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

现代蝾螈为3.65亿年前从古老的鱼类进化成第一批陆生脊椎动物的解剖结构和生活方式提供了最好的活体模型。大多数是从水中的卵孵化出来的，在水中度过它们的早期生活，然后蜕变成陆地上的成虫。不幸的是，在已知最古老的现代蝾螈和它们在古代两栖动物中可能的祖先之间，我们对2亿年前的化石记录的了解存在差距。在过去的15年里，在内蒙古和邻近中国的热河生物群底部发现了一批距今1.65亿年前的化石，填补了这一空白。这些化石中发现了有羽毛的恐龙、一些最古老的哺乳动物和古代鸟类的化石。由于它们的身体被反复的火山爆发所产生的缺氧沉积物迅速掩埋，蝾螈的遗骸被保存得非常完好，包括许多完整的、有关节的骨骼、从幼虫到成虫的生长阶段、眼睛的印记、外部鳃和肌肉。有些蝾螈的皮肤还保留着原来的纹理、色素分布的模式和肋沟，这些沟是陆生蝾螈将水从地面输送到身体两侧以辅助皮肤呼吸的。与内蒙古博物馆合作，有数十件标本可供研究。在对现代蝾螈的解剖学、生理学、个体发育和行为有丰富知识的研究生、博士后和专业同事的帮助下，我们将在道虎高地区发现至少5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家族的假定祖先进行详细的说明、描述和比较。这项研究将极大地提高我们对所有蝾螈在其整个历史中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.