Stratigraphic Record of the Neogene Globorotalid Radiation (Planktonic Foraminiferida) RICHARD CIFELLI and GEORGE SCOTT ITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY • .NUMBER 58x SERIES PUBLICATIONS OF THE SMITHSONIAN INSTITUTION Emphasis upon publication as a means of "diffusing knowledge" was expressed by the first Secretary of the Smithsonian. In his formal plan for the Institution, Joseph Henry outlined a program that included the following statement: "It is proposed to publish a series of reports, giving an account of the new discoveries in science, and of the changes made from year to year in all branches of knowledge." This theme of basic research has been adhered to through the years by thousands of titles issued in series publications under the Smithsonian imprint, commencing with Smittisonian Contributions to Knowledge in 1848 and continuing with the following active series: Smittisonian Contributions to Antliropology Smithsonian Contributions to Astrophysics Smithsonian Contributions to Botany Smithsonian Contributions to the Earth Sciences Smithsonian Contributions to the Marine Sciences Smithsonian Contributions to Paleobiology Smithsonian Contributions to Zoology Smithsonian Folklife Studies Smithsonian Studies in Air and Space Smithsonian Studies in History and Technology In these series, the Institution publishes small papers and full-scale monographs that report the research and collections of its various museums and bureaux or of professional colleagues in the world of science and scholarship. The publications are distributed by mailing lists to libraries, universities, and similar institutions throughout the world. Papers or monographs submitted for series publication are received by the Smithsonian Institution Press, subject to its own review for format and style, only through departments of the various Smithsonian museums or bureaux, where the manuscripts are given substantive review. Press requirements for manuscript and art preparation are outlined on the inside back cover. Robert McC. Adams Secretary Smithsonian Institution SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY • NUMBER 58 Stratigraphic Record of the Neogene Globorotalid Radiation (Planktonic Foraminiferida) Richard Cifelli and George Scott SMITHSONIAN INSTITUTION PRESS City of Washington 1986 ABSTRACT Cifelli, Richard, and George Scott. Stratigraphic Record of the Neogene Globorotalid Radiation (Planktonic Foraminiferida). Smithsonian Contribu­ tions to Paleobiology, number 58, pages 101, 43 figures, 1986.—The histories of lineages forming the Neogene globorotalid radiation in the planktonic foraminifera are reconstructed primarily from stratigraphic distributions. Data on major taxa are synthesized, with particular reference to the devel­ opment of shell design, and related to biogeograpy and evolutionary strate­ gies. The radiation was established about the base of the lower Miocene by three groups {Fohsella, Globorotalia zealandica lineage, and G. praescitula plexus), which probably arose from separate paragloborotalid lineages. Common trends (size increase, chamber compression, keel development, reduced wall relief) early in the radiation culminated in the evolution of disk­ like taxa which, since the middle Miocene, have been centered in the tropics. The later phase of the radiation (post middle Miocene) was marked by architectural diversification as spiroconical (e.g., G. margaritae), ventroconical (e.g., G. truncatulinoides), and globose (e.g., G. inflata) taxa arose. Architec­ tural diversification may be linked with watermass differentiation in the late Neogene. Neogene designs have close counterparts in the earlier, but phyletically isolated, Paleogene and Cretaceous radiations. There are also resemblances in ontogenetic strategies and lineage histories. Common adaptations are suggested, but specific functional explanations have not been established. Periods of major redesign are recognized in most lineages and are not confined to speciation events. Examples of stasis in adult morphology occur particularly in taxa that have evolved compressed, keeled shells. Bifurcations in lineages are indistinctly represented by wide spectra of morphotypes. Within the radiation very rapid speciation events are conspicuously absent, although they possibly occurred at the origin of some lineages. The distinctly sluggish tempo of change may be due to large population sizes and their degree of intercommunication. Good examples of allopatric and parapatric speciation were not found, but the prevalence of polytypic taxa, often distributed in contiguous populations showing clinal variation, would favor the inception of parapatric speciation. OFFICIAL PUBLICATION DATE is handstamped in a limited number of initial copies and is recorded in the Institution's annual report, Smithsonian Year. SERIES COVER DESIGN: The trilobite Phacops rana Green. Library of Congress Cataloging in Publication Data Cifelli, Richard. Stratigraphic record of the Neogene Globorotalid radiation (Planktonic foraminiferida). (Smithsonian contributions to paleobiology ; no. 58) Bibliography: p. Supt. of Docs, no.: SI 1.30:58 ]. Globorotalia, Fossil. 2. Paleontology—Tertiary. 3. Geology, Stratigraphic—Tertiary. I. Scott, George II. Title. III. Series. QE701.S56 no. 58 560s [563'.12] 84-600360 [QE772] Contents Page Introduction 1 The Neogene Succession of Globorotalids 4 Root Stocks 4 Major Evolutionary Trends 7 Origins of the Early Lineages 13 Fohsella Lineage 16 Globorotalia zealandica Lineage 19 Globorotalia praescitula Plexus 21 New Zealand Record of Globorotalia miozea 24 Encrustation 25 Northern Representatives o^ Globorotalia miozea 27 Summary of the Early History of the Plexus 29 Early Spirally Convex Forms 30 Globorotalia conoidea-Globorotalia menardii Divergence 32 The Conservative Branch, Globorotalia conoidea 32 The Innovative Branch, Globorotalia menardii 35 The Scitulines 39 Globorotalia tumida Lineage 44 Later Developments 46 Globorotalia inflata Lineage 46 Globorotalia crassaformis Plexus 49 Origin 50 Relation to Globorotalia inflata Lineage 52 Keel Development 52 Globorotalia crassula 53 Globorotalia truncatulinoides 54 Analysis of the Succession 58 Globorotalid Radiations 58 Overview 58 Evaluation 65 Biogeography 66 Some Precepts 66 Adaptive Strategy 69 An Historic Perspective on the Evolution of Form 71 Bathymetry and Architecture 76 Evolutionary Patterns 78 Shape of the Phyletic Tree 78 Pattern in Individuals 79 Pattern within the Tree 81 Evaluation 84 Retrospect 88 Literature Cited 92 iii Stratigraphic Record of the Neogene Globorotalid Radiation (Planktonic Foraminiferida) Richard Cifelli and George Scott Introduction Fossil planktonic foraminifera have been stud­ summaries hardly do justice to the record avail­ ied primarily from a geologic point of view. able. Indeed, the documented record ofthe Cen­ Research was stimulated through the expansion ozoic planktonic foraminifera is matched by few of oil exploration that followed the second world groups of organisms. This sort of record ought war and from a newly gained awareness by the to be ideally suited for in-depth evolutionary industry of the advantages of long ranged, inter­ studies that could provide a good background to continental correlations that could be obtained assess current theories and models. There are at by means of the widely distributed planktonic least two reasons why full advantage has not been foraminifera. Additional opportunities for study taken of the planktonic record in this respect. of the history of foraminifera in geologic context One reason is that biostratigraphers have were provided by the Deep Sea Drilling Project higher priorities than evolution. Their zonations (DSDP), which has resulted not only in an im­ are constructed using events (appearances and proved biostratigraphic framework and a cali­ extinctions) that occur in fixed stratigraphic or­ brated time scale but also in solutions to problems der. Lineages tend to be treated as stratigraphic in tectonic and climatic history. successions of morphotypes and species concepts The paleobiologic aspects of planktonic fora­ are sometimes quite arbitrarily restricted to spec­ minifera, by contrast, have received relatively imens closely resembling the type specimen. Usu­ little emphasis so far. On occasion, biostratigra- ally, no information is given about population phers have considered the evolutionary implica­ structure, and it is uncertain whether one or tions of their work and proposed phylogenetic more morphotypes may be present in the devel­ schemes (e.g., Walters, 1965; Berggren, 1966; opment of lineages. Lineages that contribute McGowran, 1968; Blow, 1969; Jenkins, 1971; events of little stratigraphic value are generally Srinivasan and Kennett, 1981b; Kennett and Sri- ignored, even though they may provide critical nivasan, 1983). For the most part, however, their links in the line of development. Therefore, it is difficult to obtain insight into the dynamics of Richard Cifelli, Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, Washington, D.C. transformation from most biostratigraphic re­ 20560 (deceased). George Scott, Department of Scientific and ports, even though they contain important doc­ Industrial Research, Geological Survey, Lower Hutt, New Zea­ land. umentation about species occurrences. 1 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY The other reason for the lag in evolutionary or more feet thick (e.g., Arkell, 1933). Plank­ interest is perhaps more compelling, but much tonic foraminifera
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