a marine stem-tetrapod from the devonian of western north america海洋stem-tetrapod泥盆纪的北美西部.pdfVIP

A Marine Stem-Tetrapod from the Devonian of Western North America Brian Swartz* Department of Integrative Biology and Museum of Paleontology, University of California, Berkeley, California, United States of America Abstract The origin of terrestrial vertebrates represents one of the major evolutionary and ecological transformations in the history of life, and the established timing and environment of this transition has recently come under scrutiny. The discovery and description of a well-preserved fossil sarcopterygian (fleshy-limbed vertebrate) from the Middle Devonian of Nevada helps to refine and question aspects of the temporal and anatomical framework that underpins the tetrapod condition. This new taxon, Tinirau clackae, demonstrates that substantial parallelism pervaded the early history of stem-tetrapods, raises additional questions about when digited sarcopterygians first evolved, and further documents that incipient stages of the terrestrial appendicular condition began when sarcopterygians still retained their median fins and occupied aquatic habitats. Citation: Swartz B (2012) A Marine Stem-Tetrapod from the Devonian of Western North America. PLoS ONE 7(3): e33683. doi:10.1371/journal.pone.0033683 Editor: Andrew A. Farke, Raymond M. Alf Museum of Paleontology, United States of America Received November 10, 2011; Accepted February 15, 2012; Published March 20, 2012 Copyright: 2012 Brian Swartz. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: The work was supported by Gregory family and several generous anonymous donors. No additional ext