The Ever Enigmatic EdiacaransThe Rise of Animals: Evolution and Diversification of the Kingdom Animalia by Mikhail A.Fedonkin; James G. Gehling; Kathleen Grey; Guy M. Narbonne; Patricia Vickers-RichReview by: Gregory D. EdgecombeBioScience, Vol. 59, No. 6 (June 2009), pp. 527-528Published by: Oxford University Press on behalf of the American Institute of Biological SciencesStable URL: http://www.jstor.org/stable/10.1525/bio.2009.59.6.13 .

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THE EVER ENIGMATICEDIACARANS

The Rise of Animals: Evolution andDiversification of the Kingdom Ani-malia. Mikhail A. Fedonkin, James G.Gehling, Kathleen Grey, Guy M. Nar-bonne, and Patricia Vickers-Rich. JohnsHopkins University Press, 2008. 344 pp.,illus. $75.00 (ISBN 9780801886799cloth).

The fossils that are the subject of TheRise of Animals: Evolution and Diver-

sification of the Kingdom Animalia arethe so-called Ediacarans. They are vari-ably identified as the ancestors of ani-mals, as a wholly extinct experiment inanimal relatives or an extinct kingdomof life, as giant unicellular organisms, asfungi, or as lichens. They are knownfrom thousands of specimens (at somelocalities they cover huge bedding sur-faces), span the world geographically,and existed for more than 30 millionyears. This time window is from about575 million to 542 million years ago,after which undisputed animals erupt inthe paleontological record, and apartfrom a couple of possible survivors inthe Cambrian, the Ediacarans vanished.

Ediacarans are not inconspicuouscreatures—some frondlike forms at-tained a length of two meters—and theyoften display a considerable degree ofanatomical detail. These factors wouldseem to suggest that we should be ableto place these organisms on the tree oflife with some confidence, yet the di-versity of opinion about what these fos-sils represent is wide. The who, what,where, when, and why of the Ediacaransis the subject matter of Fedonkin andcolleagues’ Rise of Animals.

The target audience is said to be “sci-entist and layperson alike,” and the bookcertainly offers much to both groups. Itslarge format and extensive use of colorgive it the look of a coffee table book,richly illustrated with photographs offossils, reconstructions of the organ-isms, and field photographs of Edi-

acarans in their geological context (andquite a few photos of the people whocollect them, too). Peter Trusler’s mag-nificent paintings of field sites of theclassic Ediacaran localities contributegreatly to the book’s visual appeal. Theauthors include leading researchers onEdiacaran fossils from three countriesthat are home to diverse, well-preserved,and historically important Ediacarans—Russia, Australia, and Canada—andmuch of the book is structured as a trav-elogue of journeys to these field sites.

Given that Ediacarans occur in remoteparts of the White Sea and the northernCanadian Cordillera, the Flinders Rangesof South Australia, and the sea-sprayedcliffs of Newfoundland, there is an ele-ment of adventure to the descriptions ofthe discovery and collection of thesecreatures. The geological context of themajor sites is depicted through colorimages of stratigraphic columns andmaps, as well as models showing howthese soft-bodied fossils came to be pre-served. The human element of researchis prominent—the reader sees and meetsthe people who have devoted their ca-reers to puzzling over Ediacarans.

For professional paleontologists, a32-page atlas of all formally named Edi-acarans is an especially useful feature.Each species is listed alphabetically, witha photograph, occurrences, synonymousnames, and a discussion on likely affini-ties and classification. The synonymiesare especially useful because many Edi-acarans that were once identified ascomplete organisms are now recognizedas parts of other Ediacarans (e.g., whatwere once thought to be jellyfish fossilsare now known to be the holdfasts of

fronds), so one name applies to bothparts of the creature, and some formerEdiacarans are no longer even identifiedas fossils, but rather as abiogenic struc-tures. The bibliography is likewise agodsend for those who are keen to col-lect literature on these fossils.

In addition to the core chapters onEdiacaran localities, the book is roundedout by (a) overviews on the history ofEarth, from the Big Bang to the meltingof glaciers, which formally marks thebeginning of the Ediacaran period; (b)trace fossils produced by the Ediacaransand the less-controversial animals thatlived alongside them; and (c) a review ofanimal body plans and the question ofwhat caused the Cambrian radiation, a15-million-year period in the EarlyCambrian when animals with skeletonsdiversified. A stand-alone chapter onmicrofossils is less chatty than some ofthe others, but it is a solid scientific con-tribution that reminds the reader thatnot all fossils are macroscopic and muchcan be learned about ecosystems fromsuch humble creatures as acritarchs.

To address the question of what theEdiacarans are, the authors accuratelyrecord the numerous alternatives formost of them, but in general the thesisof the book, as the title conveys, is thatthese fossils include the ancestors of an-i mals. Ediacarans are often referred to asanimals or metazoans, and the generalmessage is that many of today’s animalphyla were represented, at least by theirstem groups, in the Ediacaran. On page51, for example, arthropods, nematodes,molluscs, annelids, brachiopods, platy-helminths, chordates, and ctenophoresare all said to be present in Ediacaranbiota. The case for most of these is weak,and none is strong. A chordate, for ex-ample, is mentioned as a “possible chor-date” in a figure caption, but thepossibility that it could instead be apreservational variant of the mollusc-like Kimberella is raised as an alternativein the same caption. The case for platy-helminths is based on crude compar-isons of Platypholina and rhabdocoelflatworms (p. 137), and much the sameapplies to alleged Ediacaran nematodesand brachiopods. Ediacaran specialistsare notably more likely to assign Edi-

www.biosciencemag.org June 2009 / Vol. 59 No. 6 • BioScience 527

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acaran fossils to Annelida and Arthro-poda than are those who work on thosegroups.

The picture of Ediacarans as ancestralanimals means that in some respectsthe authors do not fully embrace theimplications of the “new animal phy-logeny.” The relationships between ani -mal phyla reconstructed from DNAsequences are depicted twice in the book,but in other places the grand narrativeof animal evolution devolves into no-tions from a pre-1990s textbook. Onpage 45, animal evolution is described as a scala naturae from sponges todiploblasts to platyhelminths to coelo-mates. This narrative conflicts with thecurrent view of animal phylogeny inthat platyhelminths are now seen asnested within a clade of spiral-cleavinganimals that also includes annelids andmolluscs, and coelomates are not re-garded as a monophyletic group. Insome chapters, various Ediacarans areassigned to a group named Proarticulata,which made sense when it was estab-lished in the 1980s, but now that theArticulata (annelids and arthropodssharing a single origin of segmentation)has been rejected by molecular phylo-genies, “Proarticulata” is ancestral to anongroup. In these instances, fossils aregetting shoehorned into an evolutionaryframework that is past its use-by date.

Now and then, apparent disagree-ments between the authors seem to cropup. On page 137, Dickinsonia is stated tohave the zigzag style of symmetry calledglide refection, but on page 269, it issaid to have mirror-image, bilateralsymmetry. This difference is essentialto understanding whether Dickinsonia issegmented in a way that has real bearingon affinities to extant segmented ani-mals. The discrepancy gets at the heartof what is ultimately so frustratingand fascinating about the Ediacarans—the fact that two specialists can studymyriad specimens for years, yet Edi-acarans’ basic construction remains con troversial. That Swartpuntia fromNamibia could be either “a colonialani mal or even a large alga” (says co- author Gehling) or “allied with the dick-insoniomorphs” (per coauthor Narbonne)indicates that we still have a long way to

go in making evolutionary sense of thesefossils.

Among professional paleontologistsand biologists, nonbelievers—those whodispute that any definite animals arerepresented by the Ediacarans—willprobably still be nonbelievers when theyfinish the book. Still, they will welcomethe publication of The Rise of Animalsbecause it is a one-stop shop for up-to-date information about this puzzlingmenagerie, and they will appreciate thebeauty of its imagery and admire thepersistence of our colleagues’ efforts tolearn more about what is ultimatelypaleontology’s greatest riddle. Non-professionals will likewise find that it isa fine-looking book that captures theexcitement of scientific discovery.

GREGORY D. EDGECOMBEGregory D. Edgecombe (e-mail:

g.edgecombe@nhm.ac.uk) is a researcherin the Department of Palaeontology at the

Natural History Museum in London.

NEW TITLES

Animal Osmoregulation. Timothy J.Bradley. Oxford University Press,2009. 178 pp., illus. $60.00 (ISBN9780198569961 paper).

The Annotated Origin: A Facsimile ofthe First Edition of On the Origin ofSpecies by Charles Darwin. JamesT. Costa. Harvard University Press(Belknap), 2009. 537 pp., illus. $35.00(ISBN 9780674032811 cloth).

Bioeconomics of Invasive Species:Integrating Ecology, Economics,Policy, and Management. Reuben P.Keller, David M. Lodge, Mark A.Lewis, and Jason F. Shogren, eds. Ox-ford University Press, 2009. 320 pp.,illus. $49.95 (ISBN 9780195367973paper).

The Biology of Alpine Habitats. LaszloNagy and Georg Grabherr. OxfordUniversity Press, 2009. 336 pp., illus.$55.00 (ISBN 9780198567042 paper).

Birds of Pakistan. Richard Grimmett,Tom Roberts, and Tim Inskipp. YaleUniversity Press, 2009. 256 pp., illus.$40.00 (ISBN 9780300152494 paper).

Charles Darwin’s Shorter Publica-tions, 1829–1883. John van Wyhe.Cambridge University Press, 2009.556 pp., illus. $160.00 (ISBN9780521888097 cloth).

Cork Oak Woodlands on the Edge:Ecology, Adaptive Management, andRestoration. James Aronson, Joáo S.Pereira, and Juli G. Pausas, eds. IslandPress, 2009. 352 pp., illus. $40.00(ISBN 9781597264792 paper).

The Ethics of Protocells: Moral andSocial Implications of Creating Lifein the Laboratory. Mark A Bedauand Emily C. Parke, eds. MIT Press,2009. 392 pp., illus. $28.00 (ISBN9780262512695 paper).

Food-Borne Microbes: Shaping theHost Ecosystem. Lee-Ann Jaykus,Hua H. Wang, and Larry S.Schlesinger, eds. ASM Press, 2009.410 pp., illus. $159.95 (ISBN9781555814052 cloth).

Forms of Becoming: The EvolutionaryBiology of Development. Alessan-dro Minelli. Princeton UniversityPress, 2009. 242 pp., illus. $27.95(ISBN 9780691135687 cloth).

The Fruit, the Tree, and the Serpent:Why We See So Well. Lynne A.Isbell. Harvard University Press,2009. 207 pp., illus. $45.00 (ISBN9780674033016 cloth).

The Genial Gene: Deconstructing Dar-winian Selfishness. Joan Rough -garden. University of California Press,2009. 272 pp., illus. $24.95 (ISBN9780520258266 cloth).

528 BioScience • June 2009 / Vol. 59 No. 6 www.biosciencemag.org

Books

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