Phanerozoic Diversity Patterns: Profiles in Macroevolution

by J. Valentine

Overview

Here twenty-one leading paleontologists use important refinements in fossil diversity data to provide critical evaluations of older hypotheses of diversification and extinction processes and to propose fresh interpretations.

Originally published in 1986.

The Princeton Legacy Library uses the latest print-on-demand technology to again make available previously out-of-print books from the distinguished backlist of Princeton University Press. These editions preserve the original texts of these important books while presenting them in durable paperback and hardcover editions. The goal of the Princeton Legacy Library is to vastly increase access to the rich scholarly heritage found in the thousands of books published by Princeton University Press since its founding in 1905.

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ISBN-13:	9781400855056
Publisher:	Princeton University Press
Publication date:	07/14/2014
Series:	Princeton Series in Geology and Paleontology , #44
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Phanerozoic Diversity Patterns

Profiles in Macroevolution

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By James W. Valentine

PRINCETON UNIVERSITY PRESS

Copyright © 1985 Princeton University Press
All rights reserved.
ISBN: 978-0-691-08375-9

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CHAPTER 1

AN ATLAS OF PHANEROZOIC CLADE DIVERSITY DIAGRAMS

J JOHN SEPKOSKI, Jr. and MICHAEL L. HULVER

Department of the Geophysical Sciences, University of Chicago

Clade diversity diagrams are spindle-shaped graphs that summarize patterns of taxonomic evolution within higher taxa through geologic time. Most clade diversity diagrams are constructed about a central axis that represents time (scaled either metrically or ordinally, by stratigraphic interval). Some measure or estimate of taxonomic diversity (or "richness") is then plotted symmetrically about the axis to give the diagram an overall spindle shape (e.g., Figure 1).

Diversity diagrams for individual clades convey information about their size, shape, and variability in the fossil record (cf. Gould et al., 1977). Such "morphologic" information is valuable for assessing how evolutionary rates (that is, rates of origination and extinction) vary within the taxa through geologic time. Clade diversity diagrams for groups of higher taxa hypothesized to be related by phylogeny or by function are useful for comparisons of the histories of the taxa. Common patterns of expansion or contraction may relate to general factors governing all taxa, whereas reciprocal patterns may be interpretable as negative interactions between pairs of ecologically similar taxa (e.g., Simpson, 1953; Bambach, this volume). Sets of clade diversity diagrams also are useful for summarizing variation among large numbers of clades for the purpose of testing general macroevolutionary models (e.g., Raup et al., 1973; Gould et al., 1977).

This chapter presents a collection of clade diversity diagrams which we hope will be useful for examining the general histories of a wide variety of animal taxa. The main body of the chapter is a series of 12 figures displaying spindle diagrams for orders, classes, and phyla of both marine and nonmarine (or "continental") animals for the whole of the Phanerozoic (including the Vendian). Nearly all of the diagrams are plotted at a uniform taxonomic and temporal resolution, specifically that of familial diversity per stratigraphic stage. The taxonomic rank of family is used simply because comprehensive data with good stratigraphic resolution can be obtained for all animal groups at this level. Although families do not display all of the detail of the fossil record, they should be sufficiently sensitive to show major evolutionary trends and patterns with characteristic timescales of fives to tens of million years (see also Sepkoski, 1979, 1982a; Raup and Sepkoski, 1982).

The clade diversity diagrams in most of the figures are formatted in strips that have time in the vertical dimension. Most of the strips are scaled from 625 myr at their bottoms to approximately 1 myr BP at their tops. (No data on Recent diversity are directly included in the diagrams.) Geologic eras and systems are indicated at the lefthand ends of the strips, with eras denoted by Cz = Cenozoic, Mz = Mesozoic, Pz = Paleozoic, and p [??] = latest Precambrian; systems are denoted by standard symbols, with V = Vendian. The widths of the clade diversity diagrams in each strip indicate the numbers of families known from direct fossil evidence or from interpolation between known occurrences to be present in the "clades" in each of 80 stratigraphic stages or comparable intervals (see Table 1 in Sepkoski, 1982b for a listing of the stages used). A scale for the familial diversities appears in the lower righthand part of most of the figures. All of the diagrams were produced with an IBM Personal Computer and Epson dot-matrix printer.

The first two figures in this chapter contain class-level summaries of the entire Phanerozoic fossil record. Figure 1 displays clade diversity diagrams for the 87 classes and 15 unique, problematic genera that have representatives in the marine fossil record. This illustration is an updated version of Figure 1 in Sepkoski (1981) with corrections based on new data in Sepkoski (1982b). The second figure in this chapter summarizes the continental fossil record. The diversity diagrams display numbers of freshwater and terrestrial families within the 39 animal classes known from the nonmarine fossil record; data on the classes were compiled from the literature sources listed in Table 1. Also shown at the bottom of Figure 2 are clade diversity diagrams for numbers of species within the 13 taxonomic divisions of the tracheophytes and bryophytes; the data for these diagrams were taken from Niklas, Tiffney and Knoll (this volume).

The next eight figures illustrate a breakdown of the class-level clades into their constituent orders. Time and diversity in all diagrams are plotted at the same relative scale as in Figures 1 and 2 in order to facilitate comparison. Figures 3 and 4 display family-level clade diagrams for orders within the moderately diverse marine phyla: the Protozoa, Porifera, Coelenterata, Bryozoa, Brachiopoda, Annelida, and Hemichordata. (The set of clade diversity diagrams for the Annelida includes several taxa of questionable affinities which might best be considered incertae sedis; these are in the group of diagrams beginning with Cribricyathida and ending with Cornulitidae.) The more diverse marine phyla are represented in Figures 5 to 8. Figure 5 displays orders of marine molluscs; Figure 6 orders of marine arthropods; Figure 7 orders of echinoderms; and Figure 8 orders of marine vertebrates.

The two large phyla of continental animals, the nonmarine Arthropoda and Chordata, are featured in Figures 9 and 10. Nonmarine taxa have been segregated from their marine relatives because we believe that the land and sea are best treated as separate major arenas of evolution (see also Boucot, 1983). Despite the fact that some continental clades contain secondary species which alternate between marine and nonmarine habitats, and that all clades ultimately had their origins in the oceans, the great majority of continental animals evolved in situ, isolated from evolutionary activity in the seas. Thus, the segregation of marine and continental taxa enhances assessment of evolutionary patterns within the two arenas as well as comparisons between them. Note that the time axes for the continental clade diversity diagrams in Figures 9 and 10 have been truncated below the Silurian; this is because there is virtually no nonmarine fossil record prior to the mid Paleozoic (see Boucot and Janis, 1983).

The final pair of figures in this chapter (Figures 11 and 12) contains 14 diversity diagrams for families within entire phyla, split again between marine and continental. These diagrams are formatted somewhat differently than in the preceding figures. The spindles have been cut in half and rotated so that the time axis runs horizontally. This arrangement permits easier assessment of the times and magnitudes of diversity change but impedes comparison of changes between groups.

The use of a single level of taxonomic and stratigraphic resolution in all clade diversity diagrams is intended to aid interpretation and comparison of patterns among the various taxa. However, the constancy of resolution does not imply a uniformity of quality throughout the data. The accuracy of the taxonomic and stratigraphic information varies considerably among the taxonomic groups. In general, the quality is much better for marine taxa than for nonmarine taxa. Also, as should be expected, the fossil data are much better (and much more complete) for heavily skeletonized animals than for soft-bodied and lightly sclerotized animals. In fact, many of the diagrams for the latter groups reflect little more than the geologic distribution of Lagerstätten that preserve unusual fossils. This is particularly evident in the long, thin clade diagrams for such extant groups as the Nemertinea and Priapulida (Figure 1); these diagrams show only the extension of stratigraphic ranges from the Recent to the one or more Lagerstätten that happen to contain the groups' early members.

Much of the character of the diversity diagrams for some large clades, such as insects (Figures 2 and 9), also represents the effects of Lagerstätten. For the insects, the more important Lagerstätten include the Upper Carboniferous siderite concretion deposits of North America and Europe, the mid-Permian lake deposits of Kansas and Kazakhstan, the Eocene Green River deposits of Wyoming, and especially the Oligocene Baltic Amber of northern Europe. The Baltic Amber alone contributes most of the Cenozoic bulge in the clade diversity diagrams for both insects and other lightly sclerotized terrestrial arthropods (Figures 2, 9, and 12). The effects of Lagerstätten, or of their non-occurrence, are even seen in some well-skeletonized groups with fairly extensive fossil records. The drop in the diversity of continental vertebrates in the Jurassic (Figure 12), for example, probably reflects largely a paucity of fossiliferous continental deposits between the Rhaetian and Tithonian (see also Carroll, 1977; Padian and Clemens, 1985, this volume).

These shortcomings of the fossil record, along with the problems associated with family-level data and 5 to 10 myr-long stages, do limit the value of the clade diversity diagrams presented here. However, we believe that a great deal still can be learned from them about the shape of evolution — about the success and failure of taxa and about the apparent order, or disorder, in their radiations and extinctions. Thus, we hope that this "atlas" will aid in the assessment and interpretation of evolutionary history as well as serve as a baseline for the compilation of more accurate and detailed diversity data.

CHAPTER 2

TERRESTRIAL VERTEBRATE DIVERSITY: EPISODES AND INSIGHTS

K. PADIAN and W. A. CLEMENS

Department of Paleontology, University of California, Berkeley

Dedicated to the late George Gaylord Simpson

INTRODUCTION

One of the most important contributions to the advancement of paleobiology in the past ten years has been an increased understanding of the character and pace of change of biotic diversity through time. This has been initiated by comprehensive analysis of taxonomic patterns and interpretation of the apparent results with respect to underlying evolutionary histories and processes as well as to possible sources of sampling and other biases (reviewed in Simpson, 1960; Raup, 1976, 1979b; Thomson, 1976; Hallam, 1977; Sepkoski et al., 1981; see also other papers in this volume).

Many questions and paradoxes remain in the study of paleovertebrate diversity. To what extent are some apparent patterns the result of physical processes: post-mortem sorting of bones and teeth, differences in depositional environments, or current availability of outcrops of fossiliferous strata? How do differences in intensity of study bias our perception of the fossil record, and how can nonstochastic patterns be recognized? In short, to what extent can we use the apparent fossil record of changing diversity of taxa to infer evolutionary processes, including adaptation, selection, and species replacement?

The purpose of this paper is to separate that portion of the data that comprises the fossil record of terrestrial vertebrates, and to examine some of the above questions in light of the possibilities and difficulties of the record. A basic discussion of some of these problems may explain why the available data take the shapes seen in tabulations of diversity, and show what kinds of evolutionary questions can be addressed to this record. In some cases, new advances in the field, such as application of Sepkoski's (1981) factor-analytic approach to the terrestrial data, may help to go beyond the biases to a fuller understanding of evolutionary patterns. Recent advances in many areas of vertebrate paleontology were reviewed by Hopson and Radinsky (1980); the uses of phylogenetic analysis as a baseline for other kinds of evolutionary inquiries can be found in Cracraft (1981), Lauder (1981), Fisher (1982), and Padian (1982). This paper centers on patterns, biases, and questions that arise in both general and specific analyses of vertebrate history.

Several useful studies of diversity through time in specific vertebrate groups have formed the basis for part of the present work. Fishes are largely excluded from this survey because they have been extensively considered by Thomson (1977), and to separate marine and nonmarine types here would not give a representative picture of their patterns of diversity. We have incorporated some of the tabulations and interpretations of Carroll (1977) on amphibians and Gingerich (1977) on mammals. Like these authors, we have relied largely on Romer (1966) and Harland et al. (1967) for compilation of systematic diversity, correcting somewhat for systematic revisions made during the past fifteen years. We have also referred to the taxonomic tabulations of Lillegraven (1972) on fossil mammals. Finally, we wish to acknowledge gratefully access to J. J. Sepkoski's previously unpublished tabulations of vertebrate diversity, which were compiled largely from the above sources. The phrase "fossil record" is used here in reference to those fossils in hand and available for study. As Durham (1967) and others have emphasized, these are but a small part of the total assemblage of records of prehistoric organisms preserved in the rocks of the earth's crust.

THE TERRESTRIAL VERTEBRATE RECORD

The terrestrial fossil record is far poorer than the marine record in many ways, although it is still amenable to many kinds of questions. Terrestrial sediments provide a relatively small portion of the available fossil record (Raup, 1976a,b; Niklas et al., 1980). Their representation improves toward the Recent, though biases of sampling, preservation, and taxonomic interest cannot be discounted. The terrestrial record has never been completely assessed with these factors in mind, although some data are available (e.g., Ronov, 1959, 1982) and new approaches have been offered (e.g., Bakker, 1977).

The relative representation of the marine and fossil records has not been extensively studied with respect to amount of preserved area through time. The size relationship of the shelf area to the inner continental area depends on sea level, the slope of the shelf, the absolute area of the continental mass, and other factors. Available shelf area should increase with subdivision of the continents by epicontinental seas or fragmentation of the continents by drift. Since the Permian, subdivision of the continents has increased, and at times epicontinental seas have also covered much of the continental surface. However, there are only on the order of 10,000 species of fossil terrestrial vertebrates, whereas marine fossils number on the order of 180,000 species (Raup, 1976). The great discrepancy in known diversity of marine and terrestrial species through time seems not to be related mainly to available living area, but to environmental potential for fossilization and preservation. Even the record of "terrestrial" vertebrates depends to some extent on the marine record. The Lower Jurassic limestones of southwest England and the Upper Jurassic limestones of the Solnhofen region of West Germany provide examples. The first records deposition in a transgressive sea, the second in an ancient lagoon; yet both preserve records of "terrestrial" reptiles (pterosaurs, crocodiles, and dinosaurs). In some cases such marine deposits provide most of what we know of the "terrestrial" vertebrates of one age and area (see Buffetaut, et al., 1982 for a report on the Middle Cretaceous of Europe).

The same rules for preservation of organic remains govern marine and terrestrial regimes', quick burial, quiet sedimentation, and no destruction after deposition. The paucity of terrestrial fossils reflects several major biases. In subaerial terrestrial habitats, biotic remains tend to be destroyed by oxidation, decomposition, and reworking of potential fossils and their sedimentary environments. Furthermore, in comparison to the marine realm, the terrestrial environment is primarily erosional, not depositional. On the average, terrestrial sediments are less continuously accumulated than are marine sediments (Sadler, 1981), though some terrestrial environments, such as lakes, floodplains, and stream channels, can produce relatively complete records over a long period of time if the environment remains stable and if the deposited sediments escape subsequent erosion (Behrensmeyer, 1982; Dingus and Sadler, 1982). Deposits formed in aquatic environments, such as the geographically extensive and geologically long-lived Newark Supergroup of the eastern United States, the Eocene deposits of Messel, West Germany, and the Pleistocene La Brea "tar pits" of Los Angeles, provide most of the terrestrial fossil record. But such environments occupy only a small part of the continental surface, are ephemeral in duration, and may be unlikely to preserve any records of certain kinds of organisms and their habitats. Such deposits provide the most detailed insights into fossil history, but are potentially misleading about the history and pace of terrestrial life (Bakker, 1977; see below). Their paleodemographic data cannot be taken at face value, because such Lagerstätten seldom preserve organisms from arid or upland environments.

(Continues...)

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Table of Contents

• FrontMatter, pg. i
• Contents, pg. v
• Preface, pg. ix
• Introduction. Diversity As Data, pg. 1
• Chapter 1. An Atlas of Phanerozoic Clade Diversity Diagrams, pg. 11
• Chapter 2. Terrestrial Vertebrate Diversity: Episodes and Insights, pg. 41
• Chapter 3. Patterns in Vascular Land Plant Diversification: An Analysis at the Species Level, pg. 97
• Chapter 4. Real and Apparent Trends in Species Richness Through Time, pg. 129
• Chapter 5. Evolutionary Faunas and the Distribution of Paleozoic Marine Communities in Space and Time, pg. 153
• Chapter 6. Classes and Adaptive Variety: The Ecology of Diversification in Marine Faunas Through the Phanerozoic, pg. 191
• Chapter 7. Phanerozoic Tiering in Suspension-Feeding Communities on Soft Substrata: Implications for Diversity, pg. 255
• Chapter 8. Nonequilibrium Model of Diversification: Faunal Turnover Dynamics, pg. 277
• Chapter 9. Diversification Functions and the Rate of Taxonomic Evolution, pg. 311
• Chapter 10. Marine Regressions and Mass Extinctions: A Test Using the Modern Biota, pg. 335
• Chapter 11. Modeling the Biogeographic Regulation of Evolutionary Rates, pg. 355
• Chapter 12. Testing for Adaptive Radiation: The Ptychaspid (Trilobita) Biomere of the Late Cambrian, pg. 379
• Chapter 13. Evolutionary Patterns Of Jurassic And Cretaceous Ammonites: An Analysis Of Clade Shape, pg. 399
• Chapter 14. Biotic Diversity and Clade Diversity, pg. 419
• Concluding Remark, pg. 425
• Author Index, pg. 427
• Subject Index, pg. 437