BOOKS ET AL. PALEONTOLOGY
been suggested as a possible urochordate. The authors also follow the traditional interpretation of many other Ediacara fossils as animals, although such vendobionts as rangeomorphs, with a fractal body construction, have bodyplans and lifeThe Rise of Animals them instead as having had styles that seem to have been Evolution and bodies of stitched tubes (simidistinct from those of modern Diversification of the lar to an inflated air mattress) animals. Thus, vendobionts Kingdom Animalia that were organized concenremain phylogenetic ghosts trically, radially, serially, or whose placement in the tree of by Mikhail A. Fedonkin, fractally. This unique conlife is elusive. Paleontologists James G. Gehling, struction of the body forms continue to debate whether venKathleen Grey, Guy M. Narbonne, and the basis for his recognition of dobionts are monophyletic and, Patricia Vickers-Rich a new kingdom, Vendobionta if they are, whether they fit (1). Although Seilacher admits within the crown of the animal Johns Hopkins University that there were bona fide anitree, lie along the stem leading Press, Baltimore, MD, 2008. 343 pp. $75. mals in the Ediacaran biota, to that crown, or rest someISBN 9780801886799. he argues that those animals where else in the eukaryote tree. lived in the shadows of vendoThe Rise and Fall of the bionts that are not closely Ediacaran Biota comprises a The Rise and Fall of related to extant metazoans. collection of papers that was the Ediacaran Biota He believes that the vendodeveloped from two interdisciPatricia Vickers-Rich and bionts were giant protists replinary symposia (2004 and Patricia Komarower, Eds. sembling modern xenophyo2006) held for the International The Geological Society, phoran foraminifers (2). Geological Correlation Project Bath, UK, 2007. 464 pp. $190, Many paleontologists dis493. The wide range of topics £95. ISBN 9781862392335. agree with Seilacher, and encompasses tectonics, paleoSpecial Publication 286. Fedonkin and colleagues demagnetism, and evolutionary fend the traditional interpretadevelopmental biology, but the tion. A case for affinity with more-recent ani- bulk of the book focuses on Ediacaran fossils mals has been made for such vendobionts as and contemporaneous life forms. Like most Dickinsonia and Yorgia, which left resting edited volumes, the individual chapters are of traces that are taken as evidence for animal- uneven breadth and depth like mobility. But current hypotheses about I am most impressed by the thorough how such resting traces were made and how analysis of Kimberella provided by Fedonkin these vendobionts fed find few analogues and his co-authors. Fedonkin regards Kimbeamong modern animals. Other examples of rella as the crown jewel of the Ediacaran possible animals include Ausia, which has biota, whereas Seilacher considers it as a promising newcomer that lived during the vendobiont dynasty— although both agree that it was indeed an animal. Fedonkin’s careful examination of a large collection of Kimberella specimens has revealed many anatomical structures, including a proboscis-like structure at the presumed anterior end, a dorsal shield, and a ventral foot. These structures clearly establish Kimberella as a bilaterian animal whose development involved programmed anterior-posterior and dorsal-ventral differentiation. Equally intriguing is Jerzy Dzik’s analysis of trace fossils, which provides a fresh perContemplating evolutionary relationships? A stumpy-tail lizard spective on animal activities (Tiliqua rugosa) gazing at an ancient Ediacaran fossil (Parvancorina prior to the Cambrian. His plausible and provocative take minchami) in Australia.
Shuhai Xiao
etween 1908 and 1914, German geologists P. Range and H. Schneiderhöhn discovered some enigmatic fossils— including Rangea schneiderhoehni, later named after them—in southern Namibia. Similar organisms have since been found at more than 30 localities and on most continents. These fossils are collectively known as the Ediacaran biota, after a site in South Australia. The geological age of the Ediacaran fossils is now well established as 575–542 million years ago, an interval immediately before the Cambrian radiation of animals. However, the evolutionary relationship between Ediacaran taxa and Cambrian animals remains ambiguous. Thus, the implications of Ediacara fossils for the Cambrian radiation are intensely debated among a small group of paleontologists. Two recent books authored and edited by Mikhail Fedonkin (Russian Academy of Sciences), Patricia Vickers-Rich (Monash University, Australia), and their colleagues offer new insights into the ongoing debates and unveil the Ediacara controversies to a much wider audience. In The Rise of Animals, veteran researchers, some of whom have spent their entire career unraveling Ediacaran puzzles, lead a guided tour of most of the best-known Ediacaran localities. Telling numerous stories about the fossil hunters, they chronicle decades of Ediacaran research in Newfoundland, Namibia, Australia, Russia, and other, often remote, parts of the world. Along the way, Fedonkin and his fellow authors discuss the preservation, ecology, and phylogenetic affinity of the Ediacaran fossils. Most Ediacaran fossils are preserved as casts and molds in clastic rocks; sometimes they are only ghostly impressions on the surface of coarse-grained sandstones. The organisms have been traditionally placed in extant animal phyla, including cnidarians, annelids, and arthropods. As such, they represent forerunners of Cambrian animals and support the idea of a short phylogenetic fuse to the Cambrian explosion. However, Adolf Seilacher, a University of Tübingen paleontologist, argues that most Ediacaran organisms could not have functioned as free-living animals. He interprets
B
The reviewer is at the Department of Geosciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA. E-mail:
[email protected]
1618
21 MARCH 2008
VOL 319
SCIENCE
Published by AAAS
www.sciencemag.org
CREDIT: JAMES G. GEHLING
Rise and Demise of Ghostly Animals
BOOKS ETAL. future analyses should focus NEUROSCIENCE on the evolutionary patterns and processes of the rise and demise of the Ediacaran biota. These two books would have been richer had these aspects of Ediacaran research been Evan Balaban explored in greater depth. Nonetheless, the beautifully ifferences between men and women produced books will serve as have occupied people’s thoughts for valuable references. Particua very long time. Our creation myths larly useful is the atlas in The feature them prominently; our religions and Rise of Animals, which in- governments try to use them to define our cludes illustrations of many potentialities; and our intellectual traditions important Ediacaran fossils are rife with rancorous debates about why sex that previously had been shown differences exist, what they mean, and what only in poor figures published power they should be accorded over our lives. in obscure journals. Notions about what is “natural” for, and The two books by Fedonkin, therefore what is naturally different about, Vickers-Rich, and colleagues men and women have always played a major arrive while Ediacaran re- part in this discourse. searchers celebrate the 100th The first post-Darwin analysis of human anniversary of Range and sex differences in mental abilities by an evoSchneiderhöhn’s discovery. It lutionary scientist—written at a time is perhaps coincidental that when higher education for women was a their findings in Namibia were subject of intense debate—argued that brain made at about the same time size was an adaptive, sexually dimorphic as Charles Doolittle Walcott’s characteristic and that women’s physically Ghostly animals. For Australia Post’s “Creatures of the Slime” stamp unearthing of the Middle Cam- smaller brains doomed them to an inferior issue (2005), Peter Trusler depicted six Ediacaran organisms (clockwise mental status (1). A contemporary comfrom top left): Charniodiscus, Tribrachidium, Dickinsonia, Inaria, brian Burgess Shale fauna in the Canadian Rockies. Like mentary in the British Medical Journal (2) Kimberella, and Spriggina. the Ediacaran fossils, many tepidly disagreed with the conclusion of infeon early burrows is that they represent Burgess Shale fossils have also been phylo- riority and mildly ridiculed its presumed scirefugia from early predators rather than genetic ghosts, variously interentific basis, endorsing infeeding traces (the exploitation of organic preted as members of extant anistead a “separate but equal” carbon in the sediments). Testing his inter- mal phyla, stems leading to distribution of abilities whereby Sex Differences pretation will require independent evi- such phyla, or representatives men and women emphasize in the Brain of extinct phyla. Unlike the dence for early predators. different specialties. DiscusFrom Genes to Behavior Also fascinating are the new observations Ediacaran organisms, however, sions over the ensuing 120 Jill B. Becker, Karen J. and innovative morphometric analyses of Burgess Shale animals are known years have largely replicated Berkley, Nori Geary, vendobionts by Marc Laflamme, Richard to a much larger audience, largely such arguments, simultaneElizabeth Hampson, Jenkins, Jonathan Antcliffe, and their col- thanks to Stephen Jay Gould’s ously blurring the distincJames P. Herman, and leagues as well as Erik Sperling et al.’s stimu- popular book Wonderful Life (3). tion between biological charElizabeth A. Young, Eds. lating hypothesis that the early diversification The Rise of Animals offers a acteristics that cause sex Oxford University Press, of sponges may have triggered a major distur- much-needed avenue to commudifferences and those that New York, 2008. bance in the global carbon cycle. With nicate to the general public are consequences of them. 504 pp. $98.50, £54. regard to the demise of the Ediacaran biota, the past decade’s exciting discovShould the average wages ISBN 9780195311587. Breandan MacGabhann’s careful examina- eries of Ediacaran fossils. The paid to men and women and tion of purported Ediacaran fossils from Rise and Fall of the Ediacaran the difference in the occurCambrian rocks accentuates the extinction of Biota will reward any scientist interested rence of attention deficit hyperactivity disorEdiacaran organisms before the Cambrian in the topic. I certainly recommend that der (both are higher in males in the United explosion, although the cause of this extinc- both books be placed next to Gould’s on States) be thought of as secondary sexual your bookshelf. tion is unresolved. characteristics? And are these inevitable conTo solve the puzzle of Ediacaran fossils, sequences of our biology? References paleontologists have to become more recepThe current profusion of popular books on 1. A. Seilacher, Lethaia 22, 229 (1989). tive to unorthodox thinking. They also need to 2. A. Seilacher, D. Grazhdankin, A. Legouta, Paleontol. Res. broaden their field searches to seek fossils in The reviewer is at the Behavioral Neurosciences Program, 7, 43 (2003). Stewart Biological Sciences Building N8/15, McGill such sediments as black shales, cherts, and 3. S. J. Gould, Wonderful Life: The Burgess Shale and the University, 1205 Avenue Docteur Penfield, Montreal, QC Meaning of History (Norton, New York, 1989). bituminous limestones. These unconventional H3A 1B1, Canada, and the Cognitive Neuroscience Sector, preservational windows may offer novel perSISSA, Via Lionello Stock 2/2, 34135 Trieste, Italy. E-mail: 10.1126/science.1156033 spectives on Ediacaran fossils. In addition,
[email protected]
The Female Equally with the Male I Sing
CREDIT: PETER TRUSLER/REPRODUCED WITH PERMISSION OF THE AUSTRALIAN POSTAL CORPORATION (ORIGINAL HELD IN THE NATIONAL PHILATELIC COLLECTION)
D
www.sciencemag.org
SCIENCE
VOL 319
Published by AAAS
21 MARCH 2008
1619
