Paleobiology, 26(4), 2000, pp. 625–646
Silurian trilobite alpha diversity and the end-Ordovician
mass extinction
Jonathan M. Adrain, Stephen R. Westrop, Brian D. E. Chatterton, and
Lars Ramsköld
Abstract.—Following the end-Ordovician extinction, global clade diversity of Silurian trilobites
dropped to about half of Ordovician levels. Although clade diversity failed to recover, this extinction had surprisingly little long-term impact on the number of trilobite species that occupied local
habitats (alpha diversity). A new compilation of data from Laurentia and other continents indicates
that Silurian trilobite alpha diversities in all major environments were comparable to those of the
Late Cambrian and Ordovician; shallow subtidal diversity reached an all-time high during the Late
Ordovician. The profound differences in patterns at local and global levels demonstrate the necessity for a hierarchical approach to analyses of diversity. Factors governing global clade diversity
are lodged at hierarchical levels beyond those controlling local species richness and must be sought
in studies of between-habitat (beta) or geographic (gamma) diversity.
Jonathan M. Adrain. Department of Geoscience, University of Iowa, Iowa City, Iowa 52242.
E-mail: [email protected]
Stephen R. Westrop. Oklahoma Museum of Natural History and School of Geology and Geophysics, University of Oklahoma, Norman, Oklahoma 73019. E-mail: [email protected]
Brian D. E. Chatterton. Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton,
Alberta, T6G 2E3, Canada.
Lars Ramsköld. Palaeontological Museum, University of Uppsala, Norbyvägen 22, S752 36 Uppsala, Sweden.
Accepted:
5 March 2000
Introduction
In a recent study (Westrop and Adrain
1998a) we surveyed all available quantitative
data on within-habitat species richness (alpha
diversity) in trilobites from the Late Cambrian
to Late Ordovician of the Laurentian paleocontinent. We concluded that trilobite species
richness underwent little change in any shelf
habitat during this time, that community restructuring during the great Ordovician Radiation was essentially passive in nature, and
that the apparent onshore decline of trilobites
in the wake of the radiation was primarily a
function of in situ dilution (Westrop et al.
1995) rather than active displacement. These
results were novel in suggesting that Middle
and Late Ordovician onshore trilobite diversities were maintained at levels similar to or
greater than those of the Late Cambrian, and
the study has sparked commentary (Miller et
al. 1998; Westrop and Adrain 1998b). Here, we
apply the same methodology to examine Silurian trilobite alpha diversity. In particular,
we test for net changes in habitat occupancy
q 2000 The Paleontological Society. All rights reserved.
in the context of the steeply declining relative
abundance of trilobites in Silurian benthic
communities. We also examine the effect on
alpha diversity of the end-Ordovician mass
extinction, an event that roughly halved trilobite global clade (genus and family) diversity. We have further extended the scope of the
original work by supplementing the Laurentian Middle and Late Ordovician data with 42
additional collections (an increase of 67 percent). Finally, in order to place the Laurentian
patterns in geographic context, we have
amassed all published Middle Ordovician–Silurian data sets from other paleocontinents, so
that the contribution of regional diversity histories to the combined global pattern can be
assessed.
Data
The methodology used in this study is similar to that of Westrop and Adrain (1998a). The
current data set consists of 258 collections for
which sample size (or at least minimum sample size) is known (Fig. 1); 96 of these are from
our own published and unpublished collec0094-8373/00/2604-0005/$1.00
626
JONATHAN M. ADRAIN ET AL.
TABLE 1. Distribution of collections by type, age, and
continent. ‘‘Quant’’ 5 quantitative or semiquantitative
data; ‘‘rare’’ 5 rarefiable data (i.e., quantitative sets with
901 individuals); ‘‘nonq’’ 5 nonquantitative faunal lists
based on detailed studies in which quantitative sampling information was not given.
Laurentia Baltica
Silurian quant
Silurian rare
Silurian nonq.
Ordovician quant
Ordovician rare
Ordovician nonq.
FIGURE 1. Frequency distributions of samples sizes for
Ordovician and Silurian collections (designated in Table
1 by ‘‘quant’’). The complete data set also includes 57
collections from detailed studies for which sample size
is not known.
tions. To expand geographic coverage, particularly for the Ordovician, we also included 57
collections from detailed published studies in
which sample size was not reported. We analyzed changes in alpha diversity using the
number of species (S) in the full data set of 315
collections (Table 1, Appendix). As a check on
the potential bias introduced by differences in
sample sizes, we repeated all analyses using a
smaller subset of 187 quantitative collections
on which we carried out rarefaction (using the
RAREFACT program [Bennington 1997]) to
compare expected diversity [E(Sn)] at a standard subsample size of 90 individuals. Quantitative collections excluded from the rarefaction analyses were those that either consisted
of fewer than 90 individuals or had been published in semiquantitative fashion, so that
minimum sample size could be estimated but
precise information on relative abundance
was lacking. In all analyses, we examined diversity patterns by comparing frequency distributions of S and E(Sn) using the MannWhitney U-test (M-W test) and, in the case of
rarefied data, the Kolmogorov-Smirnov test
(K-S test). All tests were performed with Statview 4.5 for the Macintosh (Statview 1995),
and results are presented in Tables 2–4.
Most of the data from outside Laurentia
come from Baltica and East Avalonia (Table 1,
77
52
2
93
70
12
46
40
7
7
3
18
E. Ava- Armorilonia
ca
Other
6
3
0
10
7
2
0
0
1
6
6
0
1
1
2
11
4
13
Fig. 2; Appendix), but the Ordovician compilation also includes collections from Armorican Gondwana, North and South China, and
elsewhere. The spectrum of environments ex-
TABLE 2. Significance levels of comparisons of frequency distributions of E(Sn) for global data (Figs. 7–9) mentioned in the text, using Mann-Whitney U- (M-W) and
Kolmogorov-Smirnov (K-S) tests. Significance levels for
nonrarefied data (S) are indicated only when conflict
with the results for E(Sn). MO, Middle Ordovician; UO,
Upper Ordovician; Ll, Llandovery; W, Wenlock; Lu,
Ludlow; C, Upper Cambrian data published by Westrop
and Adrain (1998a); , or ., significant difference; 5, no
significant difference.
Series-level
comparisons
M-W
Shallow subtidal facies
0.001
MO , UO
Ll 5 MO
0.44
0.02
W , MO
0.20
Ll 5 W
0.09
Lu 5 W
0.03
Ll . Lu [E(Sn)]
0.10
Ll 5 Lu (S)
0.09
C 5 MO [E(Sn)]
0.04
C , MO (S)
0.76
C 5 W:
0.15
C 5 Lu
Shelf carbonate buildups
W 5 C [E(Sn); K-S only]
0.03
W , C (S)
0.17
Deep subtidal facies
MO . UO [E(Sn), M-W only]
0.03
MO 5 UO (S)
0.12
0.001
MO . Ll
0.03
UO . Ll
0.02
W . MO [E(Sn)]
0.07
W 5 MO (S)
0.13
C 5 UO [E(Sn)]
0.008
UO . C [E(Sn)]
0.60
C 5 Ll
0.001
MO . C
0.001
W.C
K-S
0.006
0.82
0.08
0.14
0.26
0.03
0.012
0.36
0.07
0.08
0.11
0.001
0.01
0.01
0.21
0.90
0.001
0.001
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TRILOBITE SPECIES DIVERSITY
TABLE 3. Significance levels of comparisons of frequency distributions of E(Sn) for series-level data split by
province (Figs. 12, 13) mentioned in the text, using
Mann-Whitney U- (M-W) and Kolmogorov-Smirnov (KS) tests. Significance levels for nonrarefied data (S) are
indicated only where they conflict with the results for
E(Sn). MO, Middle Ordovician; UO, Upper Ordovician;
Ll, Llandovery; W, Wenlock; Lu, Ludlow; C, Upper Cambrian data published by Westrop and Adrain (1998a); ,
or ., significant difference; 5, no significant difference;
L, Laurentia; B, Baltica.
Series-level
comparisons
Shallow subtidal
Baltica versus Laurentia
Ordovician (nonrarefied)
MO (L) . W (B)
MO (L) . Lu (B)
C (L) 5 W (B)
C (L) 5 Lu (B)
M-W
K-S
facies
0.44
0.008
0.004
0.34
0.11
Laurentia versus E. Avalonia 1 other
Ordovician [E(Sn)]
0.02
Ordovician (S)
0.001
Laurentia
MO 5 UO
MO 5 C
MO 5 Ll
MO 5 W
Ll 5 W
MO 5 W 1 Lu
Ll 5 W 1 Lu
0.10
0.10
0.90
0.60
0.78
0.41
0.49
Baltica
Ordovician 5 Ll (S)
Ordovician . W (S)
Ordovician . Lu (S)
W 5 Lu
0.08
0.001
0.001
0.19
0.04
0.01
0.14
0.08
0.06
0.36
0.17
0.90
0.90
0.90
0.90
0.92
0.58
Deep subtidal facies
Laurentia
MO . UO (S)
MO 5 UO [E(Sn)]
UO . Ll [E(Sn)]
UO 5 Ll (S)
MO . Ll
C 5 Ll
W . MO [E(Sn)]
W 5 MO (S)
FIGURE 2.
0.005
0.07
0.05
0.07
0.001
0.60
0.03
0.17
0.24
0.23
0.001
0.52
0.02
TABLE 4. Significance levels of comparisons of frequency distributions of E(Sn) for stage-level data of Laurentia
(Fig. 15) mentioned in the text, using Mann-Whitney U(M-W) and Kolmogorov-Smirnov (K-S) tests. Significance levels for nonrarefied data (S) are indicated only
where they conflict with the results for E(Sn). M 1U Ordovician, pooled data for Middle and Upper Ordovician; , or ., significant difference; 5, no significant difference.
Stage-level comparisons
M-W
Shallow subtidal facies
M1U Ordovician 5 Late
Rhuddanian–Aeronian
0.22
Late Rhuddanian-Aeronian 1
Telychian 5 M1 U Ordovician
0.45
Late Rhuddanian-Aeronian 1
Telychian 5 Wenlock
0.81
Deep subtidal facies
M1U Ordovician . Late
Rhuddanian–Aeronian
0.03
E(Sn)
0.002
S
0.001
M1U Ordovician . Telychian
Wenlock . M 1U Ordovician
0.01
E(Sn)
0.06
S
K-S
0.19
0.49
0.49
0.20
0.001
0.006
M1U Ordovician
0.001
Deep subtidal . shallow subtidal
0.001
Late Rhuddanian–Telychian
0.48
Deep subtidal 5 shallow subtidal
0.49
amined (Fig. 3) is similar to that used previously (Westrop and Adrain 1998a) but includes a fifth category, basinal facies in lowerslope and most distal-ramp settings.
For most of the analyses, we divided the
Middle Ordovician–Late Silurian interval into
five sample units at the series level of resolution (Fig. 4). To evaluate the influence of the
end-Ordovician extinction on alpha diversity,
we also used a finer, stage-level resolution for
the Ordovician/Silurian boundary interval
and the Silurian (Fig. 5).
Geographic occurrence of samples. A, Ordovician samples. B, Silurian samples.
628
FIGURE 3.
JONATHAN M. ADRAIN ET AL.
Shelf lithofacies used to classify collections according to habitat.
Results
Global Compilation
Initial analyses used pooled data for all continents and terranes (global compilation) to
establish synoptic, ‘‘global’’ changes in alpha
diversity for each of the environmental settings. Recent work has demonstrated that
there may be considerable geographic variability in diversity patterns, both in the initial
recovery from mass extinction (Jablonski
1998) and in the background times between
major events (Miller 1997). Accordingly, we
also examined data from individual continents separately (intercontinental comparisons), although the availability of samples restricted comparisons to Laurentia, Baltica,
and, to a lesser extent, East Avalonia in shallow subtidal and deep subtidal facies.
Nearshore Facies. Westrop and Adrain
(1998a) demonstrated that nearshore diversity
was maintained at constant, low levels between the Late Cambrian and Middle Ordovician, and the new data show that this pattern continued into the Silurian. With one exception, modal species richness of both rarefied and nonrarefied samples is in the 1–5
species class between the Middle Ordovician
and Ludlow (Fig. 6), although the limited
number of samples younger than Middle Ordovician precludes the application of statistical tests.
Shallow Subtidal Facies. Westrop and Adrain (1998a) found little variation in diversity
between the Upper Cambrian and Upper Ordovician in shallow subtidal facies. However,
in the expanded data set (Table 2, Fig. 7), Upper Ordovician species richness is significant-
FIGURE 4. Series-level sample intervals used to examine
temporal changes in trilobite species alpha diversity.
FIGURE 5. Stage-level sample intervals used to examine
temporal changes in trilobite species alpha diversity
during and after the end-Ordovician extinction.
TRILOBITE SPECIES DIVERSITY
629
FIGURE 6. Frequency distributions of species richness
and rarefied data [E(Sn), at a standard sample size of 90
individuals] of all collections from Ordovician nearshore facies.
ly greater than in the Middle Ordovician. Diversity is reduced in the Llandovery, but does
not fall below the level of Middle Ordovician.
Wenlock diversity is significantly lower than
that in the Middle Ordovician, but is indistinguishable from diversity in the Llandovery;
Ludlow diversity is indistinguishable from
Wenlock diversity, but is significantly lower
than in the Llandovery. Thus, results of statistical tests indicate progressive decline in alpha diversity during the Silurian, so that the
Llandovery and Ludlow are significantly different from each other, but neither differs significantly from the intervening Wenlock.
Comparisons with the data published by
Westrop and Adrain (1998a) indicate that
shallow-subtidal species richness was maintained at Late Cambrian levels during the
Middle Ordovician but was significantly
greater than Cambrian levels in the Upper Ordovician (Table 2). However, species richness
of the Silurian portion of the data set is indis-
FIGURE 7. Frequency distributions of species richness
and rarefied data [E(Sn), at a standard sample size of 90
individuals] of all collections from Ordovician and Silurian shallow subtidal facies.
tinguishable from the Cambrian, even for the
Wenlock and Ludlow (Table 2).
Carbonate Buildups. Silurian data that can
be rarefied are restricted to shelf-interior
buildups of Llandovery and Wenlock age. The
number of collections is small, but Silurian
buildups are at least as diverse as those from
the Middle Ordovician (Fig. 8). Most of the Silurian collections are from the Wenlock, and
these have species richnesses that are comparable to the Upper Cambrian data published
by Westrop and Adrain (1998a), (Table 2; rar-
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JONATHAN M. ADRAIN ET AL.
FIGURE 8. Frequency distributions of species richness,
sample sizes, and rarefied data [E(Sn), at a standard
sample size of 90 individuals] of collections from Ordovician and Silurian carbonate buildup facies.
efied data of Wenlock samples show significantly greater diversity using an M-W test).
Westrop and Adrain (1998a) noted that
Cambrian and Middle Ordovician buildups
from shelf-margin sites were more diverse
than those from shelf-interior settings. Limited data suggest that this pattern also holds for
the Upper Ordovician (Fig. 8).
Deep Subtidal Facies. The pattern of little
net change between Upper Cambrian and Upper Ordovician deep subtidal collections
(Westrop and Adrain 1998a) extends into the
Silurian (Fig. 9). Diversity drops slightly between the Middle and Upper Ordovician, although it is significant in rarefied data only
with a M-W test (Table 2); with further decline
in the Llandovery, species richness is significantly lower than in both the Middle and Upper Ordovician (Table 2). By the Wenlock, diversity had recovered and exceeded Middle
Ordovician levels (Table 2; rarefied data only).
The number of collections from the Ludlow is
small but species richness is reduced dramatically relative to the Wenlock. Cambrian deep
FIGURE 9. Frequency distributions of species richness,
sample size and rarefied data [E(Sn), at a standard sample size of 90 individuals] of collections from Ordovician and Silurian deep subtidal facies.
subtidal collections (Westrop and Adrain
1998a) are indistinguishable from those of the
Upper Ordovician (rarefied data only) and
Llandovery but are significantly lower in diversity than the Middle Ordovician and Wenlock (Table 2).
Basinal Facies. There are only a few collections available from basinal facies, and none
include the relative abundance data required
to perform rarefaction. They display the same
pattern as the nearshore facies: constant, low
species richness between the Middle Ordovician and the Ludlow (Fig. 10).
Summary. Mean values of species richness
for each habitat are presented in Figure 11, using S, rather than E(Sn) in order to maximize
coverage across the environmental spectrum
TRILOBITE SPECIES DIVERSITY
631
FIGURE 11. Mean species richness per habitat for the
Upper Cambrian (C), Middle–Upper Ordovician (O),
Llandovery (Ll), Wenlock (W), and Ludlow (Lu). Values
are based on nonrarefied data. Cambrian data are from
Westrop and Adrain 1998a.
facies record a dramatic recovery, but sparse
data from the Ludlow hint at a major drop in
diversity, possibly to the lowest levels in the
Lower Paleozoic.
Intercontinental Comparisons
FIGURE 10. Frequency distribution of species richness
of collections from Ordovician and Silurian basinal facies.
in each sample interval. As also demonstrated
using frequency distributions, there is no evidence for changes in alpha diversity in the
nearshore and basinal facies between the
Cambrian and the Silurian. In shallow and
deep subtidal facies, maximum alpha diversity is attained in the Upper Ordovician and
Silurian, respectively, rather than the Cambrian. In shallow subtidal facies, a decline in diversity is evident in the Silurian following an
Ordovician peak, although it does not fall below Cambrian levels. In the deep subtidal, Ordovician species richness exceeds Cambrian
levels, and there is a decline into the Llandovery. Wenlock collections from deep subtidal
Shallow Subtidal Facies. Collections from
the Middle and Upper Ordovician (Fig. 12)
show high species richness in all paleocontinents; combined Ordovician data for Laurentia and Baltica, the regions with the largest
numbers of samples, are not significantly different (Table 3). Combined Middle and Upper
Ordovician collections from the remaining regions are significantly more diverse than
those from Laurentia (Table 3). In Laurentia,
Middle and Upper Ordovician diversities are
at comparable levels (Table 3) and Middle Ordovician diversity does not differ significantly
(Table 3) from the Cambrian data published
by Westrop and Adrain (1998a). There are no
net changes between the Ordovician and Silurian of Laurentia: species richness in the
Llandovery is not significantly different from
that in the Middle Ordovician (Table 3); a
small downward shift in modal species richness in the Wenlock (Fig. 12) is not significant
(Table 3). There are few Ludlow collections,
but all fall in the upper half of the range for
the Wenlock; combined data for the Wenlock
and Ludlow are indistinguishable from the
Middle Ordovician and Llandovery data (Table 3).
There are fewer collections available from
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JONATHAN M. ADRAIN ET AL.
TRILOBITE SPECIES DIVERSITY
Baltica (Fig. 12) and all but one of those from
the Ordovician lack the relative abundance
data necessary to perform rarefaction. There is
no significant difference in number of species
(S) between the Middle and Upper Ordovician
(combined data) and the Llandovery (Table 3).
However, both Wenlock and Ludlow levels are
below those for the Ordovician of Baltica (Table 3) and the Middle Ordovician of Laurentia
(Table 3); Wenlock and Ludlow diversities of
Baltica are not significantly different (Table 3).
There are no quantitative data available for the
Upper Cambrian of Baltica, but species richness of Wenlock and Ludlow collections is not
significantly different from that of collections
from the Upper Cambrian of Laurentia (Table
3).
Data are sparse for other provinces (Fig. 12),
although East Avalonia suggests no major
change in species richness until the Ludlow.
Deep Subtidal Facies. In the Ordovician,
peak diversity occurs in Laurentia, although
all paleocontinents for which we have data
show high species richness (Fig. 13). Because
most of the deep subtidal data are from Laurentia, temporal changes for that continent are
identical to those established for the ‘‘global’’
compilation, with successive falls in species
richness between the Middle and Upper Ordovician (Table 3; nonrarefied data only) and
between the Upper Ordovician and Llandovery (Table 3; rarefied data using an M-W test
only). Llandovery species richness is significantly lower than Middle Ordovician values
(Table 3) but is indistinguishable from the
Laurentian Late Cambrian deep subtidal data
published by Westrop and Adrain (1998a) (Table 3). The Wenlock of Laurentia shows a spectacular recovery to levels of diversity that exceed those of the Middle Ordovician (Table 3;
rarefied data only); sparse data suggest a Laurentian crash in deep-subtidal species richness
in the Ludlow. The number of collections
available for East Avalonia is small (Fig. 13),
633
but they also hint at a drop below Ordovician
levels in the Ludlow.
Summary. Comparisons between various
paleocontinents are summarized in Figure 14,
in which species richness is expressed by
mean values. Other regions display levels of
Ordovician diversity that are comparable to
those of Laurentia. In Laurentia, the modest
post-Llandovery fall in shallow-subtidal species richness is not significant (see above) and
the sharper Ludlow decline in deep-subtidal
diversity is based on only three collections.
Equally sparse data from the Ludlow of East
Avalonia show diversity minima in both shallow and deep subtidal settings. The decline in
shallow-subtidal species richness in Baltica,
however, is significant (see above), with Ludlow levels almost half of those of the Ordovician.
Response to the End-Ordovician Extinction
At series-level resolution, there is only muted response in the alpha diversity data to the
end-Ordovician extinction: Llandovery shallow-subtidal species richness is remarkably
high in Laurentia (Fig. 12), and even the Llandovery drop in the deep subtidal (Fig. 13) appears to be part of a more protracted decline.
However, it is possible that the relatively
coarse stratigraphic resolution may in fact be
obscuring the impact of the end-Ordovician
extinction. To bring the pattern of diversity
change into sharper focus, we conducted a
separate, stage-level analysis of collections
from Laurentia, the only paleocontinent for
which we have data from the Ordovician/Silurian boundary interval.
Shallow Subtidal Facies. Recast at the stage
level of stratigraphic resolution, the Laurentian data provide evidence of a decline in shallow-subtidal species richness in the Ordovician/Silurian boundary interval (Fig. 15).
However, the recovery of species richness appears to have been rapid, and by the late
←
FIGURE 12. Frequency distributions of species richness (upper set of histograms) and rarefied data [E(Sn), at a
standard sample size of 90 individuals; lower set of histograms] of Ordovician and Silurian shallow subtidal collections from various paleocontinents. The ‘‘other’’ category combines collections from Armorica, Gondwana (Australia), and North and South China.
634
JONATHAN M. ADRAIN ET AL.
TRILOBITE SPECIES DIVERSITY
635
FIGURE 14. Mean species richness per habitat for Upper Cambrian (C), Middle–Upper Ordovician (O), Llandovery
(Ll), Wenlock (W), and Ludlow (Lu) collections from Laurentia, Baltica, East Avalonia and North and South China.
Values are based on nonrarefied data. For the Cambrian, data from Laurentia are from Westrop and Adrain 1998a,
and data from East Avalonia (shallow subtidal) are compiled from range charts in Rushton 1982.
Rhuddanian–Aeronian, preextinction Ordovician levels had been attained (Table 4). A
small number of collections in the succeeding
Telychian stage have the same mode as the
Late Rhuddanian–Aeronian, and pooled data
for these two sample intervals are indistinguishable from the Ordovician distribution
and the Wenlock (Table 4).
Deep Subtidal Facies. A few collections from
Laurentian deep subtidal facies also show a
marked downward shift in modal diversity in
the Ordovician/Silurian boundary interval
(Fig. 15). The recovery is, however, more protracted than in shallow subtidal facies, with
late Rhuddanian–Aeronian (Table 4; M-W test
only) and Telychian (Table 4) species richness
remaining below that of the Middle–Late Ordovician. By the Wenlock, diversity had recovered completely and actually exceeded Middle–Upper Ordovician levels (Table 4; rarefied
data only). The apparent difference in the rate
of recovery may be related to the fact that deep
subtidal diversity was greater than shallow
subtidal diversity during the Middle–Upper
Ordovician (Table 4), so that the there was a
greater deficit to be regained in deep-water facies following the end-Ordovician extinction.
This is borne out by the fact that Late Rhud-
←
FIGURE 13. Frequency distributions of species richness (upper set of histograms) and rarefied data [E(Sn), at a
standard sample size of 90 individuals; lower set of histograms] of Ordovician and Silurian deep subtidal collections
from various paleocontinents. The ‘‘other’’ category combines collections from Armorica, Gondwana (Australia),
and North and South China.
636
JONATHAN M. ADRAIN ET AL.
FIGURE 15. Frequency distributions of species richness and rarefied data [E(Sn), at a standard sample size of 90
individuals] of Laurentian collections from Ordovician and Silurian shallow subtidal facies (left) and deep subtidal
facies (right).
danian–Telychian species richness was not
significantly different between shallow and
deep subtidal facies (Table 4). Thus, the more
extended period of recovery in deep subtidal
facies seems to be a by-product of the onshoreoffshore diversity gradient in trilobite biofacies.
Discussion
The single most striking pattern to emerge
from the results is the presence of high levels
of trilobite alpha diversity in all major habitats, even in the wake of the great end-Ordovician mass extinction. Silurian diversity, even
where there is evidence of a decline in species
richness in the Wenlock or Ludlow, did not
drop below Upper Cambrian levels. Trilobite
diversity in deep subtidal facies reached an
all-time maximum during the Wenlock. We
have commented earlier (Adrain et al. 1998;
Westrop and Adrain 1998b) upon the apparent decoupling of global clade and local ecological diversity, based on patterns evident in
the Middle and Upper Ordovician. The Silurian data provide definitive evidence of this
phenomenon: after the extinction, alpha diversities soon returned to preextinction levels
in all environments, despite a sudden and unreversed loss of about one half of global taxonomic diversity (Adrain et al. 1998: Fig. 1).
This mismatch between alpha diversity patterns and global taxonomic diversity likely reflects controls at hierarchical levels above
those that regulate species richness in local
habitats. That is, it must reflect a reduction in
between-habitat (beta) diversity and/or in
TRILOBITE SPECIES DIVERSITY
biogeographic differentiation of faunas (gamma diversity). Determining the relative roles
of these two components in the decline in taxonomic diversity is a subject for further research, but some preliminary observations can
be made. We suggest that beta diversity is likely to be the least important contributor. Quantitative studies of Upper Cambrian (Ludvigsen and Westrop 1983) and Middle Ordovician (Chatterton and Ludvigsen 1976; Ludvigsen 1978) biofacies reveal no marked changes
in the degree of environmental partitioning.
Silurian work has thus far been nonquantitative, but several studies (e.g., Thomas 1979;
Chlupáč 1987) indicate that environmental
distribution patterns reflect a spectrum of biofacies comparable to those that have been described from the Cambrian and Ordovician.
Certainly, there is no evidence for the kind of
profound shift in patterns of habitat occupancy that would be necessary to account fully for
the Ordovician drop in global diversity.
By contrast, studies of trilobite ‘‘provinces’’
or ‘‘realms’’ provide evidence for falling levels
of Ordovician biogeographic differentiation
(e.g., Whittington and Hughes 1972; Cocks
and Fortey 1988) as Baltica and East Avalonia
approached Laurentia, and the Silurian has
long been recognized as a time of maximum
cosmopolitanism. In addition, climatic change
during the Hirnantian also led to a breakdown of biogeographic differences, especially
in shallow-water facies (Owen 1986). Thus, a
full understanding of diversity history of trilobites demands a hierarchical approach, and
available data suggest that changes in global
taxonomic diversity of trilobites are not the result of ecological changes in local habitats.
Rather, movements of paleocontinents, along
with Late Ordovician climatic deterioration,
appear to be primary controlling factors.
The most controversial (Miller et al. 1998)
aspect of our earlier study (Westrop and Adrain 1998a) was the demonstration that onshore Laurentian trilobite diversities did not
decline in the wake of the Ordovician Radiation. The expanded data set compiled for this
study corroborates our earlier conclusions
concerning patterns of species alpha diversity
during the Lower Paleozoic in Laurentia.
There is no evidence to support declining al-
637
pha diversity in any habitat between the Upper Cambrian and the Upper Ordovician.
Nearshore and carbonate buildup settings
show no change, whereas shallow-subtidal facies record peak alpha diversity in the Upper
Ordovician and deep subtidal facies in the Silurian, rather than in the Cambrian. One of the
possibilities raised by Miller et al. (1998: p.
524) was that Laurentian patterns may not be
representative of global patterns. The global
survey presented herein, however, indicates
that comparable levels of shallow and deep
subtidal alpha diversity are recorded in Ordovician collections from other paleocontinents. All regions for which data are available
corroborate an increase in shallow-subtidal
trilobite diversity from Middle to Upper Ordovician.
Silurian diversity trajectories do differ between Laurentia and Baltica in shallow subtidal facies, the only habitat type for which we
have comparative data. The reasons for a Silurian decline in Baltica but not in Laurentia
are unclear, but these interregional differences
parallel the observations of Miller (1997) and
Jablonski (1998), who have documented differences in diversity histories between paleocontinents during the Ordovician Radiation
and during the early phases of the recovery
from the Cretaceous/Tertiary extinction, respectively. Differences in the pace of recovery
from the end-Ordovician extinction between
shallow and deep subtidal facies in Laurentia
appear to be the legacy of an offshore-directed
diversity gradient. The deep subtidal habitats
that harbored more species before the extinction took somewhat longer to regain preextinction diversity levels.
The results of this study provide further
support for the suggestion (Westrop et al.
1995; Westrop and Adrain 1998a) that the apparent decline in relative importance of trilobites in paleocommunities during and after
the Ordovician Radiation is essentially a passive process of dilution. In a recent paper, Li
and Droser (1999) attempted to use changes in
shell bed composition and abundance in the
Lower and Middle Ordovician of the Great
Basin to support their assertion that trilobites
became less common in shallow-water environments as brachiopods and other groups di-
638
JONATHAN M. ADRAIN ET AL.
versified. That is, the apparent decline in trilobites is assumed to reflect a real fall in absolute abundance. However, the data presented by Li and Droser (1999: Figs. 6, 9) do not
provide compelling evidence for their interpretation. The percentage of shell beds in the
Great Basin sequence that are dominated by
trilobites declines during the Ibexian and
drops sharply in the Whiterockian (Li and
Droser 1999: Fig. 6). However, the use of percent abundance is compromised by a dramatic, nearly fivefold increase in the total number
of shell beds in the Whiterockian (Ibexian, n
5 128; Whiterockian, n 5 698 [Li and Droser
1999: Fig. 6]). The total number of shell beds
in the basal Ibexian House Limestone (n 5 19)
is an order of magnitude lower than the peak
value for the Whiterockian (Kanosh Shale, n 5
377), so the Kanosh Shale actually contains
more trilobite beds, despite their much lower
percent abundance. The primary signal in Li
and Droser’s data is the profound expansion
in the number and type of shell beds, reflecting a broadening of community composition
during the Ordovician Radiation. As conceded by Li and Droser (1999: p. 229), at least part
of the increase in the number of shell beds in
the Whiterockian may be related to the appearance of taxa, such as calciate brachiopods,
with more durable skeletons that facilitate the
formation of shell concentrations.
Trilobite beds are relatively rare throughout
the entire Lower–Middle Ordovician sequence of the Great Basin, as demonstrated by
Li and Droser’s (1999: Fig. 9) bar chart of the
number of brachiopod and trilobite beds from
inner to middle carbonate-ramp facies (i.e.,
shallow-water facies), in which the data are
normalized for differences in stratigraphic
thicknesses in sample units. From this chart,
the Early Ibexian House Limestone yields approximately 0.9 trilobite beds per 10 m of strata (0.9/10 m). This rises to 1.3/10 m in the
overlying Fillmore Formation and reaches
1.9/10m in the youngest Ibexian WahWah
Formation. In the Early Whiterockian Juab
Limestone, frequency of trilobite beds drops
to about 0.7/10 m, reaching a minimum of
about 0.5/10 m in the Kanosh Shale, only to
return to 0.7/10 m in the Lehman Formation.
We are not unbiased in our perception, but we
find it difficult to view this change as recording a significant decline in the absolute abundance of trilobites: the difference between the
two end points (House and Lehman) is only
0.2/10 m, which is far less than the variability
within the Ibexian (House and WahWah: 1.0/
10 m). Certainly, it is far less robust than the
change in brachiopod beds, in which the oldest Ibexian and youngest Whiterockian units
differ by an order of magnitude (approximate
values read from Li and Droser 1999: Fig. 9 are
House, 0.4/10 m; Fillmore, 0.9/10m; WahWah,
0.9/10 m; Juab, 3.9/10 m; Kanosh, 10.0/10 m;
Lehman, 9.4/10 m). These data can be interpreted with equal justification as recording a
sharp increase in the number of brachiopod
beds, with little or no change in the number of
trilobite beds. This pattern bears a striking
similarity to the record of the Ordovician Radiation in nearshore environments, as expressed by the number of species present
(Westrop et al. 1995: Fig. 4). In the nearshore,
relative stasis in the number of trilobite species and diversification in other groups is the
signature of the radiation. We do not see any
compelling evidence to suppose that species
diversity and abundance of trilobites, or any
other taxon, is ‘‘decoupled’’ in the manner
proposed by Li and Droser (1999), although
‘‘decoupling’’ of local and global diversity
patterns is to be expected in a hierarchical system. In our opinion, a passive dilution model
driven by radiation of members of the Paleozoic fauna remains the most parsimonious explanation of the changes in relative importance of trilobites during the Ordovician.
Conclusions
The stability of species alpha diversity of
lower Paleozoic trilobites documented in this
study stands in sharp contrast to the decline
in relative importance of the group following
the Ordovician Radiation. This pattern can be
understood as a simple consequence of the
great expansion in composition of marine
communities as groups such as calciate brachiopods diversified rapidly. A variety of authors have emphasized the hierarchical nature
of ecological (e.g., Valentine 1973; ONeill et al.
1986) and evolutionary (e.g., Eldredge 1996)
patterns and processes, and the disjunct
TRILOBITE SPECIES DIVERSITY
changes in local species richness and global
clade-level diversity are a striking validation
of this approach. At the highest hierarchical
levels, diversity was influenced by changing
geography and climate during the Late Ordovician. The data generated in this study indicate that a rapid rebound of trilobite alpha
diversity followed the end-Ordovician extinction, whereas global clade-level diversity remained depressed in a Silurian world characterized by lower levels of provinciality. Finally, the data hint at subtle differences in trajectories between continents, suggesting that
unique, historical factors may also contribute
to diversity patterns.
Acknowledgments
Primary responsibility for the scientific content of this work is assumed by Adrain and
Westrop, the order of whose names is arbitrary and does not reflect seniority. We are
grateful to P. D. Lane (University of Keele) for
providing copies of the Ph.D. theses of Y.
Howells and G. J. Helbert. R. L. Anstey and N.
C. Hughes provided helpful comments on an
earlier draft of the manuscript.
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Appendix
Collections Used in Analysis
Information for each entry is given in the following order:
rock unit, age, geographic information, reference, type of preservation (calcareous, silicified, or moldic), gross lithology, environmental assignment, paleocontinent. Individual collections
from the same unit are listed separately. n 5 number of individuals (where a plus sign is used, the number is derived from
a semiquantitative chart and is a minimum estimate); S 5 number of species; E(Sn) 5 expected number of species at a sample
size of 90 individuals, using rarefaction. The collections given
below were supplemented in all analyses by the Middle and
Late Ordovician collections reported by Westrop and Adrain
(1998a: Appendix).
Middle Ordovician
Ardwell Flags Formation, Caradoc, Girvan area, Scotland
(Tripp 1980a), molds, deep subtidal, Laurentia (Midland
Valley Terrane).
Ardmillan, blue-gray siltstone and blocky to nodular mudstone [n 5 438, S 5 34, E(Sn) 5 20.65]
Pinmery, dark blue mudstone [n 5 127, S 5 22, E(Sn) 5 19.88]
Pinmore, greywacke [n 5 57, S 5 25]
Balclatchie Conglomerate, Caradoc, Penwhapple Burn, Girvan
area, Scotland (Tripp 1980a), molds, siltstone, deep subtidal, Laurentia (Midland Valley Terrane). [n 5 385, S 5
39, E(Sn) 5 27.03]
Balclatchie Mudstone, Caradoc, Girvan area, Scotland (Tripp
1980a), molds, deep subtidal, Laurentia (Midland Valley
Terrane).
Dalfask, blue-gray mudstone [n 5 117, S 5 21, E(Sn) 5 19.58]
Dow Hill, blue-gray nodular mudstone [n 5 802, S 5 30, E(Sn)
5 16.67]
Laggan Burn, calcareous siltstone and mudstone [n 5 81, S 5
17]
Beianzhuang Formation, late Arenig, China (Zhou and Fortey
1986), calcareous, dolomitic limestone, nearshore, North
China.
Changshangou, Zhaogezhuang, Tangshan City, Hebei Province [S 5 2]
Hanjia, Jiagou, Shuxian County, Anhui Province [n 5 221 , S
5 4]
Bromide Formation, Mohawkian, Geological Enterprises Quarry, Criner Hills, Carter County, southern Oklahoma (Westrop unpublished), calcareous, limestone, shallow subtidal, Laurentia. [n 5 95, S 5 10, E(Sn) 5 9.84]
Chedao Formation, Chedao, Huanxian, Gansu, northwest China (Zhou and Dean 1986), calcareous, limestone, deep
subtidal, North China
Bed 4, early Caradoc (Nemagraptus gracilis Zone) [S 5 14]
Bed 12, Caradoc [S 5 15]
Confinis Flags Formation, Llanvirn (murchisoni Zone), Stinchar Valley, Girvan area, Scotland (Tripp 1962), Laurentia
(Midland Valley Terrane).
Bougang, molds, calcareous sandstone and siltstone, shallow
subtidal [n 5 1341, S 5 8]
Kirkdominae, molds, decalcified mudstone, deep subtidal, [n
5 2751 , S 5 23]
Minuntion, calcareous sandstone and siltstone, shallow subtidal [n 5 671 , S 5 13]
Contaya Formation, Llanvirn (murchisoni Zone), eastern Peru
(Hughes et al. 1980), molds, shale, slope/basin, South
America. [S 5 4]
Craighead Limestone Formation, Caradoc (Dicranograptus
clingani Zone), Craighead Quarry, Girvan area, Scotland
(Tripp 1980b), Laurentia (Midland Valley Terrane).
main formation, calcareous, limestone, marginal buildup, [n
5 102, S 5 20, E(Sn) 5 18.89]
Kiln Mudstone Member, mold, mudstone, deep subtidal [n 5
640, S 5 29, E(Sn) 5 19.34]
Sericoidea Mudstone Member, molds, mudstone, shallow
subtidal [n 5 244, S 5 7, E(Sn) 5 6.33]
Craig-y-glyn Group, early Caradoc, Berwyn Hills, north Wales
642
JONATHAN M. ADRAIN ET AL.
(MacGregor 1962), molds, tuffaceous sandstone and limestone, shallow subtidal, East Avalonia. [n 5 824, S 5 15,
E(Sn) 5 8.32]
Dawangou Formation, Dawangou, Kalpin, northwest Tarim,
Xinjiang, China (Zhou et al. 1998: Text-fig. 2), calcareous,
limestone, deep subtidal, Tarim.
Collection NJ 294 (late Arenig; Baltoniodus aff. navis Zone) [n
5 621 , S 5 11]
Collection NJ 297 (early Llanvirn, Eoplacognathus suecicus
Zone) [n 5 811, S 5 9]
Collection NJ 298 (early Llanvirn, Eoplacognathus suecicus
Zone) [n 5 621, S 5 10]
Doularg Formation, Gorse Member, early Caradoc (Nemagraptus gracilis Zone), Plantation Burn, Stinchar Valley, Girvan
area, Scotland (Tripp 1965; Ingham and Tripp 1991),
molds, decalcified limestone nodules in mudstone, deep
subtidal, Laurentia (Midland Valley Terrane) [n 5 210, S
5 32, E(Sn) 5 22.88]
Elnes Formation, Llanvirn, Oslo region, Norway (Wandås
1984), calcareous, shallow subtidal, limestone, Baltica.
Furnes [S 5 21]
Helskjar {S 5 12]
Hovodden [S 5 8]
Vikersund [S 5 15]
Fengfeng Formation, early Caradoc, China (Zhou and Fortey
1986), calcareous, limestone, nearshore, North China.
Fengfeng, Handan City, Hebei Province [n 5 101 , S 5 1]
Xiaoyu, Gufang, Fuping County, Shaanxi Province [n 5 101 ,
S 5 1]
Furuburget Formation, Caradoc, Hadeland, Norway (Harper
and Owen 1984; Harper et al. 1984: Fig. 4), molds, interbedded shale and limestone, deep subtidal, Baltica. [n 5
201, S 5 14, E(Sn) 5 11.77]
Great Paxton Borehole, unnamed strata, Llanvirn (Didymograptus murchisonia Zone), Cambridgeshire, England (Rushton
and Hughes 1981), molds, silty and sandy mudstone, deep
subtidal, East Avalonia. [n 5 763, S 5 12, E(Sn) 5 10.34]
Juab Formation, early Whiterock, Ibex area, western Utah, USA
(Fortey and Droser 1996), calcareous, limestone, shallow
subtidal, Laurentia.
Section J, 8 m from base of formation [S 5 7]
Section J, 38 m from base of formation [S 5 11]
Kirkcolm Formation, Caradoc, Kilbucho, Southern Uplands,
Scotland (Owen and Clarkson 1992), molds, micaceous
mudstone, deep subtidal, Laurentia (Southern Uplands
Terrane). [n 5 78, S 5 14]
Knockerk Formation, Grangegeeth area, eastern Ireland (Romano and Owen 1993), Laurentia (Grangegeeth Terrane).
Brickworks Quarry Shale Member, ‘‘Tretaspis Bed,’’ molds,
shale, deep subtidal [n 5 251, S 5 16, E(Sn) 5 12.37]
Knockerk House Sandstone Member, molds, tuffaceous sandstone, shallow subtidal [n 5 19, S 5 8]
Komstad Limestone, late Arenig, bed 122, Killeröd, Scania,
Sweden (Nieslen 1995: Table 6), calcareous, limestone,
shallow subtidal, Baltica. [n 5 98, S 5 11, E(Sn) 5 10.73]
Lower Balclatchie Group, Caradoc (lower Diplograptus multidens
Zone), Laggan Burn, Girvan area, Scotland (Harper and
Owen 1986), molds, siltstone, slope/basin, Laurentia
(Midland Valley Terrane). [S 5 1]
Machiakou Formation, Llanvirn, China (Zhou and Fortey
1986), calcareous, limestone, nearshore, North China.
Daoqing, Hunjiang City, Jilin Province [n 5 211, S 5 3]
Laohushan, Xiaoxian County, Anhui Province [n 5 111,
S 5 2]
Mingan Formation, late Whiterock (early Caradoc), Mingan Islands, Gulf of St. Lawrence, Quebec, Canada (Shaw 1980),
calcareous, limestone, Laurentia.
Locality Qu-2, nearshore [n 5 14, S 5 1]
Locality Qu-5, shallow subtidal [n 5 92, S 5 11, E(Sn) 5 11.00]
Locality N-1, shallow subtidal [n 5 84, S 5 8]
Locality N-3, shallow subtidal [n 5 157, S 5 16, E(Sn) 5 15.52]
Nakholmen Formation, Caradoc (low Dicranograptus clingani
Zone) Bunnefjord, Oslo region, Norway (Harper et al.
1984: Fig. 4), molds, shale, deep subtidal, Baltica.
Oslo-Baerum [n 5 67, S 5 5]
Asker [n 5 70, S 5 10]
Norderhov Formation, Caradoc, Vestbråten, Ringerike, Oslo region, Norway (Owen and Harper 1982; Harper et al. 1984),
mold, shale and limestone nodules, deep subtidal, Baltica.
[n 5 84, S 5 11]
Shelve Formation, Shelve Inlier, Salop and Powys, England and
Wales (Dean in Whittard 1967; Whittard 1979), molds,
shale, deep subtidal, East Avalonia.
Mytton Member, late Arenig (Didymograptus hirundo Zone)
[n 5 811, S 5 11]
Hope Member, Llanvirn (Didymograptus bifidus Zone) [n 5
10001, S 5 36]
Stapeley Volcanic Member, Llanvirn (Didymograptus bifidus
Zone) [S 5 21]
Shihtzupu Formation, Llanvirn (Llandeillian), Zunyi, Guizhou
Province, China (Zhou et al. 1984), calcareous, shallow
subtidal, South China.
Horizon 5, calcareous mudstone [n 5 721, S 5 18]
Horizon 7, argillaceous limestone [n 5 451 , S 5 18]
Summerford Group, Caradoc, Squid Cove, New World Island,
Newfoundland, Canada (Dean 1971a), calcareous, dark
gray limestone, deep subtidal, Laurentia. [S 5 17]
Superstes Mudstone Formation, early Caradoc (Nemagraptus
gracilis Zone), Girvan area, Scotland (Tripp 1976; Tripp et
al. 1981), molds, decalcified limestone nodules in graygreen mudstone, deep subtidal, Laurentia (Midland Valley
Terrane).
Aldons Quarry (Tripp 1976 p. 370–371) [n 5 859, S 5 66, E(Sn)
5 33.39]
Craigneal (Tripp et al. 1981 p. 23) [n 5 217, S 5 25, E(Sn) 5
19.23]
unnamed strata, early Caradoc (upper Pygodus anserinus Zone
or lower Amorphognathus tvaerensis Zone), unnamed
mountain east of Mt. Burgess, northern Yukon Territory,
Canada (Ludvigsen 1980), calcareous, limestone, slope/
basin, Laurentia. [S 5 4]
Upper Balclatchie Group, Caradoc, Balclatchie, Girvan area,
Scotland (Tripp 1980a), molds, nodular dark-green mudstone, deep subtidal, Laurentia (Midland Valley Terrane).
[n 5 1460, S 5 59, E(Sn) 5 31.26]
Wulongtun Formation, Caradoc, eastern Yilehuli Shan, Heilo,
Ngjiang Province, northeast China (Nan 1985), calcareous,
limestone, shallow subtidal, Northeast China [S 5 13]
Upper Ordovician
Abercwmeiddaw Group, Ashgill (Rawtheyan), between Bala
and Corris, North Wales (Price and Magor 1984: Fig. 2),
molds, calcareous, silty mudstones, East Avalonia.
Locality 2, Craig-Ty-Nant, shallow subtidal [n 5 126, S 5 20,
E(Sn) 5 18.05]
Locality 5, Bwich Siglen and Cregiau Garn-wddog, shallow
subtidal [n 5 315, S 5 26, E(Sn) 5 19.89]
Locality 6, Maes-y-gamfa quarry, deep subtidal [n 5 303, S 5
14, E(Sn) 5 10.16]
Locality 9, Abercwmeiddaw quarry, deep subtidal [n 5 64, S
5 16]
Bancs mixtes, late Caradoc, near Almadén, eastern Sierra Morena, Spain (Hammann 1976), molds, sandstone, shallow
subtidal, Iberia.
Locality Al.I [n 5 311, S 5 13, E(Sn) 5 10.10]
643
TRILOBITE SPECIES DIVERSITY
Locality Co.Ia [n 5 123, S 5 8, E(Sn) 5 7.59]
Bohdahlec Formation, late Caradoc or early Ashgill, Prague Basin, Czech Republic (Vanêakek and Vokáč 1997), molds,
shale, deep subtidal, Perunica. [n 5 1551, S 5 26, E(Sn) 5
16.64]
Bønsnes Formation, late Ashgill, Ringerike, Oslo region, Norway (Owen 1981: Table 1), calcareous, rubbly limestone
and shale, deep subtidal, Baltica. [S 5 20]
Chair of Kildare Limestone, locality 14, near Kildare, County
Kildare, Republic of Ireland (Dean 1971b, 1974, 1978), calcareous, limestone, shelf margin buildup, East Avalonia.
[S 5 50]
Cystoid Limestone, Ashgill, Iberian Chains, east-central Spain
(Hammann 1992), molds, limestone, shallow subtidal,
Iberia.
Locality Reb I [n 5 415, S 5 24, E(Sn) 5 16.44]
Locality Reb II [n 5 671, S 5 27, E(Sn) 5 17.28]
Locality L3 [n 5 113, S 5 13, E(Sn) 5 12.15]
Locality A1 [n 5 331, S 5 31, E(Sn) 5 19.57]
Frankfort Shale, Beecher’s Trilobite Bed, Cincinnati, Cleveland’s Glen, near Rome, New York (Cisne 1973: Table 1),
pyritized, siltstone, basinal, Laurentia. [n 5 650, approx.,
S 5 4]
Galets Formation, Cincinnati (Edenian), Lac Saint-Jean area,
near Chicoutimi, Quebec, Canada (Desbiens and Lespérance 1989: Table 1), calcareous, limestone, shallow subtidal, Laurentia. [S 5 9]
Gamme Formation, Ashgill (Cautleyan-Rawtheyan), Hadeland,
Oslo region, Norway (Owen 1981: Table 1), calcareous,
rubbly limestone, deep subtidal, Baltica. [S 5 16]
Grimsøya Formation, early Ashgill (Pusgillian), Oslo-Asker,
Oslo region, Norway, (Owen 1981: Table 1), calcareous,
limestone, shallow subtidal, Baltica. [S 5 10]
Husbergøya Formation, Ashgill (Rawtheyan), Oslo region, Norway (Owen 1981: Table 1), molds, shale, deep subtidal,
Baltica. [S 5 20]
Kjørrven Formation, Ashgill (Rawtheyan), Hadeland, Oslo region, Norway (Owen 1981: Table 1), calcareous, limestone
and siltstone, shallow subtidal, Baltica. [S 5 27]
Langåra Formation, Ashgill (Rawtheyan-Hirnantian), Oslo region, Norway (Owen 1981: Table 1), calcareous, shale and
limestone, deep subtidal, Baltica. [S 5 38]
Langøyene-Langåra Formations, Ashgill (Hirnantian), OsloAsker, Oslo region, Norway (Owen 1981: Table 1), molds,
sandstone and limestone, shallow subtidal, Baltica. [S 5
16]
Langøyene Formation, Ashgill (Hirnantian), Ringerike, Oslo
region, Norway (Owen 1981: Table 1), molds, sandstone,
nearshore, Baltica. [S 5 4]
Little East Lake Formation, northwestern Maine, USA (Pollock
et al. 1994: p. 927), molds, sandstone and siltstone, nearshore, Laurentia. [S 5 3]
Lunner Formation, Ashgill, Oslo region Norway (Owen 1981:
Table 1, Text-fig. 2), shale, deep subtidal, Baltica.
Gagnum Member, Pusgillian, Hadeland [n 5 8001 , S 5 22]
Grinda Member, Cautleyan-Rawtheyan, Hadeland [n 5 85–
90, S 5 15]
Padunskij Horizon, late Caradoc, Omulezka River, near Susuman, Kolyma, northeastern Russia (Chugaeva 1975), calcareous, limestone, marginal buildup, Kolyma. [n 5 181,
S 5 20, E(Sn) 5 14.09]
Pointe-Bleue Shales, Cincinnati (Maysvillian), Lac Saint-Jean
outlier, Quebec, Canada (Desbiens and Lespérance 1989:
Table 1), molds, laminated shale, slope/basin, Laurentia.
[S 5 4]
Raheen Formation, late Caradoc, Raheen Stream, Waterford
Harbour, County Waterford, eastern Ireland (Owen et al.
1986: Table 2), molds, mudstone, deep subtidal, East Avalonia. [n 5 551, S 5 16, E(Sn) 5 11.39]
Shipshaw Formation, Cincinnati (Edenian), Lac Saint-Jean area,
near Chicoutimi, Quebec, Canada (Desbiens and Lespérance 1989: Table 1), calcareous, limestone and shale, shallow subtidal, Laurentia.
Unit 1 [S 5 24]
Unit 2 [S 5 10]
Simard Formation, Mohawk-Cincinnati (Shermanian-Edenian),
Lac Saint-Jean area, near Chicoutimi, Quebec, Canada
(Desbiens and Lespérance 1989: Table 1), calcareous, limestone, shallow subtidal, Laurentia.
Unit 2 [S 5 8]
Unit 3 [S 5 7
Unit 4 [S 5 15]
Skogerholmen Formation, Spannslokket Member, Ashgill
(Rawtheyan), Oslo-Asker, Oslo region, Norway (Owen
1981: Table 1), calcareous, limestone, shallow subtidal,
Baltica. [S 5 12]
Sørbakken Formation, Ashgill, Ringerike, Oslo region, Norway
(Owen 1981: Table 1), calcareous, limestone, shallow subtidal, Baltica.
Upper Sørbakken Formation, Rawtheyan [S 5 13]
Lower Sørbakken Formation, Pusgillian-Cautleyan [S 5 9]
Sort Tepe Formation, horizon Z.34, Sort Dere, Zap Valley, Turkey (Dean and Zhou 1988: p. 263), molds, shale and silty
mudstone, deep subtidal, Turkey. [S 5 18]
Stile End Formation, Ashgill (Cautleyan), southern Lake District, England (McNamara 1979: Table 3), molds, calcareous siltstone, nearshore, East Avalonia. [n 5 167, S 5 10,
E(Sn) 5 7.94]
Tangtou Formation, early Ashgill, Jiangsu Province, China
(Tripp et al. 1989: Table 1), molds, calcareous mudstone,
deep subtidal, South China.
Lunshan, lower Tangtou Formation [n 5 192, S 5 17, E(Sn) 5
14.14]
Lunshan, upper Tangtou Formation [n 5 1840, S 5 42, E(Sn)
5 21.89]
Tangshan, upper Tangtou Formation [n 5 61, S 5 23]
Ulunda Mudstone, Skultorp, Mt. Billingen, Västergötland,
south-central Sweden (Bergström 1973: Tables 1, 2), calcareous, siltstone and mudstone, deep subtidal, Baltica. [n
5 106, S 5 21, E(Sn) 5 19.68]
Venstøp Formation, Ashgill (Pusgillian), Oslo region, Norway
(Owen 1981: Table 1), shale, deep subtidal, Baltica.
Oslo, Lower [S 5 7]
Oslo, Upper [S 5 6]]
Ringerike [S 5 11]
Yingan Formation, near Kalpin, southern Xinjiang, northwest
China (Zhou et al. 1995), molds, calcareous and silty shale,
slope/basin, Tarim. [n 5 1231 , S 5 3]
Extinction Interval
Becscie Formation, Fox Point Member, basal Rhuddanian, just
above Ordovician/Silurian boundary, locality AN22, Anticosti Island, Gulf of St. Lawrence, Quebec, Canada,
(Chatterton unpublished), calcareous, limestone, shallow
subtidal, Laurentia. [n 5 92, S 5 5, E(Sn) 5 5.00]
High Mains Formation, Ashgill (Hirnantian), Craighead Inlier,
near Girvan, Scotland (Owen 1986: Table 1), molds, sandstone, shallow subtidal, Laurentia (Midland Valley Terrane).
Horizon H1 [n 5 18, S 5 4]
Horizon H2 [n 5 15, S 5 5]
Whittaker Formation, basal Rhuddanian, near Avalanche Lake,
central Mackenzie Mountains, Northwest Territories, Can-
644
JONATHAN M. ADRAIN ET AL.
ada (Chatterton unpublished), silicified, black limestone,
deep subtidal, Laurentia.
Section AV 4B 111.6 m [n 5 64, S 5 6]
Section AV 4B 111.8 m [n 5 98, S 5 5, E(Sn) 5 4.92]
Section AV 4B, sample bb2 [n 5 97, S 5 6, E(Sn) 5 5.92]
Lower Silurian (Llandovery)
Rhuddanian Stage
Merrimack Formation, lower Member, Anticosti Island, Gulf of
St. Lawrence, Quebec, Canada (Chatterton unpublished),
calcareous, limestone, shallow subtidal, Laurentia. [n 5
74, S 5 3]
Mulloch Hill Formation, Girvan area, Scotland (Howells 1979),
Laurentia (Midland Valley terrane).
Localities 1–7, molds, sandstone and siltstone, shallow subtidal [n 5 117, S 5 11, E(Sn) 5 9.97]
Localities 8,9, molds, siltstone, shallow subtidal [n 5 223, S 5
16, E(Sn) 5 11.88]
Locality 10, molds, mudstone, deep subtidal [n 5 55, S 5 12]
Solvik Formation, Spirodden, Aske, Oslo region, Norway (Helbert 1985), calcareous, limestone, shallow subtidal, Baltica. [n 5 442, S 5 13, E(Sn) 5 10.94]
Whittaker Formation, near Avalanche Lake, central Mackenzie
Mountains, Northwest Territories, Canada (Chatterton
unpublished), silicified, black limestone, deep subtidal,
Laurentia.
Section AV 1 95.5 m [n 5 440, S 5 11, E(Sn) 5 7.49]
Section AV 4B, collections at 128.5 m [n 5 81, S 5 7] and 136.5
m [n 5 37, S 5 7]
Woodland Formation, Locality 18, Girvan area, Scotland (Howells 1979), molds, mudstone, deep subtidal, Laurentia
(Midland Valley Terrane). [n 5 179, S 5 22, E(Sn) 5 16.57]
Aeronian Stage
Jupiter Formation, Anticosti Island, Gulf of St. Lawrence, Quebec, Canada (Chatterton unpublished), calcareous, limestone, shallow subtidal, Laurentia.
Locality An 15, Goeland Member [n 5 297, S 5 14, E(Sn) 5
9.42]
Locality An 18 [n 5 177, S 5 11, E(Sn) 5 9.35]
Locality An 42, Goeland Member [n 5 117, S 5 7, E(Sn) 5
6.88]
Locality An 44, Goeland Member [n 5 228, S 5 12, E(Sn) 5
9.31]
Locality An 49, Richardson/Cybele Members [n 5 233, S 5 7,
E(Sn) 5 5.93]
Locality An 62, Goeland Member [n 5 98, S 5 12, E(Sn) 5
11.49]
Lower Camregan Grits, Girvan are, Scotland (Howells 1979),
Laurentia (Midland Valley Terrane).
Localities 16–17, molds, sandstone, shallow subtidal [n 5 27,
S 5 6]
Locality 19, molds, sandstone, shallow subtidal [n 5 113, S 5
7, E(Sn) 5 6.55]
Newlands Formation, Girvan area, Scotland (Howells 1979),
Laurentia (Midland Valley Terrane).
Localities 11–13, molds, siltstone, deep subtidal [n 5 76,
S 5 8]
Localities 14–15, molds, siltstone, deep subtidal [n 5 1031, S
5 26, E(Sn) 5 12.74]
Saelabon Formation, Hönefoss Road, Oslo region, Norway
(Helbert 1985), calcareous, limestone, shallow subtidal,
Baltica. [n 5 263, S 5 4, E(Sn) 5 3.15]
Solvik Formation, Skytterveien, Oslo region, Norway (Helbert
1985), calcareous, limestone, shallow subtidal, Baltica. [n
5 478, S 5 9, E(Sn) 5 7.48]
unnamed strata, temporary exposure, Gustavsvik, Motala,
southern Sweden (Ramsköld 1994), calcareous, lime mudstone, shallow subtidal, Baltica. [n 5 144, S 5 10, E(Sn) 5
7.63]
Whittaker Formation, near Avalanche Lake, central Mackenzie
Mountains, Northwest Territories, Canada (Chatterton
unpublished), silicified, black limestone, deep subtidal,
Laurentia. Section AV 1 124.5 m [n 5 44, S 5 11]
Wood Burn Formation, Girvan area, Scotland (Howells 1979),
Laurentia (Midland Valley Terrane).
Locality 21, molds, shale, deep subtidal [n 5 95, S 5 14, E(Sn)
5 13.89]
Locality 22, molds, siltstone, deep subtidal [n 5 128, S 5 9,
E(Sn) 5 8.68]
Zelkovice Formation, Hyskov, Prague district, Czech Republic
(Šnajdr 1978), molds, tuffaceous shale and limestone, deep
subtidal, Perunica. [S 5 23]
Telychian Stage
Attawapiskat Formation, Attawapiskat River, northern Ontario
(Westrop and Rudkin 1999), calcareous, stromatoporoidcoral buildup, Laurentia.
Collection 14 [n 5 164, S 5 11, E(Sn) 5 10.36]
Cape Phillips Formation, Twilight Creek, Bathurst Island, arctic Canada (Adrain unpublished), molds, shale, slope/basin, Laurentia. [n 5 501 , S 5 2]
Cape Schuchert Formation, south of Kap Schuchert, Washington Land, North Greenland (Lane 1979: Table 1, with corrections and reassignments herein), calcareous, limestone,
shelf buildup, Laurentia. [n 5 121, S 5 18, E(Sn) 5 15.88]
Drommebjerg Formation, Centrumsø, Kronprins Christians
Land, northeast Greenland (Lane 1972: Table 1), calcareous, limestone, shelf buildup, Laurentia. [n 5 83, S 5 15]
Hopkinton Dolomite, Iowa (Mikulic 1979), molds, dolostone
Laurentia.
Elwood Quarry, Clinton County, shallow subtidal [n 5 62, S
5 12]
Locality John Creek II, deep subtidal [n 52 63, S 5 11]
Locality Lux, deep subtidal [n 5 95, S 5 9, E(Sn) 5 8.95]
Jupiter Formation (lower Telychian), Anticosti Island, Quebec,
Canada (Chatterton unpublished), calcareous, limestone,
shallow subtidal, Laurentia.
Locality An 12 [n 5 295, S 5 15, E(Sn) 5 12.28]
Locality An 78 [n 5 87, S 5 16]
Knockgardner Formation, Girvan area, Scotland (Howells
1979), molds, siltstone, nearshore, Laurentia (Midland
Valley Terrane). [n 5 203, S 5 5, E(Sn) 5 4.69]
Lafayette Bugt Formation, south of Kap Schuchert, Washington
Land, western North Greenland (Lane and Owens 1982:
Table 1), calcareous, limestone, shelf buildup, Laurentia.
[n 5 364, S 5 9, E(Sn) 5 5.94]
Lower Visby Formation, locality Rönnklint 1, Gotland, Sweden
(Ramsköld 1985; L. Ramsköld unpublished), calcareous,
limestone, shallow subtidal, Baltica. [n 5 252, S 5 13,
E(Sn) 5 9.78]
Longmaxi Formation, Tongzi, Wulong, southeastern Sichuan
Province, China (Wang 1989), molds, shale, basinal, South
China. [S 5 2]
Odins Fjord Formation, Peary Land, central North Greenland
(Lane 1988), calcareous, limestone, deep subtidal, Laurentia. [n 5 117, S 5 5]
Richea Sandstone, Tiger Range, Florentine Valley, near Maydena, Tasmania (Holloway and Sandford 1993), molds,
sandstone, shallow subtidal, Australia. [n 5 145, S 5 9,
E(Sn) 5 8.54]
unnamed carbonates, locality BB 131, Illtyd Range, near Wind
River, northern Yukon Territory (Ludvigsen and Tripp
TRILOBITE SPECIES DIVERSITY
1990), calcareous, limestone, shelf buildup, Laurentia. [n
5 29, S 5 11]
Whittaker Formation, near Avalanche Lake, central Mackenzie
Mountains, Northwest Territories, Canada (Chatterton
unpublished), silicified, black limestone, deep subtidal,
Laurentia.
Section AV 1, collections at 320 m [n 5 397, S 5 12, E(Sn) 5
6.58], 336 m [n 5 566, S 5 17, E(Sn) 5 9.12], 341 m [n
5 491, S 5 19, E(Sn) 5 10.35], 346 m [n 5 260, S 5 14,
E(Sn) 5 11.56], 413 m [n 5 268, S 5 17, E(Sn) 5 13.09],
416 m [n 5 90, S 5 12, E(Sn) 5 12.00], 455 m [n 5 96,
S 5 13, E(Sn) 5 12.68]
Section AV 2 47 m [n 5 214, S 5 9, E(Sn) 5 6.61]
Section AV 3 62 m [n 5 270, S 5 14, E(Sn) 5 9.87]
Lower Silurian (Wenlock)
Sheinwoodian Stage
Bruflat Formation, Garntangen, Ringerike, Oslo region, Norway
(Helbert 1985), calcareous, limestone, shallow subtidal,
Baltica. [n 5 60, S 5 4]
Cape Phillips Formation, arctic Canada (Adrain unpublished;
see Adrain 1997, Adrain and Edgecombe 1997 for locality
details), silicified, limestone, deep subtidal, Laurentia.
Baillie-Hamilton Island, Section BH 1, collections at 110 m
(mid-Sheinwoodian, Monograptus instrenuus-Cyrtogratpus kolobus Zone) [n 5 306, S 5 34, E(Sn) 5 25.73], 92
m (late Sheinwoodian, Monograptus perneri-Cyrtogratpus opimus Zone) [n 5 264, S 5 46, E(Sn) 5 29.63]
Cornwallis Island, boulder ABR TTC(3) (late Sheinwoodian,
perneri-opimus Zone) [n 5 152, S 5 30, E(Sn) 5 23.71],
boulder ABR TTD (late Sheinwoodian, perneri-opimus
Zone) [n 5 651, S 5 43, E(Sn) 5 24.16]
Delorme Group, near Avalanche Lake, southern Mackenzie
Mountains, Northwest Territories, Canada (Chatterton
unpublished), silicified, limestone, deep subtidal, Laurentia.
Section AV 4 126T m [n 5 443, S 5 47, E(Sn) 5 30.65]
Section Delorme Range (Perry and Chatterton 1979) [n 5 88,
S 5 15]
Högklint Formation, unit b, Gotland, Sweden (Ramsköld 1985),
calcareous, limestone, shallow subtidal, Baltica.
Locality Kappelshamn 2 [n 5 266, S 5 7, E(Sn) 5 5.88]
Locality Kopparsvik 3 [n 5 111, S 5 8, E(Sn) 5 7.43]
Locality Vattenfallsprofilen 1 [n 5 283, S 5 8, E(Sn) 5 6.54]
‘‘Loose slab from near Visby’’ [n 5 90, S 5 10, E(Sn) 5 10.00]
‘‘Shore 450 m SE of Hälluden, Fleringe parish’’ [n 5 246, S 5
9, E(Sn) 5 7.70]
Kielce Syncline, Swiety Krzyz Mountains, Poland (Tomczykowa 1957), molds, shale, slope/basin, Baltica.
Bardo-Stawy [S 5 5]
Mójcza [S 5 3]
Malmøya Formation, Oslo, Norway (Helbert 1985), calcareous,
limestone, shallow subtidal, Baltica. [n 5 63, S 5 6]
Racine Formation, Horlick Quarry, Racine, Racine County, Wisconsin (Mikulic 1979, except where noted), mold, dolostone, shelf buildup, Laurentia.
Collection 1 [n 5 89, S 5 3]
Collection 2 [n 5 47, S 5 6]
Collection 3 [n 5 33, S 5 5]
Collection 5 [n 5 46, S 5 7]
Collection 6 [n 5 244, S 5 13, E(Sn) 5 11.10]
(Watkins 1993) [S 5 11]
Steinsfjorden Formation, Langøya, Oslo region, Norway (Helbert 1985), calcareous, limestone, shallow subtidal, Baltica. [n 5 301, S 5 10, E(Sn) 5 7.94]
Upper Visby Formation, locality Rönnklint 1, Gotland, Sweden
645
(Ramsköld 1985), calcareous, limestone, shallow subtidal,
Baltica. [n 5 100, S 5 8, E(Sn) 5 7.80]
Wyoming Quarry, near Wyoming, Jones County, Iowa (Mikulic
1979), molds, dolostone, shelf buildup, Laurentia. [n 5 58,
S 5 9]
Homerian Stage
Annascaul Formation, Ballynane Member, Dingle Peninsula,
County Kerry, Ireland (Siveter 1989: Table 1), calcareous,
limestone, shallow subtidal, East Avalonia. [n 5 343, S 5
13, E(Sn) 5 10.73]
Cape Phillips Formation, arctic Canada (Adrain unpublished;
see Adrain 1997, Adrain and Edgecombe 1997 for locality
details), silicified, limestone, deep subtidal, Laurentia.
Baillie-Hamilton Island, Section BH 2 3 m (early Homerian,
Cyrtograptus lundgreni-Monograptus testis Zone) [n 5
97, S 5 27, E(Sn) 5 25.97]
Cornwallis Island, boulder ABR 3TT (early Homerian, lundgreni-testis Zone) [n 5 102, S 5 25, E(Sn) 5 23.52], Section ABR 1 22 m (late Homerian, Pristiograptus ludensis
Zone) [n 5 885, S 5 23, E(Sn) 5 12.31]
Clarita Formation, south-central Oklahoma (T. W. Amsden collection, Oklahoma Museum of Natural History; see Amsden 1968 for locality information), calcareous, limestone,
shallow subtidal, Laurentia.
Old Hunton Townsite, Coal County [n 5 74, S 5 7]
Chimneyhill Creek, Pontotoc County [n 5 66, S 5 7]
Delorme Group, near Avalanche Lake, southern Mackenzie
Mountains, Northwest Territories, Canada (Chatterton
unpublished), silicified, limestone, deep subtidal, Laurentia.
Section AV 4 238T m [n 5 76, S 5 9]
Section AV 5 58–60 m [n 5 305, S 5 31, E(Sn) 5 20.08]
Halla Formation, unit b, locality Hörsne 6, Gotland, Sweden
(Ramsköld 1985), calcareous, limestone, shallow subtidal,
Baltica. [n 5 115, S 5 6, E(Sn) 5 5.47]
Kielce Syncline, Swiety Krzyz Mountains, Poland (Tomczykowa 1957), mold, shale, basinal, Baltica. Three collections
[n 5 2], [n 5 1], [n 5 3]
Mulde Formation, Gotland, Sweden (Ramsköld 1985), calcareous, limestone, shallow subtidal, Baltica.
Locality Blåhäll 1 [n 5 425, S 5 11, E(Sn) 5 8.76]
Locality Bodbacke 1 [n 5 148, S 5 7, E(Sn) 5 6.85]
Locality Sudervik 1 [n 5 132, S 5 11, E(Sn) 5 10.24]
‘‘Shore 190–205 m SW of wind-mill at Skansudd’’ [n 5 129, S
5 8, E(Sn) 5 7.09]
‘‘Shore 50 m NNW of wind-mill at Skansudd’’ [n 5 133, S 5
7, E(Sn) 5 6.79]
‘‘Shore 540–560 m NE of wind-mill at Skansudd’’ [n 5 74, S
5 6]
‘‘Shore 150–180 m SW of wind-mill at Skansudd’’ [n 5 109, S
5 7, E(Sn) 5 6.80]
‘‘Shore 335 m SW of wind-mill at Skansudd’’ [n 5 66, S 5 6]
‘‘Shore 150 m NNW of road junction at Kronvall’’ [n 5 136, S
5 3, E(Sn) 5 3.00]
‘‘Shore 1450–1550 m SSW of road junction at Kronvall’’ [n 5
161, S 5 6, E(Sn) 5 5.60]
Racine Dolomite, Wisconsin and Illinois, USA (Mikulic 1979),
mold, dolostone, Laurentia.
Francy Quarry, southeastern Wisconsin (Watkins 1993), shelf
buildup [S 5 11]
Lehigh, Illinois [n 5 90, S 5 11, E(Sn) 5 11.00]
Moody reef, northern Milwaukee County, Wisconsin, shelf
buildup [n 5 442, S 5 14, E(Sn) 5 11.02]
Menomonee Falls, Waukehsa County, Wisconsin, shallow subtidal [n 5 166, S 5 10, E(Sn) 5 7.03]
646
JONATHAN M. ADRAIN ET AL.
Schoonmaker reef core, northern Milwaukee County, Wisconsin, shelf buildup [n 5 95, S 5 7, E(Sn) 5 6.89]
Schoonmaker reef flank, northern Milwaukee County, Wisconsin, shallow subtidal [n 5 192, S 5 10, E(Sn) 5 8.41]
Slite Formation, Gotland, Sweden (Ramsköld 1985), calcareous,
limestone, shallow subtidal except where noted, Baltica.
Locality Bolarve 1 [n 5 65, S 5 8]
Locality Follingbo 6–8 [n 5 1366, S 5 10, E(Sn) 5 8.28]
Locality Idå 1 [n 5 569, S 5 11, E(Sn) 5 8.66]
Locality Klintebys [n 5 65, S 5 10]
Locality Mojner 3 [n 5 111, S 5 10, E(Sn) 5 9.61]
Locality Robbjäns 1 [n 5 276, S 5 10, E(Sn) 5 8.74]
Locality Solklint 1 (Ramsköld 1991) deep subtidal [S 5 19]
Locality Svarevare 1 [n 5 658, S 5 9, E(Sn) 5 7.83]
Locality Tjäldersholm 1 [n 5 255, S 5 8, E(Sn) 5 7.16]
Locality Valbytte 1 [n 5 338, S 5 15, E(Sn) 5 9.85]
Locality Valleviken 1 [n 5 296, S 5 11, E(Sn) 5 7.96]
St. Clair Limestone, Batesville district, north-central Arkansas
(T. W. Amsden collection, Oklahoma Museum of Natural
History; see Amsden 1968 for locality information), calcareous, limestone, shallow subtidal, Laurentia.
Cason Mine [S 5 12, n 5 95, E(Sn) 5 11.89]
St. Clair Springs [S 5 10, n 5 97, E(Sn) 5 9.92]
Waldron Shale, Indiana, USA (Mikulic 1979), calcareous, shale,
shallow subtidal, Laurentia.
Bryozoan Beds, southeastern Indiana [n 5 66, S 5 12]
Blue Ridge Quarry, Waldron, Indiana [n 5 264, S 5 4, E(Sn)
5 3.34]
Walker Volcanics, Coppins Crossing, Canberra, Australian
Capital Territory, Australia (Chatterton and Campbell
1980), mold, silty mudstone, deep subtidal, Australia. [S
5 16]
Upper Silurian (Ludlow)
Gorstian Stage
Cape Phillips Formation, section ABR 1 30 m, near Abbott River, northwestern Cornwallis Island, arctic Canada (Adrain
unpublished), silicified, limestone, deep subtidal, Laurentia. [n 5 210, S 5 16, E(Sn) 5 14.58]
Cape Phillips Formation, Abbott River, northwestern Cornwallis Island, arctic Canada (Adrain unpublished), molds,
shale, slope/basin, Laurentia. [n 5 13, S 5 1]
Hardwood Mountain Formation, Baker Pond, Maine (Whittington and Campbell 1967: Table 1), silicified, silty limestone, deep(?) subtidal, Laurentia. [n 5 435, S 5 10, E(Sn)
5 8.83]
Hemse Formation, Gotland, Sweden (Ramsköld 1985), calcareous, limestone, shallow subtidal, Baltica.
unit b, Locality Garnudden [n 5 101, S 5 4, E(Sn) 5 3.89]
unit b, Locality Vidfälle 1 [n 5 58, S 5 4]
unit c, Locality Gutenviks 1 [n 5 153, S 5 5, E(Sn) 5 5.00]
Unnamed locality, ditch in Etelhem parish, lower–middle
Hemse Marl. [n 5 170, S 5 9, E(Sn) 5 7.95]
Kielce Syncline, Swiety Krzyz Mountains, Poland (Tomczykowa 1957), mold, shale, basinal, Baltica. [n 5 2]
Ludfordian Stage
Cape Phillips Formation, section BH 2 317 m, southern BaillieHamilton Island, arctic Canada (Adrain unpublished),
calcareous, limestone, deep subtidal, Laurentia. [n 5 70, S
5 4]
Cape Phillips Formation, Snowblind Creek, northeastern Cornwallis Island, arctic Canada (Adrain unpublished), mold,
shale, slope/basin, Laurentia. [n 5 8, S 5 3]
Douro Formation, arctic Canada (Adrain unpublished), calcareous, limestone, shallow subtidal, Laurentia.
Goodsir Creek ‘‘low fauna,’’ eastern Cornwallis Island [n 5
98, S 5 7, E(Sn) 5 6.92]
Garnier Bay, northern Somerset Island [n 5 77, S 5 12]
Prince Alfred Bay, northern Devon Island [n 5 40, S 5 6]
Eke Formation, Gotland, Sweden (Ramsköld 1985), calcareous,
limestone, shallow subtidal, Baltica.
Locality Gannor 1 [n 5 112, S 5 8, E(Sn) 5 7.41]
Locality Lau Backar 1 [n 5 471, S 5 12, E(Sn) 5 9.81]
Hamra Formation, Gotland, Sweden (Ramsköld 1985), calcareous, limestone, shallow subtidal, Baltica.
unit a, Locality Kättelviken 1 [n 5 212, S 5 8, E(Sn) 5 7.62]
unit b, Locality Majstre 1 [n 5 261, S 5 6, E(Sn) 5 4.63]
Hemse Formation, Gotland, Sweden (Ramsköld 1985), calcareous, limestone, shallow subtidal, Baltica.
Hemse Marl NW, Locality Likmide 1 [n 5 103, S 5 7, E(Sn) 5
6.98]
Hemse Marl NW, Locality Snoder 2 [n 5 279, S 5 9, E(Sn) 5
6.98]
Hemse Marl SE, Locality Hulte 3 [n 5 302, S 5 8, E(Sn) 5 5.69]
Lower Bringewood Beds, Welsh Borderland, England (Mikulic
and Watkins 1981: Figs. 4;c-1, 4;c-2), mold, siltstone, shallow subtidal, East Avalonia.
Lower phase of Sphaerirhynchia wilsoni association. [n 5 48, S
5 5]
Mesopholidostrophia laevigata association. [n 5 208, S 5 7, E(Sn)
5 6.65]
Middle Elton Beds, Glassia obovata association, Welsh Borderland, England (Mikulic and Watkins 1981: Figs. 4;c-1, 4;c2), mold, mudstone/shale, deep subtidal, East Avalonia.
Mudstone facies. [n 5 292, S 5 7, E(Sn) 5 5.72]
Laminated shale facies. [n 5 31, S 5 4]
Upper Elton Beds, Welsh Borderland, England (Mikulic and
Watkins 1981: Figs. 4;c-1, 4;c-2), mold, mudstone/siltstone, deep subtidal, East Avalonia. [n 5 43, S 5 4]
Road River Group, Prongs Creek, locality AA 95, Keele Range,
northern Yukon Territory, Canada (Ludvigsen and Tripp
1990), calcareous, limestone, deep subtidal, Laurentia. [n
5 171, S 5 8, E(Sn) 5 7.03]