Oct. 24-26, 2009, Yingjie Overseas Exchange Center, Peking University, Beijing, China中文版

Origin and Early Diversification of Jawed Vertebrates

Min Zhu

Key Laboratory of Evolutionary Systematics of Vertebrates,Institute of Vertebrate Paleontology and Paleoanthropology (IVPP), Chinese Academy of Sciences, PO Box 643, Beijing 100044, China; zhumin@ivpp.ac.cn

Abstract

Gnathostomes, or jawed vertebrates, can be divided into four major clades: the Placodermi, the Acanthodii, the Chondrichthyes (cartilaginous fishes) and the Osteichthyes (actinopterygians and sarcopterygians). The past two decades have seen the impressive discoveries of primitive gnathostome taxa from the Silurian and Early Devonian, expanding the diversity and disparity in early gnathostome groups. Some of these finds have yielded an unexpected mix of characters for inferring the sequence of character transformation at the base of the Osteichthyes or at the base of the Osteichthyes, thus challenging earlier assumptions and even some of deeply entrenched views about early diversification of gnathostomes, and the rise of osteichthyans from other primitive gnathostomes in particular. Among these finds, the gnathostome remains from the Xiaoxiang Fauna (Ludlow, Silurian) of China definitely push major splits in basal gnathostome evolution out of the Devonian and into the Silurian. As the oldest articulated osteichthyan, Guiyu oneiros from the Xiaoxiang Fauna provides not only the near-complete restoration of a primitive fish with mosaic gnathostome characters, but also a new minimum date for the sarcopterygian – actinopterygian split (about 419 million years ago). Further research on new gnathostome materials including early placoderms and acanthodians from promising Silurian - Early Devonian fish localities of China will constitute a challenging and rewarding opportunity to bring about new breakthroughs in the study of origin and early diversification of jawed vertebrates.

Min Zhu

Key Laboratory of Evolutionary Systematics of Vertebrates,Institute of Vertebrate Paleontology and Paleoanthropology (IVPP), Chinese Academy of Sciences, PO Box 643, Beijing 100044, China; zhumin@ivpp.ac.cn

Statement of most significant contributions to this research field

My research over the last decade on the Early Devonian and Silurian fossil fish material from Yunnan, China, has produced a series of exceptionally primitive bony fishes, which do not belong to any of the standard groups recognized after 150 years of research in Europe. My described forms (Achoania, Kenichthys, Meemannia, Styloichthys – three of these described in Nature papers), together with associated genera (Diabolepis, Psarolepis, Youngolepis) are generally acknowledged to be crucial ‘stem-group’ taxa of all the major groups of the Osteichthyes, providing clues to the initial osteichthyan evolutionary radiation which ultimately produced nearly all the vertebrate species living today (teleost fishes, and all the tetrapods). The latest described form (Guiyu, Nature 2009, 458: 469-474) from the Silurian represents the oldest near-complete gnathostome (jawed vertebrate) with the unexpected mix of gnathostome features, and offers new insights into the early divergence of gnathostomes. In addition I was the first to discover a tetrapod (first land animals) from the Devonian of Asia, also described in Nature (2002). My discoveries have attracted considerable discussion in that journal (e.g. Nature 397: 564-65, 403: 185-188; 432: 23-24). Apart from these exceptionally primitive bony fish, I have described various jawless galeaspid and placoderm genera from the Silurian and Devonian of China, and produced a major 124 page review and phylogenetic analysis of all known antiarchs, a highly endemic and diverse group well represented by primitive forms in the Devonian of China. In addition I published in 2000 (alone, or as senior author) comprehensive summaries of the geological occurrence (locality and stratigraphic horizon) of all described vertebrate species from the Silurian and Devonian of China, representing over 80 genera and one of the world’s most diverse Palaeozoic vertebrate faunas.