The other biodiversity record: Innovations in -substrate interactions through geologic time

Luis A. Buatois, Dept. of Geological Sciences, University of Saskatchewan, 114 Science Place, Saskatoon SK S7N 5E2, Canada, luis. [email protected]; and M. Gabriela Mángano, Dept. of Geological Sciences, University of Saskatchewan, 114 Science Place, Saskatoon SK S7N 5E2, Canada, [email protected]

ABSTRACT 1979; Bambach, 1977; Sepkoski, 1978, 1979, and Droser, 2004; Mángano and Buatois, Tracking biodiversity changes based on 1984, 1997). However, this has been marked 2014; Buatois et al., 2016a), rather than on body through geologic time became by controversies regarding the nature of the whole . In this study we diversity trajectories and their potential one of the main objectives of tackle this issue based on a systematic and biases (e.g., Sepkoski et al., 1981; Alroy, in the 1980s. Trace fossils represent an alter- global compilation of trace- data 2010; Crampton et al., 2003; Holland, 2010; native record to evaluate secular changes in in the stratigraphic record. We show that Bush and Bambach, 2015). In these studies, diversity. A quantitative ichnologic analysis, quantitative ichnologic analysis indicates diversity has been invariably assessed based based on a comprehensive and global data that the three main marine evolutionary on body fossils. set, has been undertaken in order to evaluate radiations inferred from body fossils, namely Trace fossils represent an alternative temporal trends in diversity of the Explosion, Great record to assess secular changes in bio- and structures. The results of this Biodiversification Event, and diversity. Trace-fossil data were given less study indicate that the three main marine Marine Revolution, are also expressed in the attention and were considered briefly in evolutionary radiations (Cambrian Explo- trace-fossil record. In addition, the trace- only one of the more classic studies of bio- sion, Great Ordovician Biodiversification fossil record of continental environments diversity through time (e.g., the so-called Event, and Mesozoic Marine Revolution) suggests variable rates of increases in diversity, consensus paper by Sepkoski et al., 1981; detected in the body-fossil record are also with major radiations in the Ludlow–Early see also Mil​ler, 2009). Ichnologic informa- , Cisuralian, Early , Late expressed in the trace-fossil record. Analysis tion in the consensus paper was based on of ichnodiversity trajectories in marine , and Eocene, and slower increases early attempts of quantifying trace-fossil or plateaus in between these periods. environments supports Sepkoski’s logistic diversity, which were supported by the very model, which was originally based on limited data available at the time (Seilacher, CONCEPTS AND METHODS analysis of marine body fossils. The trace- 1974, 1977). The decision by Dolf Seilacher Trace fossils comprise distinctive struc- fossil record of continental environments to decline co-authorship of the consensus tures of biogenic origin, reflecting organism suggests variable rates of increases in ichno- paper reflects his doubts with respect to the diversity, with major radiations in the support that trace-fossil evidence was actu- behaviors while interacting with the Ludlow–Early Devonian, Cisuralian, Early ally providing to the diversity curves based on substrate (Fig. 1). Trace fossils may be Jurassic, Late Cretaceous, and Eocene, and body fossils. In a letter addressed to Sepkoski, preserved in a wide variety of substrates. slower increases or plateaus in between these dated 23 February 1981, Seilacher stated, Bioturbation structures occur in , periods. Our study indicates that ichnologic “By lumping the two groups you may get a whereas bio-​ structures are produced information represents an independent line curve that pleases you, but this might be an in rigid substrates, such as hardgrounds, of evidence that yields valuable insights to accident. The curve you have in mind (based clasts, bones, or rocks (Frey and Wheatcroft, evaluate paleobiologic megatrends. on the record of body fossils) is mainly one of 1989). Although the same type of trace-fossil shallow marine diversity. Including the flysch can be produced by phylogenetically INTRODUCTION (i.e., the deepwater) counts (which by their unrelated , in many instances trace The astounding diversity of animals in high diversity influence the results very fossils can be attributed to a producer with modern and continents is the result of much), I am afraid will do no justice to the variable levels of confidence. For example, macroevolutionary processes operating in cause, although the result may fit the general the branching system deep time. Conservative estimates suggest the picture” (Miller, 2009, p. 379). is commonly regarded as produced by modern biosphere hosts close to 13 million No attempts to produce global compre- decapod , typically callianassids species, of which approximately only 4% hensive compilations have been done since (Fig. 1) (Frey et al., 1978). However, such are marine (Benton, 2001). Despite the the pioneer work by Seilacher (see also links are not possible to establish in the impressive growth of fields exploring other Crimes, 1974). Subsequent ichnologic com- case of ichnofossils having less distinct sources of data (e.g., molecular), the fossil pilations focused on specific environments morphologic features. The trace-fossil record record is arguably still the main line of (e.g., Buatois et al., 1998; Orr, 2001; Uchman, encompasses marine and continental evidence to reconstruct the diversity of 2004; Minter et al., 2016a, 2016b, 2017) environments and spans from to through time (Valentine, 1969; Raup, 1972, or evolutionary radiations (e.g., Mángano (Buatois and Mángano, 2016).

GSA Today, v. 28, https://doi.org/10.1130/GSATG371A.1. Copyright 2018, The Geological Society of America. CC-BY-NC. Cl Figure 1. Ichnologic equivalents of Sepkoski’s CAMBRIAN EVOLUTIONARY evolutionary faunas. Representative elements FAUNA Li of the Cambrian evolutionary fauna include Ru Sy trace fossils, such as (Ru), (Cr) and Dimorphichnus (Di), and the Cr Di inarticulate burrow Lingulichnus (Li). Trace fossils of -like organisms Ol include Syringomorpha (Sy) and (Ol), whereas Climactichnites (Cl) has been attributed to mollusk-like producers. Examples of the evolutionary fauna include Da ichnotaxa produced by worm-like animals, such as Daedalus (Da), Arthrophycus (Ar), PALEOZOIC EVOLUTIONARY FAUNA Heimdallia (He), and Dictyodora (Dy). The Ar He Modern evolutionary fauna is dominated by , such as Psilonichnus (Ps), Ophiomorpha (Op), Thalassinoides (Th), and

Dy Sinusichnus (Si), as well as bivalves, such as Hillichnus (Hi), and irregular echinoids, such as Scolicia (Sc). Structures produced by worm-like organisms include Lapispira (La), Schaubcylindrichnus (Sch), Phoebichnus (Ph), Ha Si and Haentzschelinia (Ha). For bibliographic Ps Op sources, see supplementary material in the Sch GSA Data Repository (see text footnote 1).


Th La

Sc Sc


Whereas the main focus of studies on that is more firmly established nonmarine clastic rock volume, the number biodiversity has been on the number of at ichnogenus level than at ichnospecies of ichnofossil-bearing formations, and species or higher taxa (Sepkoski, 1997), rank. Only trace-fossil data the number of trace-fossil assemblages ichnodiversity (or trace-fossil diversity) were considered. Individual curves were documented (Minter et al., 2017). Potential studies focus on the different behaviors produced for continental, shallow-marine, biases are discussed in the supplementary involved in animal-substrate interactions. and deep-marine bioturbation, and material (see footnote 1). Ichnodiversity refers to the number of marine and continental bioerosion (Fig. 2). trace-fossil types (ichnotaxa) present in Additional diversity curves were compiled RESULTS any given assemblage or geologic period, for all marine bioturbation, all marine Behavioral innovations seem to have taken therefore providing a measurement of (bio erosion plus bioturbation), and all place in pulses rather than at a steady pace behavioral richness (Bua​tois and Mángano, continental (bioerosion plus bioturbation) (Fig. 2). For marine environments, a 433% 2011, 2013). Ichnogeneric compilation was ichnogenera. A rarefaction analysis of increase in ichnodiversity occurred during based on literature and personal data (GSA the data pertaining to the Cambrian and the Terraneuvian, a 48% increase took place Data Repository Tables DR1 and DR21). The Ordovician portions of the marine curves between the Early and Late Ordovician, total number of invertebrate ichnogenera showing rapid ichnodiversity increases was and a more protracted and modest identified as valid is 534, encompassing undertaken to evaluate the effects of increase occurred later in the Mesozoic with 428 for bioturbation structures and 106 for sample size on the curves (Buatois et al., increases in the Early Jurassic (8%) and bioerosion structures (updated from Buatois 2016a). Diversity data for the continental Late Cretaceous (20%), totaling an overall et al., 2017). We follow the common practice Paleozoic were standardized by using increase of 37% (between the Late of assessing ichnodiversity at ichnogeneric the residuals method to evaluate potential and Late Cretaceous) (Table DR3 [see foot- rank, because there is a general agreement sampling biases regarding the abundance of note 1]).

1 GSA Data Repository item 2018307, Fig. DR1, Tables DR1–DR3, and further comments on concepts and methods, is available online at www.geosociety .org/ datarepository/2018. l



n H












to Renewed increase in complexity of infaunal






i tiering structure (26, 39)



ioerosio 23 ioerosio











Marine b





w w



Pa Continental Ichnodiversity decrease as result of mass extinction


io 66 t Marine and subsequent rebound (17, 38)


S Rapid increase in ichnodiversity of


s bioerosion structures in bone


N Increase in drilling predation (33, 35-36) and of paleosol trace fossils (17, 37)






Deep Slow and protracted increase in ichnodiversity of bioerosion and bioturbation structures (16, 26, 34) 145


c Increase in durophagous predation (33)

M Marked increase in complexity of infaunal tiering New rise in ichnodiversity of bioturbation

Jurassi structure (26) structures and earliest record E Rise to dominance of bivalve burrows and appearance of of bone bioerosion (31-32) 201 irregular echinoid trace fossils (26, 28-30)


c Rapid increase in ichnodiversity of

L bioerosion structures in wood (27)

iassi Appearance of archetypal decapod crustacean burrows &


M ichnodiversity rebound after mass extinction (22,25-26)

252 E Ichnodiversity decrease as result of mass extinction L (22-24)

G New rise in ichnodiversity of bioturbation structures and earliest record of

Permian wood bioerosion (18-21) 298 Cisuralian








EM 358



y M




419 P Rapid increase in ichnodiversity of L EVEN bioturbation structures (18-20) W


ilurian Ichnodiversity decrease as result of mass extinction


TION 443 S and subsequent rebound (15-17) Rapid increase in ichnodiversity of bioturbation and

ML T ORDOVICIAN of bioerosion structures (11-14)


485 GREA


BIODIVERSIFICA Ep 3 Early incursions of on land (8-10)

N Ep 2 Increased colonization of the infaunal ecospace and


R appearance of deep infaunal suspension feeders (2,7)



Te Rapid increase in ichnodiversity of bioturbation structures (2,7)


CAMB Initial slight increase in infaunalization and trace-fossil

Nam EX complexity (1-6) Ven Ma Ediac Appearance of bilaterian trace fossils (1-3) 50 100 150 200 Number of Ichnogenera

Figure 2. Ichnodiversity changes and milestones in animal-substrate interactions through geologic time as reflected by the trace-fossil record. Arrows indicate mass extinctions. Numbers correspond to bibliographic sources indicated in the supplementary material in the GSA Data Repository (see text footnote 1). The Terraneuvian increase, attributed dilution of trilobite faunas inferred from the . The bioerosion ichnogenus to the , is restricted to body-fossil record. Contr­ibution of trilo- is known since the Devonian (Ta- bioturbation (Mángano and Buatois, 2014;​ bite-produced trace fossils to alpha ichnodi- panila, 2006), but it became abundant in the Buatois et al., 2016a). The Cambrian Explo- versity at ichnospecies level in the Tremado- Mesozoic, when various ichnospecies origi- sion is characterized by the rise of the Cam- cian averages 41.5%, wher­eas only a 30.6% nated. Significant bioerosion innovations are brian evolutionary fauna, which was domi- was attained in the Floian–Darriwilian, and represented by Radulichnus (gastropods and nated by , one of the most significant just 12.1% for the Sandbian–­Hirnantian ), Teredolites (pholadid bivalves), elements not only based on the body-fossil (Mángano et al., 2016). Gnathichnus (regular echinoids), and record, but also from an ichnologic perspec- The Mesozoic ichnodiversity increase Maeandropolydora (spionid ) tive (Seilacher, 1985). In addition, inarticu- (Fig. 2, Table DR3 [see footnote 1]), concom- (Taylor and Wilson, 2003; Radley, 2010; late , another important compo- itant with the rise to dominance of the mod- Villegas-Martín et al., 2012). nent, are represented by the ichnogenus Lin- ern evolutionary fauna (MEF), is attributed Ichnodiversity in continental environments gulichnus (Pemberton and Kobluk, 1978). to the Mesozoic Marine Revolution. Bi- (Fig. 2, Table DR3 [see footnote 1]) is more However, the high ichnodiversity that char- valves, gastropods, echinoids, crustaceans, difficult to evaluate due to the patchiness of acterizes the Cambrian reflects the activity of and marine are dominant ele- the trace-fossil record (Minter et al., 2016a, soft-bodied clades that are poorly known ments (Sepkoski, 1981). Irregular echinoids, 2016b, 2017). A 967% ichnodiversity increase from the body-fossil record (and, therefore, crustaceans, and bivalves are the most im- characterizes the –Devonian transi- not listed as members of the Cambrian evolu- portant bioturbators in marine settings, in tion, followed by a plateau until the Early tionary fauna). Several ichnogenera are addition to worms (Buatois et al., 2016b), il- Mississippian (Table DR3), although the restricted to the Cambrian (e.g., Climactich- lustrating the ichnologic equivalent of the latter most likely reflects the scarcity of nites, Oldhamia, Syringomorpha). Trilobite MEF (Figs. 1 and DR1 [see footnote 1]). Upper Devonian continental strata (Minter trace fossils, as well as those ichnogenera Heart urchins (spatangoids), known since the et al., 2016b). New rises in ichnodiversity showing stratigraphic ranges restricted to Early Jurassic, are the producers of the ich- took place during the Cisuralian (65%) the Cambrian, may be regarded as the ichno- nogenera Bichordites, Cardioichnus, and and the Early Jurassic (22%) (Table DR3). logic equivalent of Sepkoski’s Cambrian Scolicia (Smith and Crimes, 1983; Plaziat Subsequent to this peak, ichnodiversity expe- evolutionary fauna (Figs. 1 and DR1 [see and Mahmoudi, 1988), all typical bioturba- rienced a gradual and continuous increase. footnote 1]). tors in post-Paleozoic seas. Crustacean bur- The earliest uncontroversial evidence of con- The Ordovician increase in ichnodiversity rows include ichnogenera that occurred for tinental bioerosion is from the late is attributed to the Great Ordovician Biodi- the first time during the Mesozoic (e.g., (Labandeira et al., 2017), but it is by the Late versification Event and is reflected not only Ophiomorpha, Psilonichnus, Sinusichnus, Triassic when rapid diversification took place by an increase in diversity of bioturbation, Spongeliomorpha) and a few that are known (Tapanila and Roberts, 2012). The earliest but also by bioerosion structures (Ordovician since the Paleozoic but became more abun- record of bone bioerosion is from bioerosion revolution of Wilson and Palmer, dant as a result of the Mesozoic Marine Rev- the Early Jurassic (Xing et al., 2015). An 2006) (Fig. 2, Table DR3 [see footnote 1]). olution (Gyrolithes, Thalassinoides) (Carmo- increase in ichnodiversity of continental This revolution in the ability of organisms to na et al., 2004). Other crustacean ichnotaxa bioerosion occurred in the Late Cretaceous penetrate skeletal material and hardgrounds occurred for the first time in the Neogene (100%) followed by a plateau that continues occurred ~80 m.y. after the Cambrian Explo- (Parmaichnus, Lepeichnus). The most com- until the Holocene (Fig. 2, Table DR3). Over- sion in bioturbation (Bua­tois et al., 2016a). mon trace fossils produced by bivalves (Pro- all, the ichnodiversity increases that took The Great Ordovician Biodiversification tovirgularia, Lockeia), although known place in continental environments by the end Event signals a shift from dominance of ele- since the early Paleozoic, became more of the Mesozoic may reflect the appearance ments of the Cambrian evolutionary fauna to abundant since the Mesozoic (Buatois et al., of sophisticated insect nesting structures in those of the Paleozoic and Modern evolu- 2016b). Siphonichnus is common in the late soils (Genise, 2016). tionary faunas (Sepkoski, 1981; Miller and Paleozoic, reflecting an evolutionary radia- Connolly, 2001). Articulate brachiopods, tion of infaunal bivalves, but it is particularly DISCUSSION: SIGNIFICANCE, rugose and tabulate corals, and crinoids are abundant since the Triassic (Knaust, 2015). CAVEATS, AND PROSPECTS dominant elements of the Paleozoic evolu- Hillichnus, attributed to the activities of tell- The concepts of Cambrian Explosion, tionary fauna (Sepkoski, 1981). Unsurpris- inacean bivalves (Bromley et al., 2003), is a Great Ordovician Biodiversification Event, ingly given their modes of life, none of these product of the Mesozoic Marine Revolution. and Mesozoic Marine Revolution are all clades are significant from an ichnologic Some of the trace fossils produced by worms based on body fossils. The fact that these evo- standpoint, obscuring characterization of an (e.g., Haentzschelinia, Lapispira, Patagon- lutionary radiations are also reflected by the equivalent of the Paleozoic evolutionary fau- ichnus, Phoebichnus) are only known in trace-fossil record provides independent sup- na. However, a few ichnogenera showing post-Paleozoic marine strata, but the vast port to the notion that these were truly mac- restriction or peak abundance during the majority (e.g., Cylindrichnus, Macaronich- roevolutionary events, rather than taphonom- Paleozoic (e.g., Arthrophycus, Dictyodora, nus, Schaubcylindrichnus) have been docu- ic artifacts (Buatois and Mángano, 2016). Daedalus, Heimdallia) may be regarded as mented since the Paleozoic. However, some Although some hard-bodied typical of the Paleozoic evolutionary fauna of these ichnogenera became much more (e.g., bivalves) produce trace fossils, most (Figs. 1 and DR1 [see footnote 1]). In addi- common since the Mesozoic (Buatois et al., biogenic structures are made by soft-bodied tion, the trace-fossil record of the Great Or- 2016b). The most significant bioeroders were organisms (sometimes collectively and infor- dovician Biodiversification Event reflects the , gastropods, bivalves, echinoids, and mally referred to as worms, but in fact encompassing a wide variety of clades) reached a plateau yet (Sepkoski, 1981, 1984). environments based on body fossils (Benton, or poorly skeletonized invertebrates (e.g., The three-phase kinetic model developed by 2001). On the contrary, a plateau seems thalassinidean crustaceans). The trace-fossil Sepkoski (1984) provided an analytical view to have been reached by the end of the record provides infor­mation on animals of marine diversification with different glob- Mesozoic in the case of continental bioero- that are typically underrepresented in the al equilibria for each of the three evolution- sion. However, our knowledge of continental body-fossil record. Assessing the record­ of ary radiations (but see Kowalewski et al., bioerosion lags considerably behind that of small and soft-bodied organisms making the 2006; Kiessling et al., 2008; Alroy et al., bioturbation, so available patterns should be majority of the biomass (“tackling the 99%” 2008; Alroy, 2010, 2014). Studies based on taken with extreme caution. in Sperling’s 2013 analogy) is of fundamen- standardized curves indicated that late Ceno- Forty of ichnologic research since tal importance to reconstructing the history zoic diversity is only slightly higher than the the compilation by Dolf Seilacher prompt us of life. Also, our results are consistent with Paleozoic maximum (e.g., Alroy et al., 2008; to question if his reluctance to get involved in the observation that each evolutionary fauna Alroy, 2010, 2014). However, recent work the consensus papers is still justified by the shows more ecologic complexity than the shows a pattern that is more consistent with now available evidence. Our study shows that previous one, revealing an increased use of the original Sepkoski’s curves, indicating after the initial burst in ichnodiversity that the ecospace (Bambach et al., 2007; Bush et diversity levels that doubled Paleo- took place during the Cambrian Explosion, al., 2007). zoic values (Bush and Bambach, 2015). subsequent diversification was most clearly Diversification curves may adopt three The curves for marine invertebrate trace manifested in the deep sea (83% increase be- different patterns, as illustrated by the fossils show a similar trajectory to that of tween the end of the Cambrian and the end of straight (representing additive increase), body fossils (Sepkoski, 1997), providing em- the Ordovician and 58% between the Middle exponential (implying doubling of diversity piric independent support to the three-phase Jurassic and the Eocene) (Table DR3 [see within fixed units of time if speciation and kinetic (logistic) model (Sepkoski, 1984) and footnote 1]). However, the increase was not extinction rates remain constant), and logis- indicating similar diversity trajectories for restricted to the deep sea, but also took tic (comprising initial slow diversification animal diversity and their behaviors. The ex- place in shallow water (42% increase followed by a rapid rise and a plateau) plosive Terraneuvian diversification in between the end of the Cambrian and the models (Benton, 2001). In turn, logistic ­bioturbation was preceded by a slow increase end of the Ordovician and 26% through the models represent equilibrium models be- during the terminal Ediacaran and followed whole Mesozoic) (Table DR3). Further cause they imply that global equilibria in by a plateau during the middle to late Cam- ichnodiversity increases are apparent for diversity is attained, whereas exponential brian, underscoring the logistic ­nature of the bioerosion, which cannot be attributed to models are non-equilibrium models imply- Cambrian Explosion. This diversification innovations in the deep sea (Fig. 2). ing that a ceiling to diversity has not been preceded the Cambrian Explosion as indicat- However, Seilacher’s original compila- reached or that there is no such ceiling ed by body fossils, which took place later in tions, showing constant ichnodiversity levels (Benton, 2001). Diversification of marine the early Cambrian (Mángano and Buatois, in shallow water and increased diversifica- invertebrates is apparently best described 2014). A similar case of logistic pattern of tion in the deep sea, were not of global ichno- by a logistic model (Sepkoski, 1978, 1984), diversification can be made for the Great Or- diversity, but of maximum alpha ichnodiver- but diversification of continental biotas dovician Biodiversification Event with a rap- sity. Therefore, these curves reflect richness may have followed an exponential model id rise taking place through the Ordovician at a community level rather than globally. (Benton, 1985, 2001; Labandeira and and a plateau lasting for roughly the remain- Ongoing work is attempting to produce a Sepkoski, 1993). However, in recent years it ing of the Paleozoic. In turn, the rapid rise in database compiling alpha ichnodiversity for has been argued that fluctuating equilibrium ichnodiversity of the Late Cretaceous was specific environments through the Phanero- diversities through time may produce a pat- preceded by a more protracted increase that zoic in order to evaluate changes in within- tern of intervals of relative stability alternat- started during the recovery after the and inter-habitat ichnodiversity. Previous ing with times of radiations, which is appar- end-Permian mass extinction and was work on deep-sea trace fossils by Uchman ently similar to a coupled logistic model, but followed by a plateau until the present. This (2004) suggested a more nuanced scenario to resulting from a different underlying evolu- represents a departure from the diversity that originally indicated by Seilacher (1974, tionary dynamics (Alroy, 2010; Foote, 2010; trajectory of post-Paleozoic faunas, which 1977). Although an overall increase in maxi- Bush et al., 2016). does not show any evidence of a plateau mum alpha ichnodiversity is apparent, this According to the logistic model, marine (Sepkoski, 1981, 1984). trend has been punctuated by several fluctua- evolutionary radiations display the pattern of Variable rates of increases in ichnodiversi- tions, including significantly low levels from early slow growth, subsequent rapid growth, ty are detected for continental bioturbation, the to the Middle Jurassic and final slowing of growth reaching a pla- with major radiations in the Ludlow–Early (Uchman, 2004). Comparative analysis of teau (Sepkoski, 1978, 1984). This is particu- Devonian, Cisuralian, Early Jurassic, Late brackish-water marginal-marine environ- larly illustrated by the Cambrian Explosion Cretaceous, Eocene, and (Fig. 2, ments indicates that, even in these stressful and the Great Ordovician Biodiversifica- Table DR3 [see footnote 1]). No plateau settings, alpha ichnodiversity has increased tion Event, which displayed very rapid indicative of an equilibrium stage is apparent, through the Phanerozoic (Buatois et al., growths of diversity in their initial stages suggesting that the invasion of the land 2005). until reaching a plateau (Sepkoski, 1978, is still an ongoing process (Miller and The explosive development of analytical 1979). In contrast, diversity rose more slowly Labandeira, 2002). This is consistent with the demonstrates the need for during the initial phase of the Mesozoic Ma- non-equilibrium nature of models currently standardizing trace-fossil data in the same rine Revolution and apparently has not envisaged for diversification in continental fashion that has been done with body-fossil data. Ongoing ichnologic work is showing Palaeoecology, v. 192, p. 157–186, https://doi­­.org­ Crampton, J.S., Beu, A.G., Cooper, R.A., Jones, the usefulness of this approach, which has /10.1016/S0031-0182(02)00684-3. 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