last 15 years, this gap has been bridged by a host of fossils from deposits as old as 165 million years, at the base of the Jehol Biota in Inner Mongolia and adjacent China that yield fossils of feathered dinosaurs, some of the oldest mammals and archaic birds. Because of the rapid burial of their bodies in anoxic sediments from repeated volcanic eruptions, the salamander remains are exquisitely preserved, including scores of complete, articulated skeletons, growth stages from larvae to adults, impressions of the eyes, external gills, and muscles. In some the skin exhibits its original texture, the pattern of pigment distribution and costal grooves that in terrestrial salamanders conduct water from the ground to the sides of the body to assist in cutaneous respiration. Scores of specimens are available for study in cooperation with the Inner Mongolian Provincial Museum. At least five, highly divergent lineages are known from the Daohugao locality that will be illustrated, describribed, and compared in detail with their putative ancestors among ancient amphibians, salamanders from elsewhere in the Jehol sequence and modern salamander families, with the assistance of gratuate and postdoctoral students and professional colleagues who are knowledgable in the anatomy, physiology, ontogeny and behavior of modern salamanders. This study will vastly improve our understanding of the relationships and of evolution among all salamanders throughout their history.