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The Great Ordovician Biodiversification 506 BOOK REVIEWS Cambro-Ordovician Studies I, Memoir 30 The Great Ordovician Biodiversi®cation of the Association of Australasian Pa- Event, Barry D. Webby, Florentin Paris, Mary L. laeontologists, J.R. Laurie, ed., 2004, Associa- Droser, and Ian G. Percival, eds., 2004, Columbia tion of Australasian Palaeontologists, Canberra, 260 University Press, New York, 484 p. (Hardcover, US p. (Softcover, US $81.75) ISBN: 0-949466-28-X. $99.50) ISBN 0231-12678-6. DOI 10.2110/palo.2004.P04-79 DOI 10.2110/palo.2004.P04-49 Our understanding of life's rich history in general, and some key ep- Have you heard the joke about the time a systematist, a taxon- isodes in that history in particular, such as the Cambrian and Ordovi- counter, and a paleoecologist walked into a bar? cian radiations, continues to grow thanks in part to volumes like this It is not surprising that a signi®cant proportion of paleontological one. Laurie, the editor of Cambro-Ordovician Studies I, has assembled attention is focused on the Cambrian Explosion; it indeed marks the a ®ne memoir, including an excellent and well-chosen team of authors. rise to dominance of skeletonized metazoans and the emergence of The papers cover a diverse range of topics and organisms, spanning the most phyla. But the Cambrian Radiation is inherently dif®cult to evolutionarily interesting and geologically important Cambrian and study: the intricacies involved in reconstructing stem-group phyloge- Ordovician periods. This volume, published by the Association of Aus- nies, the lack of a globally correlated time scale, a dearth of paleomag- tralasian Palaeontologists, focuses on the faunas of Australia, but these netic data, often sparsely fossiliferous strata, and signi®cant regional have global relevance because of their scope and diversity in the Ordo- differences in litho- and biofacies all combine to make it dif®cult to vician and, especially, the Cambrian. Further, Australian paleontolo- understand the historical underpinnings of this event, despite recent gists have an outstanding tradition of producing important paleonto- efforts to the contrary (Zhuravlev and Riding, 2000). In contrast, the logical and stratigraphic studies, and this work is no exception. The ensuing Ordovician is nearly unparalleled in its record. The strati- book is well illustrated and contains pictures and descriptions of sev- graphic record is signi®cant and nearly complete over broad cratons, eral new and important taxa, especially trilobites, along with detailed fossiliferous strata are abundant and well preserved, there is now a stratigraphic sections and geological descriptions. The ®rst paper, by relatively stable and well-constrained time scale for global correla- Kruse, Laurie, and Webby, presents a comprehensive overview and tion, and documentation of isotopic and sea-level trends is improving. analysis of the Cambrian geology and paleontology of the Ord Basin: a The interval, sometimes termed the Ordovician Radiation, also is region containing an important record of Middle and Upper Cambrian nearly equal to the Cambrian in terms of its evolutionary and ecolog- strata. The second paper is a ®ne one by Edgecombe, Banks, and Banks ical consequences. This period witnessed the appearance of dozens of that focuses on the late Ordovician trilobites of Tasmania; several new crown-group representatives of taxonomic classes and orders and the and signi®cant taxa are ®gured and described. Next follows a short pa- ®rst development of communities that would dominate the remainder per by Jago and Anderson describing a new bivalved arthropod from of the Paleozoic and even the post-Paleozoic. Despite this signi®cance, the Middle Cambrian of Tasmania; the taxon shows intriguing similar- and the presence of an active global pool of Ordovician workers, very ities to Waptia, known from various Cambrian soft-bodied faunas in- few works have focused extensively on the Ordovician Radiation. cluding the Burgess Shale. The fourth paper is by Paterson and Laurie This volume partially ®lls this lacuna. It acts as a sort of ®nal re- and analyzes late Cambrian trilobites from eastern Victoria. Several port for the IGCP 410 project, with the goal of documenting the global, new taxa are described, a very useful Cambrian correlation chart is pre- and in some cases regional, diversity trends for all major taxonomic sented, and thorough paleoenvironmental and paleoecological analyses groups during the Ordovician. In this regard, it is a major success. It are included. Brock and Holmer have a signi®cant paper on the largely is, for the most part, an authoritative compendium of Ordovician tax- endemic lingulate brachiopods from the Ordovician of Western Austra- onomic diversity, although it also summarizes aspects of the physical lia that contains several superb SEMs and summary statistics describ- Ordovician world, including tectonics, oceanography, and climate. Its ing brachiopod morphology. A paper by Engelbretsen rounds out the strengths lie in the vast systematic experience of its 96 compilers, the works focusing on brachiopods with his study of Cambrian paterinids. incredible breadth of its taxonomic coverage (protists, animals, and Three other valuable studies on trilobites also are contained. First, plantsÐessentially, fully inclusive), and the generally standardized Bentley and Jago have a paper on wuaniid trilobites that presents a treatment of these groups using the recently adopted global Ordovi- phylogenetic analysis of this enigmatic group. Then, Sloan and Laurie cian timescale and generally comparable diversity metrics. (Please are authors on a paper describing some Middle Cambrian trilobites note I will use the more common term Ordovician Radiation in this from allochthonous blocks in New South Wales that contained some review rather than the Great Ordovician Biodiversi®cation Event spectacular specimens with large spines that towered over the trilo- used in the volume. I just ®nd it less clunky.) bites' eyes. Finally, Laurie has a paper on Middle Cambrian trilobites Overall, there are very few errors in this volume; those that exist from a corehole taken in the Georgina Basin that has special relevance typically relate to text references of ®gures. I commend the editors for Cambrian biostratigraphy. and contributors for extensive documentation of the systematic liter- Brachiopods and trilobites are not the only paleontological subjects ature, with a 70-page reference section and a wide-ranging index of this volume. There are also two well-written papers on Ordovician keyed both to general topics and taxonomyÐfor the acritarchs alone, conodonts: one by Zhen and Percival, the other by Nicoll and Kelman. this index runs from Acanthodiacrodium to the possible link with the Further, there is a nice paper by Brock and Paterson describing a new Zygnematales. Early Cambrian helcionellid mollusc from South Australia. The volume begins with a thorough introduction by Barry Webby. This volume will be highly useful to anyone interested in Cambrian The review of past research is concise and apt, with a focus on the his- or Ordovician geology and paleontology. It also will appeal in partic- tory and timing of assemblage-wide transitions generally involving ular to trilobite and brachiopod workers, although other groups are evolutionary faunas and ¯oras. The marine radiations are divided represented. In addition, it contains much relevant biostratigraphic further into soft-substrate, reef, and infaunal communities. While information. It is the continued production of quality studies like useful, this review of assemblage-wide transitions is based largely on these that push our paleontological knowledge base forward. The only past research and does little to synthesize the present ®ndings. The thing that might have been useful that is lacking would have been an middle portion of the introduction includes an interesting summary of overview of the Cambrian and Ordovician geology of Australia, with the diversi®cation of all Ordovician pelagic taxa, but again without emphasis on paleobiogeographic patterns. Still, this omission is not a much synthesis. It appears his goal is to bring additional attention to serious ¯aw and the authors and the editor are to be commended for these organisms that might share similar ecological propensities (and producing such a ®ne volume. were clearly important for marine productivity), but further discus- BRUCE S. LIEBERMAN sion is needed. Indeed, the diversity trajectories for many pelagic University of Kansas taxaÐincluding graptolites, acritarchs, and conodontsÐclosely fol- Department of Geology low eustatic trends, and a quantitative comparison would be useful. 121 Lindley Hall Such a comparison would have made for an interesting stand-alone Lawrence, KS 66044 chapter if further developed with information from the rest of the vol- Copyright Q 2005, SEPM (Society for Sedimentary Geology) 0883-1351/05/0020-0506/$3.00 BOOK REVIEWS 507 ume. The remainder of the introduction is a comprehensive summary glaciation, resulting in the end-Ordovician extinction. In combination of the contributions in the volume, with several recommendations for with these factors, as well as reduced rates of magnetic reversal and future research, discussed below. the strontium excursion, Barnes raises the possibility for a Mid-Or- The rest of the volume is divided into four parts. Part One estab- dovician mantle superplume. Although additional effort is needed to lishes the standardized timescale and diversity metrics used through-
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