本期Nature封面所示為Zachelmie 采石場(chǎng)的一塊石板,，其上有一個(gè)行跡和一個(gè)有四趾印的孤立足跡,，這些印記用木炭凸顯了出來(lái),。圖片上的手是本文第一作者Grzegorz Niedzwiedzki的,。
近4億年前由四足陸地脊椎動(dòng)物踩踏出的化石行跡的發(fā)現(xiàn),，將使人們對(duì)我們關(guān)于四足動(dòng)物起源的認(rèn)識(shí)進(jìn)行較大重新評(píng)估,。
由Per Ahlberg及其同事獲得的這些發(fā)現(xiàn)來(lái)自波蘭圣十字山中的Zachelmie 采石場(chǎng)。其中一些行跡保存非常完好,，使人們可對(duì)足跡形態(tài)進(jìn)行仔細(xì)研究,，它們像是原始四足動(dòng)物“魚(yú)甲龍屬”所留下來(lái)的。但使得這些行跡顯得如此特殊的還是它們的年齡：它們比已知最早的四足動(dòng)物身體化石要早1800萬(wàn)年,，比最早的Elpistostegids（Tiktaalik,、Panderichthys和它們的近親，被看作是魚(yú)類與四足動(dòng)物之間的過(guò)渡形式）要早1000萬(wàn)年,。這些發(fā)現(xiàn)表明,，我們所知道的Elpistostegids是后來(lái)幸存下來(lái)的,，而不是直接的過(guò)渡形式，它們反映了我們對(duì)于陸地脊椎動(dòng)物最早歷史的了解有多么少,。（生物谷Bioon.com）
生物谷推薦原始出處：
Nature 463, 43-48 (7 January 2010) | doi:10.1038/nature08623
Tetrapod trackways from the early Middle Devonian period of Poland
Grzegorz Nied?wiedzki1, Piotr Szrek2,3, Katarzyna Narkiewicz3, Marek Narkiewicz3 & Per E. Ahlberg4
1 Department of Paleobiology and Evolution, Faculty of Biology, Warsaw University, 2S. Banacha Street, 02-097 Warsaw, Poland
2 Department of Paleontology, Faculty of Geology, Warsaw University, 93 ?wirki i Wigury Street, 02-089 Warsaw, Poland
3 Polish Geological Institute, 4 Rakowiecka Street, 00-975 Warsaw, Poland
4 Subdepartment of Evolutionary Organismal Biology, Department of Physiology and Developmental Biology, Uppsala University, Norbyv?gen 18A, 752 36 Uppsala, Sweden
Correspondence to: Per E. Ahlberg4 Correspondence and requests for materials should be addressed to P.E.A.
The fossil record of the earliest tetrapods (vertebrates with limbs rather than paired fins) consists of body fossils and trackways. The earliest body fossils of tetrapods date to the Late Devonian period (late Frasnian stage) and are preceded by transitional elpistostegids such as Panderichthys and Tiktaalik that still have paired fins. Claims of tetrapod trackways predating these body fossils have remained controversial with regard to both age and the identity of the track makers. Here we present well-preserved and securely dated tetrapod tracks from Polish marine tidal flat sediments of early Middle Devonian (Eifelian stage) age that are approximately 18 million years older than the earliest tetrapod body fossils and 10 million years earlier than the oldest elpistostegids. They force a radical reassessment of the timing, ecology and environmental setting of the fish–tetrapod transition, as well as the completeness of the body fossil record.
