The dynamic reef and shelly communities of the Paleozoic / La nature dynamique des communautés récifales et coquillières du Paléozoïque

Abstract

Shelly communities and reef ecosystems represent the pinnacle of generic diversity and organizational complexity in marine environments. These systems are sensitive to climatic, tectonic, eustatic, and catastrophic changes, and their evolution and extinctions help reveal the regional and global dynamics of the Paleozoic Earth. It is, therefore, not surprising that the fossil record of these ecosystems has commanded the attention of generations of researchers (e.g., Billings 1862; Ziegler 1965; Osgood 1970; and a large compendium of papers in Boucot and Lawson 1999 on paleocommunities and Kiessling et al. 2002 on reef ecosystems, such as Copper 2002 and Kiessling 2002), each with their own perspective on the dynamics of shallow-marine ecosystems. With a system approach to understanding these ancient environments in mind, it was our intention to bring together researchers of various disciplines — paleobiology, paleoecology, carbonate sedimentology, taphonomy — to present a broad yet integrated perspective on recent advances in the field of shelly communities and reef ecosystems. This special issue is a collection of papers presented at Topical Session 114 convened at the 2006 Annual Meeting of the Geological Society of America (GSA) in Philadelphia, held in honour of Dr. Paul Copper’s retirement as Professor at Laurentian University (Sudbury, Ontario, Canada). The session included researchers working on a variety of deposits, addressing different questions, but with a unified theme to explore the temporal and spatial patterns and evolution of Paleozoic shallow-marine benthic shelly and reef communities. The theme of the topic session, as well as the proceedings papers in this special issue, is very much in keeping with Paul Copper’s research career, almost equally divided between Paleozoic brachiopods and reef communities. The contributors to this volume all feel some close connection to Paul’s academic activities, either as his former graduate students, research associates, or colleagues; some of us have benefited greatly from both scientific discussions with him or from his enormous fossil collections. The articles in this issue (cited in bold) cover various aspects of Paleozoic level-bottom shelly communities and reef paleoecology. Ma et al. give a detailed account of the internal structures in the well-known and widespread Late Devonian brachiopod genus Desquamatia from Bergisches Land of Germany. This fundamental morphological study is crucial for understanding the autecology and synecology of this extremely common atrypid genus and its abrupt extinction near the end of the Devonian. Hollis and Ausich study the functional morphology of a top-tier crinoid and reinterpret its anchoring mechanism as a distal coil capable of wrapping around other crinoid columns. Zhan and Jin document a case of brachiopod migration from an upper slope setting to the Yangtze Platform in South China during the Early Ordovician. The upslope dispersal subsequently led to the development of distinct brachiopod communities and faunas of the Yangtze Platform. This study shows a relatively deepwater origin of some common brachiopod communities of the Yangtze Platform, as well as the pioneer stage of brachiopod community organization during the Early Ordovician. Jin discusses the temporal and spatial differentiation of Early Silurian pentameride brachiopod communities of Anticosti Island using multivariate analyses, and demonstrates that the Pentamerus and stricklandiid communities had largely overlapping overall ranges in terms of their water depth and water turbulence level, but stratigraphically, the two groups of communities were rather clearly segregated — a paleoecological pattern probably controlled by fluctuating oceanic water temperature. Continuing the theme on Anticosti paleontology, Li and Allen use a unique approach to explore the relationships between orthide brachiopod associations and their living environments in the Anticosti Basin during the Early Silurian, and Tapanila and Ebbestad explore a miniature island community, hosted on a large gastropod shell. Analysis of the overlapping relations of encrusters, borers, and symbiotic embedders provides a remarkable example of the spatial forcing that may have played an important evolutionary role in muddy-bottom environments. Daley provides a broad survey of the boring patterns in various types of brachiopod shells from the Late Ordovician to the Early Devonian. She uses a series of techniques to differentiate post-mortem Received 27 November 2007. Accepted 13 December 2007. Published on the NRC Research Press Web site at cjes.nrc.ca on 4 March 2008.