Early Triassic Gulliver gastropods: Spatio-temporal distribution and significance for biotic...

Earth-Science Reviews 146 (2015) 31–64

Contents lists available at ScienceDirect

Earth-Science Reviews

j ourna l homepage: www.e lsev ie r .com/ locate /earsc i rev

Early Triassic Gulliver gastropods: Spatio-temporal distribution andsignificance for biotic recovery after the end-Permian mass extinction

Arnaud Brayard a,⁎, Maximiliano Meier b, Gilles Escarguel c, Emmanuel Fara a, Alexander Nützel d,Nicolas Olivier e, Kevin G. Bylund f, James F. Jenks g, Daniel A. Stephen h, Michael Hautmann b,Emmanuelle Vennin a, Hugo Bucher b

a UMR CNRS 6282 Biogéosciences, Université de Bourgogne, 6 boulevard Gabriel, 21000 Dijon, Franceb Paläontologisches Institut und Museum, Universität Zürich, 8006 Zürich, Switzerlandc UMR CNRS 5276, Laboratoire de Géologie de Lyon: Terre, Planètes, Environnement, Université Claude Bernard Lyon 1, 27-43 Boulevard du 11 novembre 1918, 69622 Villeurbanne Cedex, Franced SNSB-Bayerische Staatssammlung für Paläontologie und Geologie, Department of Earth and Environmental Sciences, Palaeontology & Geobiology, GeoBio-Center LMU, Richard-Wagner-Str. 10,80333 München, Germanye Laboratoire Magmas et Volcans, Université Blaise Pascal, CNRS, IRD, OPGC, 5 rue Kessler, 63038 Clermont Ferrand, Francef 140 South 700 East, Spanish Fork, UT 84660, USAg 1134 Johnson Ridge Lane, West Jordan, UT 84084, USAh Department of Earth Science, Utah Valley University, 800 West University Parkway, Orem, UT 84058, USA

⁎ Corresponding author.E-mail address: [email protected] (A. B

http://dx.doi.org/10.1016/j.earscirev.2015.03.0050012-8252/© 2015 Elsevier B.V. All rights reserved.

a b s t r a c t
a r t i c l e i n f o
Article history:Received 19 October 2014Accepted 18 March 2015Available online 28 March 2015

Keywords:GastropodsEarly TriassicLilliput effectBody sizeSampling effectBiotic recovery

A reduction in body size (Lilliput effect) has been repeatedly proposed for many marine organisms in theaftermath of the Permian–Triassic (PT) mass extinction. Specifically-reduced maximum sizes of benthic marineinvertebrates have been proposed for the entire Early Triassic. This concept was originally based on observationson Early Triassic gastropods from the western USA basin and the Dolomites (N Italy) and it stimulatedsubsequent studies on other taxonomic groups. However, only a few studies have tested the validity of theLilliput effect in gastropods to determine whether the paucity of large-sized gastropods is a genuine signal orthe result of a poor fossil record and insufficient sampling. In combination with a review of the literature, wedocument numerous new, abundant, large-sized gastropods from the Griesbachian outcrops of Greenland andfrom the Smithian–early Spathian interval in the southwestern USA. We show that large-sized (“Gulliver”)gastropods (i) were present soon after the PTmass extinction, (ii) occurred in various basins, sedimentary faciesand environmental contexts (from shallow to deeper settings), and (iii) belong to diverse higher-rank taxa.Focusing on thewestern USA basin, we investigate areas fromwhichmicrogastropod shell-beds were previouslypresented as being typical. However, we show that Gulliver gastropods do occur in the very same areas.Insufficient sampling effort is probably the main reason for the rarity of reports of large Early Triassic gastropods,which is supported by preliminary rarefaction-based simulations. Finally, it appears that the recentlydocumented middle to late Smithian climate shifts and the severe end-Smithian extinction of nekto-pelagicfaunas did not reduce maximum shell sizes of gastropods.

© 2015 Elsevier B.V. All rights reserved.

Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 322. Lilliput and Gulliver gastropods in living and fossil assemblages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333. Previous reports of Early Triassic Gulliver occurrences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 354. Newly sampled Gulliver collections: the fieldwork contribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 365. Griesbachian Gullivers from Greenland . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

5.1. Geological and biostratigraphical settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 365.2. Gulliver gastropods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

rayard).

http://crossmark.crossref.org/dialog/?doi=10.1016/j.earscirev.2015.03.005&domain=pdf

http://dx.doi.org/10.1016/j.earscirev.2015.03.005

mailto:[email protected]

http://dx.doi.org/10.1016/j.earscirev.2015.03.005

http://www.sciencedirect.com/science/journal/00128252

32 A. Brayard et al. / Earth-Science Reviews 146 (2015) 31–64

6. Smithian–early Spathian Gullivers from western USA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 386.1. Geological and biostratigraphical settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 386.2. Gulliver gastropods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

6.2.1. General observations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 396.2.2. Gullivers as micro-habitat for epibionts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 436.2.3. Local lateral variations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

7. Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 537.1. Sampling and preservation effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

7.1.1. Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 537.1.2. Preservation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

7.2. Distribution within the western USA basin: local and regional controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 557.3. Early Triassic spatio-temporal distributions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 577.4. Gulliver gastropods vs. global Early Triassic environmental changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 577.5. Is there an Early Triassic Lilliput effect? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

7.5.1. Lilliput effect sensu stricto . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 587.5.2. Lilliput effect sensu lato . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 597.5.3. The paradox of the western USA basin and the risk of across-scale extrapolation . . . . . . . . . . . . . . . . . . . . . . . . . 59

8. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 609. Outlook: research challenges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

1. Introduction

Recovery from the devastating end-Permian mass extinction ismostly assumed to be a delayed process, spanning at least the entireEarly Triassic (~5 Myr). More precisely, the crisis aftermath isportrayed as a time of high ecological stress characterized by chang-es in water temperature (Sun et al., 2012; Romano et al., 2013),large-scale fluctuations of the global carbon cycle and harsh marineconditions, including a combination of ocean acidification, anoxia,euxinia, and fluctuating productivity (e.g., Payne et al., 2004, 2010;Galfetti et al., 2007a,b; Horacek et al., 2007; Payne and Kump,2007; Hinojosa et al., 2012; Clarkson et al., 2013; Grasby et al.,2013). This suggests tight links between these environmental vari-ables and the restructuring of ecosystems, but the actual drivers ofthis long-term process still remain elusive. Associated with the sce-nario of a delayed recovery, which was mainly based on global diver-sity patterns of benthic organisms such as bivalves, gastropods,brachiopods, crinoids or corals, several other Early Triassic global-scale paradigms such as a proposed “reef gap” or a “Lilliput effect”(see Erwin, 2006) have been discussed intensively. Contrastingwith these phenomena, recent analyses of nekto-pelagic taxa suchas ammonoids and conodonts document a non-delayed, explosiveEarly Triassic re-diversification (Orchard, 2007; Brayard et al.,2009b). Similarly, metazoan reefs, commonly acknowledged not tohave been re-established until the Middle Triassic, have been recent-ly reported from the Early Triassic of the western USA, suggesting afast reef rebuilding wherever permitted by environmental condi-tions (Brayard et al., 2011b; Marenco et al., 2012; Olivier et al., inpress; Vennin et al., 2015), although large metazoan reefs were cer-tainly not as widespread and frequent in the Early Triassic than in theLate Triassic.

The contention that Early Triassic benthic faunas were generallydepauperate has become controversial over the past few years, asshown by the diversified assemblages recently described from theGriesbachian of various latitudes in South China (Kaim et al., 2010;Hautmann et al., 2011), Oman (Twitchett et al., 2004; Wheeley andTwitchett, 2005) and Italy (Hofmann et al., 2011, in press); theGriesbachian–Dienerian interval of the Canadian Arctic (Zonneveldet al., 2007; Beatty et al., 2008); the Griesbachian–Smithian interval ofSouth Primorye (Far East Russia; Shigeta et al., 2009); and theGriesbachian–early Spathian interval of the western USA (McGowanet al., 2009; Hautmann et al., 2011; Hofmann et al., 2013a,b, 2014).

Although several relatively diverse Early Triassic marine invertebratefaunas have been reported during the recent years, the diversity ofLate Triassic faunas such as assemblages from the early Carnian CassianFormation is much higher than that of any known Early Triassic fauna(e.g., Hausmann and Nützel, 2015).

One of most prominent Early Triassic paradigms is the “Lilliputeffect”, i.e., a temporary body-size reduction within survivor clades. Itwas first proposed for Silurian graptolites at the species level byUrbanek (1993) and later suggested for other time intervals and taxa,including several marine Early Triassic clades: foraminifers (Songet al., 2011; Rego et al., 2012), bivalves (Hautmann and Nützel, 2005;Twitchett, 2007; Posenato, 2009; Metcalfe et al., 2011), gastropods(see references below), brachiopods (He et al., 2007, 2010, 2015; Penget al., 2007; Leighton and Schneider, 2008; Chen et al., 2009; Posenato,2009; Metcalfe et al., 2011; Posenato et al., 2014), ostracods (Forel,2013), ophiuroids (Twitchett et al., 2005), fishes (Mutter and Neuman,2009), sponges (Liu et al. 2013) and trace fossils (e.g., Twitchett andBarras, 2004; Twitchett, 2007). Luo et al. (2008) and Chen et al.(2013) also recorded a body-size reduction for some conodont lineagesin South China. However, these are restricted to a few conodont zonesduring the immediate Permian–Triassic (PT) extinction aftermath andthe following end-Smithian crisis, respectively.

Gastropods were among the first organisms used as a model for theLilliput effect, mainly based on faunas from the western USA basin(e.g., Batten, 1973; Batten and Stokes, 1986; Schubert and Bottjer,1995; Fraiser and Bottjer, 2004). Later, it was proposed that the Lilliputeffect in Early Triassic gastropods was a global phenomenon spanningthe entire Early Triassic (e.g., Fraiser and Bottjer, 2004; Fraiser et al.,2005; Payne, 2005). Several “microgastropod” (arbitrarily defined asadult specimens smaller than 1 cm; Fraiser and Bottjer, 2004) assem-blages have been reported from the Early Triassic (e.g., Batten andStokes, 1986; Schubert and Bottjer, 1995; Twitchett and Wignall,1996; Lehrmann et al., 2003; Boyer, 2004; Fraiser and Bottjer, 2004;Fraiser et al., 2005; Nützel and Schulbert, 2005; Sano et al., 2012). Upto now,most of the studies dealingwith the Lilliput effect in Early Trias-sic gastropods have focused on the proliferation ofmicrogastropods andespecially on the absence of large specimens, i.e., a reduction of themaximum size in comparison to Permian and Middle to Late Triassicfaunas. However, Brayard et al. (2010, 2011a) documented numerouslarge-sized specimens (up to an estimated maximum size of ~10 cm)representing several gastropod genera and higher taxa from Smithian(i.e., ~1 Myr after the PT extinction; Galfetti et al., 2007b) outcrops of

33A. Brayard et al. / Earth-Science Reviews 146 (2015) 31–64

thewestern USA basin. These assemblages also indicate that large-sizedspecimenswere not unusual and that size––frequency distributions arecomparable to later Mesozoic and modern gastropod faunas (Brayardet al., 2010, 2011a). As argued by Fraiser and Bottjer (2004), Payne(2005) and Nützel et al. (2010), it is more the absence or scarcity oflarge-sized gastropods, i.e., “Gulliver” specimens, that until recently ap-peared to be remarkable for the Early Triassic. Occurrence of large-sizedgastropods in the western USA basin, combined with other worldwiderecords (Brayard et al., 2010, 2011a) thus questioned the Lilliputhypothesis for this clade. Is the paucity of large-sized gastropods a gen-uine signal or the outcome of a still inadequately sampled, and thuspoorly known fossil record? Answering this question is crucial to testthe validity of the Lilliput effect in the context of the Early Triassic bioticrecovery.

The present study documents numerous new, abundant, large-sizedgastropods from Griesbachian outcrops of Greenland and from theSmithian–early Spathian interval in the western USA basin. In addition,reports of large Early Triassic gastropods from the literature are ana-lyzed. We show that Gulliver gastropods (i) were present soon afterthe PT mass extinction, (ii) occurred in various basins, sedimentaryfacies and environmental contexts (from shallow to deeper settings),and (iii) belong to different genera and higher-rank taxa. BecauseSmithian–early Spathian specimens from the western USA basin areabundant andwell dated, they provide an appropriate basis for a discus-sion of the potential factors influencing their spatial distribution andsampling. Focusing on this basin, we also investigated areas fromwhich microgastropod shell-beds were previously reported to be typi-cal (Batten and Stokes, 1986; Schubert and Bottjer, 1995; Boyer, 2004;Fraiser and Bottjer, 2004; Fraiser et al., 2005; Nützel and Schulbert,2005; Pietsch et al., 2014), but our observations suggest that size distri-butions aremuch broader and comparable to other Phanerozoic assem-blages. Taken together with other worldwide reports describingGulliver faunas, they indicate that the Lilliput effect on gastropods wasbased on incomplete size spectra and cannot be used to characterizepost-extinction deleterious environmental conditions. Furthermore,these data show that miniaturization is inapplicable to the most com-mon taxonomically-identified gastropod genera in the aftermath ofthe PT extinction and does not represent a trend at the clade level.

2. Lilliput and Gulliver gastropods in living and fossil assemblages

Published shell size–frequency distributions based on specimensmeasured individually for entire, local or regional, fossil and moderngastropod assemblages are rather scarce (e.g., Beck, 2000; Bouchetet al., 2002; Fraiser and Bottjer, 2004; McClain et al., 2005; Brayardet al., 2010; Finnegan et al., 2011; Waite and Strasser, 2011; Nawrot,2012; Pietsch et al., 2014). This understandably results from the overlyexcessive time required to collect and measure all sampled specimens.Another difficultywhen comparing fossil andmodern gastropod assem-blages relates to potential biases affecting the original size–frequencydistribution (e.g., Webber, 2005; Zuschin et al., 2005, 2006; Cooperet al., 2006; Finnegan et al., 2011; Nawrot, 2012). These sources ofbias are the result of: (i) environmental (e.g., bathymetric or latitudinalgradient, local habitat heterogeneity), (ii) biological/behavioral(e.g., adult vs. juvenile spatio-temporal distribution, habitat/feedingpreferences), (iii) taphonomic (e.g., size-selective transport, lateral var-iations, post-mortem reworking, lithification, shell preservation), (iv)sampling (e.g., surface collecting vs. bulk sampling, discarding of thesmallest specimens, main effort on largest or best preserved specimens,spatial effort), and (v) analytical effects (e.g., choice of size metrics).

The dominance of small-sized species in natural communities is awell-known macroecological pattern (Brown and Maurer, 1989;Brown, 1995; Blackburn and Gaston, 1998; Kozłowski and Gawelczyk,2002; Morand and Poulin, 2002). Extent mollusk communities are noexception, as shown by the only exhaustive survey by Bouchet et al.(2002) in Koumac, New Caledonia. This pattern is found at multiple

scales: (i) individuals within a population, (ii) species within a com-munity and, consequently, (iii) individuals within a community(e.g., Jonsson et al., 2005). Fig. 1 illustrates an example for points (ii)and (iii). In the Early Triassic fossil record, the recognition of fully-grown individuals and the taxonomic assignment of gastropod speci-mens are difficult: only few specimens have shell preservation. Con-sequently, size distributions can only be assessed at the scale ofindividuals within a community, regardless of their ontogenetic age.

Small adult individuals and species are largely dominant in tropicalmodern marine faunas, with for instance 74.7% of the New Caledoniangastropod species smaller than 2 cm, and only 9% larger than 4 cm(Bouchet et al., 2002; see below and Fig. 1). Preliminary data obtainedfrom extensive collections of the “normal-sized” and exceptionallywell-preserved tropical middle Eocene gastropod assemblage fromGrignon (Paris Basin, France) show that ~60% of the 161 sampled gen-era have a maximum shell size b2 cm and ~20% have a maximum size≥4 cm (Thomas et al., unpublished data). In summary, a majority offossil and extant gastropod taxa have a maximum adult size smallerthan ~2 cm. We use this conservative value as a threshold and refer to“Gullivers” as all gastropod specimens with sizes larger than 2 cm.

Because larger gastropod individuals and species are much rarerthan smaller ones at all spatial resolutions, size–frequency distributionsare highly right-skewed. The probability of sampling large-sized speci-mens and species is consequently very low, although their preservationpotential and good visibility in sediments may compensate to some ex-tent for this statistical expectation.

To further investigate the impact of sample size on the sampledshell-size interval for a given species or individual assemblage, webuild here on Brayard et al.'s (2011a) preliminary simulation ap-proach. Based on Bouchet et al.'s (2002) extensive sampling, includ-ing 77,481 measured adult gastropods belonging to 1941 species, wedeveloped rarefaction-based simulations to separately evaluate theeffect of species and individual random sub-sampling upon the sam-pled range of shell size. The observed distribution of species abun-dance in the dataset from Bouchet et al. (2002) non-significantlydeparts from a Log-normal Model (p = 0.16 NS), even if an excessof very rare species suggests that a Zero-Sum Multinomial Model(ZSM) may actually better describe it. On the other hand, this distri-bution departs highly significantly from a Fisher's logseries distribu-tion, as expected for a local community assemblage. Indeed, under aneutral assumption and point-mutation model, a logseries distribu-tion is expected only at the regional metacommunity level, whereasa Log-normal-like ZSM distribution is expected at the local commu-nity level (Hubbell, 2001).

In this large sample of an extant NewCaledonian gastropod commu-nity, adult shell-size (estimated as the largest shell width or height)ranges from 0.4 mm to 30 cm, with an individual median size of 6 mm(inter-quartile range: 3.5–20.5 mm) and a species median size of7.3mm (inter-quartile range: 3.5–20mm) (Fig. 1).While shell-size dis-tributions in raw size-unit for both specimens (Fig. 1a) and species(Fig. 1c) show expected highly right-skewed shapes (with only 206/77,481 [0.27%] specimens and 29/1941 [1.49%] species showing anadult shell size ≥100 mm; see insets in Fig. 1a and c), the frequencydistributions actually correspond to mixtures of two Log-normal dis-tributions (Fig. 1b, d). Log-normal rather than normal (or any othertype) distributions are logically expected here due to the geometric(i.e., multiplicative, not arithmetic/additive) nature of biological varia-tion (Gingerich, 2000). Mixture analyses (Titterington et al., 1985;Harper, 1999) of these two empirical distributions using PAST v. 2.17(Hammer et al., 2001) returned the following maximum-likelihoodparameters (in Log10-mm):

– Individuals (Fig. 1b):○ small-sized group (61%): mean = 0.552, standard-deviation =

0.2949 (untransformed mean size [1σ confidence interval]: 3.6[1.8–7.0] mm);

0 50 100 150 200 250 300Shell size (in mm)

0

100

200

300

400

500

600

700

800

900

0

4,000

8,000

12,000

16,000

20,000

24,000

28,000

32,000

36,000

40,000

-0.4 0.0 0.4 0.8 1.2 1.6 2.0 2.4Log10(Shell size, in mm)

0

20

40

60

80

100

120

140

160

180

200

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

9,000

10,000

0 50 100 150 200 250 300 -0.4 0.0 0.4 0.8 1.2 1.6 2.0 2.4

Num

ber

of in

divi

dual

sN

umbe

r of

spe

cies

a

c

b

d

100 150 200 250 3000

6

100 150 200 250 3000

50

Fig. 1. Adult shell-size distributions of individuals (a, b) and species (c, d) from the New Caledonian extant gastropod assemblage (Bouchet et al., 2002), in both raw (a, c) and Log10-transformed (b, d) size-unit. Insets in graphs a and c zoom in on the shell-size distributions beyond100mm. Log-normal curves show themaximum-likelihood results ofmixture analyses,supporting the existence of two groups of adult size for both individuals and species distributions (see text for details).


○ large-sized group (39%): mean = 1.408, standard-deviation =0.2023 (untransformedmean size [1σ C.I.]: 25.6 [16.1–40.8] mm);

– Species (Fig. 1d):○ small-sized group (52%): mean = 0.561, standard-deviation =

0.3074 (untransformed mean size [1σ C.I.]: 3.6 [1.8–7.4] mm);○ large-sized group (48%): mean = 1.298, standard-deviation =

0.3625 (untransformed mean size [1σ C.I.]: 19.9 [8.6–45.8] mm).

Optimum cut-off values (sensu Favre et al., 2008) between the twoshell-size groups are 10.8 mm for individuals (making 96% of all sam-pled individuals correctly assigned to their size-group) and 8.3 mm forspecies (making 86% of all sampled species correctly assigned to theirsize-group). Incidentally, it is worth noting that more than half of thespecies (52%) and individuals (61%) from this extant gastropod assem-blage thus fall within the micro-gastropod category (b10 mm definedby Fraiser and Bottjer, 2004, for fossil gastropods).

Starting from this large extant New Caledonian sample, we per-formed rarefaction-based simulations by randomly sampling withoutreplacement sub-sets of individuals or species, observing the changesof the minimum, median and maximum sampled shell sizes with de-creasing sampling effort (Fig. 2). Since Sanders (1968), interpolation-based rarefaction is a standard technique routinely used in populationgenetics, ecology and paleobiology to estimate the variation (usuallydecrease) of a diversity metric of interest (e.g., allelic or species

richness) with decreasing sampling effort (e.g., Hurlbert, 1971; Hecket al., 1975; Smith and Grassle, 1977; Simberloff, 1979; Coleman,1981; Kalinowski, 2004, 2005; Hammer and Harper, 2006; Gotelli andColwell, 2011; Colwell et al., 2012; among many others). On the onehand, by randomly selecting sub-sets of individuals from the full extantsample (each individual having the same sampling probability regard-less of its shell size), individual-based rarefaction (Fig. 2a) generates anull model of shell size-independent random loss of information fromthe parent assemblage due to taphonomic causes and/or less than opti-mum sampling efforts. On the other hand, by randomly selecting sub-sets of species from the full extant sample (each species having thesame sampling probability regardless of its relative abundance and av-erage shell size in the parent assemblage), species-based rarefaction(Fig. 2b) generates a null model of abundance- and size-independentloss of information due to random species extinction, thus simulatingthe effect of a “neutral”, abundance- and size-independent extinctioncrisis on the size–frequency distribution. In both cases, it is worth not-ing thatwe performed shell-size-independent randomselection of indi-viduals or species. For reasons discussed below (Section 7.1.2), thissimple working (null) hypothesis is likely to be satisfactory at a firstorder of approximation. More complex simulation approaches involv-ing shell-size-dependent random selection of individuals and/or speciesare currently under development (Escarguel et al., ongoing work).

Under this simple working hypothesis of shell-size-independent ran-dom sorting, both specimen- and species-based rarefaction simulationsclearly show that, whereas the median value of the shell size–frequencydistributions remains stable, the [Min–Max] sampled interval strongly

-0.5

0

0.5

1

1.5

2

2.5

1 10 100 1000 80,000

Log 10

(She

ll si

ze, i

n m

m)

Number of sub-sampled individuals

a

-0.5

0

0.5

1

1.5

2

2.5

1 10 100 1000 2000

Log 10

(She

ll si

ze, i

n m

m)

Number of sub-sampled species

b

Fig. 2.Results of the rarefaction-based simulations showing the evolution of theminimum(blue), median (black) andmaximum (red) sampled adult shell-size with decreasing sub-sampling of the New-Caledonian modern assemblage (including 77,481 specimens, 1941species). a) Individual-based rarefaction. b) Species-based rarefaction. Bold curves givethe median simulated estimate for each shell-size distribution parameter (Min, Med andMax), and associated thin curves give the related 95% nonparametric confidence intervals,based on: 500, 1000 and 5000 independent random sub-samples for the individual-basedrarefaction in the [77,484–10,001], [10,000–1001], and [1000–1] specimen intervals,respectively; and 1000, 5000 and 10,000 independent random sub-samples for thespecies-based rarefaction in the [1941–501], [500–101], and [100–1] species intervals,respectively.


decreaseswith sample size. Furthermore, due to the strongly asymmetric(right-skewed) shape of the shell-size distribution (Fig. 1a, c), the Minvalue only slightly increases as sample size decreases (e.g., exceeding amedian estimate of 1 mm for less than ~20 sampled specimens/17 sam-pled species), whereas the Max value dramatically decreases as samplesize decreases (e.g., falling below a median estimate of 10 cm for lessthan ~350 sampled individuals/46 sampled species, and a median esti-mate of 5 cm for less than ~50 sampled individuals/11 sampled species).Obviously, this rather counter-intuitive pattern logically results from thestrongly right-skewed shapeof the parent shell-size distribution: becausethe largest individuals are (very) rare in the parent assemblage, theirprobability to be randomly sorted through the rarefaction procedure rap-idly becomes so low that they are almost never captured in the rarefiedsamples below a few hundreds of sampled individuals/tens of sampledspecies.

These simulation results clearly indicate that, when randomlydeparting from a “standard”, non-altered shell size–frequencydistribution, noticeably reduced Max and [Min–Max] range values canbe expected without invoking any ad-hoc environmental and/or evolu-tionary driver(s) when working with relatively small, under-sampledassemblages. Thus, a shift toward small sizes of the whole size distribu-tion (see below, Section 7.5.2) does not necessarily indicate a Lilliput

effect s.l., but rather that large-sized individuals and species may begreatly under-sampled, leading to a spurious right-hand truncation ofthe size distribution. From this point of view, the minimum, medianand maximum shell-size values, obtained from the Early Triassic sam-ples presented and discussed below, rather accurately match the nullpredictions of our simulation approach (Fig. 3), strongly suggestingthat they can be seen as relatively small and species-poor samplesrandomly selected from a “standard”, non-altered shell size–frequencydistribution. Even if such a simple simulation approach does notunambiguously refute the existence of a Lilliput effect in Early Triassicgastropod assemblages, the discovery of abundant, large-sized speci-mens representing several gastropod taxa in the same areaswhere a Lil-liput effect for gastropods has previously been suggested (e.g., westernUSA basin) is highly remarkable, given the low Early Triassic gastropodrichness (b100 named species known; Nützel, 2005b).

3. Previous reports of Early Triassic Gulliver occurrences

Fig. 4 displays all known spatio-temporal occurrences of Early Trias-sic Gullivers. Fraiser and Bottjer (2004, their Fig. 1) and Fraiser andBottjer (2005, their Figs. 3 and 4) produced the same work formicrogastropod beds. The resulting diagrams suggest that Lilliput andGulliver gastropods may be found in the same regions and time inter-vals. Gulliver occurrences have not yet been documented from high lat-itudes, and reports of gastropods from the Boreal domain are rare andspecimens have thus far not been illustrated (see Dagys et al., 1979 forSiberia and Mørk et al., 1999 for Spitsbergen). Prior to the study byBrayard et al. (2010), known occurrences of large-sized gastropodswere restricted to well-studied Griesbachian assemblages from Oman(Twitchett et al., 2004;Wheeley and Twitchett, 2005) and from brief re-ports on the Griesbachian–Dienerian interval of northwestern China(Tong and Erwin, 2001) and South Primorye (Kaim, 2009), the Smithianof western Australia (Runnegar, 1969), and the Spathian of South China(Pan, 1982), Qinghai (Zhu, 1995), Serbia (Frech, 1912) and Italy (Neriand Posenato, 1985, Nützel, 2005a,b) (Fig. 4a, d). In addition, Dean(1981, his Pl. 1) illustrated two “representative” specimens (~10 and25 mm in height) from the Smithian Sinbad Formation in the Torreyarea (Utah; western USA basin), suggesting the presence of large-sized gastropods in this region. Batten and Stokes (1986) mentionedthe occurrence of three specimens of Zygopleura, Battenizyga (=Anoptychia) and Coelostylina from the same formation in the San RafaelSwell (Utah) whose respective heights are 18.8 mm, 15.3 mm, and13.9 mm. Goodspeed (1996) and Goodspeed and Lucas (2007, theirTable 1) also reported “large gastropods” from the Sinbad Formationin the SanRafael Swell. Their commentwasmainly based on field obser-vations, but some sampled packstones from their collection indeedshow several high-spired gastropods ≥1.5 cm (S.G. Lucas, personalcommunication to the first author, 2013). Pietsch et al. (2014) recentlyillustrated a 17 mm-high specimen of Coelostylina from the same beds.More problematic is the description by Yochelson et al. (1985) of alarge specimen of Retispira bittneri (Bellerophon group) with a diameterof 5 cm from the Griesbachian of the Dinwoody Formation inWyoming.Indeed, as previously discussed by Payne (2005), its stratigraphic posi-tion is uncertain, although Yochelson et al. (1985) identified an EarlyTriassic source for this material (see also Kaim and Nützel, 2011).

Brayard et al. (2010) confirmed the occurrence of large-sizedSpathian specimens in Serbia and Italy, and they documented abundantGullivers from the Smithian of west-central Utah. Turculeţ (1987) re-ported giant specimens of the gastropod Werfenella, the largest onemeasuring 71 mm in height and 48 mm in width, from the Spathian(“Campilian”) of Romania (Carpathians). Large-sized gastropods havealso been recently reported from the Griesbachian of South China(Kaim et al., 2010), the Griesbachian–Dienerian interval of the SaltRange (Kaim et al., 2013) and southeastern Idaho (Hofmann et al.,2013a), and the Smithian of southern Utah (Hofmann et al., 2014;Olivier et al., 2014).

-0.5

0

0.5

1

1.5

2

2.5

1 10 100 1000 10,000 80,000

Log 10

(She

ll si

ze, i

n m

m)

Number of sub-sampled individuals

12

34

56

7

8910

1112 13

10 mm

Mic

roga

stro

pods

“Nor

mal

-siz

ed”

gast

ropo

ds

Fig. 3.Median and [Min–Max] range values (thin horizontal and bold vertical lines, respectively) of the shell-size distributions of some of the Early Triassic gastropod samples presented anddiscussed in this workwith respect to the individual-rarefaction-based simulation results (Fig. 2a). Dark-gray area: 50% non-parametric confidence interval of theMin &Max shell-size values;light-gray area: 95% non-parametric confidence interval of the Min & Max shell-size values. 1–4 (black bars): Greenland samples (1: all localities; 2: NAS1; 2: IMMRI-SMA3; 4: WCE1); 5–13(white bars): Southwestern USA samples (5: all localities; 6: CR; 7: SRS; 8: TO; 9: MM; 10: KAN; 11: VD; 12: BRC; 13: ROC; western USA locality abbreviations are detailed in Fig. 9).


Spath (1930, his Pl. 9) and Spath (1935, his Pl. 22) illustrated a fewlarge specimens of Naticopsis arctica from the Griesbachian “Vishnuites”and “Proptychites” ammonoid beds of Greenland, but he did not includeinformation about their abundance. Extensive fieldwork in Greenlandallowed us to resample this assemblage, yielding abundant largeNaticopsis specimens from several beds. Notably, as already mentionedand illustrated by Spath (1930, 1935), many Naticopsis preserve theirshell and color patterns. In addition, intense fieldwork in Utah, Nevadaand Idaho also allowed us to complement here previous reports ofGullivers in the western USA basin.

4. Newly sampled Gulliver collections: the fieldwork contribution

In this work we show that the maximum shell size of Early Triassicgastropods was underestimated in previous studies. Extensive fieldsampling indicates that large sizes were reached in several gastropodgenera representing various high-ranked clades. Large-sized specimensincrease the known size range for gastropods and limit the significanceof the Lilliput effect for this clade. We investigated large areas in Utah(Torrey and San Rafael Swell regions), from which microgastropodshell-beds had been described in the Smithian Sinbad Formation andwhich were presented as typical of the Early Triassic (Batten andStokes, 1986; Schubert and Bottjer, 1995; Boyer, 2004; Fraiser andBottjer, 2004; Fraiser et al., 2005; Pietsch et al., 2014). Gastropod collec-tions from these key-areas and a few other regions (e.g., Werfen Forma-tion, Alps) served to argue for a Lilliput effect among gastropods,subsequently leading to a spatio-temporal extrapolation on a globalscale. Because our observations lead to alternative interpretations andconclusions, they not only have direct consequences for the significance,but they even question the existence of the Lilliput effect for gastropodson a regional scale and maybe also on a global scale.

Our new collections are stratigraphically well constrained by high-resolution ammonoid zonations (zones and horizons; e.g., Brayardet al., 2013; Jenks et al., 2013). Moreover, they integrate several sam-pling areas of thewestern USA basin. The Gulliver record from thewest-ern USA also covers the entire early/middle Smithian to early Spathianinterval. The number of sampled specimens from Greenland is lower,

but it documents several successive assemblages from the earliestTriassic.

All studied sections were carefully sampled bed by bed. Small gas-tropodswere present in all sampled assemblages as is usual for both fos-sil and recent gastropod faunas. In order to document large-sizedgastropods and to complement the known size range for this clade ef-fectively, we used a combination of extensive surface collecting andblock disintegration whenever possible. Most measured specimens arefragmented, so their original size was larger, especially for high-spiredspecimens,which are usually broken. In our dataset, each specimen rep-resents a unique individual. Consequently, the terms “specimen” and“individual” can be used interchangeably. Here, “shell size” refers tothe maximum measured height along the coiling axis for high-spiredconispiral shells and to the maximum measured width for low-spiredshells. Many specimens were measured directly in the field. Taxonomicdeterminations at the genus level follow the descriptions and classifica-tion established in Hofmann et al. (2014). Repositories of figured andmeasured specimens are abbreviated UBGD (Université de Bourgogne,Géologie Dijon — France) and PIMUZ (Paläontologisches Institut undMuseum der Universität Zürich — Switzerland), unless otherwiseindicated.

5. Griesbachian Gullivers from Greenland

5.1. Geological and biostratigraphical settings

East Greenland is a classical area for studying the PT boundary andthe Griesbachian–early Dienerian interval given its extensive sedimen-tary and fossil records (e.g., Nielsen, 1935; Spath, 1935; Trümpy, 1969;Twitchett et al., 2001; Wignall and Twitchett, 2002; Bjerager et al.,2006). All Gulliver gastropods come from theWordie Creek Formation,which is well-exposed in the northern part of HoldWith Hope Peninsu-la (Fig. 5). During the Early Triassic, this basin, which was part ofthe Greenland–Norway rift, was located at mid-latitudes in easternPanthalassa (Fig. 4d). A thorough bio- and lithostratigraphy of thisregion was published by Bjerager et al. (2006). In the Hold With HopePeninsula, the Wordie Creek Fm. was deposited on the tectonicallysunken part of a westward tilted block, thus recording more than

a

d

b

c

Fig. 4. Spatio-temporal distribution of Gulliver gastropods during the Early Triassic. a) Chronostratigraphic subdivisions of the Early Triassic (radiometric ages by Ovtcharova et al. (2006),Galfetti et al. (2007b) and Burgess et al. (2014)) with simplified trends of geochemical (δ13Ccarb; data fromGalfetti et al., 2007b) and Tethyan relative temperature fluctuations during thisperiod (data from Romano et al., 2013 [black line] and Sun et al., 2012 [gray line]; w: warmer; c: colder). Gulliver occurrence reports — Oman: Twitchett et al. (2004) andWheeley andTwitchett (2005); northwestern China: Tong and Erwin (2001); South China: Pan (1982) andKaimet al. (2010); Romania: Turculeţ (1987); Serbia: Frech (1912), Nützel (2005a,b), Nützelet al. (2010) and Brayard et al. (2010); Italy: Neri and Posenato (1985) and Brayard et al. (2010); South Primorye: Kaim (2009); Salt Range: Kaim et al. (2013); Greenland: Spath (1930,1935), this work; southwestern USA: Dean (1981), Brayard et al. (2010), Hofmann et al. (2014), Olivier et al. (2014) and this work. R? indicates uncertain stratigraphic occurrence ofRetispira bittneri reaching 5 cm in diameter (Yochelson et al., 1985). Question marks indicate uncertainty for stratigraphic position. Qinghai (Zhu, 1995) and West Australia (Runnegar,1969) illustrated specimens are not located on the figure due to the high uncertainty about their stratigraphic position. b) High-resolution temporal distribution of Gulliver gastropodsfrom southwestern USA. Ammonoid zonation is from Brayard et al. (2013) and Jenks et al. (2013). Western US locality abbreviations are given in Fig. 9. c) High-resolution temporaldistribution of Gulliver gastropods from Greenland. Ammonoid and bivalve zonations are from Bjerager et al. (2006) and Meier and Bucher (ongoing work). Locality abbreviations aregiven in Fig. 5. d) Early Triassic localities with Gulliver gastropods.


650 m of essentially deltaic sediments. At Hold With Hope, the latestPermian ismissing and the Triassic unconformably overlies the PermianRavnefjell Fm. Both formations record a succession of transgressive–regressive cycles, which are particularly well displayed within theWordie Creek Fm. This indicates a strong tectonic control on the region-al Late Permian and Early Triassic sedimentation (Bjerager et al., 2006).In the Wordie Creek Fm., successive gastropod assemblages are docu-mented from beds of late Griesbachian age (Ophiceras commune andWordieoceras decipiens Zones) and probably of early Dienerian age(Bukkenites rosenkrantzi Zone) (Fig. 4c). The uppermost part of theB. rosenkrantzi Zone is probably early Dienerian in age (Bjerager et al.,2006;Meier and Bucher, ongoingwork; Sanson-Barrera et al., submitted).Our field observations are in accordance with the original sedimentolog-ical description by Bjerager et al. (2006). Deposits of theO. commune Zonecorrespond to marine mudstones gradually passing into thin sandstonelobes (bottom-set beds of delta). The W. decipiens Zone is representedby offshore mudstones intercalated with very thin sandstone sheets inits lower part and a prominent unit of marine, channeled density-flow

sandstones in its upper part. The B. rosenkrantzi Zone also consists of off-shore mudstones and is overlain by a sandstone-dominated unitrepresenting nearshore deposition.

5.2. Gulliver gastropods

The gastropod fauna from Greenland includes taxa of varioussizes: Naticopsis, Warthia, Worthenia and high-spired “Loxonema”(or “Polygyrina”) (Spath, 1930, 1935; Kaim and Nützel, 2011). Theneritimorph Naticopsis is the dominant large-sized genus in all sam-pled assemblages from Greenland. The largest Naticopsis specimensare ~3 cm wide (Figs. 6–8). Spath (1930, 1935) also illustratedWarthia (Bellerophon) specimens ~2.1 cm-wide and high. Spath(1930, 1935) reported the occurrence of a single species ofNaticopsis: N. arctica. In accordance with Spath's descriptions, sever-al recently sampled specimens are exceptionally well-preserved,especially from the IMMRI and SMA3 localities (Figs. 4c, 5, 6, 7).Axial sections of specimens show that all original aragonitic shell

Table 1Reported maximum sizes of Early Triassic gastropod genera.

Genus Reportedmaximumsize (mm)

Associated references

“Bellerophon” 17.7 Kaim (2009)Coelostylina 40 This work“Coelostylina sp. A” 85 This workOmphaloptycha 30 This workCylindrobullina 1 Batten and Stokes (1986)Worthenia 22.4 This workAngularia 24.6 This workPseudotritonium(Kittliconcha)

7.6 Batten and Stokes (1986)

Polygyrina 72 This work; Brayard et al.(2010)

Promathilda 2.5 Batten and Stokes (1986)Neritaria 11.1 Hofmann et al. (2014)Naticopsis 32 This workVernelia 15.2 Nützel and Schulbert (2005)Chartronella 6.7 This workBattenizyga 15.3 Batten and Stokes (1986)Warthia 23.8 Kaim et al. (2013)Soleniscus 10.5 Nützel (2005b)Strobeus 38 Brayard et al. (2010)Natiria 28.6 Brayard et al. (2010)Boutillieria 7.3 Batten and Stokes (1986)Zygopleura 18.8 Batten and Stokes (1986)Werfenella 71 × 48 Turculeţ (1987)Abrekopsis 31.4 This workDicellonema 16.9 Kaim and Nützel (2011)Wannerispira 10.03 Kaim et al. (2010)Paleonarica 7.2 Kaim and Nützel (2011)Laubopsis 20 This workPachyomphalus 2.2 Batten and Stokes (1986)Jiangxispira 1.3 Pan (1982)Gradellia 10 Tong and Erwin (2001)Trypanostylus 14.5 Tong and Erwin (2001)Amberleya? 15 Tong and Erwin (2001)Toxoconcha 17.8 Tong and Erwin (2001)Ananias 7.2 Wheeley and Twitchett

(2005)Undetermined genus SRS 30.2 This workAmpezzopleura 1.9 Nützel and Schulbert (2005)“Euomphalus” 14.6 Zhu (1995)Guizhouspira 6.3 Zhu (1995)Scurriopsis 4.9 Zhu (1995)Solariconulus 9.4 Zhu (1995)Trochotoma 25.2 Pan (1982)“Loxonema” 5.2 Spath (1935)Atorcula b1 Kaim et al. (2014b)Retispira 50 Yochelson et al. (1985)


material has been dissolved (Fig. 8aa–ab); the specimens are filledwith a homogenous sediment and there are no remains of the colu-mella and internal shell walls. It is unclear whether the internalshell material of early whorls was resorbed by the animal (as is typ-ical of Neritidae) or whether it was destroyed by diagenesis. Thus,systematic placement in Neritidae (resorbed) or Naticopsidae/Neritopsidae (not resorbed) of the material from Greenland remainsopen, but at this point an assignment to Naticopsis seems reasonable.Only the outermost calcitic shell layer is well-preserved. Althoughsometimes slightly crushed, most specimens have relatively undam-aged shell surfaces that retain various color patterns ranging fromaxial zigzag stripes to small patches (Figs. 7, 8). These patternscover the entire shell surface, from the first to the last whorls. Zigzagstripes are spatially heterogeneous with different frequencies,widths and angles. In contrast, patches are more regular. Some rareNaticopsis are ornamented with folds and constrictions at largebody sizes. The shell surface is generally smooth as is typical of thediverse Late Paleozoic/Early Mesozoic genus Naticopsis and formany other neritimorph species, making the discrimination of spe-cies within Naticopsis difficult (Kaim et al., 2013; Hofmann et al.,

2014). If not resulting from polymorphism (e.g., Krawczyński,2013), the various color patterns may indicate that differentNaticopsis species have coexisted, thus questioning the low gastro-pod richness previously reported from this area (Spath, 1930,1935). Nevertheless, this hypothesis needs more substantiation asthe number of studied specimens is still low.

6. Smithian–early Spathian Gullivers from western USA

6.1. Geological and biostratigraphical settings

During the Early Triassic, thewestern USA basinwas near-equatorialin the eastern edge of Panthalassa (Fig. 4d) and records both continentalandmarine sedimentation (McKee, 1954; Blakey, 1974, 1977; Collinsonet al., 1976). Outcrops of Smithian and Spathian substages (Thaynes andMoenkopi Groups, sensu Lucas et al., 2007) are widely distributedwithin a large area covering Wyoming, Idaho, Utah and Nevada(e.g., Goodspeed and Lucas, 2007). Deposits of the Thaynes Groupconsist of alternating limestones and shales reflecting depositionwithinthe relatively shallow western USA basin. These marine sedimentarydeposits thin from the northwest to the southeast across Utah, wherethey interfinger with the more terrestrially dominated sediments ofthe Moenkopi Group (Lucas et al., 2007). During the Smithian, de-positional environments essentially transitioned from a coastal plainwith continental deposits to subtidal marine bioclastic limestones(e.g., Olivier et al., 2014, in press). This southward transgressive trendmarks a long-term sea level rise that is identified worldwide after thePT boundary (Embry, 1997; Fig. 9). The Smithian sea-level rise reachedits maximum extent within the western USA basin during the lateSmithian (i.e., Anasibirites kingianus and Xenoceltitidae gen. indet. Abeds) and was followed by a rapid sea-level fall around the Smithian/Spathian boundary (Brayard et al., 2013). A renewed transgressionmarked the early Spathian, but the shoreline did not reach themaximumsoutheastward extent of the Smithian sea (Collinson and Hasenmueller,1978; Carr and Paull, 1983; Paull and Paull, 1993; Olivier et al., 2014).

Marine deposits generally contain abundant, although often notwellpreserved benthic and nekto-pelagic fossils (e.g., Hose and Repenning,1959; Schubert and Bottjer, 1995; Fraiser and Bottjer, 2004; McGowanet al., 2009; Brayard et al., 2009a, 2010, 2011b, 2013; Stephen et al.,2010; Hofmann et al., 2013a,b, 2014; Hautmann et al., 2013). We sam-pled Smithian and early Spathian sedimentary successions in the Confu-sion Range, Mineral Mountains, Cedar City, Kanarraville, Virgin, BlackRock Canyon, Torrey and San Rafael Swell areas in Utah, Rock Canyonarea in Arizona, Palomino Ridge in Nevada, and Hot Springs in south-eastern Idaho (Fig. 9a). These Lower Triassic exposures represent vari-ous environments along a shoreline–offshore profile (Fig. 9b). Allstudied sections are relatively thick, indicating high sedimentationrates and an increase in accommodation space, but thickness also variesconsiderably from section to section (Fig. 10). This variation probablyarises from the deposition of sediments on a complex paleo-reliefformed during the Late Permian–earliest Triassic transition (Collinsonet al., 1976; Dean, 1981; Paull and Paull, 1982; Brayard et al., 2013;Olivier et al., 2014). This setting is also suggested by the presence of un-conformities, breccias, conglomerates and normal faults underlying theLower Triassic deposits in Utah and Nevada (e.g., Paull and Paull, 1982;Hofmann et al., 2014; Olivier et al., 2014).

Detailed sedimentological and biostratigraphical descriptions ofmost of these studied sections were recently published in Brayardet al. (2011b, 2013), Jenks et al. (2013), Hofmann et al. (2014), Olivieret al. (2014, in press) and Vennin et al. (2015). The Palomino Ridge(PA) and Confusion Range (CR) sections represent the deepest andquietest environments (lower to upper offshore) with thick shale inter-vals alternatingwith limestones in CR (Fig. 10). There is no evidence foractive fair-weather-wave reworking. The base of theMineralMountains(MM) section corresponds to shallow-water settings containing micro-bial andmetazoan bioconstructions (Brayard et al., 2011b; Vennin et al.,

22° 20°

74°

GaussHalvø

HOLDWITHHOPE

Clavering Ø

Kap Stosch

FaultWordie Creek Fm.

GR

EE

NLAND

25 km

IMMRINAS1

SMA3

WCE1

Fig. 5. Greenland map with outcrops of the Wordie Creek Formation within the Hold With Hope Peninsula. Site abbreviations refer to localities of Nielsen (1935).


2015; Fig. 10). The overlying Smithian sediments ofMM show a tidal in-fluence followed by deeper offshore environments with intercalatedshales and storm-induced limestones that are typical of the ThaynesGroup (Hofmann et al., 2014; Vennin et al., 2015). Smithian depositsin the Cedar City (CC) and Kanarraville (KAN) sections record shallowdepositional environments with tidal influences (Fig. 10). The VirginDam (VD) area aswell as the Black RockCanyon (BRC) andRockCanyon(ROC) sections correspond to peritidal to shallow subtidal environ-ments in southwesternmost Utah and northernmost Arizona (Blakey,1977; Lucas et al., 2007; Brayard et al., 2013; Olivier et al., 2014;Fig. 10). Deposits of the Sinbad Formation in the Torrey (TO) and San

WCE1

IMMRI-SMA3

NAS1

0 3 6 9 12 15 18 21 24 27

Width (mm)

Alln=67

n=45

n=7

n=15

Fig. 6. Raw values documenting the range of sampled Naticopsis specimens from theWordie Creek Formation.

Rafael Swell (SRS) areas were described in detail by Blakey (1974),Dean (1981), Goodspeed and Lucas (2007), Nützel and Schulbert(2005), Hofmann et al. (2014) and Olivier et al. (in press). They are rep-resented by high-energy environments similar to those of VD, BRC andROC (Fig. 10). Early Spathian gastropods from Hot Springs (HS) withinthe Columbites beds were found in concretions deposited below thestorm-wave base.

In thiswork,weuse the detailed regional biostratigraphic ammonoid-based zonation proposed by Brayard et al. (2013) for the Smithian out-crops of Utah (Fig. 4b), while the early Spathian ammonoid zonation isbased on Jenks et al. (2013). Further evidence for ages comes fromconodonts (determination by N. Goudemand) and bivalves (Brayardet al., 2013; Hofmann et al., 2014). Sections from the Sinbad Formationof the TO and SRS areaswere previously described as contemporaneous(e.g., Blakey, 1974; Fraiser and Bottjer, 2004). Actually, they are slightlydiachroneous, the TO sections representing the middle–late Smithianinterval and the SRS sections being mainly late Smithian–earliestSpathian in age (Brayard et al., 2013).

6.2. Gulliver gastropods

6.2.1. General observationsDominant large-sized gastropods in the western USA basin are

Abrekopsis, Polygyrina, Strobeus, Omphaloptycha, Coelostylina, Laubopsisand a new taxon provisionally identified as “Coelostylina sp. A”(Figs. 11–19). The largest sampled Polygyrina and “Coelostylina sp. A”fragmentary shells reach ~7.2 cm and 8.5 cm in height, respectively, foran estimated original size N10 cm (only fragments of these large high-spired gastropods have been sampled to date). The largest Abrekopsisreaches ~3.2 cm in width, and the largest Strobeus, Omphaloptycha,Coelostylina and Laubopsis specimens reach 3.8 cm, ~3 cm, 4 cm and~2 cm in height, respectively (Fig. 20). Low-spired Abrekopsis and high-spired Polygyrina, Coelostylina, Strobeus, Omphaloptycha and Laubopsiscan reach sizes ≥2 cm, and they occur in almost all studied sections.Except for Laubopsis, these genera correspond to the most frequent

Fig. 7. Large-sized Naticopsis arctica from theWordie Creek Formation of Greenland. a–c) PIMUZ 30935, loc. NAS1, Bukkenites rosenkrantzi Zone. d–f) PIMUZ 30936 showing zigzag axialbanding, loc. IMMRI,Wordieoceras decipiens Zone. g) PIMUZ 30939 showing zigzag axial banding, loc. IMMRI,Wordieoceras decipiens Zone. h–j) PIMUZ 30940 showing color patches, loc.SMA3, Wordieoceras decipiens Zone. k–l and m–o) PIMUZ 30937 and PIMUZ 30938, respectively, loc. IMMRI,Wordieoceras decipiens Zone. p–q and r–s) PIMUZ 30941 and PIMUZ 30942,respectively, loc. SMA3,Wordieoceras decipiens Zone. t–u, v–w, x–y, z–aa, ab–ac, ad–ae, af–ag, ah–ai, aj–ak) PIMUZ 30946, 30944, 30943, 30949, 30950, 30947, 30948, 30951 and 30945,respectively, loc. WCE1, Ophiceras commune Zone.


components of Early Triassic gastropod assemblages globally (Batten,1973; Erwin and Hua-zhang, 1996; Nützel, 2005a and references there-in). “Coelostylina sp. A” is apparently only present in VD, BRC and ROC,and Polygyrina is apparently absent from these localities. It mainly differs

from Polygyrina by its larger apical angle. Two other large-sizedtaxa occur in VD, BRC, and ROC: Angularia sp. and Wortheniawindowblindensis, which reach ~2.5 cm and ~2.2 cm, respectively.W. windowblindensis is also present in KAN. Most relatively large

Fig. 8. Large-sizedNaticopsis arctica from theWordie Creek Formation of Greenland. a–b, c–d, e–f, g–h, i–j, k–l, m, n–p, q–r, s–t, u–v, w–x, y–z) PIMUZ 30972, 30935, 30973, 30977, 30968,30975, 30974, 30978, 30971, 30967, 30970, 30976, 30969, respectively, loc. NAS-1, Bukkenites rosenkrantzi Zone. aa–ab) Axial sections of twoNaticopsis specimens showing that all originalaragonitic shell material has been dissolved.

NEVADA

IDAHO

ARIZONA

110°W

42°N

37°N

UTAH

100 km

CR

MM

CCKAN

SRS

TO

WY

VD

Studied localities withnew Gulliver specimens

NEVADA

IDAHO

ARIZONA

110°W

42°N

37°N

basinal facies

outer shelf facies

inner shelf facies

global trend of theSmithian transgression

a b

BRC

HS

Previously illustratedGulliver specimens

PA

Localities with previously reportedtypical microgastropod beds

ROC

Fig. 9. a) Early Triassic Gulliver gastropod occurrenceswithin thewestern USA basin. For temporal distributions, see Fig. 4b. b) Schematic extent of the Smithian openmarine depositionalfacies, based on ammonoid data (Brayard et al., 2013) and modified after Carr and Paull (1983), Collinson and Hasenmueller (1978), and Paull and Paull (1993). HS: Hot Springs; PA:Palomino Ridge; CR: Confusion Range; MM: Mineral Mountains; CC: Cedar City; KAN: Kanarraville; VD: Virgin Dam; BRC: Black Rock Canyon; ROC: Rock Canyon; SRS: San Rafael Swelland TO: Torrey area.


PE

RM

.?Cedar City

Area

25m

30m

35m

40m

45m

0m

5m

10m

15m

20m

Mas

sive

bio

cons

truc

ted

limes

tone

uni

t

A.k.

To

the

Virg

inLi

mes

tone

Fault

?O.

25m

0m

5m

10m

15m

20m

A.k.

Kanarraville

~20

0m to

the

Virg

in L

imes

tone

Hidden and faulted

Hig

hly

biot

urba

ted

limes

tone

uni

t

Eumorphotisbeds

30m

SM

ITH

IAN

TH

AY

NE

S G

rp.

25m

30m

35m

40m

45m

50m

55m

60m

65m

70m

75m

80m

85m

90m

95m

100m

v v v v

0m

5m

10m

15m

20m

RED BEDS

A.k.

O.

PERMIAN

ConfusionRange

DIE

N.?

SP

AT

HA

N

«Gas

trop

odsh

ales

2»

To

the

Biv

alve

and

Tiro

lites

bed

s«G

reen

sha

les»

«Gas

trop

odsh

ales

1»

MineralMountains

25m

30m

35m

40m

45m

50m

75m

80m

85m

0m

5m

10m

15m

20m

A.k.

I.b.

PERMIAN

Xe.

90m

100m

105m

O.

Co

V.u

Eumorphotisbeds

Mas

sive

bio

cons

truc

ted

limes

tone

uni

t

I.b.

P.K.

?

?

?

?

?O.

?

?

?

I.o.

I.o.

?

25m

v v v v

0m

5m

10m

15m

20m

A.k.

San RafaelSwell

Hidden

Red

uni

tY

ello

w u

nit

Gre

y un

itB

lue

unit

TorreyArea

25m

30m

35m

40m

45m

50m

0m

5m

10m

15m

20m

O.

Co

Mas

sive

bio

cons

truc

ted

limes

tone

uni

t

A.k.

Yel

low

uni

t

PERMIAN

?

O.

v v

To

the

Virg

in L

imes

tone

25m

0m

5m

10m

15m

20m

30m

35m

40m

45m

60m

VirginDam

??

PERMIAN

Co

Mas

sive

bio

cons

truc

ted

limes

tone

uni

tC

ongl

omer

atic

uni

t

A. k.

25m

0m

5m

10m

15m

20m

30m

Black RockCanyon

Mas

sive

bio

cons

truc

ted

limes

tone

uni

t

Conglo-meratic

unit

?

Hidden

Biostratigraphical correlations

Lithological correlations

Xe. Xenoceltitidae gen. indet. A beds

A.k. Anasibirites kingianus beds

O. Owenites beds

Fle. Flemingites sp. indet. bed

I.b. Inyoites beaverensis beds

P.K. Preflorianites-Kashmirites beds

M.m. Meekoceras millardense bed

M.o. Meekoceras olivieri beds

R.e. Radioceras aff. evolvens beds

V.u Vercherites undulatus bed

I.o. Inyoites oweni horizons

NEVADA

IDAHO

ARIZONA

UTAH

CR

MM

CCKAN

SRS

TO

VDBRC

Smithianbasinal configuration

DH1-0A

DH1-2

GS1C2

GS2

DH1-9

A. k.

v v

0m

5m

10m

15m

RockCanyon

Conglo-meratic

unit

Mas

sive

bio

cons

truc

ted

limes

tone

uni

t

? I.o.

ROC

ROC1

ROC2

ROC3

sandstone

limestone

sandy-limestone

shelly-limestone

calcareousshale

shale

conglomerates

Lithologies

microbial dep.

RED BEDS

REDBEDS

v v



gastropods are present as fragmented steinkerns and hence their taxo-nomic and systematic placement is unclear.

In the deepest part of the basin (CR, PA), Gullivers are represented by alarge variety of more or less poorly preserved imprints, internal orexternalmolds. These various preservation types coexist in some shale in-tervals at CR (Figs. 11 and 12). Calcite infillings are observed in specimensfrom all other sections, as well as a siliceous preservation of the shell inrare individuals from the basal bioconstructions in MM (Brayard et al.,2011b) and TO. Some specimens from KAN, VD and BRC have exception-ally well-preserved shells (Figs. 12t, 16e–r, and 17k–o). In these cases, asin the Griesbachian assemblages with dominant neritimorphs fromGreenland, Abrekopsis specimens sometimes show residual color patternsin natural light asweakly perceptible axial dark bands, especially near theaperture (Fig. 16e–r). Additional Triassic neritimorphs with preservedcolor patterns are from the Salt Range (Fig. 4d; Kaim et al., 2013). Thesespecimens are latest Smithian–early Spathian in age and show a well-developed punctuation over the entire shell surface. Unlike other gastro-pods, preservation of color patterns in neritimorphs is relatively frequent.This phenomenon is explained by a thin outer calcitic layer, typical of thisgroup, that may preserve pigments and color patterns (e.g., Nützel et al.,2007; Kaim et al., 2013; Krawczyński, 2013). All size ranges from micro-to large-sized gastropods were found in the same beds in all studiedareas (Figs. 20 and 21). Fig. 20 displays the raw values that documentthe range of large-sized specimens. Microgastropods (maximum shellsize b1 cm by definition for fossil gastropods; Fraiser and Bottjer, 2004)do occur but have not always been measured. Even though the largestsample of Gullivers studied herein comes from CR, the gastropod assem-blages from VD, BRC and ROC are the most intriguing. These are mostlyrepresented by the largest Gullivers present in the studied material,with only rare occurrences of small specimens (Figs. 18 and 19). These as-semblages are difficult to detect in the field and specimens are often vis-ible only after block disintegration. They occur in the first bed overlyingthemassivemicrobial constructions forVD (Olivier et al., 2014), andwith-inmicrobial deposits embedded in conglomerates for BRC andROC.With-in the Inyoites owenihorizons (latemiddle Smithian) of CR, only countlessphosphatic microgastropods were documented (Fig. 21b, c) and theyprobably correspond to a restricted event in the deepest part of thebasin. A similar assemblage of countless microgastropods was found inthe correlative I. oweni horizons of PA. However, these microgastropodsare associated with large specimens at this site (Fig. 13q–v). EarlySpathian gastropods at HS are extremely rare, but they are comparativelywell-preserved. From this site, an undescribed and still undeterminedvetigastropodwith spiral ornament (clearly a distinct species in the stud-ied collections), probably representing Pleurotomarioidea or Turbinidae,reaches 3.3 cm in diameter (Fig. 13m–p).

6.2.2. Gullivers as micro-habitat for epibiontsInterestingly, some middle Smithian specimens from the CR, PA and

VD areas (Figs. 4, 11 and 14–17) show traces of epibionts. No epibiontswere found on neritimorphs, even on the largest specimens with pre-served shell material.

At VD, epibionts were observed on “Coelostylina sp. A” only. Thesespecimens are represented by poorly-preserved internal molds; ~15%show various epibionts that can coexist on the same specimen. Theyconsist of undetermined tubes, attached bivalves and enigmatic traces(Fig. 22). Their taxonomic determination is often precluded due topoor preservation. Undetermined tubes, which colonized the innershell surface, both near the aperture and within the inner whorls(Fig. 22a), are characterized by a small diameter (~0.5 mm) and a rela-tively large length (up to ~1 cm). These traces are found all over theshell and it is unlikely that they represent dissolution traces. They aresinuous and sometimes appear to branch, although this pattern may

Fig. 10.Detailed biostratigraphical correlation between the studied Smithian sections illustratingof Gulliver gastropods is indicated by the gastropod symbol. Not all studied sections are depictedof the region. Co: occurrence of Smithian conodonts.

correspond to superimposed individuals. Such epibionts probably colo-nized empty shells before these were filled with sediment.

A second category of enigmatic shell inhabitants, characterized bymarked paired negative reliefs (Fig. 22d), are solitary, sinuous andsometimes very long (≥7 cm). Trace diameter is also rather large(~5mm). These traces, observed on several specimens, generally followthewhorl coiling near the aperture before abruptly crossing other juve-nile whorls. These reliefs were filled by sediments different from themold matrix; their upper surface was shaped by the shell curvature.After infilling by sediments, this organism bored through the innerside of the gastropod shell before the latter dissolved. Such traces bettercharacterize bioerosion than epibiont coverage.

With regard to other VD gastropod epibionts, small (up to ~1.5 cm)epibysally-attached bivalves are frequent (Fig. 22b, c). Theses bivalvescolonized the mold after the final dissolution of the shell. Such epizoanbivalves are also frequently observed at CR in the umbilical area of inter-nal molds of the ammonoid Inyoites beaverensis (see Brayard et al.,2013: their Fig. 52). In both cases, they have not been observed in co-occurring ammonoid and gastropod taxa. Whether this selectivity is bi-ological (preferential hosts) and/or represents a taphonomic signal re-mains to be investigated. The same type of epizoan bivalves has beendescribed from the ammonoid assemblage that occurs in the DienerianCandelaria Formation of Nevada (Ware et al., 2011).

To summarize, three different types of gastropod epibionts werefound at VD, and they represent different colonizing phases. The firstsettlement took place before sediment infill, and it corresponds to acryptic habitat where worm tubes formed on the inner shell surface.After sediment infill but probably before the end of lithification andshell dissolution, an enigmatic organism bored and burrowed largetraces below the inner shell surface. After shell dissolution, a thirdphase corresponds to the arrival of epibysally-attached bivalves. TheGulliver assemblage from VD thus represents a micro-habitat wheresuccessive secondary tierers had enough time to settle and flourish.

In the CR and PA areas, epibionts are much rarer (a few specimens forhundreds of gastropods) andwere observed only on≥1 cm Strobeus andPolygyrina individuals. In the CR, epibionts consist of small, sub-circulartraces probably corresponding to attached bivalves. One? Strobeus speci-men also shows an undetermined sinuous worm tube in its inner whorls(Fig. 22f). In the PA, small bivalves (~1 mm, Fig. 22e; up to 2 coexistingspecimens) are found directly attached to preserved shells.

Smithian gastropod epibionts are documented here for thefirst time.Despite considerable efforts, previous studies of the diversity of epi- andendoskeletozoans in diverse Lower Triassic outcrops from the westernUSA basin did not document any epibiont in the Smithian or colonizingEarly Triassic gastropods (Schubert and Bottjer, 1995; Fraiser, 2011).These authors linked this absence to the small size of the studied gastro-pod specimens, which represented a physically unstable environment.All colonized gastropods reported here are N1 cm in size; this may ex-plain why epizoans associated with Smithian gastropods have notbeen previously reported, as only microgastropods were studied andbecause originally aragonitic shells are not preserved.

Observed epibionts are contemporaneously present in thedeepest (CR, PA) and shallowest (VD) parts of the basin. They appearmore diverse in nearshore environments, but this may result fromthe larger size reached by the VD gastropods. Shell size is likely amajor factor controlling their installation as (i) no epizoan wasfound to date on specimen b1 cm, (ii) the largest gastropods in VDare frequently colonized, and (ii) observed epizoans often displayrelatively large sizes (N5 mm). Epibionts were not observed in BRCand ROC although large-sized gastropods are abundant. This may re-sult from the often poorly preserved, highly recrystallized internalmolds.

the diachronismof sedimentary deposits (see Brayard et al., 2013, for details). Occurrencehere, but each illustrated section log corresponds to the best biostratigraphical succession

Fig. 11. Large-sized gastropods from the Confusion Range, middle Smithian, Utah (Figs. 9 and 10). a–b) Coelostylina sp., UBGD 278268, loc. C2. c) Polygyrina sp. A, UBGD 278269, loc. C2. d–e) Strobeus batteni, UBGD 277109, loc. GS1. f) Strobeus batteni, UBGD 277110, loc. GS1. g) Polygyrina sp. A, UBGD 277111, loc. DH1-0A. h) Polygyrina sp. A, UBGD 278270, loc. C2. i) Strobeusbatteni, UBGD 278271, loc. GS1. j–k) Strobeus batteni, UBGD 278272, loc. C2. l) Strobeus batteni, UBGD 278273, loc. GS1. m) Strobeus batteni, UBGD 278274, loc. GS1. n–o) Strobeus batteni,UBGD278275, loc. GS1. p) Polygyrina sp. A, UBGD277113, loc. GS1. q)whorl section of Polygyrina sp. A, UBGD278276, loc. C2. r) Strobeus batteni, UBGD278277, loc. GS1. s) Stroebus batteni,UBGD 278278, loc. GS1. t) Polygyrina sp. A, UBGD 277112, loc. GS1. u–v) Polygyrina sp. A, UBGD 277114, loc. GS1.w) Coelostylina sp., UBGD 278279, loc. GS2. x–y) Abrekopsis depressispirus,UBGD278280, loc. GS1. z) Strobeus batteni, UBGD278281, loc. GS1. aa) Polygyrina sp. A, UBGD278282, loc. GS1. ab) Polygyrina sp. A, UBGD278283, loc. C2. ac–ad) Abrekopsis depressispirus,UBGD 278284, loc. C2. ae) Abrekopsis depressispirus, UBGD 278285, loc. C2. af) Polygyrina sp. A, UBGD 277116, loc. GS1. ag) Polygyrina sp. A, UBGD 278286, loc. GS1. ah) Polygyrina sp. A,UBGD 278287, loc. GS1. ai–aj) Strobeus batteni, UBGD 278288, loc. GS2. ak) Strobeus batteni, UBGD 278289, loc. GS2. al) Strobeus batteni, UBGD 278290, loc. GS2. am–an) Strobeus batteni,UBGD 278291, loc. GS2.


Fig. 12. Large-sizedgastropods from the Confusion Range (CR), Kanarraville (KAN) and Torrey area (TO), early andmiddle Smithian, Utah (Figs. 9 and 10). IllustratedKAN specimens are allfrom loc. Ka2, Owenites koeneni beds. Illustrated TO specimens are all from units B and C (Dean 1981), O. koeneni beds. a, b, c–d) Polygyrina sp. A, UBGD 278292, UBGD 278293 and UBGD277115, respectively, all from loc. DH1-0A, base of the Preflorianites–Kashmirites beds, CR. e, f, h–i) Strobeus batteni and Abrekopsis depressispirus, UBGD 278294, UBGD 278295and UBGD278296, respectively, all from loc. DH1–2, Preflorianites-Kashmirites beds, CR. g) Strobeus batteni, UBGD 278297, loc. DH1–9, base of the O. koeneni beds, CR. j–l, m–n) Laubopsis sp. indet.,UBGD 278803 and UBGD 278804, loc. GS2. o–p) Polygyrina sp. indet., UBGD 278298, KAN. q) Polygyrina sp. indet., UBGD 278299, KAN. r) Polygyrina sp. indet., UBGD 278300, KAN. s–t)Abrekopsis depressispirus, UBGD 278301, KAN. u) Polygyrina sp. indet., UBGD 278302, KAN. v) Polygyrina sp. indet., UBGD 278303, KAN. w–x, y–aa) Polygyrina sp. A, UBGD 278304 andUBGD 278305, TO. ab, ac) Polygyrina sp. A, UBGD 278306 and UBGD 278307, TO. ad) Coelostylina sp.,UBGD 278308, TO. ae) Polygyrina sp. A, UBGD 278309, TO. af–ag) Strobeus batteni,UBGD 278310, TO. ah) Polygyrina sp. indet., UBGD 278311, TO. ai) Polygyrina sp. indet., UBGD 278312, TO.


Fig. 13. Large-sized gastropods from Palomino Ridge (PA), San Rafael Swell (SRS), Hot Springs (HS), middle, late Smithian and early Spathian, Nevada, Utah and Idaho (Figs. 9 and 10). a–j)Undetermined taxon, UBGD278313 to UBGD278322, loc. RC43, earliest Spathian, SRS. k–l) packstones showing several high-spired specimens,Anasibirites kingianusbeds, SRS (specimensfrom the lectostratotype of the Sinbad Fm., which is Section 10 in Goodspeed and Lucas, 2007; image courtesy of S.G. Lucas, Albuquerque). m–p) Vetigastropoda indet., J. Jenks privatecollection, Columbites beds, early Spathian, HS. q–r) Polygyrina sp. A, PIMUZ30952, loc. PLR11, Inyoites oweni horizons,middle Smithian, PA (microgastropods co-occur and are representedby black calcitic micro-molds and white phosphatic molds). s–t) Polygyrina sp. A, PIMUZ 30954, loc. PLR12, middle Smithian, PA. u–v) Coelostylina sp., PIMUZ 30952, loc. PLR71, middleSmithian, PA.


Fig. 14. Large-sized gastropods from Virgin Dam, all from loc. VD4A, Owenites koeneni beds, middle Smithian, Utah (Figs. 9 and 10; see Olivier et al., 2014). a–b, c–d) “Coelostylina sp. A”,UBGD 278323 and UBGD 278324. e–g) “Coelostylina sp. A”, UBGD 275164. h–j) “Coelostylina sp. A”, UBGD 278325. k, l) “Coelostylina sp. A”, UBGD 278843 and UBGD 278844, respectively.


6.2.3. Local lateral variationsWe carefully explored the Torrey (TO; Fig. 23) and San Rafael Swell

(SRS; Fig. 24) areas in Utah, fromwhichmicrogastropod shell bedswerepreviously reported to be common (Batten and Stokes, 1986; Schubertand Bottjer, 1995; Boyer, 2004; Fraiser and Bottjer, 2004; Fraiser et al.,2005; Nützel and Schulbert, 2005; Pietsch et al., 2014).

In the Torrey area (Fig. 23), we investigated sections previouslydescribed by Dean (1981) that were expected to contain large-sizedgastropods according to the two specimens illustrated by this author,but that have been neglected in previous works. Other paleontologicalstudies of the Early Triassic marine outcropswithin this area are sparse:Schubert and Bottjer (1995) sampled three sections (without providing

Fig. 15. Large-sized gastropods from Virgin Dam, all from loc. VD4A, Owenites koeneni beds, middle Smithian, Utah (Figs. 9 and 10; see Olivier et al., 2014). a–t) “Coelostylina sp. A”, UBGD278326 to UBGD 278336; n: UBGD 278845; o; UBGD 278846; p: UBGD 278847.


detailed information about the locations), Fraiser and Bottjer (2004)sampled two sections, and Nützel and Schulbert (2005) a single section.We thus extended our sampling to new sites that these authors did notinclude in their reports of typical microgastropod beds (Fig. 23a). Ac-cording to lithological descriptions of Dean (1981), the units that wesampled in the new localities were the same units that were studied

by Fraiser and Bottjer (2004) (units A, B and D of Dean) and additionalbeds (units C and E of Dean) at various localities within the Torrey area(Dean's sections and eight supplementary sites). According to the fig-ures of the studied facies, Nützel and Schulbert (2005) likely sampledDean's unit A. Our spatially expanded sampling of this area indicatesthat large-sized gastropods are frequently present and that micro-

Fig. 16. Large-sized gastropods from Virgin Dam, all from loc. VD4A, Owenites koeneni beds, middle Smithian, Utah (Figs. 9 and 10; see Olivier et al., 2014). Arrows indicate color patternremains. a–d) “Coelostylina sp. A”, UBGD278337 toUBGD278339. e–g, h–i, j–k, l–o) Abrekopsis depressispirus, UBGD278340, UBGD 278341, UBGD278848 andUBGD278342, respectively;o: close-up view of the dark band remains at the aperture. p–p) Abrekopsis depressispirus, UBGD 278343.


and Gulliver gastropods do occur in the same units and beds at sev-eral localities (Figs. 20 and 23b, c). Clearly, the shell-size range ofgastropods within the TO area has been underestimated. The largestsampled gastropod fragment measures ~4.5 cm in height, which,considering its incompleteness, suggests that the original shell

length was likely 7 cm or more (Fig. 12w–x), whereas the largestcomplete specimen observed in the field reaches ~5 cm (Fig. 23c).

Well-sorted microgastropod concentrations often occur, especiallyin unit A, confirming the observation by Dean (1981) and Fraiser andBottjer (2004). The gastropod fauna studied by Nützel and Schulbert

Fig. 17. Large-sized gastropods fromVirginDam (VD) and Black Rock Canyon (BRC),middle Smithian, Utah (Figs. 9 and 10). Illustrated VD specimens (a–j) are all from loc. VD4A,Oweniteskoeneni beds. Illustrated BRC specimens (k–w) are all from the beds underlying the Anasibirites kingianus beds, at the base of the section. a–b) “Coelostylina sp. A”, UBGD 278849, VD. c–d)Angularia sp., UBGD 278850, VD. e–f) Worthenia windowblindensis, UBGD 278851, VD. g–k) “Coelostylina sp. A”, UBGD 278852 to UBGD 278856. l–n) Angularia sp., UBGD 278857.o) Angularia sp., UBGD 278858. p–t) “Coelostylina sp. A”, UBGD 278859 to 278862. u) Block with several specimens of “Coelostylina sp. A” (UBGD 278863 to 278865) and one specimenof Angularia sp. (“A”; UBGD 278866). v–w) Blocks with specimens of “Coelostylina sp. A” (UBGD 278867 to 278871).


(2005) was derived from a single, graded shell bed, typical oftempestites, including size sorting by transport. Based on our field ob-servations, some of the mentioned coquinas laterally correspond to ho-rizons with Gullivers. Some large specimens observed in the different

TO units are illustrated in Fig. 23c. Large-sized specimens appear to bemore abundant in units B, C and D in the western and southern partsof the area. Large bivalves are also abundant in unit D. Overall, Gulliversseem to be absent only at the base of unit A. Although microgastropod

Fig. 18. Field illustrations of large-sized gastropods from various localities in Utah. MM: specimens from loc. MIA1, Vercherites undulatus beds, early Smithian, Mineral Mountains (seeBrayard et al. 2011b). CC: specimens from TW12, early?–middle Smithian, Cedar City area. SRS: specimens from loc. RC43, earliest Spathian, San Rafael Swell (see Fig. 10). BRC: specimensfrom the Anasibirites kingianus beds, late Smithian, Black Rock Canyon.


beds are present, they are not exclusive of units A–D since Gulliversoccur contemporaneously with them in nearly the entire sedimentarysequence. Both size classes display a heterogeneous distribution withinthe same bed, site and also within the entire TO area. This may be ex-plained by the complex interplay of local environments, ranging fromdominant tidal flats to subtidal and more open-marine settings (Dean,1981; Hofmann et al., 2014; see environmental reconstructions inOlivier et al., in press). Qualitatively, Gullivers seem to be more abun-dant within slightly more open-marine environments (sites #1–3 and7 in Fig. 23a), whereas microgastropods appear often concentratedwithin the lower microbial deposits of unit A (see also Olivier et al., in

press for a likely explanation based on autocyclic processes). Neverthe-less, inmost cases they coexist. This spatially-expanded sampling proto-col therefore suggests that, due to spatial heterogeneity, a widespreadsampling effort has a significant impact on estimated diversity andshell-size range, as much as, if not more than sampling intensity perse (number of samples and specimens).

Concerning the large SRS area (Fig. 24), we concentrated our sam-pling effort to the top of the Sinbad Formation, from which field ob-servations of large-sized gastropods were succinctly reported byGoodspeed (1996) and Goodspeed and Lucas (2007). Diversifiedsmall-sized mollusk assemblages (mainly gastropods, bivalves and

Fig. 19. Field illustrations of large-sized gastropods from various localities in Utah and Arizona. BRC: specimens from the basalmicrobial beds, middle? Smithian, Black Rock Canyon. ROC:specimens from loc. ROC1 and 3, middle and late Smithian, Rock Canyon.


scaphopods) are characteristic of the A. kingianus beds (late Smithian)and of underlying levels (roughly correlative of Dean's (1981) unit Din TO), as previously discussed by Batten and Stokes (1986), Boyer(2004), Fraiser and Bottjer (2004), Hautmann and Nützel (2005),Nützel and Schulbert (2005), Goodspeed and Lucas (2007), Hofmannet al. (2014), and Pietsch et al. (2014). The environments are oftendescribed as being influenced by storms, which may have resulted insubstantial size-sorting. However, transport seems to have been limited,resulting in poor sedimentary sorting and the presence of numerous ar-ticulated bivalves and unbroken ammonoid conchs (Brayard et al.,2013; Hofmann et al., 2014). These storm-induced deposits are re-cognized over the entire SRS area, although lateral variations may bepronounced (Goodspeed and Lucas, 2007). Batten and Stokes (1986)reported 16 genera, but only three high-spired specimens with a sizeN13 mm: Zygopleura, Battenizyga (Anoptychia) and Coelostylina. Thematerial of Nützel and Schulbert (2005); same occurrence as Battenand Stokes (1986) yielded several specimens larger than 1 cm,

e.g., “Zygopleura”: 18.5 mm in height and 3.7 mm in width, and Verneliavenestravella: 15.2 mm in height and 10 mm in width. Nützel (2005b)added the occurrence of a fragmented specimen of Strobeus orSoleniscus with a size N10.5 mm from the same locality. Field observa-tions and collections by Goodspeed (1996) (nine reported genera)and Goodspeed and Lucas (2007) indicate that correlative packstonescontain accumulations of high-spired specimens N15 mm in someplaces, as illustrated in Fig. 13k and l. These specimens were found inthe lectostratotype of the Sinbad Formation (section 10 in Goodspeedand Lucas, 2007). Pietsch et al. (2014) also reported a Coelostylina spec-imen of 17 mm from this site.

Taken together, these observations thus indicate that the abundanceof large specimens may vary greatly laterally and that Gulliver gastro-pods co-occur with abundant minute representatives. Overlying bedsare much less fossiliferous and correspond to tidal and peritidal de-posits. We note that an abundant and apparently monospecific gastro-pod assemblage with large-sized specimens is present in the topmost

NEVADA

IDAHO

Smithianbasinal configuration VD

KAN

TO

SRS

CR

0 8 16 24 32 40 48 56 64 72

Size (mm)

n=2513All

PA

BRC

CC

MM

HS

n=1619

n=67

n=349

n=9

n=245

n=93

Neritimorph Strobeus

Polygyrina, Coelostylina or “Coelostylina sp. A”

ROC

80 88 96

n=46

n=71

Fig. 20. Rawvalues documenting the range of sampled gastropod specimenswithin thewestern USA basin. Horizontal dotted lines indicate prolonged size ranges by field and thin-sectionobservations. Dashed area shows themicrogastropod range 0–1 cm. HS, PA, KAN, VD, BRC and ROC: from blocks reduced to fragments by hammer (KAN: 2 replicates of ~600 cm2). CR, CC:surface collecting. SRS, TO, MM: surface collecting and from blocks reduced to fragments by hammer.


beds of the Sinbad Formation at some places in northernmost SRS. Thelargest individual reaches ~3 cm (Figs. 13, 18, 20). This assemblage maybe earliest Spathian in age (Fig. 4b; see Brayard et al., 2013). It reinforcesthe idea that environmental lateral variations strongly determine the het-erogeneous spatial distributions of microgastropods and Gullivers, whichin turn calls for spatially-widespread sampling strategies to recoverbetter-constrained estimates of diversity and shell-size range.

7. Discussion

7.1. Sampling and preservation effects

Because the mode of preservation and type of sampling influenceobserved richness and shell-size range, it is worth distinguishing theirpotential role in controlling the observed size distribution amongEarly Triassic gastropods.

7.1.1. SamplingIn the case of Early Triassic gastropods, four sampling issues regard-

ing the full assessment of body size are most relevant sources of bias:(1) the lack of repeated sampling of fossil sites and insufficient regionalcoverage; (2) large specimens are usually rare in living assemblages,which results in a paradoxical sampling bias against large-bodied spec-imens; (3) an incomplete survey of the scientific literature; and (4) aninsufficient taxonomic work.

(1) Spatial clustering and local rarity are among themain factors de-termining the efficiency of sampling in both neontological andpaleontological studies. Therefore, repeated sampling and suffi-cient geographic coverage are necessary to increase the

probability of recovering rare taxa including rare large speci-mens due to the patchiness of their occurrence. Sampling inten-sity also enhances statistical confidence of relative abundances(Hayek and Buzas, 1997; Bennington and Rutherford, 1999;Bennington, 2003, Zuschin et al., 2005, 2006, McGowan et al.,2009). However, Early Triassic gastropod faunas have rarelybeen collected to a sufficiently intense degree. Many of the sam-pled outcrops correspond to shallow-marine depositional envi-ronments that are characterized by strong lateral variation andpatchiness at local scale. Thus, sufficient spatial coverage andhigh sampling intensity are mandatory.

(2) Most of the large Early Triassic gastropods reportedhere are poorlypreserved fragments of internal molds. Therefore, their taxonomicvalue is very limited, which might explain why these specimenshave not been recognized previously, although they come fromthe very same outcrops and horizons fromwhichmicrogastropodswere first reported. Moreover, large and incomplete internalmolds of gastropods can be difficult to detect in thefield, especiallywhen the apical part is not visible — the characteristic helicoidalshape can be hard to spot when only the last whorls are exposed(see, e.g., Olivier et al., 2014, their Fig. 8). The present reportshows that large gastropods have been overlooked in the fielduntil recently, although they are usually collected preferentiallydue to their attractiveness to fossil collectors and are easier to de-tect by surface collection (e.g., Kidwell and Bosence, 1991; Cooperet al., 2006). In addition, the evaluation of gastropod richness ordensity based on observation of thin sections has obviously fa-vored the reports of diminutive specimens.

(3) Research on the Lilliput effect in Early Triassic gastropods alsosuffered from an insufficient assessment of the literature which

Fig. 21. a) Field sample illustrating the co-occurrence of Gulliver andmicrogastropods (black calciticmicro-molds) within the same bed, GS2, Confusion Range, middle Smithian (Fig. 10).b–c) Close-up views of late middle Smithian microgastropod accumulation from the Inyoites oweni horizons, CR. Diameter of Inyoites oweni in c is ~3 cm. d–e) Field illustrations of co-occurring large- and small-sized specimens within a “typical”microgastropod bed, Kanarraville, middle Smithian (Fig. 10).


reported large specimens. To some degree, this literature is noteasily available and known only to specialists, but it still must beconsidered.

(4) When compared to ammonoids or bivalves, Early Triassic

Fig. 22. Smithian gastropod epibionts from the Sinbad (Timpoweap) Formation in theVirginDamRange (CR: f). a) Undeterminedworm tubeswhich colonized the inner shell surface (VD). b–c,several Gullivers from VD. f) Undetermined worm tube in inner whorls (CR).

gastropods were rarely collected with a taxonomic goal andmonographed (with Batten and Stokes, 1986, being one noticeableexception). This likely results from their poor preservation andmay explain at least partially the paucity of documentation of

(VD: a–d) area and from the ThaynesGroup at PalominoRidge (PA: e) and the Confusione) Epibysally attached bivalves. d) Close-up of an enigmatic burrowed large trace found on


large-sized specimens prior to our work. Since gastropods are notused for biostratigraphy, intense stratified collection is thereforeless common than in ammonoids.

7.1.2. PreservationThe issue of preservation is a recurring theme in the ongoing de-

bate about post-crisis recovery, whether for assessing the Lazarus ef-fect and taphonomic megabiases on a global scale (e.g., Erwin andHua-zhang, 1996; Kauffman and Harries, 1996; Wignall and Benton,1999; Fara, 2001; Twitchett, 2001; Fraiser and Bottjer, 2005), or forevaluating the fidelity of fossil assemblages on a regional or localscale (Fraiser and Bottjer, 2004). Assessing the quality of the fossilrecord is difficult because preservation processes integrate both bio-logical traits (e.g., generation time, body size, shell thickness andmineralogy, population density) and paleoenvironmental/tapho-nomic features (e.g., time-averaging, sedimentation rates, hydrody-namics) that may act at various spatiotemporal scales (Valentine,1989; Kidwell and Bosence, 1991; Kidwell and Flessa, 1996; Stonerand Ray, 1996; Cherns and Wright, 2000; Wright et al., 2003;Tomašových, 2004, 2006; Fraiser and Bottjer, 2005). In addition,some of these associated parameters may have opposite effects onpreservation potential. For example, short-lived mollusks would beexpected to be overrepresented in fossil assemblages due to theirhigh population turnover (Levington, 1970; Kidwell and Flessa,1996; Vermeij and Herbert, 2004), but these taxa are usually small-bodied and should, therefore, be more prone to dissolution(e.g., Cummins et al., 1986; Kidwell and Flessa, 1996). Conversely,large mollusks will tend to be taphonomically robust, but their gen-eration time is usually slow and their population density low(e.g., Powell and Cummins, 1985; Powell and Stanton, 1985;Valentine and Jablonski, 1986; Stoner and Ray, 1996). Overall,these opposite effects probably compensate for each other on alarge scale, at least in the generation of thanatocoenoses (Kidwell,2001). This is the reason why the simulations presented above(Section 2) were achieved under the working hypothesis of a shell-size independent random selection of individuals or species.

Fraiser and Bottjer (2005) acknowledged that shell preservation candepend on facies-controlled factors and that the comparison of body-size ranges and extent of epibiont cover will help to detect selectiveshell dissolution. For the Early Triassic gastropods, we found no signifi-cant preservation contrast between large and small specimens in termsof facies or diagenetic controls. Molds and recrystallized fossils occur inall of the size classes we investigated, as well as rare cases of shell silic-ification. A lack of size-controlled differential preservation is expectedbecause, as far as we know, there is no evidence of a correlation be-tween shell size and mineralogy (aragonite predominates in the shellsof most marine gastropod clades). In addition, data from VD suggestthat the frequency of epizoans and bioeroders positively correlateswith shell size and occurs at various taphonomic stages.

Furthermore, we found no relationship between shell size andshape, corroborating the absence of selective transportation or pres-ervation processes based on these shell parameters. Organic-rich mi-crostructures have also been suspected as being a factor lesseningthe probability of shell preservation (e.g., Kidwell and Flessa,1996). However, evidence for this relationship is lacking, and thereis no apparent correlation between shell size and richness in organiccompounds among gastropod shells. The actual composition ofamino acids seems to be a better predictor of diagenesis than thesimple richness of organic molecules (e.g., Jackson and Bischoff,1971; Marin and Gautret, 1994).

Overall, sampling biases and stochastic effects linked to the lowknown Early Triassic gastropod diversity are probably the main reasonsfor the rarity of reports of large Early Triassic gastropods. The role of pres-ervation is secondary and is much more difficult to qualify and quantify.

7.2. Distribution within the western USA basin: local and regional controls

The common occurrence of Gullivers in thewestern USA basin strik-ingly contrasts with the Early Triassic microgastropod concentrationsthat were first described from this basin. We found that small-sizedand Gulliver gastropods have a patchy distribution at all spatial scales(site or basin), and they can occur within the same beds (Figs. 23, 24).Sampling of a few shell beds only in a restricted number of sections istherefore insufficient to characterize the local/regional fauna in termsof diversity and size–frequency distribution. Sampling intensity(i.e., the numbers of sampled beds and specimens) is important, butits geographical (i.e., number of sampled environments) and temporalresolution (i.e., detailed biostratigraphy and correlation) is of prime im-portance. Focusing on a single outcrop, even if the number of countedspecimens is high, leads to an underestimation of the neighboring diver-sity components. Sufficient spatial sampling coverage, based on high-resolution correlations, is often missing in Early Triassic studies (see Heet al., 2015 for an exception) so that the observed patterns may be biasedto various degrees.

Recently, Marenco et al. (2013) described successive microgastro-pod beds from an Early Triassic shallow-marine environment inMontana. By comparison with large specimens from the deeper envi-ronments of the Confusion Range section (Brayard et al., 2010), theypostulated that gastropods were subject to differential environmentalconstraints on shell size along a bathymetric gradient, leading to ahigher frequency of large specimens in deeper settings. They also stated“extreme abundances of smaller-than-1mmgastropods per kg of rock”.In our opinion, they may have actually sampled an assemblage of larvalshells and early juvenile shells similar to that reported from the EarlyTriassic of Vietnam by Kaim et al. (2014a,b). Late Paleozoic/Early Meso-zoic caenogastropod larvae have typical shell sizes of 0.5–1 mm. Suchthanatocoenoses are also known from the Late Paleozoic and mayoccur in oxygen depleted (or otherwise limited) settings where meta-morphosis of planktic larvae and maturation are impossible (Nützeland Mapes, 2001; Mapes and Nützel, 2009; Nützel, 2014).

The widespread occurrence of Gullivers within a large array of envi-ronments of thewestern USA basin demonstrates that microgastropodsand large gastropods coexisted in all sampled environments, even inshallow nearshore settings. Moreover, in three shallow-water environ-ments (VD, BRC and ROC), Gullivers are dominant, contradicting the hy-pothesis of Marenco et al. (2013) that large gastropods were restrictedto deeper offshore environments. However, more information aboutthe assemblage studied by Marenco et al. (2013) is needed becausethis work has been published as an abstract, greatly limiting the amountof information available for this fauna. For instance, a detailed biostrat-igraphic framework for the Marenco et al. (2013) data would enabledirect and robust comparison of both settings. Relative abundances ofthe Smithian Gulliver taxa identified in the deeper parts of the basin(mainly Polygyrina, Strobeus, Abrekopsis, Laubopsis, Coelostylina andOmphaloptycha) tend to bemore equable than those in shallow settingsin which mainly Polygyrina, Abrekopsis, Strobeus, “Coelostylina sp. A”,Angularia and Worthenia are found. Slightly more abundant Gulliverspecimens can be found locally in deeper settings, e.g., in the Torreyarea. Observed maximum sizes of “deep” and “shallow” gastropodsat the specimen- or species-levels are nonetheless similar, with,e.g., Abrekopsis specimens and high-spired taxa reaching in both envi-ronments ~3 cm and N7 cm, respectively (Fig. 20).

The regional spatial distribution of body sizes between juveniles andadults, or among species or guilds, is common in modern gastropods. Itmainly results from habitat suitability, feeding preferences, biotic inter-actions and dispersal ability. This is often documented in tidal environ-ments (e.g., Chapman, 1994, 2000; Ray and Stoner, 1995; Stoner, 2003;Haubois et al., 2004). During the Smithian–Spathian interval, the west-ern USA basin was mainly a relatively shallow epicontinental sea withlarge bay systems dominated by tidal deposits. In this context, it is notsurprising that gastropods show large lateral variation in richness,

#2 - unit BSites with Gullivers (this work)

Dean’s (1981) localities

Sites with previously reportedtypical microgastropod beds:- F: Fraiser and Bottjer (2004)- N: Nützel and Schulbert (2005)

TORREY

GROVER

5 km

D1

D2/F

D3

D4

D5D6D7

D8

D9/F

D10

D11

D12

Fremont River

Pleasant

Cre ek

Sulphur Creek

CAPITOL REEFNATIONAL PARK

24

12

#1

#2 #3 #4

N

TorreyArea (#1)

25m

30m

35m

40m

45m

50m

0m

5m

10m

15m

20m

O.

A.k.

Yello

w u

nit

REDBEDS

PERMIAN

LithofaciesDean (1981)

A

B

C

D

Gulliversthis work

µ

µ

µ

Microgastropod bedsFraiser and Bottjer (2004)

Nützel and Schulbert (2005)

a

b

c

#4 - unit B#4 - unit C

#6 - unit D

#3 - unit A (topmost) #3 - unit B (lowermost)

#1 - unit A #3 - unit A

10 mm

#6

#5#7

#3unit B

#6 - unit B



abundance and body size. Microgastropods may have accumulated forreasons independent of stressful conditions. Small-sized specimensmay have aggregated according to current strength and food availabili-ty, and sheltered in the available pool habitats, whereas more mobilelarger individuals may have moved more easily to other habitats (seepaleoenvironmental reconstructions in Olivier et al., 2014, in press, forVD and TO, respectively). Such tidal shelters may also explain the com-mon preservation and dominance of microgastropods in some shallowenvironments (e.g., microbial deposits in TO), without excluding con-temporaneous, dense clusters of large specimens at some sites (e.g., inthe VD area). The abundant microbial mats, as well as the variablesources of nutrients from the continent, may have provided profuse re-sources for grazing taxa such as many gastropods (e.g., Browne et al.,2000), thus explaining their high abundance in peritidal settings ofthe western USA basin.

7.3. Early Triassic spatio-temporal distributions

Brayard et al. (2010, 2011a) and a survey of the literature showedthat several large gastropod taxa were already present soon afterthe mass extinction (e.g., during the Griesbachian Ophiceras Zone inSouth China; Kaim et al., 2010), at different localities during theGriesbachian–Dienerian interval (Fig. 1). Naticopsis is the most wide-spread taxon yielding large specimens early in the Griesbachianup into the Dienerian; it often reached ~3 cm in width at different lati-tudes and in various environments. Many other taxa also have a size≥1 cm (Bellerophon, Amberleya?, Gradellia, Toxoconcha, Trypanostylus,Wannerispira) or even N2 cm (Coelostylina, Warthia, Neritaria), some-times co-occurring (e.g., Tong and Erwin, 2001). Assemblages fromGreenland, South China, South Primorye or Oman (see Fig. 4) showsize distributions that do not differ from those of the Late Triassic orthe present-day (Nützel, 2005b; Nützel et al. 2010), thus calling intoquestion the existence of a Lilliput effect on gastropods during the ear-liest Triassic. The Dienerian is the most poorly-documented time inter-val in the Early Triassic, and this poor record complicates the analysis ofbody-size trends for taxa persisting from the Griesbachian to theSmithian. The Smithian is the best documented substage in terms of en-vironmental settings and taxonomic identifications. Several Gullivertaxa have been reported for this time interval (Polygyrina, Strobeus,Abrekopsis, Laubopsis, Coelostylina, Omphaloptycha, “Coelostylina sp. A”,Angularia, Worthenia) along with some other forms with sizes N1 cm(Battenizyga, Soleniscus?, Zygopleura). Several Smithian gastropods hadbody-sizes larger than the largest known Late Permian as well asmany Anisian (earlyMiddle Triassic) taxa (Payne, 2005). This reinforcesBrayard et al.'s (2010) view that the Lilliput effect is not applicable at theclade level at that time. As a first-order approximation, based on pub-lished measurements or illustrated specimens, Early Triassic generacomprising large gastropods were as diversified as microgastropods(Table 1), contradicting previous observations by Fraiser and Bottjer(2004). Occurrences of Spathian gastropods nearly always compriseseveral genera yielding large individuals (e.g., Natiria, Werfenella,Vetigastropoda indet.; Nützel, 2005b; Brayard et al., 2010; this work),suggesting that large body sizes have a wide phylogenetic distributionalso in this time interval.

7.4. Gulliver gastropods vs. global Early Triassic environmental changes

Rediversification after the end-Permian mass extinction was explo-sive for some nekto-pelagic groups such as ammonoids (Brayard et al.,2009b) and conodonts (Orchard, 2007). However, it was clearly not a

Fig. 23. Spatio-temporal distribution of Gullivers within the Torrey area. a) Explored Gulliver2004; Nützel and Schulbert, 2005). b) Temporal distribution of sampled large-sized gastropodsoccurrences. Depicted section #1 is for illustration purpose, but succession and ages of lithologvarious localities and units.

continuous process. Indeed, it was interrupted at least once during abrief, marked extinction event at the end of the Smithian (e.g., Tozer,1982; Dagys, 1988; Brayard et al., 2006; Orchard, 2007; Brosse et al.,2013). This episode is concomitant with a drastic ecological turnoverof floras during which a middle Smithian major spore peak was follow-ed by an early recovery of gymnosperms during the late Smithian(Hermann et al., 2011). The Smithian–Spathian boundary correspondsto an abrupt, global change from hygrophytic to xerophytic plant asso-ciations (Galfetti et al., 2007c; Hermann et al., 2011). The global carbonisotope record is characterized by a marked negative peak during themiddle Smithian, followed by an abrupt positive shift in the lateSmithian (e.g., Payne et al., 2004; Galfetti et al., 2007b; Horacek et al.,2007; Clarkson et al., 2013; Grasby et al., 2013; Fig. 4). In the Tethys,the oxygen isotope record from biogenic phosphate tends to track thecarbon isotope record and indicates a temperature drop of ~8 °C nearthe Smithian–Spathian boundary (Romano et al., 2013; Fig. 4). Theend-Smithian event therefore had a deep impact on the rediver-sification of nekto-pelagic organisms. The most likely explanations callupon the combined roles of the carbon cycle (e.g., Galfetti et al.,2007b, 2008; Goudemand, 2014), sea-level change (e.g., Embry, 1997;Olivier et al., 2014), and climate change (Sun et al., 2012; Romanoet al., 2013). Based onmarine faunas from the western USA basin, it ap-pears that benthic communities were taxonomically and ecological-ly rather stable throughout the Smithian and were not affected bysignificant turnovers at this time (Hofmann et al., 2014). Despite a re-duced taxonomic richness and a few disappearances of gastropod genera(e.g., among the Bellerophontoidea and Strobeus; Kaim and Nützel, 2011;Kaim et al., 2013), there is currently no evidence for a major extinctionevent of benthic faunas at the Smithian–Spathian boundary. Within thewestern USA basin, this boundary ismarked by important bivalve blooms(Brayard et al., 2013; Hofmann et al., 2014).

The Lilliput effect in the marine realm is commonly attributed to theoutcome of deleterious environmental conditions such as anoxia, salinityfluctuations, acidification and high water temperatures, which may havelimited the growth of organisms, or accelerated their development, ormodified their population growth and generation time (e.g., Twitchett,2007). These abiotic parameters fluctuated widely during the Early Trias-sic, especially during the Smithian (Fig. 4a). For instance, the middle andearly late Smithianmay havewitnessed the highest temperature reachedin the Tethys during the Early Triassic (Sun et al., 2012; Romano et al.,2013). Numerous hypotheses state that such a warming should be bene-ficial for dwarf forms but unfavorable for large taxa (e.g., Sibly andAtkinson, 1994; Daufresne et al., 2009; Smith et al., 2009; Sheridan andBickford, 2011; Ohlberger, 2013). However, the largest living gastropodsare known from the tropics and the largest Permian gastropods are alsoknown from the tropical shallow-water carbonates (Nützel andNakazawa, 2012). Smithian Gulliver specimens and species occur bothin deep and shallow environments within the western USA basin, espe-cially at a time when global temperature and carbon cycle perturbationswere most severe (e.g., during the middle and late Smithian; Fig. 4a). Incontrast to recent statements by Sun et al. (2012), Song et al. (2014)and Pietsch et al. (2014), the middle to end-Smithian event did not pre-vent the occurrence of Gullivers, although it corresponds to a globaloceanographic and climatic event. It may be argued that this observationis valid only for the epicontinental western USA basin (e.g., Fraiser et al.,2011), which was acting as a potential ecological refugium for largetaxa. However, although gastropod data are very scarce, large taxa(e.g., Strobeus and Naticopsis) are also known from correlative beds fromthe Salt Range, Pakistan (Nützel, 2005b; Kaimet al., 2013; Fig. 4), in an en-tirely different tectonic and environmental context. Thus, if we rule out a

localities (this work) and previously described microgastropod sites (Fraiser and Bottjer,compared with distribution of microgastropods beds, highlighting their contemporaneousical units are identical within all areas. c) Field illustrations of large-sized gastropods from

G1

G5 G4

G12

G8

G14G15

G13

G9

G17G18G10P

G11G21

G22G20

G19

G4

GREENRIVER

10 km

24

70 F1F5

AMNH3026F2, N, P

F3

F4

Sites with Gullivers (this work)

Studied localities of Goodspeed (1996)and Goodspeed and Lucas (2007; G)

Sites with previously reported typicalmicrogastropod beds:- F: Fraiser and Bottjer (2004)- N: Nützel and Schulbert (2005)- P: Pietsch et al. (2014)- AMNH3026: Batten and Stokes (1986)

Fig. 24. Distribution of large gastropods within the San Rafael Swell area with previously detailed microgastropod sites (Batten and Stokes, 1986; Fraiser and Bottjer, 2004; Nützel andSchulbert, 2005; Pietsch et al., 2014). Extensive studies of Goodspeed (1996) and Goodspeed and Lucas (2007) refer to “large gastropods”, but without specific sampling sites.


regional refugium effect, gastropod shell size was likely not influenced bythe globally fluctuating environments during the Smithian. Studies ofsome present-day organisms indicate synergistic effects of at least pH,hypoxia and temperature on gastropod shell-size and morphologicalplasticity (e.g.,Melatunan et al., 2013), but this link does not always cor-respond to data from natural populations (e.g., Angilletta and Dunham,2003; Vanden Byllaardt and Cyr, 2011). The upper limits of tolerabletemperatures are high in modern gastropods, especially in intertidal taxa(e.g., Song et al., 2014). This suggests that elevated temperatures duringthe middle–late Smithian interval had no or little impact on the diversityand distribution of these benthic organisms in all depositional environ-ments of the epicontinental sea of the western USA basin. This agreeswith our observation of abundant Gullivers at that time.

Gullivers thus demonstrably occurred during thewarmperiod of themiddle–late Smithian. Although represented by different families andmorphologies, they are also present in the potentially colder environ-ments of the Spathian (e.g., Vetigastropoda indet., Werfenella, andNatiria). Unfortunately, no survivors of the Smithian/Spathian boundaryhave been recorded in any basin at this point, thus preventing an anal-ysis of size trends before, during and after the end-Smithian event (suchan analysis has been performed for conodonts; Chen et al., 2013).

Neritimorphs (e.g., Naticopsis, Abrekopsis, and Neritaria) probablyrepresent the longest ranging group during the Early Triassic, and thusmay provide some indication of the within-clade body-size evolution.The maximum size of neritimorph gastropods (~3 cm in width) appar-ently did not vary during the late Griesbachian (three successive zones),nor during the Smithian. This suggests that the influence of global envi-ronmental fluctuations on their maximum size was probably limited.

7.5. Is there an Early Triassic Lilliput effect?

7.5.1. Lilliput effect sensu strictoA Lilliput effect sensu stricto, i.e., size reduction in surviving species

(Urbanek, 1993; Harries and Knorr, 2009), is not applicable to

gastropods at the Permian/Triassic boundary because there is not a sin-gle known nominate gastropod species crossing the boundary. Triassicspecies must obviously be derived from Permian ancestors, but thereis currently no evidence to document any phylogenetical link at the spe-cies level. The Lilliput effect has been generally proposed for marine in-vertebrates at supra-specific taxonomic levels and at a restrictedgeographical scale for the Early Triassic (e.g., Luo et al., 2008; Metcalfeet al., 2011). This approach (i.e., sensu lato; see Section 7.5.2) resultsfrom: (i) the low number of boundary-crossers at low taxonomic levelsavailable for statistical treatment, (ii) the low number of species with atemporal range long enough to identify statistically significant trends,(iii) uncertainties in taxonomic assignments when working withsmall, poorly-preserved specimens, and (iv) the lack of a good fossil re-cord spanning the PT boundary and/or representing a long-enough in-terval of the Early Triassic. It is also commonly difficult to find outwhether small individuals are fully grown adults, all the more whenonly poorly preserved internal molds are available (see Metcalfe et al.,2011, for an exception).

The studied Smithian gastropod faunas from the western USA com-prise large and small individuals with highly heterogeneous spatial dis-tributions. In modern contexts, spatial distributions are controlled byseveral factors such as habitat/feeding preferences, biotic interactions(e.g., predation), reproductive strategies (e.g., fecundity) or migrationof adults (Ray and Stoner, 1995; Takada, 1996; Ray-Culp et al., 1999;Stoner, 2003; Haubois et al., 2004). These fluctuating parameters alsobecomemuchmore complex when applied to environmental gradients(e.g., latitude or depth; McClain et al., 2005, 2009), trophic groups (Roy,2002) and different clades (e.g., Beck, 2000; Chapman, 2000).

To our knowledge, no previous study of the Lilliput effect during theEarly Triassic has repeated the same analytical procedures over two ormore distant basins to test whether the proposed size-reduction is(i) not a local environmental phenomenon and/or (ii) results of an en-vironmental (e.g., latitudinal or depth) gradient (see Roy, 2002;McClain et al., 2005). This lack of spatially-replicated observation is


rather understandable due for instance to the prohibitively time-consuming analyses required. For gastropods, it is also very difficult tomatch larval or juvenile shells to later growth stages. For instance, it ispossible that some of the microgastropods reported from the westernUSA basin are actually early stages of Gullivers (e.g., Battenizygaeotriassica could be a juvenile of “Polygyrina”). Other genera, such asthe Early Triassic to Jurassic Sinuarbullina (Cylindrobullina) are generallysmall, and even Late Triassic and Jurassic species never exceed a size of10 mm. Moreover, the preservation of gastropods is commonly so poorthat species identity of pre- and post-extinction material is commonlyimpossible to recognize. These problems and the lack of highly-resolved temporal framework and correlation as well as taphonomicand sampling biases make it nearly impossible to detect the Lilliputeffect sensu stricto in gastropods at the Permian/Triassic boundary.For Early Triassic gastropods, the Lilliput effect s.s. has not yet beendemonstrated in spite of the wealth of papers dealing with this phe-nomenon, simply because not a single species is known both from theChanghsingian and the Griesbachian (Nützel, 2005b; Twitchett, 2007;Brayard et al., 2011a). For bivalves, two examples of boundary-crossing species have recently been described by Wasmer et al.(2012): Leptochondria curtocardinalis and Permophorus costatus. Forthe latter, Permian (Zechstein) size data are available from Logan(1967), showing no significantly larger body size in comparisonwith the Early Triassic data from Wasmer et al. (2012) (shell length ofPermian specimens: n = 6, Min = 6.7 mm, Max = 25.9 mm,Median = 14 mm; shell length of Triassic specimens: n = 4, Min =6 mm, Max = 22 mm, Median = 15.5 mm).

7.5.2. Lilliput effect sensu latoTo circumvent these issues, many authors consider a Lilliput effect

sensu lato, i.e., they consider taxa above the species level and newlyoriginating taxa during the Early Triassic, or compare global size-distribution of pre- and post-extinction faunas (Harries and Knorr,2009). The consideration of supra-specific taxonomic levels implies ahypothesized phyletic lineage or an entire clade (e.g., Payne, 2005;Peng et al., 2007). On that ground, and although representatives ofsome Early Triassic clades do have small body sizes (e.g., heterodont bi-valves, Hautmann and Nützel, 2005; chondrichtyans, Mutter andNeuman, 2009; foraminifers, Song et al., 2011; Rego et al., 2012), theLilliput effect has been inappropriately generalized as a global-scaledecrease in size characterizing all clade members, or more rarely allclades over a large part of or the entire Early Triassic (e.g., Twitchett,2001, p. 341; Twitchett, 2007, p. 143; Fraiser and Bottjer, 2004, p. 272;Peng et al., 2007, p. 124; Metcalfe et al., 2013: their Fig. 12). The lackof thorough taxonomic identification and of a robust phylogeneticframework, combined with low-resolution stratigraphic scalesand paleoenvironmental reconstructions, may impede the study ofactual size trends (Harries and Knorr, 2009; Huttenlocker, 2014).These shortcomings make it difficult to answer the followingquestions:

– Did the mass extinction select against large-sized species (“faunalstunting” of Harries and Knorr, 2009)?

– Did the presumably harsh environments in the aftermath of the PTcrisis directly select in favor of small-sized species (e.g., due to lifehistory traits such as rapid growth, short longevity and generationtime, early sexual maturity, high fecundity and semelparity, all ofwhich are usually associated with relatively small body sizes andclassically related to stressed, instable and/or unpredictable environ-ments; e.g., Pianka, 1970; Reznick et al., 2002; Twitchett, 2007)?

– Are body-size distributions observed during the Early Triassic a sto-chastic assemblage-scale result from the random removal of speciesduring the extinction crisis and/or random selection of specimensduring the sampling procedure, as suggested by the simulations pre-sented above (see Section 2)?

– Are species originating in the Early Triassic just small by nature —

whatever the evolutionary mechanism driving the body-size de-crease during the speciation process?

This has important implications because the last two hypothesesrepresent simple alternative explanations for an apparent Lilliput effect.In the literature, this phenomenon is almost invariably related to delete-rious, stressful environmental conditions thought to prevail in the after-math of an extinction crisis, although the nature of these conditions aswell as proximate causes and processes driving the proposed body-size reduction remain elusive (Twitchett, 2001, 2006; Harries andKnorr, 2009; Wade and Twitchett, 2009).

7.5.3. The paradox of the western USA basin and the risk ofacross-scale extrapolation

The definitions, analyses and underlying explanations of the Lilli-put effect during and after the PT mass extinction are highly variable(Harries and Knorr, 2009; Huang et al., 2010). Local observations ofSmithian gastropods from the western USA basin initiated a largediscussion about the Lilliput effect s.l. in the wake of the end-Permian mass extinction (e.g., Schubert and Bottjer, 1995; Fraiserand Bottjer, 2004), including extrapolation to other geographicaland temporal Early Triassic contexts. Paradoxically, we found thelargest known Early Triassic gastropods in the western USA basin.We also showed that microgastropod accumulations supposedlytypical of Early Triassic assemblages actually correspond to assem-blages of coexisting small- and large-sized specimens. This demon-strates that the Early Triassic fossil record is still insufficientlyknown, especially for poorly-preserved fossils such as gastropods,even in what may be considered as a “well-sampled and well-studied” basin. Occurrences of Gulliver gastropods are actually fre-quent in the western USA basin in the very same beds where “typi-cal” Early Triassic microgastropod assemblages were firstdescribed, thus invalidating the worldwide extrapolation of typicalmicrogastropod assemblages in the Early Triassic.

In a similar manner, some recent contributions have also questionedor downplayed the Lilliput effect previously suggested for Early Triassicophiuroids (Twitchett et al., 2005), lingulid brachiopods (Rodland andBottjer, 2001) or fishes (Mutter and Neuman, 2009). Indeed, Chen andMcNamara (2006) and Zatoń et al. (2008) documented Paleozoic andMiddle Triassic ophiuroid assemblages with much smaller specimensthan those of the Early Triassic. In addition, Romano et al. (in press) andScheyer et al. (2014) showed thatfishes andmarine tetrapods did not ex-perience a global size reduction during the Early Triassic. Similarly, the ex-haustive study of the benthic fauna from the Spathian Virgin Formation insouthern Utah by McGowan et al. (2009) did not find any support for asignificant reduction in body size when compared to later Triassic faunas.

Overall, our own observations together with those of the above-mentioned recent studies show that dense, well-dated and geographi-cally dispersed field data at the basin-scale level are a prerequisitebefore extrapolating local observations to a more general model. Inany case, although some Early Triassic taxa are particularly small(e.g., Hautmann and Nützel, 2005; Mutter and Neuman, 2009), a globalextrapolation seems to be unwarranted at present. Concerning gastro-pods, a Lilliput effect neither s.s. nor s.l. can be demonstrated based onthe current state of knowledge. Furthermore, the Greenland samplessuggest that a global-scale Lilliput effect (either s.s. or s.l.) for gastropodscannot be demonstrated for the earliest Triassic (≲0.3 Myr after the PTboundary). Indeed, the gastropod body size distributions sampledfrom Griesbachian Greenland assemblages show essentially thesame range as those from the Smithian of the western USA basin(compare Figs. 6 and 20). In both cases, the body size ranges are com-patible with the expectation of individuals or species randomlydrawn from a “standard”, non-altered shell size–frequencydistribution (Fig. 3).

PERMIAN TRIASSIC

LadinianAnisianGriesb. Dien. Smithian SpathianEarly Middle Wuchia.

2 cm

Changhsing.

R. bittneri

Fig. 25.Maximum estimated width and height of known large gastropods from the Permian to Middle Triassic. Trendmodified after Payne (2005; light gray conical shapes) by includingdata discussed in this work (dark gray conical shapes). Corrected data for the (Middle Permian) from Nützel and Nakazawa (2012). Assel.: Asselian; Sak.: Sakmarian; Wuchia.:Wuchiapingian; Changhsin.: Changhsingian.


8. Conclusions

We have documented abundant large-sized gastropods from dif-ferent levels and environments in the Griesbachian–earliestDienerian of Greenland and the Smithian–early Spathian of the west-ern USA. When coupled with a literature survey, it clearly appearsthat the maximum size of numerous Early Triassic gastropods hasbeen repeatedly underestimated for all Early Triassic substages.Our new data show that previous reports on gastropod maximumsizes (Griesbachian specimens were b1.5 cm, Smithian specimenswere b2 cm and that specimens N2 cm only occur in the Spathian;e.g., Fraiser and Bottjer, 2004; Payne, 2005) must be updated(Fig. 25). The newly reported large-sized specimens from theGriesbachian outcrops of Greenland highlight that Gulliver gastro-pods were present rapidly after the PT mass extinction, thereforequestioning the existence of a Lilliput effect on gastropods at theclade-level during the earliest Triassic.

We demonstrate that the western USA basin records a high numberof gastropod taxa and specimens characterized by a large body size, wellabove the 1 cm cut-off value separating microgastropods and largegastropods (Fraiser and Bottjer, 2004; Figs. 1, 3, 6 and 20). The questionis no longer: “where andwhen, if any, doGulliver gastropods occur dur-ing the Early Triassic?” but rather: “where and when, if any, do Gullivergastropods not co-occur alongside micro-gastropods during the EarlyTriassic?”. The Lilliput effect in gastropods was first proposed mainlybased on studies of “typical microgastropod beds” from this basin(e.g., Fraiser and Bottjer, 2004) and subsequently often considered asa global Early Triassic phenomenon (e.g., Pietsch et al., 2014). As smalland large size classes occur contemporaneously within the same areaand environments, the paradigmatic character of microgastropod bedsin the western USA basin has to be rejected. Heterogeneous distribu-tions of large and small specimens within the western USA basin arelikely related to normal lateral variations as observed in present-daycontexts. The observed distribution of large and small taxa does notseem to be constrained by a bathymetric gradient or any stressfulcondition.

The fossil record of the western USA basin covers most of the timeinterval in which severe oceanographic and climatic perturbations oc-curred, i.e., during the Smithian–early Spathian interval (e.g., Payneet al., 2004; Galfetti et al., 2007b; Hermann et al., 2011; Kaim et al.,2013; Romano et al., 2013). Contrary to ecological predictions and state-ments by Sun et al. (2012), Song et al. (2014) and Pietsch et al. (2014),these potential deleterious conditions apparently did not select againstlarge-sized gastropods. On the contrary, the largest individuals andtaxa occur during the warmest periods, which strongly suggeststhat, whether at local community or at global levels, the structuringand evolution of gastropod body-size distributions during the EarlyTriassic were disconnected from major climate fluctuations. Poten-tial drivers may have to be searched within the still poorly knowninter-species interactions in Early Triassic ecological networks.These biotic interactions result from the complex interplay of com-petition, predation, mutualism and parasitism, and also involve therichness, abundance and evenness of the various components ofeach trophic layer (e.g., Goudemand, 2014). From this point ofview, our observations on gastropod assemblages from the westernUSA basin call for an in-depth appraisal of food resources whichhave sustained the proliferation of large-sized specimens and spe-cies at several places in this basin.

9. Outlook: research challenges

This study exemplifies that the knowledge of the Early Triassic fossilrecord is still incomplete for a major group of benthic organisms – gas-tropods – and that new field data are required before general conclu-sions about macroevolutionary patterns for that time can be made. Italso highlights that a comprehensive spatio-temporal survey of abasin, i.e., at a meaningful (paleo)ecological level, is more appropriatethan an extrapolation of local lines of evidence for building globalmacroecological/macroevolutionary models.

Accordingly, the first challenge is the correct taxonomic identificationof accurately-sampled specimens of all size-classes, despite an often poorstate of preservation. The temporal and geographic scales of such


taxonomical studiesmust also be carefully considered: spatially extendedfield data calibrated by high-resolution temporal zonations are routinelyrequired. Furthermore, there are still methodological challenges to over-come and new standards to adopt collectively, notably for sampling pro-tocol and for evaluating size distributions. This calls for a commonagreement on a unified or at least an explicit sampling methodology.

Parallel to this mandatory field and systematic effort, the effect ofsample-size on several diversity and disparity (e.g., body size) met-rics remains to be further investigated. While realistic direct experi-mental approaches of the various biotic and abiotic parametersdriving the construction of a taphocoenosis from a parent biocoeno-sis may prove difficult, all the more in the context of deep-time localto regional marine assemblages, a numerical simulation-based ap-proach building on the one presented here is expected to provideuseful information. For instance, the behavior (unbiasedness, accu-racy, robustness, etc.) of various metrics of the body-size range(e.g., Min–Max range, inter-quartile range, standard-deviation, Coef-ficient of Variation) may be investigated in order to better constraincomparisons between Early Triassic and other fossil or extant assem-blages. In this manner, it may become possible to describe the diver-sity and disparity of gastropod assemblages in the aftermath of theend-Permian crisis more realistically.

Acknowledgments

Thiswork is a contribution to the CNRS-INSU Interrvie 2011, 2012 and2013 programs, and to the ANR project AFTER (ANR-13-JS06-0001-01).A.N. thanks the Deutsche Forschungsgemeinschaft (Project NU 96/6-1).Most fossil localities in thewestern USmentioned in this report are locat-ed on US public land under the stewardship of the Bureau of Land Man-agement (BLM) of the US Department of the Interior; theirmanagement and permits to access to these lands are much appreciated.The sections located in the Capitol Reef National Park were studied andcollected under permits #CARE-2013-SCI-0005 and CARE-2014-SCI-0011, thanks to SandyBorthwick for her helpwith the permittingprocess.N. Goudemand (Zurich) is thanked for help on the field. P. Bouchet and P.Lozouet (MNHN, Paris) kindly provided us their New Caledonian datasetuponwhich the rarefaction-based simulations presented in this work arebased, and J. Thomas (Dijon) kindly shared his data on Eocene gastropodsfrom Grignon (France). E. Steinmetz (Dijon) is thanked for her help withgastropod measurements. We thank F. Marin (Dijon) for the fruitful dis-cussion on mollusk shell mineralogy. S.G. Lucas (Albuquerque) is ac-knowledged for his help on gastropod specimens from the San RafaelSwell. A. Strasser, S.G. Lucas and P.J. Harries provided constructive re-views, which helped us to improve the paper.

References

Angilletta, M.J.J., Dunham, A.E., 2003. The temperature-size rule in ectotherms: simpleevolutionary explanations may not be general. Am. Nat. 162, 332–342.

Batten, R.L., 1973. The vicissitudes of the gastropods during the interval of Guadalupian–Ladinian time. In: Logan, A., Hills, L.V. (Eds.), Permian Triassic Systems and Their Mu-tual Boundary. Can. Soc. Petrol. Geol., pp. 596–607.

Batten, R.L., Stokes, W.L., 1986. Early Triassic gastropods from the Sinbad Member of theMoenkopi Formation, San Rafael Swell, Utah. Am. Mus. Novit. 2864, 1–33.

Beatty, T.W., Zonneveld, J.-P., Henderson, C.M., 2008. Anomalously diverse Early Triassicichnofossil assemblages in northwest Pangea: a case for a shallow-marine habitablezone. Geology 36, 771–774.

Beck, M.W., 2000. Separating the elements of habitat structure: independent effects ofhabitat complexity and structural components on rocky intertidal gastropods.J. Exp. Mar. Biol. Ecol. 249, 29–49.

Bennington, J.B., 2003. Transcending patchiness in the comparative analysis ofpaleocommunities: a test case from the Upper Cretaceous of New Jersey. Palaios 18,22–33.

Bennington, J.B., Rutherford, S.D., 1999. Precision and reliability in paleocommunity com-parisons based on cluster-confidence intervals: how to get more statistical bang foryour sampling buck. Palaios 14, 506–515.

Bjerager, M., Seidler, L., Stemmerik, L., Surlyk, F., 2006. Ammonoid stratigraphy and sedi-mentary evolution across the Permian-Triassic boundary in East Greenland. Geol.Mag. 143, 635–656.

Blackburn, T.M., Gaston, K.J., 1998. Somemethodological issues inmacroecology. Am. Nat.151, 68–83.

Blakey, R.C., 1974. Stratigraphic and depositional analysis of the Moenkopi FormationSoutheastern Utah. Utah Geol. Min. Surv. Bull. 104, 1–81.

Blakey, R.C., 1977. Petroliferous lithosomes in the Moenkopi Formation Southern Utah.Utah Geol. 4, 67–84.

Bouchet, P., Lozouet, P., Maestrati, P., Heros, V., 2002. Assessing the magnitude of speciesrichness in tropical marine environments: exceptionally high numbers of molluscs ata New Caledonia site. Biol. J. Linn. Soc. 75, 421–436.

Boyer, D.L., 2004. Ecological signature of Lower Triassic shell beds of the Western UnitedStates. Palaios 19, 372–380.

Brayard, A., Bucher, H., Escarguel, G., Fluteau, F., Bourquin, S., Galfetti, T., 2006. The EarlyTriassic ammonoid recovery: paleoclimatic significance of diversity gradients.Palaeogeogr. Palaeoclim. Palaeoecol. 239, 374–395.

Brayard, A., Brühwiler, T., Bucher, H., Jenks, J., 2009a. Guodunites, a low-palaeolatitude andtrans-Panthalassic Smithian (Early Triassic) ammonoid genus. Palaeontology 52,471–481.

Brayard, A., Escarguel, G., Bucher, H., Monnet, C., Bruhwiler, T., Goudemand, N., Galfetti, T.,Guex, J., 2009b. Good genes and good luck: ammonoid diversity and the end-Permianmass extinction. Science 325, 1118–1121.

Brayard, A., Nützel, A., Stephen, D.A., Bylund, K.G., Jenks, J., Bucher, H., 2010. Gastropod ev-idence against the Early Triassic Lilliput effect. Geology 38, 147–150.

Brayard, A., Nützel, A., Kaim, A., Escarguel, G., Hautmann, M., Stephen, D.A., Bylund, K.G.,Jenks, J., Bucher, H., 2011a. Gastropod evidence against the Early Triassic Lilliput ef-fect: reply. Geology 39, e233.

Brayard, A., Vennin, E., Olivier, N., Bylund, K.G., Jenks, J., Stephen, D.A., Bucher, H.,Hofmann, R., Goudemand, N., Escarguel, G., 2011b. Transient metazoan reefs in theaftermath of the end-Permian mass extinction. Nat. Geosci. 4, 693–697.

Brayard, A., Bylund, K., Jenks, J., Stephen, D., Olivier, N., Escarguel, G., Fara, E.,Vennin, E., 2013. Smithian ammonoid faunas from Utah: implications for Early Tri-assic biostratigraphy, correlation and basinal paleogeography Swiss. J. Pal. 132,141–219.

Brosse, M., Brayard, A., Fara, E., Neige, P., 2013. Ammonoid recovery after the Permian–Triassic mass extinction: a re-exploration of morphological and phylogenetic diversi-ty patterns. J. Geol. Soc. Lond. 170, 225–236.

Brown, J.H., 1995. Macroecology. The University of Chicago Press, Chicago (284 pp.).Brown, J.H., Maurer, B.A., 1989. Macroecology — the division of food and space among

species on the continents. Science 243, 1145–1150.Browne, K.M., Golubic, S., Seong-Joo, L., 2000. Shallow marine microbial carbonate de-

posits. In: Riding, R.E., Awramik, S.M. (Eds.), Microbial Sediments. Springer, NewYork,pp. 233–249.

Burgess, S.D., Bowring, S., Shen, S.-z., 2014. High-precision timeline for Earth's most se-vere extinction. Proc. Natl. Acad. Sci. U. S. A. 111, 3316–3321.

Carr, T.R., Paull, R.K., 1983. Early Triassic stratigraphy and paleogeography of the Cordille-ran Miogeocline. In: Reynolds, A., Dolly, E.D. (Eds.), Mesozoic Paleogeography of theWest-Central United States. SEPM, Denver, pp. 39–55.

Chapman, M., 1994. Small-scale patterns of distribution and size-structure of the intertid-al littorinid Littorina unifasciata (Gastropoda: Littorinidae) in New South Wales. Mar.Freshw. Res. 45, 635–652.

Chapman, M.G., 2000. A comparative study of differences among species and patches ofhabitat on movements of three species of intertidal gastropods. J. Exp. Mar. Biol.Ecol. 244, 181–201.

Chen, Z.Q., McNamara, K.J., 2006. End-Permian extinction and subsequent recoveryof the Ophiuroidea (Echinodermata). Palaeogeogr. Palaeoclim. Palaeoecol. 236,321–344.

Chen, Z.Q., Tong, J., Zhang, K., Yang, H., Liao, Z., Song, H., Chen, J., 2009. Environmental andbiotic turnover across the Permian–Triassic boundary on a shallow carbonate plat-form in western Zhejiang South China. Aust. J. Earth Sci. 56, 775–797.

Chen, Y., Twitchett, R.J., Jiang, H., Richoz, S., Lai, X., Yan, C., Sun, Y., Liu, X., Wang, L., 2013.Size variation of conodonts during the Smithian–Spathian (Early Triassic) globalwarming event. Geology 41, 823–826.

Cherns, L., Wright, P., 2000. Missingmolluscs as evidence of large-scale, early skeletal ara-gonite dissolution in a Silurian sea. Geology 28, 791–794.

Clarkson, M.O., Richoz, S., Wood, R.A., Maurer, F., Krystyn, L., McGurty, D.J., Astratti, D.,2013. A new high-resolution δ

13C record for the Early Triassic: insights from the Ara-

bian platform. Gondwana Res. 24, 233–242.Coleman, B.D., 1981. On random placement and species–area relations. Math. Biosci. 54,

191–215.Collinson, J.W., Hasenmueller, W.A., 1978. Early Triassic paleogeography and biostratigra-

phy of the Cordilleranmiogeosyncline. In: Reynolds, M.W., Dolly, E.D. (Eds.), Mesozo-ic Paleogeography of the Western United States. Society of Economic Paleontologistsand Mineralogists, Pacific Section, pp. 175–186.

Collinson, J.W., Kendall, C.G.S.C., Marcantel, J.B., 1976. Permian–Triassic boundary in east-ern Nevada and west-central Utah. Bull. Geol. Soc. Am. 87, 821–824.

Colwell, R.K., Chao, A., Gotelli, N.J., Lin, S.-Y., Mao, C.X., Chazdon, R.L., Longino, J.T., 2012.Models and estimators linking individual-based and sample-based rarefaction, ex-trapolation and comparison of assemblages. J. Plant Ecol. 5, 3–21.

Cooper, R.A., Maxwell, P.A., Crampton, J.S., Beu, A.G., Jones, C.M., Marshall, B.A., 2006.Completeness of the fossil record: estimating losses due to small body size. Geology34, 241–244.

Cummins, H., Powell, E.N., Stanton, R.J.J., Staff, G., 1986. The size–frequency distribution inpaleoecology: effects of taphonomic processes during formation of molluscan deathassemblages in Texas bays. Palaeontology 29, 495–518.

Dagys, A.S., 1988. Major features of the geographic differentiation of Triassic ammo-noids. In: Wiedmann, J., Kullmann, J. (Eds.), Cephalopods — Present and Past.Schweizerbart'sche Verlagsbuchhandlung, Stuttgart, pp. 341–349.

http://refhub.elsevier.com/S0012-8252(15)00057-4/rf0005






































































































Dagys, A.S., Arkhipov, Y.V., Bychkov, Y.M., 1979. Stratigraphy of the Triassic System of theNorth-еastern Asia. Nauka, Moscow (144 pp.).

Daufresne, M., Lengfellner, K., Sommer, U., 2009. Global warming benefits the small inaquatic ecosystems. Proc. Natl. Acad. Sci. U. S. A. 106, 12788–12793.

Dean, J.S., 1981. Carbonate petrology and depositional environments of the Sinbad Lime-stone Member of the Moenkopi Formation in the Teasdale Dome Area, Wayne andGarfield Counties Utah. Brigham Young Univ. Geol. Studies 28, 19–51.

Embry, A.F., 1997. Global sequence boundaries of the Triassic and their identification inthe Western Canada sedimentary basin. Bull. Can. Petrol. Geol. 45, 415–433.

Erwin, D.H., 2006. Extinction. How Life on Earth Nearly Ended 250 Million Years Ago.Princeton University Press, Princeton 296 pp.

Erwin, D.H., Hua-zhang, Pan, 1996. Recoveries and radiations: gastropods after thePermo-Triassic mass extinction. In: Hart, M.B. (Ed.), Biotic Recovery From Mass Ex-tinction Events. Geol. Soc. Spec. Pub., pp. 223–229 The Geological Society, Plymouth.

Fara, E., 2001. What are Lazarus taxa? Geol. J. 36, 291–303.Favre, E., Escarguel, G., Suc, J.-P., Vidal, G., Thévenod, L., 2008. A contribution to

deciphering the meaning of AP/NAP with respect to vegetation cover. Rev. Palaeobot.Palynol. 148, 13–35.

Finnegan, S., McClain, C.M., Kosnik, M.A., Payne, J.L., 2011. Escargots through time: an en-ergetic comparison of marine gastropod assemblages before and after the MesozoicMarine Revolution. Paleobiology 37, 252–269.

Forel, M.-B., 2013. The Permian–Triassic mass extinction: ostracods (Crustacea) andmicrobialites. C. R. Geosci. 345, 203–211.

Fraiser, M.L., 2011. Paleoecology of secondary tierers fromWestern Pangean tropical ma-rine environments during the aftermath of the end-Permian mass extinction.Palaeogeogr. Palaeoclimatol. Palaeoecol. 308, 181–189.

Fraiser, M.L., Bottjer, D.J., 2004. The non-actualistic Early Triassic gastropod fauna: a casestudy of the Lower Triassic Sinbad Limestone member. Palaios 19, 259–275.

Fraiser, M.L., Bottjer, D.J., 2005. Fossil preservation during the aftermath of the end-Permian mass extinction: taphonomic processes and palaeoecological signals. In:Over, D.J., Morrow, J.R., Wignall, P.B. (Eds.), Understanding Late Devonian and Perm-ian–Triassic Biotic and Climatic Events: Towards an Integrated Approach. Elsevier,Amsterdam, pp. 299–311.

Fraiser, M.L., Twitchett, R.J., Bottjer, D.J., 2005. Unique microgastropod biofacies in theEarly Triassic: indicator of long-term biotic stress and the pattern of biotic recoveryafter the end-Permian mass extinction. C.R. Palevol 4, 475–484.

Fraiser, M.L., Twitchett, R.J., Frederickson, J.A., Metcalfe, B., Bottjer, D.J., 2011. Gastropodevidence against the Early Triassic Lilliput effect: comment. Geology 39, e232.

Frech, F., 1912. Die Leitfossilien der Werfener Schichten und Nachträge zur Fauna desMuschelkalkes der Cassianer und Raibler Schichten. In: Hölzel, E. (Ed.), Resultateder wissenschaftlichen Erforschung des Balatonsees. Budapest, Wien, pp. 1–96.

Galfetti, T., Bucher, H., Brayard, A., Hochuli, P.A., Weissert, H., Guodun, K., Atudorei, V.,Guex, J., 2007a. Late Early Triassic climate change: insights from carbonate carbonisotopes, sedimentary evolution and ammonoid paleobiogeography. Palaeogeogr.Palaeoclimatol. Palaeoecol. 243, 394–411.

Galfetti, T., Bucher, H., Ovtcharova, M., Schaltegger, U., Brayard, A., Brühwiler, T.,Goudemand, N., Weissert, H., Hochuli, P.A., Cordey, F., Guodun, K.A., 2007b. Timingof the Early Triassic carbon cycle perturbations inferred from new U–Pb ages and am-monoid biochronozones. Earth Planet. Sci. Lett. 258, 593–604.

Galfetti, T., Hochuli, P.A., Brayard, A., Bucher, H., Weissert, H., Vigran, J.O., 2007c. TheSmithian/Spathian boundary event: evidence for global climatic change in the wakeof the end-Permian biotic crisis. Geology 35, 291–294.

Galfetti, T., Bucher, H., Martini, R., Hochuli, P.A., Weissert, H., Crasquin-Soleau, S., Brayard,A., Goudemand, N., Brühwiler, T., Guodun, K., 2008. Evolution of Early Triassic outerplatformpaleoenvironments in the Nanpanjiang Basin (South China) and their signif-icance for the biotic recovery. Sed. Geol. 204, 36–60.

Gingerich, P.D., 2000. Arithmetic or geometric normality of biological variation: an empir-ical test of theory. J. Theoret. Biol. 204, 201–221.

Goodspeed, T.H., 1996. Stratigraphic, sedimentologic, and paleontological analysis of theSinbad Formation of the Lower Triassic Thaynes Group, San Rafael Swell Region,southeastern Utah. University of New Mexico, Albuquerque (152 pp.).

Goodspeed, T.H., Lucas, S.G., 2007. Stratigraphy, sedimentology, and sequence stratigraphyof the Lower Triassic Sinbad Formation, San Rafael Swell. Nat. Hist. Sci. Bull. 40, 91–101.

Gotelli, N.J., Colwell, R.K., 2011. Estimating species richness. In: Magurran, A.E., McGill, B.J.(Eds.), Frontiers in Measuring Biodiversity. Oxford University Press, New York,pp. 39–54.

Grasby, S.E., Beauchamp, B., Embry, A., Sanei, H., 2013. Recurrent Early Triassic Ocean An-oxia. Geology 41, 175–178.

Goudemand, N., 2014. Towards an evolutionary sound definition of ‘recovery’? Albertiana42, 86–87.

Hammer, Ø., Harper, D.A.T., 2006. Paleontological Data Analysis. Blackwell Publishing, Ox-ford (351 pp.).

Hammer, Ø., Harper, D.A.T., Ryan, P.D., 2001. PAST: paleontological statistics softwarepackage for education and data analysis. Pal. Elec. 4, 1–9.

Harper, D.A.T., 1999. Numerical Palaeobiology. JohnWiley and Sons, Chichester (468 pp.).Harries, P.J., Knorr, P.O., 2009. What does the “Lilliput Effect” mean? Palaeogeogr.

Palaeoclimatol. Palaeoecol. 284, 4–10.Haubois, A.G., Guarini, J.M., Richard, P., Hemon, A., Arotcharen, E., Blanchard, G.F., 2004.

Differences in spatial structures between juveniles and adults of the gastropodHydrobia ulvae on an intertidal mudflat (Marennes-Oléron Bay, France) potentiallyaffect estimates of local demographic processes. J. Sea Res. 51, 63–68.

Hausmann, I.M., Nützel, A., 2015. Diversity and palaeoecology of a highly diverse Late Tri-assic marine biota from the Cassian Formation of north Italy. Lethaia 48, 235–255.

Hautmann, M., Nützel, A., 2005. First record of a heterodont bivalve (Mollusca) from theEarly Triassic: palaeocological significance and implications for the “Lazarus prob-lem”. Palaeontology 48, 1131–1138.

Hautmann, M., Bucher, H., Brühwiler, T., Goudemand, N., Kaim, A., Nützel, A., 2011. An un-usually diverse mollusc fauna from the earliest Triassic of South China and its impli-cations for benthic recovery after the end-Permian biotic crisis. Geobios 44, 71–85.

Hautmann, M., Smith, A.B., McGowan, A.J., Bucher, H., 2013. Bivalves from the Olenekian(Early Triassic) of south-western Utah: systematics and evolutionary significance.J. Syst. Palaeontol. 11, 263–293.

Hayek, L.C., Buzas, M.A., 1997. Surveying Natural Populations. Columbia University Press,New York (448 pp.).

He, W., Shi, G.R., Feng, Q., Campi, M.J., Gu, S., Bu, J., Peng, Y., Meng, Y., 2007. Brachiopodminiaturization and its possible causes during the Permian–Triassic crisis in deepwater environments, South China. Palaeogeogr. Palaeoclimatol. Palaeoecol. 252,145–163.

He, W.H., Twitchett, R.J., Zhang, Y., Shi, G.R., Feng, Q.L., Yu, J.X., Wu, S.B., Peng, X.F., 2010.Controls on body size during the Late Permian mass extinction event. Geobiology 8,391–402.

He, W., Shi, G.R., Twitchett, R.J., Zhang, Y., Zhang, K.-X., Song, H.-J., Yue, M.-L., Wu, S.-B.,Wu, H.-T., Yang, T.-L., Xiao, Y.-F., 2015. Late Permian marine ecosystem collapsebegan in deeper waters: evidence from brachiopod diversity and body size changes.Geobiology 13, 123–138.

Heck Jr., K.L., van Belle, G., Simberloff, D., 1975. Explicit calculation of the rarefaction di-versity measurement and the determination of sufficient sample size. Ecology 56,1459–1461.

Hermann, E., Hochuli, P.A., Bucher, H., Brühwiler, T., Hautmann, M., Ware, D., Roohi, G.,2011. Terrestrial ecosystems on North Gondwana following the end-Permian massextinction. Gondwana Res. 20, 630–637.

Hinojosa, J.L., Brown, S.T., Chen, J., DePaolo, D.J., Paytan, A., Shen, S.-Z., Payne, J.L., 2012. Ev-idence for end-Permian ocean acidification from calcium isotopes in biogenic apatite.Geology 40, 743–746.

Hofmann, R., Goudemand, N., Wasmer, M., Bucher, H., Hautmann, M., 2011. New tracefossil evidence for an early recovery signal in the aftermath of the end-Permianmass extinction. Palaeogeogr. Palaeoclimatol. Palaeoecol. 310, 216–226.

Hofmann, R., Hautmann, M., Bucher, H., 2013a. A new paleoecological look at theDinwoody Formation (Lower Triassic, Western USA): intrinsic versus extrinsic con-trols on ecosystem recovery after the end-Permian mass extinction. J. Pal. 87,854–880.

Hofmann, R., Hautmann, M., Wasmer, M., Bucher, H., 2013b. Palaeoecology of theSpathian Virgin Formation (Utah, USA) and its implications for the Early Triassic re-covery. Acta Palaeontol. Pol. 58, 149–173.

Hofmann, R., Hautmann, M., Brayard, A., Nützel, A., Bylund, K.G., Jenks, J.F., Vennin, E.,Olivier, N., Bucher, H., 2014. Recovery of benthic marine communities from theend-Permian mass extinction at the low latitudes of eastern Panthalassa.Palaeontology 57, 547–589.

Hofmann, R., Hautmann, M. and Bucher, H., in press. Recovery dynamics of benthic ma-rine communities from the Lower Triassic Werfen Formation (northern Italy).Lethaia, Early View, http://dx.doi>org/10.1111/let.12121.

Horacek, M., Richoz, S., Brandner, R., Krystyn, L., Spötl, C., 2007. Evidence for recurrentchanges in Lower Triassic oceanic circulation of the Tethys: the δ

13C record from ma-

rine sections in Iran. Palaeogeogr. Palaeoclimatol. Palaeoecol. 252, 355–369.Hose, R.K., Repenning, C.A., 1959. Stratigraphy of Pennsylvanian, Permian, and Lower Tri-

assic rocks of Confusion Range, west-central Utah. Bull. Am. Assoc. Pet. Geol. 43,2167–2196.

Huang, B., Harper, D.A.T., Zhan, R., Rong, J., 2010. Can the Lilliput effect be detected in thebrachiopod faunas of South China following the terminal Ordovician mass extinc-tion? Palaeogeogr. Palaeoclimatol. Palaeoecol. 285, 277–286.

Hubbell, S.P., 2001. The Unified Neutral Theory of Biodiversity and Biogeography. Mono-graphs in Population Biology 32. Princeton University Press, Princeton and Oxford(375 pp.).

Hurlbert, S.H., 1971. The nonconcept of species diversity: a critique and alternative pa-rameters. Ecology 52, 577–586.

Huttenlocker, A.K., 2014. Body size reductions in nonmammalian eutheriodont therapsids(Synapsida) during the end-Permian mass extinction. PLoS ONE 9, e87553.

Jackson, T.A., Bischoff, J.L., 1971. The influence of amino acids in the kinetics of the recrys-tallization of aragonite to calcite. J. Geol. 79, 493–497.

Jenks, J., Guex, J., Hungerbühler, A., Taylor, D., Bucher, H., 2013. Ammonoid biostratigra-phy of the Early Spathian Columbites parisianus Zone (Early Triassic) at Bear LakeHot Springs Idaho, New Mexico. N. M. Mus. Nat. Hist. Sci. Bull. 61, 268–283.

Jonsson, T., Cohen, J.E., Carpenter, S.R., 2005. Food webs, body size, and species abundancein ecological community description. Adv. Ecol. Res. 36, 1–84.

Kaim, A., 2009. Gastropods. In: Shigeta, Y., Zakharov, Y.D., Maeda, H., Popov, A.M. (Eds.),The Lower Triassic System in the Abrek Bay area, South Primorye. Russia. NationalMuseum of Nature and Science, Tokyo, pp. 141–156.

Kaim, A., Nützel, A., 2011. Dead bellerophontids walking— the short Mesozoic history of theBellerophontoidea (Gastropoda). Palaeogeogr. Palaeoclimatol. Palaeoecol. 308, 190–199.

Kaim, A., Nützel, A., Bucher, H., Brühwiler, T., Goudemand, N., 2010. Early Triassic (lateGriesbachian) gastropods from South China (Shanggan, Guangxi). Swiss J. Geosci.103, 121–128.

Kaim, A., Nützel, A., Hautmann, M., Bucher, H., 2013. Early Triassic gastropods from SaltRange, Pakistan. Bull. Geosci. 88, 505–516.

Kaim, A., Nützel, A., Maekawa, T., 2014a. Smithian gastropod assemblages of the Bac ThuyFormation. In: Shigeta, Y., Komatsu, T., Maekawa, T., Tran, H.D. (Eds.), Olenekian(Early Triassic) Stratigraphy and Fossil Assemblages in Northeastern Vietnam. Na-tional Museum of Nature and Science, Tokyo, pp. 63–64.

Kaim, A., Nützel, A., Maekawa, T., 2014b. Gastropods. In: Shigeta, Y., Komatsu, T.,Maekawa, T., Tran, H.D. (Eds.), Olenekian (Early Triassic) Stratigraphy and Fossil As-semblages in Northeastern Vietnam. National Museum of Nature and Science, Tokyo,pp. 167–184.




































































































































































Kalinowski, S.T., 2004. Counting alleles with rarefaction: private alleles and hierarchicalsampling designs. Conserv. Genet. 5, 539–543.

Kalinowski, S.T., 2005. HP-RARE 1.0: a computer program for performing rarefaction onmeasures of allelic richness. Mol. Ecol. Notes 5, 187–189.

Kauffman, E.G., Harries, P.J., 1996. The importance of crisis progenitors in recovery frommass extinction. In: Hart, M.B. (Ed.), Biotic Recovery From Mass Extinction Events.Geol. Soc. Spec. Pub., pp. 15–39.

Kidwell, S.M., 2001. Preservation of species abundance in marine death assemblages. Sci-ence 294, 1091–1094.

Kidwell, S.M., Bosence, D.W.J., 1991. Taphonomy and time-averaging of marine shellyfaunas. In: Allison, P.A., Briggs, D.E.G. (Eds.), Taphonomy: Releasing the Data Lockedin the Fossil Record. Plenum, New York, pp. 116–209.

Kidwell, S.M., Flessa, K.W., 1996. The quality of the fossil record: populations, species, andcommunities. Ann. Rev. Earth Planet. Sci. 24, 433–464.

Kozłowski, J., Gawelczyk, A.T., 2002. Why are species' body size distributions usuallyskewed to the right? Funct. Ecol. 16, 419–432.

Krawczyński, W., 2013. Colour patterns of Naticopsis planispira (Neritimorpha,Gastropoda) shell from Upper Carboniferous of Upper Silesian coal basin, southernPoland. Ann. Soc. Geol. Pol. 83, 87–97.

Lehrmann, D.J., Payne, J.L., Felix, S.V., Dillett, P.M., Hongmei, W., Youyi, Y., Jiayong,W., 2003. Permian–Triassic boundary sections from shallow-marine carbonateplatforms of the Nanpanjiang basin, South China: implications for oceanic condi-tions associated with the End-Permian extinction and its aftermath. Palaios 18,138–152.

Leighton, L.R., Schneider, C.L., 2008. Taxon characteristics that promote survivorshipthrough the Permian–Triassic interval: transition from the Paleozoic to the Mesozoicbrachiopod fauna. Paleobiology 34, 65–79.

Levington, J.S., 1970. The paleoecological significance of opportunistic species. Lethaia 3,69–78.

Liu, G., Feng, Q., Shen, J., Yu, J., He, W., Algeo, T.J., 2013. Decline of siliceous sponges andspicule miniaturization induced by marine productivity collapse and expanding an-oxia during the Permian–Triassic crisis in South China. Palaios 28, 664–679.

Logan, A., 1967. The Permian Bivalvia of northern England. Monogr. Pathol. Soc. Lond.121, 1–72.

Lucas, S.G., Krainer, K., Milner, A.R., 2007. The type section and age of the TimpoweapMember and stratigraphic nomenclature of the Triassic Moenkopi Group in South-western Utah. N. M. Mus. Nat. Hist. Sci. Bull. 40, 109–117.

Luo, G., Lai, X., Shi, G.R., Jiang, H., Yin, H., Xie, S., Tong, J., Zhang, K., He, W., Wignall, P.B.,2008. Size variation of conodont elements of the Hindeodus–Isarcicella clade duringthe Permian–Triassic transition in South China and its implication for mass extinc-tion. Palaeogeogr. Palaeoclimatol. Palaeoecol. 264, 176–187.

Mapes, R.H., Nützel, A., 2009. Where did Upper Paleozoic cephalopods lay their eggs? Ev-idence from cephalopod embryos and gastropod and pelecypod veliger larvae.Lethaia 42, 341–356.

Marenco, P.J., Griffin, J.M., Fraiser, M.L., Clapham, M.E., 2012. Paleoecology and geochem-istry of Early Triassic (Spathian) microbial mounds and implications for anoxia fol-lowing the end-Permian mass extinction. Geology 40, 715–718.

Marenco, P.J., Fraiser, M.L., Clapham, M.E., Gatz-Miller, H., 2013. Extreme microgastropodsize-limitation in Early Triassic shallow marine settings, Hidden Pasture, Montana:implications for environmental conditions following the end-Permian mass extinc-tion. Geol. Soc. Am. Abstr. Programs 45, 88.

Marin, F., Gautret, P., 1994. Les teneurs en acides aminés acides des matrices organiquessolubles associées aux squelettes calcaires des démosponges et des cnidaires : uneimplication possible dans leur transformation diagénétique. Bull. Soc. Geol. Fr. 165,77–84.

McClain, C.R., Rex, M.A., Jabbour, R., 2005. Deconstructing bathymetric body size patternsin deep-sea gastropods. Mar. Ecol. Prog. Ser. 297, 181–187.

McClain, C.M., Rex, M.A., Etter, R.J., 2009. Patterns in deep-sea macroecology. In: Witman,J.D., Roy, K. (Eds.), Marine Macroecology. University of Chicago, Chicago, pp. 65–100.

McGowan, A.J., Smith, A.B., Taylor, P.D., 2009. Faunal diversity, heterogeneity and bodysize in the Early Triassic: testing post-extinction paradigms in the Virgin Limestoneof Utah, USA. Aust. J. Earth Sci. 56, 859–872.

McKee, E.D., 1954. Stratigraphy and history of the Moenkopi Formation of Triassic age.The Geological Society of America Memoir. 61. Geological Society of America, NewYork (133 pp.).

Melatunan, S., Calosi, P., Rundle, S.D., Widdicombe, S., Moody, A.J., 2013. Effects of oceanacidification and elevated temperature on shell plasticity and its energetic basis inan intertidal gastropod. Mar. Ecol. Prog. Ser. 472, 155–168.

Metcalfe, B., Twitchett, R.J., Price-Lloyd, N., 2011. Changes in size and growth rate of ‘Lil-liput’ animals in the earliest Triassic. Palaeogeogr. Palaeoclimatol. Palaeoecol. 308,171–180.

Metcalfe, I., Nicoll, R.S., Willink, R., Ladjavadi, M., Grice, K., 2013. Early Triassic (Induan–Olenekian) conodont biostratigraphy, global anoxia, carbon isotope excursions andenvironmental perturbations: new data from Western Australian Gondwana. Gond-wana Res. 23, 1136–1150.

Morand, S., Poulin, R., 2002. Body size–density relationships and species diversity in par-asitic nematodes: patterns and likely processes. Evol. Ecol. Res. 4, 951–961.

Mørk, A., Elvebakk, G., Forsberg, A.W., Hounslow, M.W., Nakrem, H.A., Vigran, J.O.,Weitschat, W., 1999. The type section of the Vikinghôgda Formation: a new LowerTriassic unit in central and eastern Svalbard. Polar Res. 18, 51–82.

Mutter, R.J., Neuman, A.G., 2009. Recovery from the end-Permian extinction event: evi-dence from “Lilliput Listracanthus”. Palaeogeogr. Palaeoclimatol. Palaeoecol. 284,22–28.

Nawrot, R., 2012. Decomposing lithification bias: preservation of local diversity structurein recently cemented storm-beach carbonate sands, San Salvador Island, Bahamas.Palaios 27, 190–205.

Neri, C., Posenato, R., 1985. New biostratigraphical data on uppermost Werfen Formationof western Dolomites (Trento, Italy). Geol.-Pal. Mitt. Insbruck 14, 83–107.

Nielsen, E., 1935. The Permian and Eotriassic vertebrate-bearing beds at Godthaab Gulf(East Greenland). Medd. Om. Gronland 98, 1–111.

Nützel, A., 2005a. A new Early Triassic gastropod genus and the recovery of gastropodsfrom the Permian/Triassic extinction. Acta Palaeontol. Pol. 50, 19–24.

Nützel, A., 2005b. Recovery of gastropods in the Early Triassic. C.R. Palevol 4,501–515.

Nützel, A., 2014. Larval ecology and morphology in fossil gastropods. Palaeontology 57,479–503.

Nützel, A., Mapes, R.H., 2001. Larval and juvenile gastropods from a Carboniferous blackshale: palaeoecology and implications for the evolution of the Gastropoda. Lethaia34, 143–162.

Nützel, A., Nakazawa, K., 2012. Permian (Capitanian) gastropods from the Akasaka Lime-stone (Gifu Prefecture, Japan). J. Syst. Palaeontol. 10, 103–169.

Nützel, A., Schulbert, C., 2005. Facies of two important Early Triassic gastropodlagerstätten: implications for diversity patterns in the aftermath of the end-Permian mass extinction. Facies 51, 480–500.

Nützel, A., Fŕyda, J., Yancey, T., Anderson, J., 2007. Larval shells of Late Palaeozoicnaticopsid gastropods (Neritopsoidea: Neritimorpha) with a discussion of the earlyneritimorph evolution. Palaeontol. Z. 81, 213–228.

Nützel, A., Mannani, M., Senowbari-Daryan, B., Yazdi, M., 2010. Gastropods from the LateTriassic Nayband Formation (Iran), their relationships to other Tethyan faunas andremarks on the Triassic gastropod body size problem. N. Jb. Geol. Paläont. (Abh.)256, 213–228.

Ohlberger, J., 2013. Climate warming and ectotherm body size— from individual physiol-ogy to community ecology. Funct. Ecol. 27, 991–1001.

Olivier, N., Brayard, A., Fara, E., Bylund, K.G., Jenks, J.F., Vennin, E., Stephen, D.A., Escarguel,G., 2014. Smithian shorelinemigrations and depositional settings in Timpoweap Can-yon (Early Triassic, Utah, USA). Geol. Mag. 151, 938–955.

Olivier, N., Brayard, A., Vennin, E., Escarguel, G., Fara, E., Bylund, K.G., Jenks, J.F., CaravacaG. and Stephen, D.A., in press. Evolution of depositional settings in the Torrey areaduring the Smithian (Early Triassic, Utah, USA) and their significance for the biotic re-covery. Geol. J.

Orchard, M.J., 2007. Conodont diversity and evolution through the latest Permianand Early Triassic upheavals. Palaeogeogr. Palaeoclimatol. Palaeoecol. 252,93–117.

Ovtcharova, M., Bucher, H., Schaltegger, U., Galfetti, T., Brayard, A., Guex, J., 2006. NewEarly to Middle Triassic U–Pb ages from South China: calibration with ammonoidbiochronozones and implications for the timing of the Triassic biotic recovery.Earth Planet. Sci. Lett. 243, 463–475.

Pan, H.Z., 1982. Triassic marine fossil gastropods from SW China. Bull. Nanjing Inst. Geol.Pal. Acad. Sinica 4, 153–188.

Paull, R.K., Paull, R.A., 1982. Permian–Triassic unconformity in the Terrace Mountains,northwestern Utah. Geology 10, 582–587.

Paull, R.A., Paull, R.K., 1993. Interpretation of Early Triassic nonmarine-marine relations,Utah, U.S.A. N. M. Mus. Nat. Hist. Sci. Bull. 3, 403–409.

Payne, J.L., 2005. Evolutionary dynamics of gastropod size across the end-Permian extinc-tion and through the Triassic recovery interval. Paleobiology 31, 269–290.

Payne, J.L., Kump, L.R., 2007. Evidence for recurrent Early Triassic massive volcanism fromquantitative interpretation of carbon isotope fluctuations. Earth Planet. Sci. Lett. 256,264–277.

Payne, J.L., Lehrmann, D.J., Wei, J., Orchard, M.J., Schrag, D.P., Knoll, A.H., 2004. Large per-turbations of the carbon cycle during recovery from the end-Permian extinction. Sci-ence 305, 506–509.

Payne, J.L., Turchyn, A.V., Paytan, A., DePaolo, D.J., Lehrmann, D.J., Yu, M., Wei, J., 2010. Cal-cium isotope constraints on the end-Permian mass extinction. Proc. Natl. Acad. Sci. U.S. A. 107, 8543–8548.

Peng, Y., Shi, G.R., Gao, Y., He, W., Shen, S., 2007. How and why did the Lingulidae(Brachiopoda) not only survive the end-Permian mass extinction but also thrive inits aftermath? Palaeogeogr. Palaeoclimatol. Palaeoecol. 252, 118–131.

Pianka, E.R., 1970. On r and K selection. Am. Nat. 104, 592–597.Pietsch, C., Mata, S.A., Bottjer, D.J., 2014. High temperature and low oxygen perturbations

drive contrasting benthic recovery dynamics following the end-Permianmass extinc-tion. Palaeogeogr. Palaeoclimatol. Palaeoecol. 399, 98–113.

Posenato, R., 2009. Survival patterns of macrobenthic marine assemblages during theend-Permian mass extinction in the western Tethys (Dolomites, Italy). Palaeogeogr.Palaeoclimatol. Palaeoecol. 280, 150–167.

Posenato, R., Holmer, L.E., Prinoth, H., 2014. Adaptive strategies and environmental signif-icance of lingulid brachiopods across the late Permian extinction. Palaeogeogr.Palaeoclimatol. Palaeoecol. 399, 373–384.

Powell, E.N., Cummins, H., 1985. Are molluscan maximum life spans determined by long-term cycles in benthic communities? Oecologia 67, 177–182.

Powell, E.N., Stanton Jr., R.J., 1985. Estimating biomass and energy flow of molluscs inpalaeo-communities. Palaeontology 28, 1–34.

Ray, M., Stoner, A., 1995. Growth, survivorship, and habitat choice in a newly settledseagrass gastropod Strombus gigas. Mar Ecol. Prog. Ser. 123, 83–94.

Ray-Culp, M., Davis, M., Stoner, A.W., 1999. Predation by xanthid crabs on early post-settlement gastropods: the role of prey size, prey density, and habitat complexity.J. Exp. Mar. Biol. Ecol. 240, 303–321.

Rego, B.L., Wang, S.C., Altiner, D., Payne, J.L., 2012. Within- and among-genus com-ponents of size evolution during mass extinction, recovery, and backgroundintervals: a case study of Late Permian through Late Triassic foraminifera. Paleobiol-ogy 38, 627–643.

Reznick, D., Bryant, M.J., Bashey, F., 2002. r- and K-selection revisited: the role of popula-tion regulation in life-history evolution. Ecology 83, 1509–1520.






































































































































































Rodland, D.L., Bottjer, D.J., 2001. Biotic recovery from the end-Permian mass extinc-tion: behavior of the inarticulate brachiopod Lingula as a disater taxon. Palaios16, 95–101.

Romano, C., Goudemand, N., Vennemann, T.W., Ware, D., Schneebeli-Hermann, E.,Hochuli, P.A., Brühwiler, T., Brinkmann, W., Bucher, H., 2013. Climatic and biotic up-heavals following the end-Permian mass extinction. Nat. Geosci. 6, 57–60.

Romano, C., Koot, M., Kogan, I., Brayard, A., Minikh, A., Brinkmann, W., Bucher, H. andKriwet, J., in press. Permian–Triassic Osteichthyes (bony fishes): Diversity dynamicsand body size evolution. Biol. Reviews.

Roy, K., 2002. Bathymetry and body size in marine gastropods: a shallow water perspec-tive. Mar. Ecol. Prog. Ser. 237, 143–149.

Runnegar, B., 1969. A Lower Triassic ammonoid fauna from southeast Queensland.J. Paleontol. 43, 818–828.

Sanders, H.L., 1968. Marine benthic diversity: a comparative study. Am. Nat. 102,243–282.

Sano, H., Onoue, T., Orchard, M., Martini, R., 2012. Early Triassic peritidal carbonate sedi-mentation on a Panthalassan seamount: the Jesmond succession, Cache Creek Ter-rane, British Columbia, Canada. Facies 58, 113–130.

Sanson-Barrera, A., Hochuli, P.A., Bucher, H., Schneebeli-Hermann, E., Meier, M., Weissert,H. and Bernasconi, S.M., submitted. Late Permian–earliest Triassic high resolution car-bon isotope and palynofacies record from Kap Stosch (East Greenland)

Scheyer, T.M., Romano, C., Jenks, J., Bucher, H., 2014. Early Triassic marine biotic recovery:the predators' perspective. PLoS ONE 9, e88987.

Schubert, J.K., Bottjer, D.J., 1995. Aftermath of the Permian–Triassic mass extinction event:paleoecology of Lower Triassic carbonates in the western USA. Palaeogeogr.Palaeoclimatol. Palaeoecol. 116, 1–39.

Sheridan, J.A., Bickford, D., 2011. Shrinking body size as an ecological response to climatechange. Nat. Clim. Chang. 1, 401–406.

Shigeta, Y., Zakharov, Y.D., Maeda, H., Popov, A.M., 2009. The Lower Triassic System in theAbrek Bay Area, South Primorye. Russia. National Museum of Nature and Science,Tokyo (218 pp.).

Sibly, R.M., Atkinson, D., 1994. How rearing temperature affects optimal adult size in ec-totherms. Funct. Ecol. 8, 486–493.

Simberloff, D., 1979. Rarefaction as a distribution-free method of expressing and estimat-ing diversity. In: Grassle, J.F., Patil, G.P., Smith, W.K., Taillie, C. (Eds.), Ecological Diver-sity in Theory and Practice. International Cooperative Publishing House, Fairland,pp. 159–176.

Smith, W., Grassle, F., 1977. Sampling properties of a family of diversity measures. Bio-metrics 33, 283–292.

Smith, J.J., Hasiotis, S.T., Kraus, M.J., Woody, D.T., 2009. Transient dwarfism of soil faunaduring the Paleocene/Eocene Thermal Maximum. Proc. Natl. Acad. Sci. 106,17655–17660.

Song, H., Tong, J., Chen, Z.Q., 2011. Evolutionary dynamics of the Permian–Triassic fora-minifer size: evidence for Lilliput effect in the end-Permian mass extinction and itsaftermath. Palaeogeogr. Palaeoclimatol. Palaeoecol. 308, 98–110.

Song, H., Wignall, P.B., Chu, D., Tong, J., Sun, Y., Song, H., He, W., Tian, L., 2014. Anoxia/hightemperature double whammy during the Permian–Triassic marine crisis and its af-termath. Sci. Rep. 4.

Spath, L.F., 1930. The Eotriassic invertebrate fauna of east Greenland. Saertryk Medd. omGronland 83, 1–90.

Spath, L.F., 1935. Additions to the Eo-Triassic invertebrate fauna of East Greenland. Medd.om Gronland 98, 1–115.

Stephen, D.A., Bylund, K., Bybee, P.J., Ream, W.J., 2010. Ammonoid beds in the Lower Tri-assic Thaynes Formation of western Utah, USA. In: Tanabe, K., Shigeta, Y., Sasaki, T.,Hirano, H. (Eds.), Cephalopods — Present and Past. Tokai University Press, Tokyo,pp. 243–252.

Stoner, A.W., 2003. What constitutes essential nursery habitat for a marine species? Acase study of habitat form and function for queen conch. Mar. Ecol. Prog. Ser. 257,275–289.

Stoner, A.W., Ray, M., 1996. Shell remains provide clues to historical distribution andabundance patterns in a large seagrass-associated gastropod (Strombus gigas). Mar.Ecol. Prog. Ser. 135, 101–108.

Sun, Y., Joachimski, M.M., Wignall, P.B., Yan, C., Chen, Y., Jiang, H., Wang, L., Lai, X., 2012.Lethally hot temperatures during the Early Triassic greenhouse. Science 338,366–370.

Takada, Y., 1996. Vertical migration during the life history of the intertidal gastropodMonodonta labio on a boulder shore. Mar. Ecol. Prog. Ser. 130, 117–123.

Titterington, D.M., Smith, A.F.M., Makov, U.E., 1985. Statistical Analysis of Finite MixtureDistributions. John Wiley and Sons, Chichester (243 pp.).

Tomašových, A., 2004. Postmortem durability and population dynamics affecting the fi-delity of size–frequency distributions. Palaios 19, 477–496.

Tomašových, A., 2006. Linking taphonomy to community-level abundance, insights intocompositional fidelity of the Upper shell concentration (Eastern Alps). Palaeogeogr.Palaeoclimatol. Palaeoecol. 235, 355–381.

Tong, J., Erwin, D.H., 2001. Triassic gastropods of the southern Qinling Mountains, China.Smithson. Contrib. Paleobiol. 92, 1–47.

Tozer, E.T., 1982. Marine Triassic faunas of North America: their significance for assessingplate and terrane movements. Geol. Rundsch. 71, 1077–1104.

Trümpy, R., 1969. Lower Triassic ammonites from Jameson Land (East Greenland). Medd.om Gronland 168, 78–116.

Turculeţ, I., 1987. Turbo rectecostatus altograndis — une nouvelle sous-espèce degastéropodes campiliennes de la région de Rarau (Carpathes orientales roumaines).Analele Stiintifice ale Universitatii “Al. I. Cuza” Din Iasi (Serie Noua), Sectiunea II.Geologie-Geografie 35, 15–16.

Twitchett, R.J., 2001. Incompleteness of the Permian–Triassic fossil record: a consequenceof productivity decline? Geol. J. 36, 341–353.

Twitchett, R.J., 2006. The palaeoclimatology, palaeoecology and palaeoenvironmentalanalysis of mass extinction events. Palaeogeogr. Palaeoclimatol. Palaeoecol. 232,190–213.

Twitchett, R.J., 2007. The Lillliput effect in the aftermath of the end-Permian extinctionevent. Palaeogeogr. Palaeoclimatol. Palaeoecol. 252, 132–144.

Twitchett, R.J., Barras, C.G., 2004. Trace fossils in the aftermath of mass extinction events.Geol. Soc. Lond. Spec. Publ. 228, 397–418.

Twitchett, R.J., Wignall, P.B., 1996. Trace fossils and the aftermath of the Permo-Triassicmass extinction: evidence from northern Italy. Palaeogeogr. Palaeoclimatol.Palaeoecol. 124, 137–151.

Twitchett, R.J., Looy, C.V., Morante, R., Visscher, H., Wignall, P.B., 2001. Rapid and synchro-nous collapse of marine and terrestrial ecosystems during the end-Permian biotic cri-sis. Geology 29, 351–354.

Twitchett, R.J., Krystyn, L., Baud, A., Wheeley, J.R., Richoz, S., 2004. Rapid marine recoveryafter the end-Permian mass-extinction event in the absence of marine anoxia. Geol-ogy 32, 805–808.

Twitchett, R.J., Feinberg, J.M., O'Connor, D.D., Alavarez, W., McCollum, L.B., 2005. Early Tri-assic ophiuroids: their paleoecology, taphonomy, and distribution. Palaios 20,213–223.

Urbanek, A., 1993. Biotic crises in the history of Upper Silurian graptoloids: apalaeobiological model. Hist. Biol. 7, 29–50.

Valentine, J.W., 1989. How good was the fossil record? Clues from the Californian Pleisto-cene. Paleobiology 15, 83–94.

Valentine, J.W., Jablonski, D., 1986. Mass extinctions: sensitivity of marine larval types.Proc. Natl. Acad. Sci. U. S. A. 83, 6912–6914.

Vanden Byllaardt, J., Cyr, H., 2011. Does a warmer lake mean smaller benthic algae? Evi-dence against the importance of temperature–size relationships in natural systems.Oikos 120, 162–169.

Vennin, E., Olivier, N., Brayard, A., Bour, I., Thomazo, C., Escarguel, G., Fara, E., Bylund, K.G.,Jenks, J.F., Stephen, D.A., Hofmann, R., 2015. Microbial deposits in the aftermath of theend-Permian mass extinction: a diverging case from the Mineral Mountains (Utah,USA). Sedimentology 62, 753–792.

Vermeij, G.J., Herbert, G.S., 2004. Measuring relative abundance in fossil and living assem-blages. Paleobiology 30, 1–4.

Wade, B.S., Twitchett, R.J., 2009. Extinction, dwarfing and the Lilliput effect. Palaeogeogr.Palaeoclimatol. Palaeoecol. 284, 1–3.

Waite, R., Strasser, A., 2011. A comparison of recent and fossil large, high-spired gastro-pods and their environments: the Nopparat Thara tidal Xat in Krabi, SouthThailand, versus the Swiss Kimmeridgian carbonate platform. Facies 57, 223–248.

Ware, D., Jenks, J., Hautmann, M., Bucher, H., 2011. Dienerian (Early Triassic) ammonoidsfrom the Candelaria Hills (Nevada, USA) and their significance forpalaeobiogeography and palaeoceanography. Swiss J. Geosci. 104, 161–181.

Wasmer, M., Hautmann, M., Hermann, E., Ware, D., Roohi, G., Ur-Rehman, K., Yaseen, A.,Bucher, H., 2012. Olenekian (Early Triassic) bivalves from the Salt Range and SurgharRange, Pakistan. Palaeontology 55, 1043–1073.

Webber, A.J., 2005. The effects of spatial patchiness on the stratigraphic signal of bioticcomposition (Type Cincinnatian Series; Upper Ordovician). Palaios 20, 37–50.

Wheeley, J.R., Twitchett, R.J., 2005. Palaeoecological significance of a new Griesbachian(Early Triassic) gastropod assemblage from Oman. Lethaia 38, 37–45.

Wignall, P.B., Benton, M.J., 1999. Lazarus taxa and fossil abundance at times of biotic crisis.J. Geol. Soc. Lond. 156, 453–456.

Wignall, P.B., Twitchett, R.J., 2002. Permian–Triassic sedimentology of Jameson Land, EastGreenland: incised submarine channels in an anoxic basin. J. Geol. Soc. Lond. 159,691–703.

Wright, P., Cherns, L., Hodges, P., 2003. Missing molluscs: field testing taphonomic loss inthe Mesozoic through early large-scale aragonite dissolution. Geology 31, 211–214.

Yochelson, E.L., Boyd, D.W., Wardlaw, B.R., 1985. Redescription of Bellerophon bittneri(Gastropoda; Triassic) from Wyoming. Rocky Mount. Geol. 23, 99–104.

Zatoń, M., Salamon, M.A., Boczarowski, A., Sitek, S., 2008. Taphonomy of dense ophiuroidaccumulations from the Middle Triassic of Poland. Lethaia 41, 47–58.

Zhu, X.G., 1995. Gastropods. In: Sha, J.G. (Ed.), Palaeontology of the Hoh Xil Region. Qing-hai. Science Press, Beijing, pp. 69–81.

Zonneveld, J.P., Beatty, T.W., Pemberton, S.G., 2007. Lingulid brachiopods and the tracefossil Lingulichnus from the Triassic of western Canada: implications for faunal recov-ery after the end-Permian mass extinction. Palaios 22, 74–97.

Zuschin, M., Harzhauser, M., Mandic, O., 2005. Influence of size-sorting on diversity esti-mates from tempestitic shell beds in the middle Miocene of Austria. Palaios 20,142–158.

Zuschin, M., Harzhauser, M., Sauermoser, K., 2006. Patchiness of local species richness andits implication for large-scale diversity patterns: an example from the middle Mio-cene of the Paratethys. Lethaia 39, 65–80.




















































































































































Early Triassic Gulliver gastropods: Spatio-temporal distribution and significance for biotic...

Documents

Transcript of Early Triassic Gulliver gastropods: Spatio-temporal distribution and significance for biotic...