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SUPPLEMENTARY MATERIAL
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Contents
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Taxon ranges and diversity estimates
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Outcrop area estimates - Methods
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Facies bias analysis
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References
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Table S1 – Facies analysis
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Table S2 – European outcrop data
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Fig. S1 – Relative abundance of cetacean occurrences per rock type
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Taxon ranges and diversity estimates
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The earliest cetaceans most likely evolved in the area of modern Pakistan and India about 55
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million years ago during the early Eocene (Thewissen and Williams 2002), and started to
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spread through Tethys and, ultimately, round the world, during the middle and late Eocene
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(Fordyce 2002). Whilst the oldest sirenians reach a similar age (Domning 2002),
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pinnipedimorphs are somewhat younger, with the oldest fossils dating back only to the late
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Oligocene about 25-27 Ma (Berta 2002). Raw taxon counts for all three groups, sampled at
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the genus level and recorded at the level of the geological stage were downloaded from the
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Palaeobiology Database (http://paleodb.org) on the 05th October 2008, using the group taxon
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names 'Cetacea', 'Pinnipedimorpha' and 'Sirenia', and the following parameters: continents or
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paleocontinents = Europe, time fields = stage. A sampled-in-bin taxon counting protocol was
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used, i.e. genera were not ranged through time intervals in which they had not actually been
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sampled.
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Outcrop area estimates
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European outcrop area was estimated at the level of the geological epoch for marine
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sedimentary rocks ranging in age from the Eocene to the Pleistocene, using the International
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Geological Map of Europe and the Mediterranean Regions 2nd/3rd edition, scale
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1:1.500.000, consisting of 45 separate sheets issued by the German Federal Institute for
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Geosciences and Natural Resources and UNESCO, Hannover 1964-2000. In order to include
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all potential European occurrences of marine mammals, outcrops ranging in age from the
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Eocene to the present were recorded. Approximate outcrop area was obtained for the area
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defined by 11°W (west coast of Ireland), 58°E (Ural mountains), 34°N (south coast of Crete)
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and 72°N (North Cape/Knivskjellodden, Norway), with North Africa, Turkey, the southern
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Caucasus and the area east of the Caspian Sea being excluded. The map was divided into 30 x
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30 km squares aligned to 11°W. For every single square the presence or absence of marine
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sedimentary rock of a given geological epoch, according to the Gradstein et al. (2004)
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geological timescale, was scored. Where an outcrop spanned more than one epoch, rock was
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scored as present for all the epochs covered, with the single exception of rock defined to be
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‘Tertiary and Cretaceous’ in nature, which was assumed to be mostly Palaeocene in age.
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Molasse (post-orogenic deposits formed in depression zones either side of the Alps) was only
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recorded where explicitly defined as marine.
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In order to make fine-scale stage-level comparisons with the diversity estimates
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possible, outcrop area data for a given epoch were apportioned to geological stages within
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that epoch (Gradstein et al. 2004) according to their relative durations, following the
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approach taken by Crampton et al. (2003). Whilst this procedure makes an a priori
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assumption of constant sedimentation rates within epochs, which is unlikely to be accurate, it
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has been speculated that this kind of error will not confound the overall pattern of outcrop
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abundance (Crampton et al. 2003). However, because this study relies on an equal-grid
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sampling method, the apportioned data had to be corrected for the fact that any given map
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square could potentially contain outcrops belonging to more than one stage. To illustrate this,
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suppose two stages of equal length (stages A and B) were represented by outcrops in ten map
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squares each, with five squares being unique to either stage and a further five being shared. If
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outcrop area could be scored at the level of the stage, ten map squares would thus be recorded
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per stage. Yet, with outcrop area being recorded at the level of the epoch with no way of
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distinguishing between stages, only 15 squares would be scored: five unique to stage A, five
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unique to stage B and five in which rock of both ages occurred. If these data were then
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apportioned to stages according to stage duration, as had been done in this paper, only 7.5
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squares would be apportioned to either stage. Whilst this is not a problem within any given
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epoch, since relative proportions should stay the same, this bias will lead to a distorting
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boundary effect at epoch transitions, caused by the varying number of stages constituting
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each epoch. For example, whilst the Oligocene consists of only two stages, the subsequent
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Miocene comprises six. This means that the chance of any given map square containing rocks
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belonging to more than one stage being apportioned to the Chattian (the upper stage of the
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Oligocene) is considerably higher (a chance of 1 in 2) than such a square being apportioned
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to the Aquitanian (the lowest stage of the Miocene, with a chance of 1 in 6), leading to an
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overestimate of Oligocene outcrop area with respect to the Miocene, and thus distortion of
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the overall record. In order to counteract this effect, the number of map squares apportioned
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to each geological stage was multiplied by the total number of stages within the epoch the
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stage was part of. Whilst this approach is oversimplifying the matter in assuming that map
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squares containing rock belonging to more than one stage will always include all stages of
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that epoch, the correction afforded by this should restore the overall pattern of changes in
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outcrop area through time.
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Facies bias analysis
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When analysing groups of taxa as small as a mammalian order, the level of lithological
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resolution of the diversity and outcrop data used may become important. Unlike estimates of
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global diversity, smaller clades may exhibit associations with certain types of rock facies,
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making their stratigraphic distribution non-random (Holland 1995; Marshall 1997).
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Intriguingly, in term of marine animals this type of facies control has been found to apply not
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only to relatively immobile benthic (Dodd and Stanton 1990), but also to a number of
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planktonic and nektonic clades, such as ammonites (Bayer and McGhee 1985) or graptolites
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(Lenz and Xu 1985).
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In order to test whether any of the three groups of marine mammals was associated
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with a particular rock facies, lithological classifications of the deposits yielding marine
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mammal fossils around the world were downloaded for the Eocene, Oligocene, Miocene and
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Pliocene from the Palaeobiology Database on the 24th September 2008, using the group
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taxon names 'Cetacea', 'Pinnipedimorpha' and 'Sirenia', together with the following
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parameters: continents or paleocontinents = global, lithologies = carbonate, mixed and
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siliciclastic. These data were then adjusted for changes in rock type abundance through time
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using the lithological abundance estimates of Ronov et al. (1980).
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Analysis of the cetacean abundance data downloaded from the Paleobiology Database
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showed that, in absolute terms, cetaceans occur more often in siliciclastic rocks than in
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carbonates (Table S1). However, once the data had been adjusted for the varying proportions
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of different rock facies, it became clear that, with exception of the Pliocene, carbonates are
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relatively more abundant in cetacean occurrences (Figure S1), an observation normally
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obscured by the overwhelming abundance of siliciclastic rocks during parts of the Caenozoic.
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In addition, it turned out that rocks of mixed lithology provided the (relative) majority of
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fossils during the Oligocene and the Pliocene. The extent to which carbonates are more
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productive with respect to siliciclastics varied with epoch, with the smallest difference
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observed during the Miocene (Fig. S1). Unfortunately there were not enough data available to
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allow a reliable analysis of the pinnipedimorph and sirenian data. However, pinnipedimorphs
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seems to occur mainly in siliciclastic deposits, whereas sirenians appeared to show a shift
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from carbonates during the Eocene and Oligocene to siliciclastic deposits during the Miocene
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and Pliocene (Table 1).
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The admittedly rather crude facies analysis of the cetacean abundance data performed
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here suggested a relatively greater abundance of cetaceans in carbonates than in siliciclastics.
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However, the difference between these different types of rock was rather variable and
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decreased to a more or less negligible extent during the Miocene. Moreover, even though
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carbonates seemed to yield relatively more cetacean fossils, their low abundance during the
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Caenozoic led to the overprinting of this abundance signal by the relatively less abundant, but
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absolutely much more numerous fossils found in siliciclastic rocks. For these reasons, the
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exclusion of neither type of rock from this analysis seems justified, as exclusion of the
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siliciclastics would mean dumping most of the data, whilst the exclusion of carbonates would
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target the more productive type of rock. This conclusion can be extended to the putative
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trends observed pinnipedimorphs and sirenians. In terms of the former, occurrences seem to
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be concentrated in the most abundant sediment type, anyway, whilst for the latter both
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carbonates and siliciclastic deposits seem to be important. Thus, whilst the relative abundance
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of cetaceans in carbonates and the putative trends in pinnipedimorphs and sirenians warrant
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further research, it was decided to keep both types of rock in the analysis for the time being.
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References
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Bayer, U. and McGhee, G. R. 1985 Evolution in marginal epicontinental basins: the role of
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phylogenetic and ecologic factors (ammonite replacements in the German Lower and
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Middle Jurassic). In Bayer, U. and Seilacher, A. (eds.) Sedimentary and Evolutionary
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Cycles (eds U. Bayer and A. Seilacher). New York: Springer.
9
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Berta, A. 2002 Pinniped Evolution. In Encyclopedia of Marine Mammals (eds W. F. Perrin,
B. Würsig and J. G. M. Thewissen). San Diego: Academic Press.
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Crampton, J. S., Beau, A. G., Cooper, R. A., Jones, C. A., Marshall, B. and Maxwell, P. A.
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2003 Estimating the rock volume bias in paleobiodiversity studies. Science 301, 358-
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360.
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Dodd, J. R. and Stanton, R. J. 1990 Paleoecology: concepts and applications. New York:
Wiley.
Fordyce, R. E. 2002. Cetacean Evolution. In Encyclopedia of Marine Mammals (eds W. F.
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Perrin, B. Würsig and J. G. M. Thewissen). San Diego: Academic Press.
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Gradstein, F. M., Ogg, J. G. and Smith, A. G. et al. 2004 A geologic time scale 2004.
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Cambridge: Cambridge University Press.
Holland, S. M. 1995 The stratigraphic distribution of fossils. Paleobiology 21, 92-109.
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1
2
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Lenz, A. C. and Xu, C. 1985 Graptolite distribution and lithofacies: some case histories. J.
Paleontol. 59, 636-642.
Marshall, C. R. 1997 Confidence intervals on stratigraphic ranges with non-random
distributions of fossil horizons. Paleobiology 23, 165-173.
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Miller, K. G., Kominz, M. A., Browning, J. V., Wright, J. D., Mountain, G. S., Katz, M. E.,
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Sugarman, P. J., Cramer, B. S., Christie-Blick, N. and Pekar, S. F. 2005 The
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Phanerozoic record of global sea-level change. Science 310, 1293-1298.
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Ronov, A. B., Khain, V. E, Balukhovsky, A. N. and Seslavinsky, K. B. 1980 Quantitative
analysis of Phanerozoic sedimentation. Sediment. Geol. 25, 311-325.
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Thewissen, J. G. M. and Williams, E. M. 2002 The early radiations of Cetacea (Mammalia):
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evolutionary pattern and developmental correlations. Annu. Rev. Ecol. Syst. 33, 73-90.
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lithology
carbonate
siliciclastic
mixed
Eocene
7.3/11.53
28.6/45.18
27.4/43.29
Oligocene
4.6/7.85
50.2/85.67
3.8/6.49
Miocene
5.4/11.20
32.6/67.64
10.2/21.16
Pliocene
1.3/4.25
28.1/91.83
1.2/3.92
cetacean fossil
occurrences
carbonate
siliciclastic
mixed
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67
27
4
24
7
63
350
33
1
94
9
pinnipedimorph fossil
occurrences
carbonate
siliciclastic
mixed
n/a
n/a
n/a
0
3
0
5
102
1
0
40
1
sirenian fossil
occurrences
carbonate
siliciclastic
mixed
14
7
5
5
10
5
3
80
2
1
18
1
abundance of
lithologies
total/relative
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Table S1 Total and relative abundances of different lithologies and cetacean fossil
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occurrences. The first number in each cell in the ‘abundance of lithologies’ block shows the
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abundance of the three rock types under study as a percentage of global rock volume (Ronov
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1980; the missing percent are comprised of coal-bearing strata, evaporates, volcanics and
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terrestrial lithologies), whilst the second number shows the relative abundance of these three
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rock types only. Below this the total number of marine mammal occurrences per rock type
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and epoch as downloaded from the Paleobiology Database are shown.
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midpoint
(Ma)
stage
duration
(Ma)
%
epoch
total rock
(grid squares)
Ypresian
52.2
7.2
32.9
2095.0
0
70.6
Lutetian
44.5
8.2
37.4
2381.6
0
3
58.00
Bartonian
38.8
3.2
14.6
929.7
2
3
18.0
Priabonian
35.5
3.3
15.1
961.6
0
0
4
35.9
Rupelian
31.2
5.5
50.5
1160.5
3
1
1
10.0
Chattian
25.7
5.4
49.5
1137.5
8
1
2
-2.2
Aquitanian
21.7
2.6
14.7
1388.3
14
0
3
-4.1
Burdigalian
18.2
4.5
25.4
2398.8
28
3
5
6.8
Langhian
14.8
2.3
13.0
1227.7
7
2
0
1.2
Serravallian
12.6
2
11.3
1067.2
28
10
0
5.1
Tortonian
9.4
4.4
24.9
2349.8
45
8
1
4.1
Messinian
6.2
1.9
10.7
1010.5
0
1
0
-2.6
Zanclean
4.5
1.7
48.6
2363.4
14
7
1
-6.1
Piacenzian
3.1
1
28.6
1390.8
22
4
0
-14.6
Gelasian
2.2
0.8
22.9
1113.6
18
2
1
-18.7
Pleistocene
0.9
1.8
100
833.0
11
6
0
-52.9
stage
Cetacea
Pinnipedimorpha
Sirenia
sea-level
(m)
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Table S2 Table showing absolute and relative stage duration (% epoch), European outcrop
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area as observed in this study (total rock), as well as marine mammal diversities and global
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sea-level change (Miller et al. 2005). Marine mammal diversities are given as genera counts.
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All data are shown in their raw, non-detrended and non-transformed form.
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10
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Fig. S1 Relative abundance of cetacean occurrences per rock type (in %) after the varying
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amounts of available rock have been accounted for. This number was calculated in two steps,
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first by dividing the total number of occurrences by the relative abundance of each lithology,
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and then calculating the relative proportion of the resulting number as a percentage per
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epoch. Because there were not enough data available, no attempt was made to calculate
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relative abundances of pinnipedimorph and sirenian occurrences.
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