The Cambrian Fossils of Chengjiang, China: The Flowering of Early Animal Life

  • Xian-Guang Hou,
  • Richard J. Aldridge,
  • Jan Bergström,
  • David J. Siveter,
  • Derek J. Siveter &
  • Xiang-Hong Feng
Blackwell: 2004. 248 pp. $99.95, 60 pound 1405106735. | ISBN: 1-405-10673-5
Fossils found at Chengjiang provide evidence of the rapid evolution of a vast range of body plans. Credit: DEREK SIVETER/HOU ET AL. (2004)

In the Early Cambrian period (544 million to 520 million years ago) there was a great evolutionary radiation of animal life. Within a short geological time, the vast majority of modern animal phyla (groups defined by their distinctive body plans) appeared in the fossil record worldwide. These early fossils represent the roots for the tree of all modern animal life.

Some of the jewels in the crown of Early Cambrian fossils are embedded in the mudstones of Chengjiang in southern China, where tens of thousands of exceptionally preserved and soft-bodied fossils have been discovered during the past 20 years. More than 130 species of 13 animal phyla have been recognized, and the number of organisms that are new to science is still growing. Aptly subtitled The Flowering of Early Animal Life, this beautifully produced book by Xian-Guang Hou and colleagues is the best systematic compendium of the entire Chengjiang biota, offering a rare view of this great episode in the diversification of animal life.

The book recounts the serendipitous discovery of this Lagerstätte, or great mother lode, of soft-bodied fossils in 1984. It also describes the persistent exploration over the next two decades by Hou, Jun-Yuan Chen, De-Gan Shu and their many collaborators that revealed the wealth of this site for studies of the early evolution of animal life. Several organisms from Chengjiang are so extraordinary that they cannot easily be placed in any modern animal phylum. For example, Vetulicola looks like a crustacean, judging by its tail, but has gill slits that some palaeontologists would argue indicate chordate affinities. These new fossils further widen the range of body plans for deuterostomes, a lineage that already includes echinoderms (sea urchins), various chordates and vertebrates.

These beautiful and unique fossils have inspired new scientific insights and led to the clashing of ideas. There is a great debate on the likely positions of Chengjiang animals such as the yunnanozoans in the deuterostome family tree. Such debates will surely redefine the phylogenetic framework for establishing the earliest evolution of key features of chordates.

The publication of this book is timely for several reasons. It is not only a fitting Festschrift to celebrate the twentieth anniversary of Hou's discovery of the Chengjiang Lagerstätte, but it also provides an update on the fast-paced attempts to decipher the full evolutionary significance of this palaeontological treasure. It is also the first review in English on the Chengjiang biota. For palaeontologists and evolutionary biologists whose native tongue is not Chinese, this volume is a useful gateway to a much larger body of literature on the Chengjiang fossils, including some extensive Chinese monographs. For specialists, the book provides an extensive systematic survey of the Chengjiang organisms; each taxon has a synoptic review with key references. For generalists with an interest in early animal evolution, the book offers a concise overview of the geochronology, taphonomy, palaeoenvironment and palaeoecology of the Chengjiang fossil sites. The book is lavishly illustrated with hundreds of colour photographs and accurate artistic rendering of many fossil organisms.

But beyond its utilitarian value as an informative reference resource, the book has much to offer those interested in a multidisciplinary approach to studying early animal evolution. The early animal fossil record, however incomplete, can tell us about the early diversification of major animal lineages, a hot topic for molecular evolutionary studies, especially with regard to the timing of early animal evolution. The Chengjiang fossils are the best source of evidence about the emergence of animal body plans, and have attracted interest from students of evolutionary development.

Many of my colleagues have proclaimed that the Chengjiang mudstone is China's answer to Canada's Burgess Shale. Notwithstanding my fondness for vertebrates, what makes Chengjiang special is the presence of new species of the earliest vertebrates and their putative chordate and deuterostome relatives that are not known elsewhere; the Early Cambrian sea of Chengjiang really is a cradle of early chordate evolution. In such a context, this otherwise quite exhaustive book is a bit limited on what are Chengjiang's highlights: its vertebrates and their putative relatives. The authors cautiously avoided endorsing any of the competing interpretations of several enigmatic organisms, such as Yunnanozoon, almost to a fault.

The book's authors — six experts from five institutions in three countries — are a microcosm of the world community of palaeontologists who have long cherished collaborative research that transcends national boundaries. Such collaborations have accelerated the pace at which the major discoveries from Chengjiang are disseminated to the worldwide scientific community. This has not only won worldwide recognition for China's great fossil treasure, but has made the point that truly great science has no national boundaries.