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

现代火蜥蜴为3.65亿年前从古代鱼类进化为第一批陆地脊椎动物的动物的解剖和生活方式提供了最好的活模型。大多数是从水生卵孵化出来的，早期生活在水中，然后蜕变成陆生成虫。不幸的是，我们对已知的最古老的现代火蜥蜴及其可能的两栖动物祖先之间2亿年的化石记录的了解存在差距。在过去的15年里，内蒙古热河生物群底部和邻近的中国的大量化石弥合了这一差距，这些化石来自1.65亿年前的沉积物，这些化石产生了有羽毛的恐龙的化石，这些恐龙是一些最古老的哺乳动物和古代鸟类。由于不断喷发的火山喷发会迅速将它们的身体埋葬在缺氧的沉积物中，因此它们的遗骸被保存得很好，包括数十具完整的关节骨骼，从幼虫到成年的生长阶段，眼睛的印记，外部的鳃和肌肉。在某些情况下，皮肤表现出其原始的质地、色素分布的模式和陆栖火蜥蜴的肋骨凹槽，这些凹槽将水从地面输送到身体两侧，帮助皮肤呼吸。与内蒙古博物馆合作，有数十件标本可供研究。道虎高地区至少有五个高度不同的谱系，将在对现代火蜥蜴的解剖学、生理学、个体发育和行为方面的知识的帮助下，在古代两栖动物、来自热河序列其他地方的火蜥蜴和现代火蜥蜴家族中的假定祖先中进行详细的说明、描述和比较。这项研究将极大地提高我们对所有火蜥蜴在其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.