Phanerozoic Trends in the Global
Diversity of Marine Invertebrates
John Alroy,1
* Martin Aberhan,2
David J. Bottjer,3
Michael Foote,4
Franz T. Fürsich,5
Peter J. Harries,6
Austin J. W. Hendy,7,8
Steven M. Holland,9
Linda C. Ivany,10
Wolfgang Kiessling,2
Matthew A. Kosnik,11
Charles R. Marshall,12
Alistair J. McGowan,13
Arnold I. Miller,7
Thomas D. Olszewski,14
Mark E. Patzkowsky,15
Shanan E. Peters,4,16
Loc Villier,17
Peter J. Wagner,11
Nicole Bonuso,3,18
Philip S. Borkow,19
Benjamin Brenneis,2
Matthew E. Clapham,3,20
Leigh M. Fall,14
Chad A. Ferguson,7
Victoria L. Hanson,4,9
Andrew Z. Krug,4,15
Karen M. Layou,7,9,21
Erin H. Leckey,22
Sabine Nürnberg,2
Catherine M. Powers,3
Jocelyn A. Sessa,7,15
Carl Simpson,4,23
Adam Tomašových,4,24
Christy C. Visaggi10,25
It has previously been thought that there was a steep Cretaceous and Cenozoic radiation
of marine invertebrates. This pattern can be replicated with a new data set of fossil
occurrences representing 3.5 million specimens, but only when older analytical protocols
are used. Moreover, analyses that employ sampling standardization and more robust
counting methods show a modest rise in diversity with no clear trend after the
mid-Cretaceous. Globally, locally, and at both high and low latitudes, diversity was less
than twice as high in the Neogene as in the mid-Paleozoic. The ratio of global to
local richness has changed little, and a latitudinal diversity gradient was present in the early
Paleozoic.
D
iversity curves showing changes through
the geological record in the number of
fossil marine genera or families have
fueled decades of macroevolutionary research
(1­10). Traditionally, these curves were based on
literature compilations that recorded only the first
and last appearances of taxa (3, 5). These compilations
suggested that diversity rapidly rose
during the Cambrian and Ordovician and then
either stayed at a plateau (3) or declined erratically
(5) through the Paleozoic. There was a
modest rebound after the end-Permian mass extinction,
the largest (11) and most ecologically
important (9, 12) of the Phanerozoic. Diversity in
these curves then rose steadily and with a possibly
increasing absolute rate, suggesting to some
an exponential radiation (4, 6, 9, 10).
The appearance of a Paleozoic equilibrium
followed by a nearly unbridled Meso-Cenozoic
radiation has presented a puzzle: How could
global diversity reach limits and then much
later cast them off, rising to far higher levels
than those seen during the Paleozoic? The possibility
that the apparent radiation was exaggerated
by secular trends in the quality and
especially quantity of the preserved fossil record
(8, 13­15) was first proposed more than
three decades ago (16). This claim was at first
put aside because sampling effects were thought
to be minor and could not be assessed without
more detailed information (2, 8).
The Paleobiology Database (http://paleodb.
org) makes it possible to address the problem
with the use of contemporary statistical methods
because it records occurrences of genera
and species within particular fossil collections.
An intensive data collection effort has quadrupled
the database since data for two long
Phanerozoic intervals were presented in 2001
(17). This initiative has focused on both filling
gaps and sampling the Cenozoic at a high level
(18). The data set includes 44,446 collections
with individually recorded ages and geographic
coordinates. The collections comprise 284,816
fossil occurrences of 18,702 genera that equate
to ~3.5 million specimens and derive from 5384
literature sources.
Sampling and counting. The amount of data
per time interval and, therefore, the shape of a
diversity curve may vary greatly as a result of uneven
preservation and sampling effort. The key
advantage of collection data is that this variation
can be removed by subsampling (17). A random
subset of the available collections is drawn until
each interval, called a sampling bin, includes the
same estimated number of specimens. Genera
are counted, and the procedure is repeated to obtain
averages. We tallied actual specimen counts
when available and otherwise estimated them using
a gently curved, one-parameter empirical function
that relates the logarithms of specimen and genus
counts in each collection (18). The parameter
is called a calibrated weight. Previous studies
(17, 19­22) all presumed that this relation was
log-log linear and had the same shape in every
time interval, or else that there was little change
through time in the average size of collections.
We instead rarefied actual abundances to produce
a separate estimation curve for each interval.
Additionally, we weighted the chance of
drawing each collection inversely by its specimen
count to distribute sampling both spatially
and environmentally, which avoids underestimation
of global diversity (18). We excluded
samples from entirely unlithified rocks, sieved
samples from poorly lithified rocks, and samples
that preserve original aragonite because it
is easier to collect small and fragile specimens
in such cases. Furthermore, samples falling into
any of these categories are extremely uncommon
before the Cenozoic, and the Cenozoic
samples are concentrated in a narrow region of
the temperate zone [supporting online material
(SOM) text]. Finally, before each round of subsampling
we restricted the data set to 65 randomly
drawn references per interval, exceeding
this figure only when more are needed to provide
the quota of specimens used in subsampling.
Use of a reference quota holds the effective size
of the sampling universe more constant, which
avoids such problems as a correlation between
apparent diversity and the geographic extent of
fossil collections (SOM text).
A second issue is how to tally genera (17).
Conventional protocols count not only genera
sampled inside a temporal bin but also genera
found at any time before and after a bin (but not
inside it). Adding these unsampled taxa to the
count creates dropoffs at the edges of curves,
1
National Center for Ecological Analysis and Synthesis, University
of California­Santa Barbara, 735 State Street, Santa
Barbara, CA 93101, USA. 2
Museum für Naturkunde der
Humboldt-Universität zu Berlin, Invalidenstrasse 43, D-10115
Berlin, Germany. 3
Department of Earth Sciences, University
of Southern California, Los Angeles, CA 90089­0740, USA.
4
Department of the Geophysical Sciences, University of Chicago,
Chicago, IL 60637, USA. 5
Geozentrum Nordbayern,
Friedrich-Alexander Universität Erlangen, Loewenichstrasse
28, D-91054, Germany. 6
Department of Geology, University
of South Florida, Tampa, FL 33620­5201, USA. 7
Department
of Geology, University of Cincinnati, Cincinnati, OH 45221­
0013, USA. 8
Department of Geology and Geophysics, Yale
University, New Haven, CT 06520­8109, USA. 9
Department
of Geology, University of Georgia, Athens, GA 30602­2501,
USA. 10
Department of Earth Sciences, Syracuse University,
Syracuse, NY 13244, USA. 11
Department of Paleobiology,
Smithsonian Institution, Washington, DC 20013­7012, USA.
12
Museum of Comparative Zoology, Harvard University, Cambridge,
MA 02138, USA. 13
Department of Palaeontology,
Natural History Museum, Cromwell Road, London SW7 5BD,
UK. 14
Department of Geology and Geophysics and Faculty of
Ecology and Evolutionary Biology, Texas A&M University,
College Station, TX 77843­3115, USA. 15
Department of
Geosciences, Pennsylvania State University, University Park,
PA 16802­2714, USA. 16
Department of Geology and Geophysics,
University of Wisconsin­Madison, Madison, WI 53706,
USA. 17
Centre de Sédimentologie-Paléontologie, Université
de Provence, 13 331 Marseille Cedex 3, France. 18
Department
of Geological Sciences, California State University, Fullerton,
CA 92834­6850. 19
Science Department, Hamilton Local
School District, Columbus, OH 43207, USA. 20
Department of
Earth and Planetary Sciences, University of California­Santa
Cruz, Santa Cruz, CA 95064, USA. 21
Department of Geology,
College of William and Mary, Post Office Box 8795,
Williamsburg, VA 23187, USA. 22
Department of Geological
Sciences, University of Colorado, Boulder, CO 80309­0399,
USA. 23
Department of Biology, Duke University, Durham, NC
27708­0338, USA. 24
Geological Institute, Slovak Academy
of Sciences, Dúbravskácesta 9, 84005, Bratislava 45, Slovakia.
25
Department of Biology and Marine Biology, University of
North Carolina­Wilmington, Wilmington, NC 28403.
*To whom correspondence should be addressed. E-mail:
alroy@nceas.ucsb.edu
RESEARCH ARTICLE
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local depression of curves near extinction and
origination events [the Signor-Lipps effect
(23)], and interpolated presences of polyphyletic
("wastebasket") genera that have artificially
long ranges with large gaps connecting
unrelated species. Our direct documentation of
occurrences allowed us to avoid all such problems
by counting only genera that have actually
been sampled. We used a variant of this
sampled-in-bin method (20) that corrects for
residual error by assessing the proportion of
genera found immediately before and after a
sampling bin but not inside it. This correction
has little effect other than reducing some shortterm
variation (18).
Global diversity. The sampling-standardized
diversity curve (Fig. 1) shows many key features
of older curves (e.g., 5), such as the CambroOrdovician
radiation, 78% end-Permian extinction,
and 63% end-Triassic extinction (18).
However, it also includes features that are not
highly visible in earlier published curves. Some
of them are short-term excursions that may not
be robust, such as the brief peak in our sixth
Cretaceous bin. Others, however, are seen in
numerous treatments of our data (SOM text).
(i) The curve suggests that there was a large
mid-Devonian drop with no clear recovery until
the Permian, instead of a mid-Paleozoic plateau
(3, 6). The initial decline begins well before
the Frasnian-Famennian ecological collapse,
and diversity does not fall across that boundary.
(ii) The onset of the late Paleozoic glacial interval
was no earlier than the late Famennian
(24). However, the curve's large mid-Permian
increase roughly corresponds with the end of
glaciation and an increase in the number of
latitudinally restricted tropical genera (25). (iii)
The recovery from the Permo-Triassic mass extinction
is so rapid that Early Triassic standing
diversity is only 32% lower than Late Permian
standing diversity. (iv) For similar reasons, the
55% Cretaceous-Tertiary mass extinction does
not register as a visible net change in diversity at
our curve's level of resolution.
Most importantly, the curve casts doubt on
the existence of an exponential radiation extending
throughout the Mesozoic and Cenozoic.
The Triassic data points are higher than the
early Jurassic points instead of lower, and there
is little net change from the mid-Cretaceous
through the Paleogene. Even the Neogene peak
is subdued: The curve's last data point is only a
factor of 1.14 and 1.37 higher than the two
highest points in the early and mid-Paleozoic
(both in the Early Devonian) and a factor of
1.74 higher than the median Paleozoic point.
Older subsampling methods suggest an even
smaller increase (18), and the Neogene values
may be exaggerated by geographic factors (SOM
text). Thus, the new results suggest that any
post-Paleozoic radiation was largely confined
to the Jurassic and Early Cretaceous.
In sum, the net increase in global diversity
over nearly a half-billion years was proportionately
not much larger than some of the changes
in genus counts between neighboring 11-millionyear
(My) intervals. However, some treatments
of Sepkoski's genus-level compilation imply
that the mid-Paleozoic­to­Neogene increase
was by a factor of 3.5 (7), or even 4.1 (6). We
next show that within-collection diversity patterns
and changes in latitudinal gradients are
only consistent with the new curve.
Collection-level diversity and evenness.
Abundance distributions are even when each
taxon is represented by a similar number of
specimens. Evenness is of intrinsic ecological
interest because it controls sampled richness
when collections are of the size normally studied
by paleoecologists (about 100 to 300 specimens)
(26­28). Fortuitously, the single governing parameter
estimated by the calibrated-weights
method is easily translated into Hurlbert's
probability of interspecific encounter (PIE)
Fig. 1. Genus-level diversity
of both extant
and extinct marine invertebrates
(metazoans
less tetrapods) during the
Phanerozoic, based on a
sampling-standardized
analysis of the Paleobiology
Database. Points
represent 48 temporal
bins defined to be of
roughly equal length
(averaging 11 My) by
grouping short geological
stages when necessary.
Vertical lines show
the 95% confidence intervals
based on Chernoff
bounds, which are
always conservative regardless
of the number
of genera that could be
sampled or variation in their sampling probabilities (18). Data are standardized by repeatedly drawing
collections from a randomly generated set of 65 publications until a quota of 16,200 specimens has been
recovered in each bin. On average, 461 collections had to be drawn to reach this total. The curve shows
average values found across 20 separate subsampling trials--enough to yield high precision with
such large sample sizes. Ma, million years ago. Cm, Cambrian; O, Ordovician; S, Silurian; D, Devonian;
C, Carboniferous; P, Permian; Tr, Triassic; J, Jurassic; K, Cretaceous; Pg, Paleogene; Ng, Neogene.
Time (Ma)
Numberofgenera
Cm O S D C P Tr J K Pg Ng
500 400 300 200 100 0
0200400600800
Time (Ma)
Numberofgenera
Evenness
Cm O S D C P Tr J K Pg Ng
500 400 300 200 100 0
0200400600800
0.550.600.650.700.750.80
Fig. 2. Evenness estimates (thick line) for 11-My-long bins, based on Hurlbert's PIE index (27). The values are
computed from the calibrated occurrence weights used in subsampling, and each is a weighted moving averages
across five consecutive bins. Changes in global diversity (thin line, same as in Fig. 1) are shown for comparison.
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index of evenness (27). PIE bears no necessary
relation to the total number of taxa that might be
sampled.
Evenness changed substantially through the
Phanerozoic, if not as dramatically as sometimes
suggested (29), and the greatest values
are seen in the late Cretaceous and Cenozoic
(Fig. 2). They imply, for example, that 200
specimens will yield about 11.3 genera in the
latest Ordovician, 22.2 in the Paleocene, and
19.3 in the late Neogene. The general pattern of
a long-term increase is confirmed by related
(but more restricted) studies (26, 30). However,
the evenness curve (Fig. 2) does not simply
increase. It suggests a plateau between the Late
Ordovician and Carboniferous and then a large
rise through the Permian. After a weak recovery
from the Permo-Triassic decline, it
shows little change until a rise in the Late Cretaceous
(18). All of these features are broadly
consistent with the idea that local diversity
reached its maximum sometime during the past
100 My (29) as the number of occupied niches
expanded (31). However, they do not suggest a
radical increase between the early Paleozoic
and Cenozoic. They also do not mirror the shift
in abundance distributions from simple to
complex shapes at the Permo-Triassic boundary
(12), because evenness dropped across this
boundary instead of rising, and the Triassic
figures are well within the narrow range seen
throughout most of the Paleozoic.
Theoretically, if biogeographic and environmental
gradients (i.e., beta diversity) do not
change, global diversity should track local sampled
diversity and, therefore, evenness. Furthermore,
the global curve is methodologically
grounded on the evenness data because the
calibrated function estimates fewer specimens
per collection when evenness is high, which
causes more collections to be drawn. Hence, it is
no surprise that after logging and differencing
the global and local curves (Fig. 2), we find a
significant correlation (Spearman's rank-order
correlation r = 0.332, P = 0.023). Specific
similarities include the parallel increase during
the Cambro-Ordovician radiation, the joint rise
during the Permian, and the drop in evenness
during the severe global extinction at the PermoTriassic
boundary (9, 11, 12).
However, the curves depart from one another
for long stretches of time. Evenness
remained relatively high during the long late
Paleozoic trough in global richness (Fig. 2).
The offset may be driven by geography: The
continents were widely dispersed during the
early Paleozoic, late Mesozoic, and Cenozoic,
and the late Paleozoic low roughly corresponds
with the assembly of the supercontinent
Pangaea. Thus, steeper biogeographic gradients
during the late Phanerozoic may have accommodated
greater global diversity (1), and the
same may have been true during the early
Paleozoic. Nevertheless, this hypothesis needs
to be explored in more detail because the midPhanerozoic
offset between the curves is not
consistent, and nonbiogeographic factors such
as onshore-offshore gradients also may have
changed.
Latitudinal diversity gradients. To ensure
that the global curve captured any radiation in
the tropics that might have occurred, we deliberately
focused on the Neogene tropics while
simultaneously establishing a baseline sampling
level for the entire Phanerozoic. Counts
of references in the Paleobiology Database,
Sepkoski's compendium, GeoRef, and the Treatise
on Invertebrate Paleontology suggest that
our data sample the tropics as well as, or better
than, those compilations (SOM text). Enough
data are available to compare latitudinal belts
within several key time intervals.
Subsampling curves for individual Neogene
bins show that low-latitude diversity
(within 30° paleolatitude of the equator) was
substantially higher than northern temperate
zone diversity (Fig. 3A). The Neogene tropical
curves overlap, and the high-latitude curves are
also very similar to each other. In the Ordovician,
there was little benthic habitat in the north,
so we have computed low-latitude and southern
temperate zone curves (Fig. 3B). They show a
clear latitudinal diversity gradient for one bin
but not the other. Thus, regardless of whether
the modern gradient came into existence recently,
at least some much older intervals did
witness similar patterns. Furthermore, because
there is a large difference between the Neogene
and Ordovician at both high and low latitudes
(Fig. 3), the moderate net increase through the
Phanerozoic (Fig. 1) seems to have been a global
phenomenon instead of being driven strictly
by a radiation in the tropics.
Previous data sets. The fact that most treatments
of older compilations depict a massive
Cretaceous-Cenozoic radiation (1­7, 9, 10) raises
the question of whether the differences are primarily
methodological or primarily related to
coverage of the literature. We answer this question
by tabulating our data set and Sepkoski's
range-based, genus-level compendium (5) in
exactly the same way. Because it is impossible
to either sample-standardize or take sampledin-bin
counts if only ranges are available (5),
we use raw, unstandardized data and treat our
genus age ranges as if they were continuously
sampled.
The two data sets yield similarly shaped
curves of a comparable magnitude (Fig. 4). The
genus-level curves (Fig. 4) virtually overlap,
and the same is true for ordinal-level data sets
(SOM text). The new genus-level curve is
higher than Sepkoski's throughout much of the
Mesozoic but still suggests a large Cenozoic
radiation, albeit smaller than that in Sepkoski's
data. Our raw curve suggests a 3.74 times difference
between the late Neogene and the median
Ordovician, Silurian, or Devonian interval--
slightly more than the factor of 3.54 seen in
Sepkoski's compendium (Fig. 4). Both curves
identify not just major but also minor features,
such as a peak in the late Jurassic.
Thus, the dramatic differences between the
standardized and conventional curves (Figs. 1
and 4) do not result from data-quality or -quantity
Fig. 3. Low- (30°S to 30°N paleolatitude)
and high-latitude subsampling
curves for individual 11-My-long bins.
Gray lines indicate low-latitude data. (A)
Data for the Cenozoic bins, including the
Early/Middle Miocene (dotted lines) and
Late Miocene/Pliocene/Pleistocene (solid
lines). Black lines indicate data from
above 30°N. (B) Data for the Ordovician
bins, including the Llanvirn (dotted lines)
and Caradoc (solid lines). Black lines denote
data from below 30°S.
Number of specimens
Numberofgenera
A
Neogene tropics
Neogene north
0 3000 6000 9000 12000 15000
02004006008001000
Number of specimens
Numberofgenera
B
Ordovician tropics
Ordovician south
0 3000 6000 9000 12000 15000
02004006008001000
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problems. We instead attribute these differences
to two biases that can only be removed
with standardized sampling and sampled-inbin
counting of occurrence data (SOM text).
First, we have exceeded the magnitude of
Sepkoski's curve in the mid-Phanerozoic with
a modest data set but fallen just short of it in the
Cenozoic with a massive data set (18). Fully
matching his curve would require us to make
our sampling even more heterogeneous. Hence,
the literature compiled by Sepkoski seems
likely to contain a strong Cenozoic sampling
bias. Second, counting each extant taxon as
sampled everywhere from its last fossil appearance
to the Recent [i.e., the Pull of the Recent
(7, 32)] exaggerates the artifactual Cretaceous
and Cenozoic increase. This problem cannot
affect counts of sampled taxa because they take
no note of which genera are extant or which
extend beyond a particular bin.
Conclusion. The new diversity curve (Fig. 1)
records substantial volatility, including some
potentially meaningful excursions that might
relate to evolutionary innovations, paleogeographic
shifts, global climate change, sealevel
change, or other factors. In particular,
the fact that local and global diversity have
not always changed in tandem (Fig. 2) implies
that compositional differences between environments
or geographic regions have waxed
and waned.
Regardless of whether this is true, a more
general and important pattern is evident: Most
of the Meso-Cenozoic radiation took place
well before the Late Cretaceous and Cenozoic,
and the net increase through the Phanerozoic
was proportionately small relative to the
enormous amount of time that elapsed. Strong
latitudinal diversity gradients as far back as
the Ordovician and modest changes in localscale
sampled diversity (Fig. 2) (26, 29, 30)
are consistent with the suggestion that global
biodiversity is constrained. Additional evidence
includes rapid rebounds from all of
the major extinction episodes (Fig. 1) (3).
Although any limit to diversity could not
have been static and must have had a net
increase (3, 13, 16, 17, 33), our results cannot
be reconciled with previous studies that argued
for exponential long-term growth on the basis
of raw, unstandardized data (1, 4, 6, 9, 10).
Allowing for ecological reorganizations in the
wake of mass extinction (9) or for the addition
of ecological niches by means of evolutionary
innovation (31, 34) does not explain
how diversification could have been limitless
in the face of interval-to-interval changes
that rivaled the entire net increase over the
Phanerozoic.
Thus, we now must ask what mechanisms
could have led to saturation. They may have
involved the way that energy is captured from
lower trophic levels. This capture could have
remained roughly constant (35). Alternatively,
if total energy capture did increase (36), this
change may have been offset by the diversification
of groups with high metabolic rates
(9), making it energetically difficult for a large
net radiation to occur.
References and Notes
1. J. W. Valentine, Palaeontology 12, 684 (1969).
2. J. J. Sepkoski Jr., R. K. Bambach, D. M. Raup,
J. W. Valentine, Nature 293, 435 (1981).
3. J. J. Sepkoski Jr., Paleobiology 10, 246 (1984).
4. M. J. Benton, Science 268, 52 (1995).
5. J. J. Sepkoski Jr., in Global Events and Event Stratigraphy,
O. H. Walliser, Ed. (Springer, Berlin, 1996), pp. 35­52.
6. R. K. Bambach, Geobios 32, 131 (1999).
7. M. Foote, Paleobiology 26, (suppl. 1), 74 (2000).
8. A. I. Miller, Paleobiology 26, (suppl. 1), 53
(2000).
9. R. K. Bambach, A. H. Knoll, J. J. Sepkoski Jr., Proc. Natl.
Acad. Sci. U.S.A. 99, 6854 (2002).
10. S. M. Stanley, Paleobiology 33, (suppl. to no. 4),
1 (2007).
11. D. M. Raup, J. J. Sepkoski Jr., Science 215, 1501
(1982).
12. P. J. Wagner, M. A. Kosnik, S. Lidgard, Science 314, 1289
(2006).
13. D. M. Raup, Paleobiology 2, 289 (1976).
14. S. E. Peters, M. Foote, Paleobiology 27, 583
(2001).
15. J. S. Crampton et al., Science 301, 358 (2003); published
online 12 June 2003, 10.1126/science.1085075.
16. D. M. Raup, Science 177, 1065 (1972).
17. J. Alroy et al., Proc. Natl. Acad. Sci. U.S.A. 98, 6261
(2001).
18. Materials and methods are available as supporting
material on Science Online.
19. J. Alroy, Palaeogeogr. Palaeoclimatol. Palaeoecol. 127,
285 (1996).
20. A. I. Miller, M. Foote, Paleobiology 22, 304 (1996).
21. J. Alroy, Paleobiology 26, 707 (2000).
22. A. M. Bush, M. J. Markey, C. R. Marshall, Paleobiology
30, 666 (2004).
23. P. W. Signor, J. H. Lipps, Geol. Soc. Am. Spec. Pap. 190,
291 (1982).
24. M. Streel, M. V. Caputo, S. Loboziak, J. H. G. Melo,
Earth Sci. Rev. 52, 121 (2000).
25. M. G. Powell, Geology 33, 381 (2005).
26. M. G. Powell, M. Kowalewski, Geology 30, 331
(2002).
27. T. D. Olszewski, Oikos 104, 377 (2004).
28. S. E. Peters, Paleobiology 30, 325 (2004).
29. A. M. Bush, R. K. Bambach, J. Geol. 112, 625
(2004).
30. M. Kowalewski et al., Paleobiology 32, 533 (2006).
31. R. K. Bambach, in Biotic Interactions in Recent
and Fossil Benthic Communities, M. J. S. Tevesz,
P. L. McCall, Eds. (Plenum, New York, 1983),
pp. 719­746.
32. D. M. Raup, Bull. Carnegie Mus. Nat. Hist. 13, 85
(1979).
33. G. G. Simpson, in Evolution After Darwin, Vol. I, The
Evolution of Life, S. Tax, Ed. (Univ. of Chicago Press,
Chicago, 1960), pp. 117­180.
34. W. I. Ausich, D. J. Bottjer, Science 216, 173 (1982).
35. L. Van Valen, Evol. Theory 1, 179 (1973).
36. R. K. Bambach, Paleobiology 19, 372 (1993).
37. We thank R. Bambach and D. Jablonski for extensive
and helpful discussions and M. Apel, M. Bosnakoff,
D. Buick, K. Bulinski, M. Gibson, N. Heim, M. Hethke,
D. Korn, K. Koverman, J. Millet, K. Nell,
P. Novack-Gottshall, T. Schossleitner, C. Schweitzer,
M. Uhen, P. Wall and especially D. Hempfling, S. Hicks,
and U. Merkel for contributing to the data set. This work
was funded by the NSF Division of Environmental
Biology (grant DEB-0083893 to C.R.M., J.A., A.I.M.,
J. M. Hayes, and D. H. Rothman), the NSF Sedimentary
Geology and Paleontology program (grants
EAR-0521425 and EAR-0545059 to J.A., EAR-0434443
to D.J.B., and EAR-0105609 to M.F.), the NASA
Program in Exobiology and Evolutionary Biology
(grants to A.I.M. and M.E.P.), and the
VolkswagenStiftung (grant to W.K.). Our research was
conducted while J.A. was a Center Associate at the
National Center for Ecological Analysis and Synthesis, a
Center funded by NSF (grant DEB-0553768), the
University of California­Santa Barbara, and the state of
California. This is Paleobiology Database publication
number 80.
Supporting Online Material
www.sciencemag.org/cgi/content/full/321/5885/97/DC1
Materials and Methods
SOM Text
Figs. S1 to S21
References
25 February 2008; accepted 2 June 2008
10.1126/science.1156963
Fig. 4. Genus-level
diversity curves based
on Sepkoski's compendium
[thin line (5)] and
our new data (thick line).
Counts are of marine
metazoan genera crossing
boundaries between
temporal bins (boundary
crossers) and exclude
tetrapods. Ranges are
pulled forward from
first fossil appearances
to the Recent, instead of
ending at the last known
fossil appearance. Extant
genera are systematically
marked as such based
on Sepkoski's compendium
and the primary
literature. There is no
correction for sampling,
and genera are assumed to be sampled everywhere within their ranges because Sepkoski's traditional
synoptic data (5) do not record occurrences within individual collections.
Time (Ma)
Numberofgenera
Cm O S D C P Tr J K Pg Ng
500 400 300 200 100 0
01000200030004000
4 JULY 2008 VOL 321 SCIENCE www.sciencemag.org100
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