Diversity Patterns and Palaeobiogeographical Relationships of Latest Devonian-Lower Carboniferous Foraminifers from South China: What Is Global, What Is Local?

Journal of Palaeogeography 2014, 3(1): 35-59 DOI: 10.3724/SP.J.1261.2014.00002

Biopalaeogeography andPalaeogeography palaeoecology

Diversity patterns and palaeobiogeographical relationships of latest Devonian-Lower Carboniferous foraminifers from South China: What is global, what is local?

Markus Aretz1, *, Elise Nardin1, Daniel Vachard2 1. Géosciences Environnement Toulouse (GET), Observatoire Midi Pyrénées, Université de Toulouse, CNRS, IRD, 14 Avenue E. Belin, F-31400 Toulouse, France 2. Université Lille 1, UMR 8217 Géosystèmes, Bâtiment SN5, Avenue Paul Langevin, F-59655 Villeneuve d’Ascq cedex, France

Abstract During latest Devonian and early Carboniferous times, calcareous foraminifers were abundant, widely distributed, and showed the most rapid rate of evolution in the shallow‑ sea deposits. These factors, especially their fast phylogenetic changes, make them an essen‑ tial element in biostratigraphic schemes of this time interval. However, the distribution patterns of calcareous foraminifers depend on a series of biological and non‑biological factors, such as population sizes, dispersion, oceanic currents and temperatures, and substrate types, which are not always well‑controlled when interpreting spatial and temporal distribution patterns. For this study, a dataset of calcareous foraminifers was compiled containing the tempo‑ ral distribution (biozone level) of 420 species belonging to 155 genera currently described from Strunian (latest Devonian) to basal Serpukhovian (Lower Carboniferous) key sections in southern China, and the presence of those species in eleven palaeobiogeographical units. The comparison of the regional Chinese diversity curve, which has a bell‑shaped form with a dou‑ ble peak in the Ivorian, to a global curve shows the influence of local and regional factors. Mini‑ mum values in the Chinese Strunian, basal Tournaisian and early late Visean can be explained by the small number of studied outcrops, unfavourable facies and depositional gaps in these stratigraphic intervals in South China. This is especially obvious in the late Visean and Serpuk‑ hovian, which is a peak time of global diversity. The fall observed at that time interval in southern China is easily explained by the fact that this time peried is far less intensively studied and thus fewer data are present in the database. The opposite situation is seen around the Tournaisian- Visean boundary. Here, a peak is found in both regional and global curves, but that up to 87% of all known species are found in southern China seems to be unlikely, especially when the normal average value are 35%-40%. This anomalously high percentage is a consequence of the work undertaken on the Global Stratotype Section and Point (GSSP), and it shows that a species deficit may exist in the global curve. * Cluster, hierarchical cluster and Nonmetric multidimensienal Scalingel (NMDS) analyses have been calculated to study the palaeobiogeographical affinities of the southern Chinese calcareous foraminifers. The palaeobiogeographical patterns for the complete studied interval or parts of it (substages) are comparable on the genus and species level and stable through

* Corresponding author. E-mail: [email protected]. Received: 2013-09-17 Accepted: 2013-11-21 36 JOURNAL OF PALAEOGEOGRAPHY Jan. 2014

time. The assemblages found in southern China are well connected to other palaeo(bio)geo‑ graphical entities supporting the idea of relatively abundant widespread and cosmopolitan taxa in the studied interval. A cluster of South China, Europe and the Russian Platform is found in all analyses. This cluster often attached to the units Far‑East Russia and Turkey rep‑ resents the northern Palaeotethyan Realm. The relatively close affinities between South China and North America cannot be well discussed yet. Chinese data for endemicity, geographical spread and biodiversity in the Tournaisian-Visean boundary interval can be roughly correlated to 3rd-order sea-level fluctuations. Migration patterns into and out of South China can only be suspected, but not yet quantified.

Key words South China, Devonian, Carboniferous, foraminifers, diversity patterns, sta‑ tistical analyses, palaeobiogeography

1 Introduction 2010). Although the influence of factors like grain-size and texture is indisputable, these information data are rarely Foraminifers with a calcareous wall (i.e., of the class taken into consideration in biostratigraphic discussions. Fusulinata sensu Vachard et al., 2010) are among the most The same is true for other palaeobiological factors like abundant and widely distributed organisms in latest De- life mode. All Palaeozoic calcareous foraminifers were vonian and Carboniferous strata (e.g., see references in benthic, with epibenthic and endobenthic modes as well Vachard et al., 2010, Somerville et al., 2013). Their abun- as vagile and attached forms. These life modes clearly in- dance and rapid phylogenetic changes make them essential fluenced the distribution patterns, and among others, the elements for biostratigraphic schemes of the latest Devo- dispersion of the different foraminifers (species or mor- nian and Carboniferous on local to global scales (e.g., Ma- phological groups) is crucial for our understanding of pat- met and Skipp, 1970; Cózar, 2003; Poty et al., 2006; Cózar terns in deep time. Alve (1999) listed four principal pos- et al., 2011; Hance et al., 2011). Although the amount of sibilities for dispersion: release of propagules following data for foraminifers with agglutinated walls (Kaminski et reproduction, meroplanktonic life stage, self locomotion al., 2010) is increasing, they remain unstudied in many re- and passive entrainment and transport of growth stages. gions, and thus are excluded in the following study. The effective distances for dispersal are very different and Southern China illustrates well the importance of cal- range from much localized (self locomotion) to larger dis- careous foraminifers for global correlation in the Carbon- tances (e.g., zygotes and embryonic juveniles, which may iferous. The Global Stratotype Section and Point (GSSP) be pseudoplanktonic to planktonic for several days). The for the Tournaisian-Visean boundary situated at Peng- many taxa in the Upper Devonian and Lower Carbonifer- chong in Guangxi Zhuang Autonomous Region (Devuyst ous with wide palaeogeographical distribution indicate ef- et al., 2003; Hou et al., 2011) is so far, the only Devonian ficient quick dispersal, which supports the biostratigraphi- and Carboniferous GSSP not based on the first appearance cal usefulness of calcareous foraminifers. In fact, due to dutum (FAD) of a conodont, but on a calcareous foramini- the benthic, and often endofaunal mode of life of Early fer (Eoparastaffella simplex). The GSSP is one result of Carboniferous foraminifers, and the absence of demon- the fruitful collaboration between Belgian and Chinese strated sexual reproduction during this period (Vachard et institutions (e.g., Conil et al., 1988; Coen et al., 1996; al., 2010), self locomotion, passive transport by acceler- Hance et al., 1997; Aretz et al., 2012). This collaboration ated bottom currents, or rafting with macroalgae lifted by is certainly highlighted by the recently published atlas on strong streams or hurricanes, are most likely. Strunian-Visean foraminifers from South China (Hance Strunian-Serpukhovian calcareous foraminifers have et al., 2011), which summarizes the work of two decades. been intensively studied over the last fifty years and there Although calcareous foraminifers are important for are hundreds of papers describing foraminifers from al- biostratigraphy, their palaeobiological requirements and most all palaeocontinents. Although the community of limitations are currently often neglected. The relative fa- workers has been very productive, surprisingly little has cies dependencies of taxa have been described in several been done on the quantification of diversity or palaeogeo- studies (e.g., Gallagher, 1998 or models in Vachard et al., graphical patterns. A few exceptions can be found for di- Markus Aretz et al.: Diversity patterns and palaeobiogeographical relationships of latest Devonian-Lower Carboniferous foraminifers Vol. 3 No. 1 from South China: What is global, what is local? 37 versity plots, in e.g. Groves and Wang (2009), but overall, palaeogeography resembling a vast tropical archipelago the interest in Upper Carboniferous-Permian fusulinids (Figure 1). Landmasses (Old lands in the Chinese nomen- overshadows the older forms and time slices (e.g., Leven, clature) consolidated and deformed during Early Palaeo- 1993; Groves and Wang, 2009). Bio-events impacted the zoic times are surrounded by carbonate platforms, which abundance and evolution of foraminifers, but the clear are either directly attached to the landmasses (numerous separation of assemblages for specific time intervals (e.g., terrigenous clastic interbeds) or isolated from the land and three assemblages for the three Visean substages) does not situated above intra-basinal highs (without terrigenous necessarily correspond to global bio-events (Vachard et clastic interbeds). Narrow intra-platform basins, in which al., 2010). Groves and Lee (2008) in referring to the data detrital mud and siliceous strata dominate, separate and of Rauser-Chernousova et al. (1996) and Mamet (1977) dissect the carbonate platforms. Moreover, as indicated estimated that 66% of all Mississippian foraminiferal gen- by Hance et al. (2011), notable breaks of slope affect the era were cosmopolitan. This number supports the idea intra-platform basins, and input of shallow- water compo- of relatively few large palaeobiogeographical realms for nents into the basins by calciturbidites and debris flows Upper Devonian-Lower Carboniferous foraminifers (see can be seen in intercalated limestones in the basinal facies below). However, more regional models show distinct fo- (Jin et al., 2007). On the other hand, the distribution of raminiferal assemblages, and thus allow the separation of a these major facies realms can fluctuate and be modified by number of provinces or other regional subunits within the a series of transgressive-regressive cycles, due to local tec- photic, inner carbonate platform realms (e.g., Xu, 1987; tonic movements and/or global glacioeustatic movements. Kalvoda, 2002; Somerville et al., 2013). In consequence of this complex palaeogeography, dif- Early Carboniferous calcareous foraminifers have es- ferent lithostratigraphic subdivisions (Figure 2) have sentially three differences from the modern foraminifers been established not only for specific facies realms, but (Vachard et al., 2010), that complicate much of the palaeo- also for the various provinces and regions in China (Hu- biogeographical analyses and comparisons: (1) they are nan, Guangxi and Guizhou in our study area). Hance et almost all endofaunistic; (2) they occupy only the upper al. (1997, 2011) have proposed correlations between the parts of the inner carbonate platforms; (3) their dominant, different facies realms and regions, but so far they are ten- endothyrid-type of coiling is particular and does not exist tative and not yet formalized. The application of the bi- in modern times. As underlined above, the study of the ag- ostratigraphic scheme of Poty et al. (2006) to the study glutinated foraminifers (i.e., the class Textulariata) would area has been proven successful (Hance et al., 2011; Poty be very interesting for deeper and/or cooler waters (e.g., et al., 2011) and allowed some very detailed biostrati- reddish or pink nodular limestones), but there are many graphic correlations. Currently, these are restricted to palaeobiological, microstructural, and taxonomical prob- specific sections, and bearing in mind the large extent of lems with the Devonian-Carboniferous taxa assigned to Carboniferous strata in southern China, further studies are Textulariata (Vachard et al., 2010). required to foster correlations between regions and prov- In this study, we use data compiled for Strunian (latest inces, but also within them. Devonian), Tournaisian, Visean and Serpukhovian (Lower Hance et al. (2011) presented an example for the very Carboniferous) foraminifers from southern China to dis- different facies and thicknesses encountered around the cuss diversity patterns and palaeobiogeographical affinities Tournaisian-Visean boundary in Guangxi, even in neigh- of these forms. It is the aim to discuss and identify the influ- bouring sections in the same facies realm of the same car- encing factors and to test if the diversity patterns in South bonate platform. Thus, the large facies realms and the use China are comparable to those from other palaeocontinents of few formations names should not hide the facies vari- or to which degree a local signal is preserved in these data. ability on a smaller scale, which also comprises specific facies types for few outcrops (e.g., mud mounds and reefs; 2 Setting Jin et al., 2007; Aretz et al., 2012).

During latest Devonian-Early Carboniferous times, the 3 Data and methods South China Block was located just north of the palaeo- equator in a key position between the eastern Palaeotethy- 3.1 Data sources an Ocean and the Panthalassa Ocean (e.g., Blakey, 2007). Characteristic for the South China Block is a differentiated A Microsoft Excel spreadsheet has been compiled for 38 JOURNAL OF PALAEOGEOGRAPHY Jan. 2014

Figure 1 Localisation and palaeogeographic map for the study area. The palaeogeography is for the Tournaisian-Visean boundary interval, but most basic features can be generalized for the entire studied interval. Modified from Hanceet al. (2011).

Strunian (latest Devonian), Tournaisian, Visean and Ser- an, respectively) and palaeobiogeographical information pukhovian (Early Carboniferous) calcareous foraminifers have been extracted. If necessary, missing information, from key sections in southern China. The spreadsheet especially palaeobiogeographical information data were contains 420 species assigned to 155 genera. The main added, based on literature researches and our own unpub- source for the data is the atlas of Hance et al. (2011). This lished data. For the purpose of the study, eleven palaeobio- limitation was chosen for two reasons: (1) the atlas is the geographical units were differentiated (see below). These most recent comprehensive taxonomic work with the most units correspond to well-studied areas and have already detailed biostratigraphic correlation, which takes into ac- been regrouped in previous studies (e.g., Lipina, 1973; count the previously published studies of Chinese work- Kalvoda, 1990, 2002; Okuyucu et al., 2013). However, ers, and (2) the taxonomic concept is homogeneous, and future studies will have to further subdivide these units, thus the bias due to different taxonomic concepts should but in the current state of play, the data for regions like Far be largely reduced. East Russia are too heterogeneous and need to be revised All taxa mentioned and described in Hance et al. first. The atlas contains relatively few data on latest Vi- (2011), their given stratigraphic ranges (foraminiferal sean and Serpukhovian foraminifers, because Hance et al. zones DFZ and MFZ for the Devonian and Mississippi- (2011) did not study many sections covering this time in- Markus Aretz et al.: Diversity patterns and palaeobiogeographical relationships of latest Devonian-Lower Carboniferous foraminifers Vol. 3 No. 1 from South China: What is global, what is local? 39

GUANGXI HUNAN Intra- GUIZHOU Slope Off-shore Nearshore Restricted platform platform platform

S 16 Pen. Zimenqiao Fm Shangsi Fm 15

14 Luocheng Fm 13 Ceshui/Simen Coal Series Luzhai Fm Jiusi Fm Visean 12 Huangjin Fm Visean

Livian Warnantian Shidengzi Fm Baping

an 11 ci Pengchong Fm MFZ 10

lina Mb 9 Mo 8 Du’an Fm Xiangbai Fm 7 Yingang Fm Jiguangshan 6 Shidengzi Fm Ivorian 5 Duolingao Fm Tianeping Fm Fe Fe Luzhai 4 3 Fm Long’an Fm Tournaisian Tournaisian 2 Malanbian Fm Yaoyunling Fm Tangbagou

Hastarian Fm 1 8 7 Gelaohe Fm Fam Menggonao Fm Rongxian Fm DFZ Etoucun Fm Fam 6 (pars)

Strunian 5

Figure 2 Tentative stratigraphic correlation for the latest Famennian (Fam) to Serpukhovian (S) of the different facies realms in Hunan, Guangxi and Guizhou. The color code is the same as in Figure 1. White intervals indicate stratigraphic gaps. Yellow shaded intervals are dolomitic. Horizon of mud banks in off-shore platform section indicated by solid triangles. Modified from Hance et al. (1997, 2011), Aretz et al. (2012). terval. The currently best-known section for shallow-water sian and Visean. For simplification of the text, the biozone carbonates of the latest Visean-Serpukhovian in South MFZ 4 is attributed to the Hastarian, although its upper China, the Yashui section, Guizhou Province, was only part extends into the Ivorian (Poty et al., 2006, in press). preliminary studied and sampled by Hance et al. (2011). This simplification can be justified with the unsuitability To partly close this gap, the recent data on the Yashui sec- of facies for foraminifers in the basal Ivorian (Poty et al., tion (Groves et al., 2012) were integrated into the dataset, in press) and the correlation of MFZ 4 to the Maurenne but the taxonomy was corrected according to the concept Formation (Poty et al., 2006) in the Namur-Dinant Basin. used in the atlas. Then all data were controlled and some The latter is late Hastarian in age. mistakes corrected by one of us (D.V.). 3.3 Geographical units 3.2 Time units The data used in this study are all from the South China The exact lengths of the foraminiferal biozones (DFZ, Block situated in the north-eastern Palaeotethyan Realm. MFZ) have not yet been calculated. They represent time In order to discuss the relationship to near, middle and units of unequal lengths. In order to compare the diversity far distanced regions, the South Chinese data have been trends, more chronological precision is needed. An attempt compared to ten other palaeobiogeographical units (Fig- is made herein to estimate the duration of each biozone ures 7-11). The palaeogeographical positions in respect (see Figures 4-10). It uses (i) the dates for the base of the to South China and the availability of data were an essen- stages from the Geological Time Scale (GTS) 2012 (Grad- tial element for the definition of these units. A set of units stein et al., 2012), (ii) the estimated lengths of 3rd-order comprise the immediate palaeogeographical neighbours of sequences of Hance et al. (2001) correlated to the biozones South China (SE Asia, Western Australia, Far East Russia of Poty et al. (2006), (iii) an unpublished attempt for the and neighbouring countries). More distant in the Palaeo- length of coral biozones in the same interval, and (iv) sedi- tethyan Realm were Turkey and Iran (Arabian Plate ex- ment thicknesses observed in the time intervals of the bio- cluded), the Russian Platform including the Urals, Western zones. The GTS dates have been used as fixed points, but and Central Europe and Northwest Africa. To test relation- these dates may underestimate the duration of the Tournai- ships to palaeogeographically more isolated regions, three 40 JOURNAL OF PALAEOGEOGRAPHY Jan. 2014 units have been added; Eastern Australia (eastern mar- group averaging methods (Sokal and Michener, 1958) gin of Gondwana), Japan (Panthalassa Ocean) and North or the distance Sørensen associated to the Ward linkage America including Alaska and northern Canada. The latter method (Ward, 1963), to respect the concavity (McCune region may indicate closer palaeobiogeographical con- and Grace, 2002). The Nonmetric Multidimensional Scal- nections than traditionally seen for the North American ing (NMDS) ordination method was also based on Raup- Realm. Crick distance measures to verify the expected palaeobiogeographical relationships (Clarke, 1993). All statistical 3.4 Diversity dynamics and similarity analyses analyses were computed with the libraries cluster, vegan, Diversity measures are expressed in terms of the total stats for R2.9.1. 5 (R. Development Core Team, 2009). diversity per capita (total number of genera or species recorded in a time interval divided by the estimated length 4 Palaeodiversity of the interval; see Cooper, 2004) applied to the matrix constituted by the observed occurrences of the taxa (genus 4.1 Global diversity or species) in the fossil record and to the matrix constituted by the theoretical range of the taxa. Observed diversity is Although calcareous foraminifers are intensively stud- supposed to be more affected by sampling and effort bi- ied, quantitative diversity data are rare. On the genus level, ases in addition to the potential presence of Lazarus taxa data are available from Sepkoski (2002) who compiled the (Cascales-Miñana et al., 2013). Therefore, most of our rea- stratigraphic and taxonomic data from Loeblich and Tap- soning will be based on the theoretical diversity per capita. pan (1987). Groves and Lee (2008) provided a first curve at Evolution measures are based on metrics described by the species level when discussing originations and extinc- Foote (2000a). Per-taxon rates have been selected to nor- tions of foraminifers during the Late Palaeozoic Ice Age. malize the number of originations and extinctions by the The database was expanded subsequently, and Groves and total diversity per capita. Those rates were the basis for the Wang (2009) presented two curves, one for the diversity of calculation of the turnover and diversification rates (Nar- North American foraminifers and a second for the global din and Lefebvre, 2010). diversity. The difference between the two curves should Palaeobiogeographical closeness was evaluated using reflect the diversity in what the authors called the Arctic- similarity and ordination methods. Cluster analyses used Eurasian association, and thus show the diversity for the the dissimilarity distance Raup-Crick method, the simi- Arctic-Eurasian realm (see section 5.1). larity distances Euclidean and Jaccard (Raup and Crick, The methodological approach for the analysis was the 1979) accompanied by the agglomerative nesting with same as in this study of southern China, but the data of

NA PT PG

Figure 3 Palaeobiogeographic realms for late Devonian-Lower Carboniferous calcareous foraminifers according to the Kalvoda Model (2002) illustrated on the palaeogeographic map of Blakey (2007). Boundaries between realms are approximative and may fluctuate with time. NA-North American Realm, PT−Palaeotethyan Realm, S−Siberian Realm, PG−Peri-Gondwanan Realm. Markus Aretz et al.: Diversity patterns and palaeobiogeographical relationships of latest Devonian-Lower Carboniferous foraminifers Vol. 3 No. 1 from South China: What is global, what is local? 41 the Groves and Lee (2008) and Groves and Wang (2009) plained the initial low diversity of the latest Devonian and studies have not been calibrated to biozones, but to 1 Ma early Tournaisian was explained as the earliest phase of intervals. This calibration was achieved by graphic cor- recovery after the Frasnian/Famennian extinction crises. relation, which used as an absolute reference time scale 4.2 Observations in South China the dates given by the GTS 2004 (Gradstein et al., 2004). However, the updated version of this chart (Gradstein et 4.2.1 Diversity al., 2012) results in new dates for the base of the Visean and Serpukhovian stages. In assuming that the total dura- The diversity of calcareous foraminifers, which is basi- tion of the stage changed equally over the entire length of cally the expression of the ratio of originations and extinc- the stage, the Groves curve has been corrected for the Mis- tions, has been calibrated to the duration of the foraminif- sissippian to enable a better comparison to be made to the eral biozones of the Strunian to Pendleian (DFZ 5 - MFZ results obtained in southern China (Figure 4). 16). Foraminiferal species and genus diversity show the Groves and Wang (2009) noted an overall diversity in- same overall pattern for observed and theoretical diversity crease for the Carboniferous, mainly based on the radia- (Figure 5), and the latter is used in the following. tion of fusulinoideans in the Pennsylvanian. The Missis- Singletons (taxa only found in a single biozone) have sippian curve can be described as a double bell-shaped been included in the analyses contrary to the recommenda- increasing line, with the two maxima in the late Tournaisi- tion of using only boundary-crossing taxa (Foote, 2000a, an and late Visean (Figure 4). Somerville (2008) described 2000b). This is based on the analysis that the datasheet a very similar curve for the diversity of western European contains 71% singletons on the species level (299 species) foraminifers (genus level) with two maxima; the first in and 41% singletons on the genus level (64 genera). If it the Chadian (basal Visean). Groves and Wang (2009) ex- assumed that the presence of a taxon coincides with the

Global

not recorded in China

North America nb. of species

40 80 120 160 200 240 China 0

5 6 7 89123 4 5 6 7 8 10 11 12 13 14 15 16 DFZ MFZ StrunianFam HastarianTournaisianIvorian Molinacian LivianVisean Warnantian Pen. Fam (pars) Tournaisian MISSISSIPPIANVisean S (pars) DEV MISSISSIPPIAN (pars) (pars) CARBONIFEROUS (pars)

360 355 350 345 340 335 330

Figure 4 Biodiversity of South Chinese calcareous foraminifers (Strunian-Pendleian): Comparison between global, North America and Chinese species diversity. The amount of taxa not recorded in China is in relation to the global diversity. Global diversity and North American diversity modified from Groves and Wang (2009) according to the revised absolute dates for the base of the substages (Gradstein et al., 2012). 42 JOURNAL OF PALAEOGEOGRAPHY Jan. 2014

diversity origination/ diversification/ A extinction turnover diversity estimators rate rate 0 20 40 0.0 0.2 0.4 0.6 0.8 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2

l theoretical diversity origination turnover observed diversity 325 extinction diversification Arnsberg.

16 Serpukhovian 330

15 335 14 13 l ve

Visean 12 Visean 340 Livian Warnantian Pen.

11 MFZ

enus le enus 10 MISSISSIPPIAN 345 9 Molinacian 8 7 6 350 Ivorian 5

4 3 Tournaisian 355 Tournaisian 2 l Hastarian 1 8 360 7 l Fam DFZ Fam 6

Strunian 5

diversity estimators rate rate B 0 20 40 60 80 100 120 0.0 0.2 0.4 0.6 0.8 1.0 -0.5 0.0 0.5 1.0 1.5 2.0

l theoretical diversity origination turnover observed diversity 325 extinction diversification Arnsberg.

16 Serpukhovian 330

15 335 14

lg 13 ve

Visean 12 Visean 340 Livian Warnantian Pen.

MFZ 10 MISSISSIPPIAN 345

species le 9 Molinacian 8 7 6 350 Ivorian 5

4 3 Tournaisian 355 Tournaisian 2 Hastarian 1 8 360 7 Fam DFZ Fam 6

Strunian 5

Figure 5 Biodiversity of South Chinese calcareous foraminifers (Strunian-Pendleian): Comparison on the genus and species level of theoretical and observed diversities, origination and extinction rates and turnover and diversification rates for South Chinese calcareous foraminifers. The shaded areas indicate the 95% confidence interval. Markus Aretz et al.: Diversity patterns and palaeobiogeographical relationships of latest Devonian-Lower Carboniferous foraminifers Vol. 3 No. 1 from South China: What is global, what is local? 43 duration of the biozone in which it is recorded, a maximum extinction, the highest amplitudes of these rates corre- theoretical life time for each taxon can be calculated. The spond to the rapid diversity increase of the late Hastarian, average duration of a species is 3.66 Ma (0.8-22.4 Ma), which in absolute numbers is less important than those of and those for a genus is 6.27 Ma (0.8-24.4 Ma). Long the Ivorian. It is evident that for the Tournaisian the origi- life times are rare among species, only 10% are known in nation rate exceeds the extinction rate, however the drop in more than 3 biozones. For genera the number rises to 30%. total diversity in the Visean and Serpukhovian is not due to These values can be positively interpreted to reflect the a constant higher extinction rate. Rates are rather variable, fast evolutionary rates for calcareous foraminifers. A more and thus the diversity curve shows several small-scale ups conservative interpretation could evoke taxonomic over- and downs in the younger intervals. This is also seen in the splitting due to concentration on specific biozones or too diversification rate, which fluctuates around 0 for most of poorly defined intraspecific variabilities. the Visean and Serpukhovian. The diversification rate in For the studied time interval, the diversity curve is bell- the Strunian and Tournaisian is in generally higher, which shaped (Figure 5). Diversity in the Strunian and Hastar- not surprisingly results in the bell-shaped diversity curve. ian is low, and the extinctions events of the latest Devo- On the genus level, the highest turnover rates are found nian (Hangenberg Crisis) are visible in a slightly lower in the Strunian (DFZ 7) and in the late Hastarian (MFZ diversity in the early Hastarian (MFZ 1-2) compared to 3) (Figure 5A). Only the latter peak is found on the spe- the Strunian (DFZ 5-8). Recovery takes the entire early cies level (Figure 5B), indicating that the diversity peak in Hastarian, but then markedly accelerates within the late the DFZ 7 results mainly from the origination of genera. Hastarian. In biozone MFZ 3, the numbers are as twice Species origination contributed only subordinately to the as much as in the Devonian. The Ivorian is characterised Strunian diversity increase, because even high origina- by an important diversity increase culminating in its last tion rates were levelled out by a high extinction rate. The biozone (MFZ 8). Two of the three highest foraminiferal Hangenberg Crises seems to be mainly a problem of low species diversities observed in the studied interval are origination and not of extinction, when only using the data found in this substage (MFZ 6, MFZ 8). The peak in MFZ for the DFZ 8-MFZ 1 interval. However, DFZ 8 is poorly 6 corresponds to the arrival of genera, such as Dainella, known and when enlarging the focus, the net extinction Eoforschia and Spinobrunsiina; MFZ 8 is characterised and high turnover in the latest Devonian, just below the by the arrival of new genera and important originations Devonian-Carboniferous boundary are well illustrated. in the existing stock. The third highest species diversity This overall trend completely changes in the late Hastarian is found just at the base of the following substage (MFZ when higher origination rates result in high diversification 9) and initiates in South China the diversity decrease of and turnover rates. the Visean and Serpukhovian. The genus diversity of the 4.3 Discussion Visean-Serpukhovian interval follows the same trend, but the peak values are more evenly distributed between the The regional North American diversity curve shows the Ivorian and Molinacian. same general trends as the global diversity curve (Groves and Wang, 2009; Figure 4). The main difference between 4.2.2 Evolutionary rates these curves is the amplitude of changes. The same is true Origination, extinction, diversification and turnover for the Arctic-Eurasian curve (difference between global rates were calculated per time interval (Figure 5). On the and North America values). The diversity curve for south- genus and species level, the origination and extinction ern China does not show the same parallelism as these curves are relatively parallel, indicating that times of high three other curves. It shares the diversity increase in the origination are also characterised by times of high extinc- Tournaisian, and also shows peak values in the late Tour- tions. The same can be postulated for times of low origina- naisian, but the typical diversity increase of the Visean and tion rate, when extinction rate is low as well. There is one the high values around the Visean-Serpukhovian bound- significant exception of the parallelism in the top of the ary of the Groves and Wang curves have not been found. Devonian during the extinction events of the Hangenberg Only 10% of the global diversity is recorded for the late crises (top DFZ 8). The shape of the curves for origination Visean and Serpukhovian in southern China, which is re- and extinction rates resembles the diversity curve, when markably low compared to the average of 35%-40% for the overall diversity is low. Although the high peaks in the other Mississippian substages. This is even more surpris- diversity correspond to elevated rates of origination and ing because in many other regions in Eurasia, the late Vi- 44 JOURNAL OF PALAEOGEOGRAPHY Jan. 2014 sean is a major time period for foraminiferal diversifica- The opposite effect can be seen at the diversity peak tion (e.g., Europe: Conil and Lys, 1964; Vachard, 1977; in the late Tournaisian when comparing the global and Cózar and Somerville, 2004; North Africa: Vachard and Chinese diversity curves. In the latest Ivorian, the diver- Fadli, 1991; Vachard and Tahiri, 1991; Cózar et al., 2011, sity curve for South China almost attains the values of the 2013; Somerville et al., 2013). global diversity curve, when 87% of all known species of Hence, such a decoupling from the general trend may this biozone are recorded in South China. This value is have palaeoenvironmental, palaeobiological or geological more than twice the normal average of 35%-40% for well- reasons. A major geological event can be excluded here, studied biozones in the Ivorian, Molinacian and Livian. since South China was not affected by major tectonic or Due to the search for the GSSP for the base of the Visean, geodynamic events, such as the Variscan Orogeny, and the calcareous foraminifers from the upper Tournaisian remained in tropical latitudes during the Carboniferous. and lower Visean strata of South China have been studied Palaeobiological factors can be excluded also, because no in great details (Hance et al., 1997, 2011; Devuyst et al., important change in the life strategies of calcareous fora- 2003; Devuyst, 2006; Hou et al., 2011). The associations minifers is known in the Mississippian (e.g., Groves and in different facies and different time slices (biozone and Lee, 2008; Vachard et al., 2010). More likely are palaeoen- subzones) are very well known and documented. This very vironmental changes. High-frequency sea-level fluctua- detailed knowledge is rather unique. In the two decades, tions common in the late Visean and Serpukhovian, often more detailed studies of the same time interval have been related to major glaciations in southern Gondwana (e.g., published for Europe (Devuyst and Kalvoda, 2007; Kal- Hance et al., 2001; Late Palaeozoic Ice Age), may have voda et al., 2010, 2012). Those studies further increase the increased pressure on habitat stability. Habitats may have number of species known in this time interval, but these become more instable, but this should not necessarily re- data are too recent to have been integrated in the curve of sult in a diversity decrease. According to Groves and Lee Groves and Wang (2009). Thus, with an updated global (2008), it could be even the opposite, because foraminifers curve, the distance between the global and the Chinese show higher origination rates in times of habitat instabil- curves should increase. ity probably resulting in a diversity increase. This is seen The low diversity in the early Hastarian is a combined on the carbonate platforms in other Eurasian regions (see effect of palaeobiological and environmental factors. Most above), where calcareous foraminifers were facing the of the complex and large forms (e.g., Quasiendothyridae) same environmental pressures as in South China. have become extinct at the Devonian-Carboniferous Hence, other factors should contribute to the low War- boundary in the Hangenberg Crises. The first biozone of nantian-Pendleian diversity in South China. One factor the Mississippian contains mainly the name-giving small was already mentioned previously (section 3), Hance et unilocular foraminifers. Thus, a ‘Lilliput Effect’ could be al. (2011) studied significantly fewer outcrops in upper Vi- proposed in the scenario for the aftermath of the Hangen- sean and Serpukhovian strata than in older substages, mak- berg extinction, since the abundance of unilocular fora- ing the dataset less complete for these time slices. It should minifers and the general size relations at the base of the be noted that Hance et al. (2011) only correlated strata to Hastarian are also known outside South China (e.g., Bel- the lower Warnantian, but did not directly find MFZ 13 gium: Poty et al., 2006; and references in Vachard et al., and 14, which is the prime reason for the Chinese diversity 2010). Recovery took apparently as long as the lower Has- low in the lower Warnantian. This can be at least partly tarian (MFZ 1, 2), before a rapid diversity increase is seen explained with a facies problem. In some regions in South in the late Hastarian (MFZ 3) with a major diversification China, the Warnantian strata are characterised by the pres- in the Tournayellidae, Septabrunsiinidae and Chernysh- ence of widespread terrigenous clastic facies (Figure 2) inellidae. This long recovery phase and the following rapid and locally peloidal, micritic and even stromatolithic fa- diversity increase in South China are a regional signal. The cies (Shen and Qing, 2010). These unsuitable facies for reappearance of plurilocular foraminifers in MFZ 2 (Poty calcareous foraminifers reduced the potential habitat sur- et al., 2006) is poorly documented in South China (Hance face on the platform systems. This certainly contributed to et al., 2011) and it only starts in this region in zone MFZ 3. the low diversity in the Warnantian in South China, further Thus, the diversity increase in South China is delayed for accentuated by the generally poor knowledge of the late about one biozone and steeper compared to regions like Visean and Serpukhovian in large regions such as central Western Europe. However, during MFZ 2 time interval a and northern Guangxi. facies problem existed. The carbonate factory was largely Markus Aretz et al.: Diversity patterns and palaeobiogeographical relationships of latest Devonian-Lower Carboniferous foraminifers Vol. 3 No. 1 from South China: What is global, what is local? 45 stopped and marly and shaly marine facies dominated on cies have been studied. To better evaluate this potential the platforms. These were unfavourable conditions for cal- bias, more detailed data are needed on the carbonate mi- careous foraminifers, which contribute to the poor record crofacies containing the calcareous foraminifers have been of Hance et al. (2011). The deposition of this facies on the found in. In the present state, it can only be suspected that platforms is generally attributed to the transgression of the the Chinese data for MFZ 2, 10, 13-16 are biased through Lower Alum Shale Event (Siegmund et al., 2002). This a low number of studied sections and facies. global event was largely modified on the regional scale, Data for the global diversity of Strunian foraminifers but the reason why it impacted much more severely on have so far not been published, and such a curve is beyond the foraminiferal associations in South China than in other the scope of this study. However, in order to compare the regions is not known. Chinese data, a datasheet has been compiled for calcareous This example of facies impact is probably the most ex- foraminifers from the Devonian-Carboniferous boundary treme in the studied interval. However, the influence of (DCB) interval in the Urals (Kulagina, 2013). It has to be shale content, carbonate textures, grain sizes, etc. on the stressed that only the data of Kulagina (2013) have been distribution patterns of particular calcareous foraminifers taken into consideration, which represent a new interpre- has already been mentioned. It cannot be neglected that tation of foraminiferal evolution around the DCB in the a bias is introduced. The facies dependency of particular Urals. The foraminiferal zones of Kulagina (2013) have taxa should only become significant when a limited num- been approximately correlated to the DFZ and MFZ zones ber of samples from a limited number of sections and fa- of Poty et al. (2006). The DCB has been placed between

theoretical diversity origination/extinction A nb. of taxa B rate species C rate genera diversity estimators rate rate 020406080 100 120 0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.2 0.4 0.6 0.8

species China origination China origination Urals origination China origination Urals genera China extinction China extinction Urals extinction China extinction Urals species Urals

MFZ 4 MFZ genera Urals MFZ 3 MFZ 355 Hastarian MFZ 2 MFZ Tournaisian MFZ 1 MFZ DFZ 8 360 DFZ 7 Strunian Fam 6 Fammenian DFZ 5

Figure 6 Biodiversity of South Chinese calcareous foraminifers (Strunian-Pendleian): Devonian-Carboniferous Boundary interval. Comparison of theoretical diversity and extinction and origination rates on the genus and species level for South China and the Urals. 46 JOURNAL OF PALAEOGEOGRAPHY Jan. 2014 the remnant Quasiendothyra Beds - Tournayellina beata calcareous foraminifers. The idea that increased origina- pseudobeata Zone (= DFZ 8) and the Earlandia minima tion and extinction rates characterise glacial episodes Zone (MFZ 1), i.e. the biozone of unilocular and bilocular (Groves and Lee, 2008) was not confirmed by the exten- foraminifers affected by a Lilliput Effect, where plurilocu- sive analysis of Groves and Wang (2009), which took into lar taxa are rare or absent. consideration that the LPIA is much more complex than a The curves for diversity and origination and extinction single glaciation in the Pennsylvanian (Isbell et al., 2003; rates for the Urals and southern China (Figure 6) show in Fielding et al., 2008). The data from southern China can contrast to the Strunian only in the Hastarian a higher de- only contribute to the discussion of the initial stages of gree of parallelism. The amplitude and absolute values are the LPIA. A first glacial interval is today acknowledged always higher in the Urals than in South China (Figure in the late Famennian, but it is uncertain if it extends into 6A). Common to both regions is a low diversity time dur- the Tournaisian (e.g., Isbell et al., 2003; Issacson et al., ing the early Hastarian and the rapid diversity increase in 2008) or not (e.g., Marshall et al., 2013; Poty et al., 2013). MFZ 3. Within the Strunian the evolution of the diversity If the concept that a glacial climate should result in higher is antithetic (Figure 6B, 6C). The diversity peak of DFZ 6 origination and extinction rates (Groves and Lee, 2008) is in the Urals corresponds to a diversity low in South Chi- applied to the Chinese data, then apart from the lower Has- na, whereas the small diversity peaks in the Chinese DFZ tarian, the Strunian to lower Molinacian climate should be 5 and 7 correspond to intervals of lower diversity in the glacial. This is in contrast to any reconstruction for the Urals. Common to both regions is the subsequent diversity Mississippian climate (see references above and Buggisch drop at the Devonian-Carboniferous boundary and the et al., 2008). Therefore, the positive correlation of glacial disappearance of Quasiendothyridea. It should be noted climate and high origination rates is not followed herein, that in several sections quasiendothyrids are known in the especially since the Chinese rates for the Tournaisian and basal beds of the Tournaisian (Kalvoda et al., in press). early Visean are comparable to the contemporaneous rates The discrepancy between the Urals and South China could proposed by Groves and Wang (2009). have multiple origins. The translation of the Uralian biozones into the DFZ and MFZ scheme may have induced 5 Palaeobiogeographical relations errors, but many important taxa for these two schemes occur in the Urals and South China and the parallelism of 5.1 Palaeobiogeographical units the Hastarian curves seems to indicate a correct correlation. Differences in the biodiversity could also be related Global biogeography of late Devonian-Carboniferous to different treatment of morphological differences for the calcareous foraminifers has been the focus of numerous taxonomy and/or less studied material in morphological qualitative studies (e.g., Mamet, 1977; Kalvoda, 1990, complex forms. The Uralian sections contain many spe- 2002). The understanding of the palaeobiogeography of cies of genera like Septaglomospiranella and Quasien- this time slice is often largely influenced by concepts de- dothyra. These genera are also found in South China, but veloped for Pennsylvanian and Permian times (e.g., Ross, with significantly fewer species. The reasons could be pal- 1973; Groves and Wang, 2009). aeoenvironmental differences, palaeobiogeographical bar- The simplest palaeobiogeographical models are bipolar riers, taxonomic over-splitting or insufficient sampling of and differentiate a North American or Midcontinent-Ande- specific time intervals or facies. Currently, none of these an Realm from a Tethyan Realm (e.g., Ross, 1973; Groves reasons can be excluded. Kulagina (2013) mentioned ma- and Wang, 2009). Other models (Mamet and Belford, 1968; jor differences in the composition of contemporaneous fo- Lipina, 1973; Kalvoda, 1990) differentiate three realms: a raminiferal assemblages in the Urals related to facies dif- subtropical/tropical Palaeotethyan Realm, a subtropical/ ferences. These local and regional differences may mask tropical North American Realm and a northern boreal Si- or accentuate the differences existing between the Urals berian Realm. Kalvoda (2002) modified the tripolar model and South China. In the future, more quantitative data are in adding a southern boreal Perigondwana Realm compris- needed to decide if any of the two patterns is consistent ing parts of the northern Gondwana margin (Arabia and with the global picture. neighbouring regions) and terranes in Afghanistan and the Groves and Lee (2008) and Groves and Wang (2009) Himalaya region (Figure 3). The boundaries between the were concerned about the impact of the Late Palaeozoic realms are not important palaeo(bio)geographical barriers, Ice Age (LPIA) on the origination and extinction rates of since otherwise the high degree of cosmopolitism of Mis- Markus Aretz et al.: Diversity patterns and palaeobiogeographical relationships of latest Devonian-Lower Carboniferous foraminifers Vol. 3 No. 1 from South China: What is global, what is local? 47 sissippian calcareous foraminifers (according to the distri- tion of almost all the foraminiferal lineages during the butions mentioned by Rauser-Chernousova et al., 1996) Lower Carboniferous. Although the absolute number of would not be possible. The evaluation of the degree of taxa in the Palaeotethyan Realm was higher (see section faunal interchange between the realms is the main differ- 4.3; Figure 4), the uneven size of the two realms has to be ence between the models. In any case, unless a quantitative taken into consideration. Absolute numbers are lacking for global analysis for Mississippian foraminiferal biogeogra- the potential habitat surface in the realms, but this surface phy has been performed the arguments for all models can seems to have been much larger in the vast Palaeotethyan not be validated, although the Kalvoda Model seems to be Realms according to most palaeogeographical maps (e.g., the most appropriate one. Blakey, 2007). Thus, a higher diversity compared to the One important difference between the two tropical/sub- North American Realm could be simply an expression of tropical realms is the higher diversity of thick-walled, com- the larger size of the Palaeotethyan Realm. plex calcareous foraminifers in the Palaeotethyan Realm Within the realms, smaller palaeobiogeographical units (Kalvoda, 2002; Groves and Wang, 2009). In this context, (provinces or subprovinces) have been differentiated (e.g., Groves and Wang (2009) tried to confirm the hypothesis Kalvoda, 1990, 2001, 2002; Somerville et al., 2013). of Mamet (1977), indicating that the Palaeotethyan Realm However, for the definition of these units the same prob- was the biogeographical centre of origination and radia- lems exist as for the realms, but the smaller the size of

A genus level B species level palaeogeographic units palaeogeographic units 0 1 2 3 4 5 6 7 8 9 10 11 0 1 2 3 4 5 6 7 8 9 10 11 325 325 Arnsberg. Arnsberg.

16 16 Serpukhovian Serpukhovian 330 330

15 15 335 335 rnantian Pen. 14 14 Wa 13 13 Visean Visean 12 12 Visean Visean 340 340 Livian Livian Warnantian Pen.

11 11 MFZ 10 MFZ 10 MISSISSIPPIAN MISSISSIPPIAN 345 345 9 9 Molinacian Molinacian 8 8 7 7 6 6 350 350 Ivorian Ivorian n 5 5

4 4 3 3 Tournaisian Tournaisian 355 355 Tournaisia Tournaisian 2 2 Hastarian Hastarian 1 1 8 8 360 7 360 7 Fam Fam DFZ DFZ Fam 6 Fam 6 Strunian Strunian 5 5

0 10 20 30 0 10 20 30 40 Endemicity Endemicity

Figure 7 Palaeobiogeographical affinities of the South Chinese foraminiferal microfauna: Overview on palaeobiogeographical spread and endemicity for each biozone of the studied interval on the genus and species level. The red bar indicates the number of palaeobiogeographical units known in this biozone. The grey bars indicate the range between minimum and maximum spread. The dark bar gives the average spread. Endemicity is expressed in % of the total known taxa in that biozone. 48 JOURNAL OF PALAEOGEOGRAPHY Jan. 2014 those units is, the more important becomes the influence Strunian and lower Hastarian taxa are geographical- of facies on the distribution patterns of the calcareous fora- ly widespread, and no endemic taxon is found in South minifers. Hence, there is the risk that these units become China. It is interesting to note that only in the DFZ 7 are independent from palaeogeographical features. truly cosmopolitan taxa present, which are found in all Three palaeobiogeographical provinces called South 8 palaeobiogeographical units (2-9). Especially, the first Province, Middle Province and North Province were iden- biozones of the Mississippian (MFZ 1-2) show a very tified in the Chinese Carboniferous based on foraminifers, high degree of widespread taxa during a time of overall brachiopods and corals (Xu, 1987). The boundaries below total diversity. This interval corresponds to the time tween these provinces are horizontal lines on the recent when foraminiferal associations are dominated by simple geography (34° and 42° latitudes), and thus do not neces- and small forms. From the upper Hastarian onward (MFZ sarily represent former plate boundaries. The North Prov- 3-4), the entire range of palaeobiogeographical spread ince is thought to represent the Boreal Realm (Xu, 1987), is found, from endemic to cosmopolitan forms. The only and seems to comprise the Chinese part of the Siberian exception is MFZ 5, where no taxa colonized all poten- Plate. The South Province representing the Tethys Realm tial palaeobiogeographical units. Genera are more wide (Xu, 1987) corresponds to the South China Block (Yang- spread than species in the entire study interval, which is Tse) and several peri-Gondwanan Terranes (e.g., Baoshan the expression of the larger geographical stability of the Block). The study area is a part of this Province. The Mid- higher taxonomic rank. dle Province has a transitional character (Xu, 1987). It may Looking at the mean values for the geographical dis- correspond to the North China blocks (Sino-Korea). tribution of genera, this value fluctuates between 5 and 6, thus about the half of all possible units, for the Ivorian 5.2 Observations in South China to the Pendleian biozones. In the Strunian and Hastarian, Three palaeobiogeographical provinces called South this value is higher. Since species are less widespread than Province, Middle Province and North Province were iden- genera, the values on the species level are lower. The re- tified in the Chinese Carboniferous based on foraminifers, sulting curve shows more variation than the genus curve, brachiopods and corals (Xu, 1987). The boundaries be- and especially the amplitudes are more pronounced. The tween these provinces are horizontal lines on the recent Strunian and Hastarian show pronounced changes, but geography map (34° and 42° latitudes), and thus do not these changes are often the result from the integration of necessarily represent former plate boundaries. The North poorly diversified or known biozones (e.g., DFZ 6, MFZ Province is thought to represent the Boreal Realm (Xu, 2). The values for the better studied and known biozones 1987), and seems to comprise the Chinese part of the Si- are relatively similar. During the Ivorian to Pendleian, berian Plate. The South Province representing the Tethys the amplitude of changes is lower than in the two older Realm (Xu, 1987) corresponds to the South China Block substages. The highs and lows in the curve correspond to (Yang-Tse) and several peri-Gondwanan Terranes (e.g., the peaks in the curve for genera, but again they are more Baoshan Block). The study area is a part of this latter pronounced. The highest mean values for the geographi- Province. The Middle Province has a transitional character cal spread in this interval are those of biozones MFZ 13 (Xu, 1987). It may correspond to the North China (Sino- and 14 (Figure 7A, 7B), again periods where simple forms Korean) Block. dominated. A first analysis (Figure 7) describes for all the 20 bio- The endemicity curves show the development of en- zones the palaeobiogeographical spread of a taxon in the demic taxa from the upper Hastarian onwards, prior to this 11 units and the endemicity. The theoretical total diver- not a single endemic taxon is known in DFZ 7. On the sity was used herein to partly compensate for the lack of genus level, the endemicity rises with minor fluctuations data for biozones in the Strunian, Hastarian and Warnan- until the lower Warnantian, before it starts to drop (Fig- tian (Figure 4). The results for both taxonomic levels are ure 7A). Endemicity values for species are higher and the comparable. The number of palaeogeographical units from fluctuations are more important than for the genera. The which calcareous foraminifers have been described raises Ivorian to Livian interval forms a dissected plateau with units from the Strunian to the Ivorian from an initial 8 to a mean of 27% (14.7%-34.1%) before endemicity drops 11 units. Then, a plateau is reached, and only in the Pend- considerably in the Warnantion (Figure 7B). The endemic- leian the number decreases due to the absence of calcare- ity on the species level correlates relatively well with the ous foraminifers in Eastern Australia. intensively studied intervals by Hance et al. (2011) and Markus Aretz et al.: Diversity patterns and palaeobiogeographical relationships of latest Devonian-Lower Carboniferous foraminifers Vol. 3 No. 1 from South China: What is global, what is local? 49

genus level species level

Raup-Crick Similarity Index 0.9018 Raup-Crick Similarity Index 0.9090 0.6 0.6 Height Height China China 0.0 0.0 ey Am Am rk rkey sAus sAus Japan Japan EsAus EsAus Tu Tu Europe SEAsia Europe SEAsia Rus Pla Rus Pla We We North North East Rus NW Africa NW East Rus NW Africa NW F. A F. B

Jaccard Similarity Index 0.4864 Jaccard Similarity Index 0.3828 0.9 0.8 sAus 0.6 Height Height sAus EsAus 0.4 EsAus We Am We ey ey Japan Japan SEAsia rk rk 0.0 0.3 North North Am North SEAsia NW Africa NW Tu Tu China NW Africa NW China Europe East Rus East Rus Rus Pla F. F. Europe C D Rus Pla

Euclidean Similarity Index 0.7082 Euclidean Similarity Index 0.7192 20 30 20 10 Height Height 10 5 y Am 0 0 ke China rkey sAus China Tu Japan Europe Japan Tur sAus SEAsia Rus Pla EsAus SEAsia EsAus Rus Pla North North Am North East Rus Europe We East Rus NW Africa NW We NW Africa NW F.

E F. F

Figure 8 Palaeobiogeographical affinities of the South Chinese foraminiferal microfauna: Dendrograms for the totality of taxa on the genus and species level using three different similarity indices, Raup-Creek, Jaccard and Euclidean. Cluster analysis agglomerative coefficients for each analysis is indicated in the top right corner. Palaeobiogeographical units: China: South China; EsAus: Eastern Aus- tralia; Europe: Western and Central Europe; F. East Rus: Far-East Russia and neighbouring countries; Japan; North Am: North America including Alaska and northern Arctic Canada; NW Africa: Northwest Africa mainly Morocco and Algeria; Rus Pla: wider Russian Plat- form including the Urals; SEAsia: South East Asia (Thailand, Vietnam, Laos); Turkey: Turkey and Iran; WesAus: Western Australia. partly with the total biodiversity; on the genus level this graphical relations between the eleven regions, because correlation is less pronounced. taxa known only outside South China were not included Clusters have been calculated on the genus and species into the analysis. level for the entire study interval (Figure 8) and individual Independently from the taxonomic level, the two den- substages (not shown herein) to obtain an overview on drograms for the same index are similar (Figures 8-10). possible palaeogeographical affinities of the South Chi- On the dendrograms calculated with the Raup-Crick in- nese fauna. To evaluate the influence of the calculation dex, South China is situated at the opposite corner of the method, the clusters have been calculated with three com- dendrogram isolated from all other palaeobiogeographical monly used similarity indices (Raup-Crick, Jaccard and units, which are all connected to each other at the base Euclidean similarity indices). It is important to note that of the dendrogram (Figure 8A, 8B). It is visually difficult these analyses show palaeogeographical affinities of the to differentiate distinctive clusters, with an exception for south Chinese fauna and do not show the palaeobiogeo- Eastern Australian and for Western Australian associated 50 JOURNAL OF PALAEOGEOGRAPHY Jan. 2014 to the North American genera. The shape of the dendro- integration of data for Western Australia. The periods of grams results from one particularity when applying the high diversity in South China are often poorly known or Raup-Crick index to our data matrix. In contrast to the usu- less diverse in Western Australia (e.g., Read et al., 1973). al palaeobiogeographical analyses, there is one unit (South On the other hand, the rich late Visean assemblages from China) with 100% taxa present. This unit dominates all the Bonaparte Basin (Mamet and Belford, 1968) falls in a calculations using the Raup-Crick algorithm. period when data from South China are less abundant, and The dendrograms calculated with Jaccard and Euclid- thus the palaeobiogeographical affinities of the Bonaparte ean indices show better resolved clusters, which resemble assemblages are not expressed by the comparison with the an uneven bar-bell (Figure 8C-8F). Common to both is Chinese data. The relative closeness of North America to a stable cluster of South China, Europe and the Russian South China is documented on the species and genus lev- Platform. With the Euclidean index, this cluster is well els; in fact North America is directly attached to the north- separated from a second large digitated cluster comprising ern Palaeotethyan cluster. all other units (Figure 8E, 8F). In the dendrogram using To detect possible changing palaeogeographical affini- the Jaccard index the cluster containing China is part of ties of southern China through time, hierarchical clusters a larger digitated cluster. Stable on both taxonomic levels (Figures 9, 10) and the above-mentioned Raup-Crick, Jac- is the order of cluster branching. The Far-East Russia and card and Euclidean indices clusters (not shown here) have Turkey cluster connects to North America on one side of been calculated for every substage. There are two principal the dendrogram and the cluster SE Asia, Japan and NW patterns for the position of South China in those dendro- Africa constitues the second side of the dendrogram (Fig- grams. The first pattern is that found in the general den- ure 8C, 8D). Depending on the similarity matric used, the drogram in which South China is attached to a cluster of Australian units from a cluster clearly separated from all Europe and Russian Platform. This pattern is found in the other units or as a cluster connected to the second side of Ivorian, Molinacian and Livian substages (Figures 9D- the dendrogram. 9F; 10D-10F). Before and after, China forms a cluster Hierarchical clusters and non-metric multivariate or- with the Russian Platform. The position of this cluster and dination analysis (NMDS) were calculated to foster and thus the closeness to the other regions varies between the question the results of the previously presented cluster different substages, but also on the taxonomic level. analyses (Figures 9-11). The two hierarchical clusters on This is an expression of the important differences be- the genus and species level for each studied time interval tween the dendrograms of the different substages and (Figures 9, 10) show the same pattern, which is overall taxonomical levels. On the genus level the units represent- comparable to the Jaccard clusters (Figure 8). As in the ing the northern Palaeotethys are mostly part of a larger Jaccard and Euclidean clusters, South China is closest to cluster from the Strunian to the Livian (Figures 9B-9F; a bundle formed by Western and Central Europe and the 10B-10F). During several substages, North America is wider Russian Platform. To this cluster is attached the clus- part of this larger cluster. The Warnantian and Pendle- ter of Far-East Russia and Turkey/Iran, thus the two palae- ian dendrograms (Figures 9G-9H; 10G-10H) show the obiogeographical units situated between South China and gradual disappearance of this Palaeotethyan constant. Es- the Russian Platform. This clearly indicates the good fau- pecially, the Pendleian dendrogram shows a clustering of nal interconnection in the northern Palaeotethyan Realm. palaeobiogeographical units (Figures 9H, 10H), which do The large distance in the cluster analysis between South not correspond to palaeogeographical proximities of these China and its southward neighbouring palaeogeographical units. The Palaeotethyan cluster can also be identified on units (SE Asia, Western Australia) indicates less important the species level. It can be a little more pronounced as in faunal interchange between these regions. However, on the Strunian and Livian or more diluted as in the Ivorian. the species and genus level, the Australian faunas are the The NMDS analyses (Figure 11) show a similar pattern. regions with the least interchange with China. This was Overall, the analysis on the genus level results in a dens- expected for Eastern Australia, since its faunal exchange er cluster (Figure 11A), with Eastern Australia being the with the Palaeotethyan Realm is hampered by ocean circu- most isolated entity on both taxonomic levels. The clus- lation patterns (Webb, 2000; Aretz et al., 2013). The poor ter of South China, Europe and Russian Platform is well exchange with Western Australia may be partly rooted in identified and this cluster is nearest to Far-East Russia and oceanic current patterns in the Palaeotethyan Realm (Aretz Turkey. Differences exist between the genus and species et al., 2013), but the analysis is certainly affected by the for the position and attachment of the other units. North Markus Aretz et al.: Diversity patterns and palaeobiogeographical relationships of latest Devonian-Lower Carboniferous foraminifers Vol. 3 No. 1 from South China: What is global, what is local? 51

All Strunian .0 .0 1.2

76 45 81 56 .6 0. 81 .6 0. 81

76 36 90 30 74 42 68 46 Height 94 75 Height 92 33

93 18 100 92 .2 0. 40

100 97 .2 0. 40 90 36 96 80 98 26

0. 00 99 64 0. 00 y ey ke rk sAus China Japan EsAus China Tu Europe SEAsia Tur Rus Pla Europe SEAsia WesAus Rus Pla We North Am North NW Africa NW A B Am North F. East Rus F. East Rus .4 .4 Hastarian Ivorian .0 1. 21 .0 1. 21

94 53

.6 0. 81 92 42 .6 0. 81 99 63 69 37 Height

Height 85 41 100 88 91 56 98 68 90 45 .2 0. 40 .2 0. 40 82 32 91 70

100 96 88 55 97 26 100 89 100 86 0. 00 0. 00 ey ey rk rk sAus sAus China Japan China EsAus Tu Tu Europe SEAsia Europe SEAsia Rus Pla Rus Pla We We North Am North North Am North East Rus East East Rus East NW Africa NW

C Africa NW D F. F.

.0 Molinacian Livian

82 14 76 7 .8 1.0 1.2 .6 0. 81 76 5 89 37 74 7 91 35

74 21 Height Height .4 0. 60 92 55 83 25 93 35

78 30 91 54 99 78 98 60

83 44 81 44 0. 20 84 43 98 76 0.0 0.0 0.2 0. 40 s s y ey rk ke China Japan EsAus Tu China Japan Europe SEAsia EsAus Rus Pla Tur Au Wes Europe SEAsia East Rus East Rus Pla North Am North Au Wes

E F Africa NW North Am North F. NW Africa NW F. East Rus F.

Warnantian Pendleian 1.5 .8 1.0 1.0

96 50 16

98 55 88 .4 0. 60

Height 97 59 93 24 Height .5 96 25 83 12 89 32 80 7

93 23 0. 20 85 12 90 19 94 41 89 27 88 26 100 82 99 58 0.0 0. 00 s rkey rkey sAus China Japan China Japan EsAus Tu Tu Europe SEAsia Europe SEAsia Rus Pla We Rus Pla Au Wes North Am North North Am North NW Africa NW . East Rus G H Africa NW F F. East Rus F.

Figure 9 Palaeobiogeographical affinities of the South Chinese foraminiferal microfauna: Dendrograms for hierarchical cluster analyses on the genus level for the entire studied interval (all) and the substages. Percentages of node robustness: Approximately unbiased p-value (green), bootstrap probability (red). Distance: Uncentered. Cluster method: Ward. Abbreviations for palaeobiogeographical units see Figure 8. 52 JOURNAL OF PALAEOGEOGRAPHY Jan. 2014

All Strunian .0 1.2

94 84 .6 0.8 80 20

96 86 80 14

.6 0. 81 86 44

79 50 81 47 85 35 86 26

Height 79 47 Height 95 75

98 96 .2 0. 40

.2 0. 40 99 97 97 68

100 87 0. 00 0. 00 ey ey rk sAus rk sAus China Japan China EsAus Tu Tu SEAsia Europe Europe SEAsia Rus Pla We We North Am North NW Africa NW Rus Pla A B Am North F. East Rus F. East Rus .5 Hastarian .4 Ivorian .0 1. 21

1. 01 97 65

98 58

.6 0. 81 87 59 96 77 94 54 Height Height .5 96 55 90 48 94 67 79 50

96 39 98 93

91 29 .2 0. 40 86 43 100 99 100 82 100 88 0. 00 0. 00 sAus China China Japan EsAus Turkey Turkey Europe Europe SEAsia Rus Pla Rus Pla SEAsia We WesAus North Am North North Am North NW Africa NW C D Africa NW F. East Rus F. East Rus Molinacian Livian .0 1.2

86 33

77 35

.8 1.0 1.2 1.4 93 53

84 17 .6 0. 81 73 12 94 42 71 37 86 47 85 41 Height Height 92 48 99 87

96 50 95 54 93 58

.2 0. 40 87 46

98 67 .2 0.4 0. 60 88 70

100 96 0. 00 0. 00 s ey rk sAus China China Japan Japan EsAus EsAus Tu Turkey Europe Europe SEAsia SEAsia Rus Pla Rus Pla We Au Wes North Am North North Am North NW Africa NW E Africa NW F F. East Rus F. East Rus

Warnantian Pendleian 1.5 .8 1.0

1.0 99 63 74 9

98 62 72 18

Height 92 28 Height 98 63 85 17 .5 76 26 92 35 88 21 94 25 89 37 87 11 85 12 92 35 98 76 98 60 0.0 0.2 0.4 0. 60 0. 00 s s ey rk China Japan China Japan Tu EsAus Europe Turkey SEAsia Europe SEAsia Rus Pla Au Wes Rus Pla Au Wes North Am North North Am North NW Africa NW G Africa NW H F. East Rus F. East Rus

Figure 10 Palaeobiogeographical affinities of the South Chinese foraminiferal microfauna: Dendrograms for hierarchical cluster analyses on the species level for the entire studied interval (all) and the substages. Percentages of node robustness: Approximately unbiased p-value (green), bootstrap probability (red). Distance: Uncentered. Cluster method: Ward. Abbreviations for palaeobiogeographical units see Figure 8. Markus Aretz et al.: Diversity patterns and palaeobiogeographical relationships of latest Devonian-Lower Carboniferous foraminifers Vol. 3 No. 1 from South China: What is global, what is local? 53

A genus level B species level 0.3 stress 0,09635 stress 0,06832 50 50 WA

0.15 Obtained rank WA Obtained rank 0.2 0 0 0 50 0 50 Target rank Target rank NA 0.10

0.1

0.05 C FER RP Coordinate 2 Coordinate 2 NA J 0 E 0 SEA SEA RP FER EA E T T EA C -0.1 -0.05 NWA NWA

J -0.2 -0.1 00.1 0.20.3 0.40.50.6 0.70.8 0.9 -0.1-0.2-0.3 0 0.60.50.40.30.20.1 Coordinate 1 Coordinate 1

Figure 11 Palaeobiogeographical affinities of the South Chinese foraminiferal microfauna: Plots for NMDS analyses with Dice similarity index for all taxa. Minimum span tree is given for the 11 palaeogeographical units. Inlet shows the Shepard plot and stress of the analysis. C-South China; EA-Eastern Australia; E-Western and Central Europe; FER-Far East Russia and neighbouring countries; J-Japan; NA-North America including Alaska and northern Arctic Canada; NWA-Northwest Africa mainly Morocco and Algeria; RP-Wider Russian Platform including the Urals; SEA-South East Asia (Thailand, Vietnam, Laos); T-Turkey and Iran; WA-Western Australia.

America is situated not too far from the core cluster, but 9 palaeobiogeographical units, but there are also taxa with while the minimum span tree indicates on the genus level a more reduced geographical extent, indicating that they a connection to Western Australia (Figure 11A), it forms a are not necessarily cosmopolitan. The dominance of these dead end at the species level (Figure 11B). The position of simple forms in the lowermost Hastarian can be linked to the other units changes between species and genus level, the aftermath of a global extinction event (‘Lilliput-Ef- but the two Australian units are always the most distanced fect’), but their dominance is not necessarily correlated to and isolated units, confirming the cluster analyses. The a possible extinction event, as evidenced in the case of the minimum span tree for the genus level shows a peculiar lower Warnantian. Indeed, a global bioevent is unknown relationship of North-West Africa, which is attached to at the Livian/Warnantian boundary, and the dominance of Eastern Australia (Figure 11A) in contrast to the cluster simple forms in South China is the effect of a deteriora- analyses and the NMDS on the species level, where it clus- tion in the regional palaeoenvironmental conditions (see ters with SE Asia and Japan (Figure 11B). above). Moreover, the wide geographical distribution of simple forms can be also explained by their simple test, 5.3 Discussion which do not offer many morphological characters to dif- The highest mean values for the geographical spread ferentiate taxa (e.g., Krainer and Vachard, 2011). One may of foraminifers have been observed in the lower Hastarian ask if several genotypes are lumped together, but it also and lower Warnantian, which are intervals characterised helps to prevent taxonomic over-splitting. by low total diversity and dominance of small, simple (of- Increasing endemicity in southern China goes hand in ten unilocular or bilocular) forms. These forms are often hand with the development of morphologically complex called disaster forms or ecological opportunists and their forms (e.g., appearance and evolution of Dainellidae). wide geographically distribution or even cosmopolitan This does not mean that large, complex forms are mainly character seems to be evident. In the South Chinese data- endemic, because the database contains numerous exam- set, simple forms are among those taxa known from at least ples of large, complex, cosmopolitan taxa. However, some 54 JOURNAL OF PALAEOGEOGRAPHY Jan. 2014 of these complex forms seem to be adapted to specific en- Hance et al. (2001). A more detailed temporal resolution vironments (see discussions in Vachard et al., 2010), thus of the data would be needed to test in detail the relations increasing the potential for oligotrophy and possible end- of 3rd-order sequences, biodiversity and palaeobiogeo- emism. graphical patterns. In South China, possible endemicity shows a peak in The analyses of palaeobiogeographical affinities clearly the Livian (MFZ 12) on the species level (Figure 7B). Tax- show that the fauna of the northern Palaeotethyan Realm onomic over-splitting can be ruled out as an explanation. is well interconnected. This result was expected, based on The fauna is taxonomically diversified, but does not show the qualitative palaeobiogeographical models (Kalvoda, extreme values. Endemic forms are widely distributed 1990; 2002). However, the better connection between among species and genera. The Livian endemism points South China and North America than between South to the establishment of palaeobiogeographical barriers China and palaeobiogeographical units of the southern between South China and neighbouring regions, prob- Palaeotethyan Realm (e.g., NW Africa) raises some ques- ably connected to a lower global sea-level. It is interesting tions. They partly originate from the analyses themselves, to note that in several platform systems and regions, the because only species present in China are analysed. Thus, Livian is difficult to identify or is unknown (e.g., North the relative poorness of late Visean foraminifers in South Africa) or characterised by major advances of terrigenous China excludes the full integration of the diversified late clastic facies (e.g., North-West Carboniferous Basin, Ire- Visean assemblages of Western Australia and North Af- land) (Aretz et al., 2010), Northumberland Trough (Waters rica (see references above). The Palaeotethyan affinity of et al., 2011). It cannot be ruled out that the poorer knowl- Alaska and northern Canada included in North America edge and documentation of the Livian in other regions is certainly one crucial element for the position of North could contribute to accentuated endemicity in South China America in our palaeobiogeographical analyses (Figures where the interval is well-studied. This points to the more 8-11). These two regions are in other analyses included general problem of a lack of quantitative data from other into the Palaeotethyan Realm (e.g., Groves and Wang, well-studied regions. The Belgian Namur-Dinant Basin is 2009). On the other hand, the foraminiferal assemblages a standard for the study of Carboniferous biostratigraphy of North America are more diverse and better studied than and calcareous foraminifers and a wealth of data is acces- regions like NW Africa or Western Australia, supposedly sible (see for references Poty et al., 2006 and in press), but better connected to South China. The separate analyses no synthesis has been published so far. for the Warnantian substage, where the datasheet contains Poty (2007) showed the global break-down of bioge- more African than North American taxa, does not change ographical barriers and intensive faunal exchange in the the general pattern. Thus, the conclusion that the closeness uppermost Ivorian. The most important Mississippian sea- between South China and North America could (partly) level drop (Hance et al., 2001; Poty, 2007) follows this be the expression of work effort and not of palaeobiogeo- so-called ‘Avins Event’ resulting in considerably reduced graphical connections is not supported. However, it is con- and geographically isolated platform areas. This develop- spicuous that the well-studied palaeobiogeographical units ment can be seen in South China in the endemicity peak of form a stable cluster in the analyses (Figures 10, 11), and MFZ 9, and its decrease during MFZ 10, probably due to that those regions with less well-known or more discon- sea-level rise causing the break-down of barriers. Hence, tinuous records are more remote. the global sea-level curve highly influences the faunal The clustering of the palaeobiogeographical affinities in interchange, and endemicity and biodiversity are thus the Serpukhovian has been relatively different than those consequences of regional origination patterns. Using the in earlier substages (Figures 8-11). This reorganisation 3rd-order sequence model of Hance et al. (2001), the low- cannot be connected to the closing of the Rheic Ocean, stand and transgressive system tracts should correspond which is often the origin for changes in palaeobiogeo- to times of elevated endemicity and regional origination graphical models in late Visean-Serpukhovian times (e.g., rates, whereas the highstand system tracts should corre- Korn et al., 2012) and the establishment of well-separated spond to wide geographical spread and low endemicity. North American and Palaeotethyan Realms. The pattern is This causality is difficult to see in the Chinese data. It random and it does not follow the positioning of palaeo- is most evident for the interval MFZ 8-MFZ 10, which geographical units or closeness of palaeobiogeographical can be roughly correlated to the HST (MFZ 8), LST and affinities/units. It must be suspected that, as for the bio- TST (MFZ 9) and HST (MFZ 10) of sequences 4 and 5 of diversity, the analyses suffer in this time slice from poor Markus Aretz et al.: Diversity patterns and palaeobiogeographical relationships of latest Devonian-Lower Carboniferous foraminifers Vol. 3 No. 1 from South China: What is global, what is local? 55 data. The same problem may exist for the Warnantian. in the Ivorian. Its shape is partly influenced by regional There are changes in the clustering compared to the older palaeoenvironmental conditions, which hamper the devel- Visean substages, which could be seen as a prelude to the opment of rich foraminiferal associations (MFZ 2, 13, 14). situation in the Serpukhovian. Diversity in the Strunian and basal Hastarian is rather low. Dispersal of foraminifers in the northern Palaeotethyan The extinction event of the Hangenberg crises in the latest Realm was efficient, as seen in the closeness of the five Devonian is documented in a biodiversity drop at the DCB palaeobiogeographical units in the clusters, hierarchi- and by the composition of the basal Mississippian biozone. cal clusters and NMDS, and the overall high values of The latter is characterised by abundant small unilocular geographical spread. The present study cannot answer the and bilocular foraminifers (mainly, Bisphaera spp. and question where the biogeographical centre of origination Earlandia spp.) and the absence of complex, large forms, is situated. South China would be an interesting candidate which became extinct during the crises. Hence, MFZ 1 ex- along with other regions like the Urals, Namur-Dinant Ba- hibits the classical characteristics of a ‘Lilliput-Effect’ in sin or Siberia. Westward oceanic currents have been pro- the aftermath of a global mass extinction. In South China posed (e.g., Webb, 2000) and also modelled (Aretz et al., the onset of the diversification in the Hastarian is delayed 2013) for this part of the Palaeotethyan Ocean. However, by one biozone compared to other regions due to unsuit- our study lacks the temporal resolution to show impor- able facies for foraminifers (MFZ 2).The highest diversi- tant migration flux of calcareous foraminifers from South ties are found around the Tournaisian-Visean boundary China to other regions. The comparison of the Strunian and can be directly related to the very detailed work done foraminifers showed the higher abundance and earlier ap- for the GSSP at Pengchong. The impact of this work can pearances of quasiendothyrids in the Urals than in South be directly seen in an exceptionally high value. In the last China (see 4.2). It seems to be reasonable to propose a Tournaisian biozone, 87% of all known species are found migration of these forms into South China. The absence in southern China (mean for other biozones with medium of any significant endemicity may also be used as an ar- to high biodiversity is 30%-40%). The opposite is seen in gument that South China was more likely to import taxa, the late Visean-Serpukhovian. In South China, this time because it would be very unusual that all indigenous taxa interval is not so well exposed and less studied than the would be exported. Moreover, the eastward migration has older substages. In consequence, South China is complete- also been found among Mississippian rugose corals (Poty ly decoupled from the global trend. In all other subtropi- et al., 2011; Aretz et al., 2013), although the dispersion of cal and tropical palaeobiogeographical provinces the late corals is often much slower than for calcareous foramini- Visean-Serpukhovian shows the highest diversity of the fers. This does not minimize the possibilities of westward entire Mississippian; in South China it is rather low. migration or dispersal starting in South China. It further Hence, there is a clear link between work effort and questions a single biogeographical centre, but in any case biodiversity data, at least on the regional scale of South the high degree of geographical spread and abundance of China. It can be expected that this is also true for other even cosmopolitan taxa in calcareous foraminifers occur- regions, and thus our current knowledge of quantitative ring in the same biozones advocates for very efficient and biodiversity data on regional and global scales may be fast distribution. It may be questionable if the temporal largely biased. The idea that the Palaeotethyan Realm was resolution in deep time records enables the identification the centre of origination (Mamet, 1977) to explain differ- of these fast processes. ences between diversity curves for the North American and Palaeotethyan Realm (Groves and Wang, 2009) is 6 Conclusions not confirmed here. The non-normalisation of the potential habitat surface in these two realms simply favours a The analysis of the dataset compiled for South China higher diversity in the larger realm, which is the case for based on recent taxonomic and biostratigraphic work in the Palaeotethys. Thus, the size relation of the realms has several key sections in Guangxi, Guizhou and Hunan is to be corrected, more data from regions in the central and one of the first attempts to quantify regional diversity and southern Palaeotethys should be included (regions which palaeobiogeographical affinities of latest Famennian to have largely been excluded in the dataset of Groves and Serpukhovian calcareous foraminifers. Wang, 2009), and finally a tripolar or quadrupolar palaeo- The diversity curve for the Strunian to Pendleian of biogeographical model should be applied. southern China has a bell-shaped form, with a double peak Palaeobiogeographical affinities of the south Chinese 56 JOURNAL OF PALAEOGEOGRAPHY Jan. 2014 calcareous foraminifers are stable through time, and only origination should occur during times of geographical iso- minor differences exist between the genus and species lation. However, the temporal resolution of the South Chi- level. They are closest to two regions, the wider Russian nese data is too large to work on this problem. Platform including the Urals and Western and Central Eu- rope. These three regions form with very few exceptions a Acknowledgements stable cluster in most analyses (cluster, hierarchical cluster and NMDS). The two palaeobiogeographical units situ- We thank Ian Somerville (Dublin) for his constructive ated between the Russian Platform and South China are review and Yuan Wang, Min Liu and Xiu-Fang Hu for often closely connected to the basic tripolar cluster, and editorial support. The authors would like to acknowledge thus characterise important faunal exchange in the north- their Chinese and Belgian colleagues who generated the ern Palaeotethyan Realm. For the moment, it is impossi- data used in this study. ble to determine the amount of migration into and out of South China. Although oceanic currents may favour the References migration from South China towards the west, there are increasing evidences that eastward migration was pos- Alve, E., 1999. Colonization of new habitats by benthic foraminif- sible as well. Strunian quasiendothyrids are one possible era: A review. Earth-Science Reviews, 46: 167-185. example of eastward migration; from the Urals (West) into Aretz, M., Dera, G., Lefebvre, V., Donnadieu, Y., Goddéris, Y., Ma- South China (East). couin, M., Nardin, E., 2013. The spatial and temporal distribution of Mississippian rugose corals: Contribution of modelled oce- An unresolved problem is the closer palaeobiogeo- anic currents and temperature data to this problem. In: Nardin, E., graphical affinity of South China to North America com- Aretz, M., (eds). Pre-Cenozoic climates international workshop. pared to neighbouring palaeo(bio)geographical units in the When data and modelling meet. Strata, Série 1, 14: 8-9. southern Palaeotethys (SE Asia, Western Australia). The Aretz, M., Herbig, H. -G., Somerville, I. D., Cózar, P., 2010. Rugose contour for North America chosen in this study may in- coral biostromes in the late Visean (Mississippian) of NW Ire- fluence the analyses because the northern regions of the land: Bioevents on an extensive carbonate platform. Palaeogeog- continent have been included although they show affinities raphy, Palaeoclimatology, Palaeoecology, 292: 488-506. to the Palaeotethyan Realm. However, even in Warnantian Aretz, M., Poty, E., Devuyst, F. -X., Hance, L., Hou, H., 2012. Late times, when more species are found in the southern Pal- Tournaisian Waulsortian-like carbonate mud banks from South aeotethys than in North America, the latter is still closer China (Longdianshan Hill, central Guangxi): Preliminary inves- clustered to South China. This is one example when sam- tigations. Geological Journal, 47: 450-461. ple size may not influence the analyses, but overall the Blakey, R. C., 2007. 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