Subdepartment of Evolution and Development, Department of Organismal Biology, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18A, 752 36, Uppsala, Sweden.
Polish Geological Institute-National Research Institute, Rakowiecka 4 Street, 00-075, Warszawa, Poland.
Sci Rep. 2018 Jan 18;8(1):1074. doi: 10.1038/s41598-018-19220-5.
Opinions differ on whether the evolution of tetrapods (limbed vertebrates) from lobe-finned fishes was directly linked to terrestrialization. The earliest known tetrapod fossils, from the Middle Devonian (approximately 390 million years old) of Zachełmie Quarry in Poland, are trackways made by limbs with digits; they document a direct environmental association and thus have the potential to help answer this question. However, the tetrapod identity of the tracks has recently been challenged, despite their well-preserved morphology, on account of their great age and supposedly shallow marine (intertidal or lagoonal) depositional environment. Here we present a new palaeoenvironmental interpretation of the track-bearing interval from Zachełmie, showing that it represents a succession of ephemeral lakes with a restricted and non-marine biota, rather than a marginal marine environment as originally thought. This context suggests that the trackmaker was capable of terrestrial locomotion, consistent with the appendage morphology recorded by the footprints, and thus provides additional support for a tetrapod identification.
对于四足动物（有肢脊椎动物）是否是从肉鳍鱼类直接进化而来的，人们的观点存在分歧。最早的已知四足动物化石来自波兰扎切赫米亚采石场的中泥盆世（约 3.9 亿年前），是具有趾的肢体留下的足迹；它们记录了直接的环境关联，因此有可能有助于回答这个问题。然而，尽管这些足迹形态保存完好，但由于其年代久远，而且据称所处的沉积环境是浅海（潮间带或泻湖），最近有人对这些足迹的四足动物身份提出了质疑。在这里，我们提出了一个对扎切赫米亚含足迹地层的新古环境解释，表明它代表了一系列短暂存在的湖泊，其生物群受限且非海洋生物群，而不是最初认为的边缘海洋环境。这种背景表明，造迹者能够进行陆地运动，这与足迹所记录的附肢形态一致，因此为四足动物的鉴定提供了额外的支持。
