Beta Diversity in Triassic and Modern Reef Basin Assemblages Beta-Diversität in Triassischen Und Rezenten Riffbeckenfaunen

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Beta diversity in Triassic and modern reef basin assemblages Beta-Diversität in triassischen und rezenten Riffbeckenfaunen

Der Naturwissenschaftlichen Fakultät

der Friedrich-Alexander-Universität Erlangen-Nürnberg

zur

Erlangung des Doktorgrades Dr. rer. nat.

vorgelegt von Vanessa Julie Roden

Als Dissertation genehmigt

von der Naturwissenschaftlichen Fakultät

der Friedrich-Alexander-Universität Erlangen-Nürnberg

Tag der mündlichen Prüfung: 20. Dezember 2019

Vorsitzender des Promotionsorgans: Prof. Dr. Georg Kreimer

Gutachter: Prof. Dr. Wolfgang Kiessling PD Dr. Kenneth De Baets

Summary

Changes in alpha and gamma diversity throughout the Phanerozoic have long been of interest in paleontology, but beta diversity remains understudied, particularly in the post-Paleozoic. Beta diversity – the compositional variation among communities or assemblages – is a key aspect of biodiversity and is crucial to revealing the principles of diversity assembly. Studying the biodiversity patterns of well-preserved fossil and modern assemblages can provide insight into how these patterns arise, how they change through time, and whether there are unifying principles in community composition and assembly.

Taphonomic effects and sampling biases complicate the assessment of changes in biodiversity over time. Intensively sampled and well-preserved fossil assemblages are ideal to study biodiversity patterns and compare them with modern assemblages. The Middle to Late Triassic (Ladinian–Carnian) Cassian Formation, exposed in the Dolomites, Southern Alps, northern Italy, is characterized by high diversity and excellent preservation of fossils. The Cassian Formation comprises shallow and deeper water sediments deposited between carbonate platforms in a warm, tropical setting in the Western Tethys, comparable with modern tropical environments. A wide breadth of depositional environments are recorded in the Cassian Formation: a nearshore back-reef area with patch reefs and the sediments intercalated between these, the carbonate platform, and the shallow and deeper reef basin.

With 1421 invertebrate species, the Cassian Formation yields the highest species richness reported from any known spatially constrained pre-Quaternary formation. This is due to (1) excellent presser- vation of fossils and the ease with which they are extracted from the poorly lithified sediments as well as (2) the high primary diversity, which is probably due to the tropical reef-associated setting, high alpha diversity, and a wide breadth of habitat types, driving beta diversity. Beta diversity is partitioned into a large species turnover and a small nestedness component. Particularly notable for a fossil assemblage is the high proportion of molluscs, particularly gastropods. Molluscs comprise 67% of all invertebrate species in the Cassian Formation, and the proportion of gastropods (39%) is almost level with modern tropical settings. Studying more 'liberation lagerstätten' like the Cassian Formation can greatly contribute to our understanding of biodiversity of reef basin assemblages and other habitats, and may lead us to rethink the concept of a substantial rise of gastropods in the Cenozoic.

Testing which factors drive biodiversity, specifically beta diversity, in the Cassian Formation and other comparable assemblages is the main focus of this thesis. Mean pairwise proportional dissimilarity is a very suitable measure to express beta diversity, as it is relatively robust to differences in sample size and grain and can be used to quantify overall beta diversity in a region or between samples as well as along gradients. Beta diversity as pairwise proportional dissimilarity is driven by dominant species. The role of rare species can be neglected in large-scale assessments of beta diversity. This finding not only makes it easier to accumulate larger amounts of data to be used in beta diversity studies but also makes incorrect taxon identification less significant.

To disentangle the drivers of biodiversity patterns in the Cassian Formation and another reef- associated soft-bottom environment from the modern Bay of Safaga in the Red Sea, Egypt, beta diversity is evaluated with regard to age, water depth, and geographic distance. Results are compares with a null model to evaluate the stochasticity of community assembly. Only the ten most abundant species per sample are included to determine mean pairwise proportional dissimilarity. As in the

previous studies, overall beta diversity is found to be very high in the Cassian Formation. The Bay of Safaga yields a similarly high value.

The variation in community composition is found to be independent of geographic or temporal distance. Beta diversity between shallow- and deep-water communities is relatively high. Samples from deeper-water settings yield a slightly higher beta diversity than those from shallower areas. A similar pattern is seen in both assemblages. Although water depth has been a driving factor in other studies on beta diversity, it is not considered to be a major driver in the studied assemblages. Priority effects are postulated to be the main driver of beta diversity in these reef basin assemblages.

In summary, results from this thesis show that dominant species drive beta diversity. Species turnover, not species loss, are the ecological cause of beta diversity in the Cassian Formation, probably resulting from the evolution of new species within this heterogeneous environment. The high diversity in the Cassian Formation results from high local diversity and large differences in community composition between assemblages driving beta diversity. Reasons for the high preserved diversity are ascribed to taphonomic conditions. Biodiversity in the Cassian Formation is similar to comparable modern environments. The high number of species and the large proportion of gastropods in the Cassian Formation are close to those found in modern soft-bottom assemblages. Values of alpha, beta and gamma diversity are similarly high. And while the heterogeneity and breadth of environments is thought to increase beta diversity, priority effects may also play an important role.

Zusammenfassung

Die Entwicklung von Alpha- und Gamma-Diversität während des Phanerozoikums wurde bereits in verschiedenen Studien untersucht, jedoch wurde die Beta-Diversität in paläontologischen Arbeiten meist vernachlässigt. Beta-Diversität – die Variation in der Zusammensetzung zwischen Lebensgemeinschaften oder Ansammlungen von Taxa – ist ein Schlüsselaspekt der Biodiversität und von besonderer Bedeutung, um die Mechanismen von Biodiversitätsmustern aufzudecken. Biodiversitätsmuster von gut erhaltenen fossilen sowie rezenten Lebensgemeinschaften können Rückschlüsse auf ihre Entstehung und Entwicklung über die Zeit ermöglichen, sowie einheitliche Mechanismen der Etablierung von Artengemeinschaften aufdecken. Erschwert wird die Erforschung von Biodiversität über die Zeit durch Unterschiede in der Taphonomie oder in der Probengröße und -intensität. Intensiv beprobte und gut erhaltene Fossilgemeinschaften eignen sich ideal, um Biodiversitätsmuster zu untersuchen und sie mit heutigen Lebensgemeinschaften zu vergleichen. Die Cassian-Formation (Ladinium bis Karnium, Mittel- bis Obertrias), aufgeschlossen in den Dolomiten (südliche Kalkalpen, Nord-Italien), zeichnet sich durch hohe Diversität und sehr gute Erhaltung aus. Sie umfasst Flachwassersedimente und Sedimente aus tieferen Bereichen, abgelagert zwischen Karbonatplattformen in warmen, tropischen Gewässern der westlichen Tethys, vergleichbar mit heutigen tropischen Habitaten. Die Cassian-Formation verfügt somit über eine große Bandbreite an Ablagerungsräumen: Ein küstennahes Rückriff mit Fleckriffen und dazwischen eingeschalteten Sedimenten, eine Karbonatplattform sowie ein flaches und tieferes Riffbecken. Mit 1421 Invertebraten-Arten verfügt die Cassian-Formation über das größte Artenreichtum unter allen bekannten räumlich begrenzten, präquartären Formationen. Dies liegt einerseits an der sehr guten Fossilerhaltung und der Leichtigkeit, mit der diese aus den geringlithifizierten Sedimenten erschlossen werden können, gleichzeitig aber auch an der hohen primären Diversität. Die hohe primäre Diversität resultiert vermutlich aus dem tropischen, riffnahen Habitat, der hohen Alpha-Diversität sowie der Bandbreite an Habitattypen, welche die Beta-Diversität erhöhen. Die Beta-Diversität besteht aus einer großen species turnover Komponente und einer kleinen nestedness Komponente. Besonders hervorzuheben ist der hohe Anteil an Mollusken, insbesondere Gastropoden. Mollusken umfassen 67 % aller Invertebraten-Arten in der Cassian Formation, und der Anteil an Gastropoden (39 %) ist fast so hoch wie in heutigen tropischen Habitaten. Mehr Forschung an sogenannten “Liberation Lagerstätten” wie der Cassian-Formation kann dazu beitragen, unser Wissen um Biodiversität in Riffbeckenfaunen und anderen Habitaten zu erweitern. Dies wiederum kann dazu führen, das Konzept eines erheblichen Anstiegs der Gastropoden im Känozoikum zu überdenken. Das Hauptaugenmerk dieser Arbeit liegt auf der Untersuchung der Faktoren, welche die Biodiversität, insbesondere die Beta-Diversität, in der Cassian-Formation und vergleichbaren Faunengemeinschaften bestimmen. Die mittlere pairwise proportional dissimilarity eignet sich gut als Index für die Beschreibung der Beta-Diversität. Sie ist relativ robust gegenüber Unterschieden in der Probengröße und -aufteilung und kann verwendet werden, um die gesamte Beta-Diversität einer Region oder zwischen Proben sowie auch entlang von Gradienten zu berechnen. Beta-Diversität als pairwise proportional dissimilarity wird von häufigen Arten bestimmt. Die Rolle seltener Arten kann in Beta- Diversitätsstudien von größerem Maßstab vernachlässigt werden. Diese Erkenntnis vereinfacht nicht nur die Akkumulation größerer Datenmengen, sondern verringert auch die Auswirkungen fehlerhafter Taxonbestimmungen. Um herauszufinden, welche Faktoren die Biodiversitätsmuster in der Cassian-Formation und einem weiteren, riff-assoziierten Weichbodenhabitat in der heutigen Safaga-Bucht (Rotes Meer, Ägypten) bestimmen, wurde Beta-Diversität in Bezug auf Alter, Wassertiefe und geographischer Distanz

berechnet. Die Ergebnisse wurden mit einem Nullmodell verglichen, um die Stochastizität der Zusammensetzung der Faunengemeinschaften auszuwerten. Lediglich die zehn häufigsten Arten aus jeder Probe wurden berücksichtigt, um die mittlere pairwise proportional dissimilarity zu berechnen. Wie bereits in den beiden anderen Arbeiten gezeigt, ergibt sich für die Cassian-Formation eine sehr hohe Beta-Diversität. Die Safaga-Bucht weist einen ähnlich hohen Wert auf. Die Variation in der Zusammensetzung der Faunengemeinschaften ist unabhängig von der geographischen oder zeitlichen Distanz. Die Beta-Diversität zwischen Faunen aus flacheren und tieferen Bereichen ist relativ hoch. Proben aus tieferen Bereichen des Riffbeckens haben eine geringfügig höhere Beta-Diversität als die aus flacheren Bereichen. Beide Datensätze weisen ein ähnliches Muster auf. Obwohl andere Studien die Wassertiefe als bestimmenden Faktor der Beta-Diversität erkannt haben, ist diese kein maßgeblicher Treiber der Beta-Diversität in den untersuchten Faunen. Stattdessen werden sogenannte priority effects als größter Einflussfaktor auf die Beta-Diversität in diesen Riffbeckenfaunen postuliert. Zusammenfassend zeigen die Ergebnisse, dass dominante Arten die Beta-Diversität maßgeblich bestimmen. Veränderungen in der Artenzusammensetzung (species turnover), im Gegensatz zu Artenverlust (species loss), sind die ökologische Ursache für die Beta-Diversität in der Cassian- Formation. Möglicherweise ist dies auf die Entwicklung neuer Arten innerhalb dieses heterogenen Habitats zurückzuführen. Die hohe Diversität ist das Resultat hoher Alpha- und Beta-Diversität, die sich wiederum aus großen Unterschieden in der Faunenzusammensetzung in den Proben ergibt. Taphonomische Bedingungen sind die Gründe für die Erhaltung der Diversität. Die Biodiversität in der Cassian-Formation ist damit heutigen, vergleichbaren Habitaten ähnlich. Die hohe Anzahl an Arten und der große Anteil an Gastropoden in der Cassian-Formation untermauern dies. Die Werte von Alpha-, Beta- und Gamma-Diversität sind ähnlich hoch. Und obwohl die Heterogenität und Bandbreite an Habitaten wahrscheinlich die Beta-Diversität erhöht, spielen möglicherweise auch priority effects eine wichtige Rolle.

Contents

Introduction ...... 1 Beta diversity...... 3 Different measures ...... 3 Ecological significance ...... 7 Problems (and some solutions) ...... 8 Common and rare species ...... 9 Beta diversity in different environments ...... 10 The Cassian Formation ...... 11 Geology ...... 11 Stratigraphy ...... 15 Environment ...... 15 Preservation ...... 17 The biota ...... 19 Alpha diversity ...... 20 Beta diversity ...... 20 Outlook ...... 23 References ...... 24 List of manuscripts and declaration of own contribution to manuscripts ...... 33 Manuscripts ...... Roden V. J., Kocsis, Á., Zuschin, M. & Kießling, W. 2018. Reliable estimates of beta diversity with incomplete sampling. Ecology 99: 1051-1062. https://doi.org/10.1002/ecy.2201. and the supplementary data package available with the online version of the article Roden, V. J., Hausmann, I. M., Nützel, A., Seuss, B., Reich, M., Urlichs, M., Hagdorn, H. & Kiessling, W. 2019. Fossil liberation: A model to explain high biodiversity in the Triassic Cassian Formation. Palaeontology. https://doi.org/10.1111/pala.12441. and the supplementary data package: Roden, V. J., Hausmann, I. M., Nützel, A., Seuss, B., Reich, M., Urlichs, M., Hagdorn, H. & Kiessling, W. 2019. Data from: Fossil liberation: a model to explain high biodiversity in the Triassic Cassian Formation. Dryad Digital Repository. https://doi.org/10.5061/dryad.6s5651k. Roden, V. J., Zuschin, M., Nützel, A., Hausmann, I. M. & Kiessling, W. Drivers of beta diversity in modern and ancient reef-associated soft-bottom environments. PeerJ. In review. and the supplementary data package available with the online version of the article Hausmann, I. M., Nützel, A., Roden, V. J. & Reich, M. 2019. Diversity and palaeoecology of Late Triassic invertebrate assemblages from the tropical marine basins near Lake Misurina (Dolomites, Italy). Acta Palaeontologica Polonica. Accepted pending revisions.

Introduction

Uncovering how biodiversity patterns have changed through time and space is essential to understanding the principles of community assembly, one of the central questions in ecology (Remmer et al. 2019, Stegen et al. 2013). Beta diversity, the differences in diversity among communities, is a key component in disentangling sources and drivers of biodiversity. It is driven by biotic and abiotic factors and can therefore shed light on processes of community assembly and influence of environmental factors (Melo et al. 2009, Soininen 2010, Vellend 2010).

Bambach (1977) estimated global marine invertebrate species richness to have increased by about four times since the Middle Paleozoic, and Sepkoski (1986, 1988) and Sepkoski and Sheehan (1983) estimated generic and familial diversity in the Paleozoic to have increased by about 300 %. However, alpha diversity, measured as the median number of species in a community, only increased by approximately 50 % in the Paleozoic (Bambach 1977). Sepkoski (1988) discussed the problem of “missing diversity” between the local and the global level, i.e. beta diversity in the Paleozoic marine realm. He found that beta diversity in soft-bottom communities increased significantly from the Cambrian to the later Paleozoic but did not continually increase in the later Paleozoic. An increase in ecological specialization due to increased habitat differentiation from the early to later Paleozoic is inferred (Sepkoski 1988). However, the processes driving beta diversity are unknown (Signor 1990). Throughout the Middle and Upper Paleozoic and the Mesozoic, alpha diversity in open marine environments did not significantly increase, but then doubled from the Mesozoic to the Cenozoic (Bambach 1977). However, all Mesozoic assemblages were grouped together and no Triassic faunas were included, therefore not allowing for the assessment of changes in alpha diversity within the Mesozoic. Based on five independent studies on diversity of marine taxa (including Bambach’s), Sepkoski Jr et al. (1981) found an underlying pattern of both alpha and gamma (global) diversity: Diversity was low in the early Mesozoic era, particularly in the Triassic, increased throughout the Mesozoic, and reached a maximum in the Cenozoic. Though there is a marked increase of ecologically complex communities after the Permian-Triassic boundary (Wagner et al. 2006), it is not clear where and how these communities arose (Kiessling 2006). A reorganization of ecosystems during the Marine Mesozoic Revolution due to increased biotic interactions and utilization of ecospace is likely to explain higher diversity in marine benthic ecosystems of the late Mesozoic (Hofmann et al. 2019). Beta diversity of benthic communities remained low in the early Triassic due to species inhabiting broad environmental ranges (Hofmann et al. 2014). An increase in alpha diversity followed the Late Permian mass extinction during the biotic recovery phase, perhaps due to a scarcity of competition (Hofmann et al. 2014, Miller and Sepkoski 1988, Sepkoski and Miller 1998). With time, a phase of taxonomic differentiation between habitats took place, leading to higher beta diversity in benthic marine communities and therefore an overall more rapid diversity increase in the Middle and Late Triassic (Hautmann 2014, Hofmann et al. 2014, Hofmann et al. 2016). This is supported by Aberhan and Kiessling (2012), who find a large decrease in global beta diversity from the Permian to the Triassic and a similarly large increase to the middle and later Triassic (Fig. 1). Valentine et al. (1978) argued that the large increase in alpha and gamma diversity after the Triassic was driven by an increase in marine faunal provinces. Miller et al. (2009) assess the global geographic disparity among several marine taxa. Assuming a relationship between the degree of provinciality and beta diversity, they define geo-disparity as ‘the degree of global compositional disparity among coeval biotas as a function of geographic distance’ (p. 613). They do not find an increase in global geo- disparity throughout the Phanerozoic, but point out that geo-disparity should not be treated as a synonym for beta diversity, questioning the whether the drivers behind geo-disparity and beta diversity

1 are the same. Sampling-standardized global marine diversity curves show a moderate rise from the Paleozoic to the Cenozoic (Aberhan and Kiessling 2012, Alroy et al. 2008). The increase in alpha diversity is similarly modest (Aberhan and Kiessling 2012). A curve on Phanerozoic beta diversity (Fig. 1) shows no long-term trend. Biases in the fossil record, such as variations in taphonomy, availability of fossil strata, and sampling intensity, complicate the assessment of biodiversity patterns (Koch and Sohl 1983, Raup 1972, Smith and McGowan 2011). A simple and intuitive way of addressing research questions regarding biodiversity is by analysis of very well-preserved assemblages from the first phase of this increase in complex communities. The Middle to Late Triassic Cassian Formation from the Dolomites (Southern Alps, northern Italy), a tropical reef basin assemblage, is characterized by high diversity, excellent preservation of fossils, and a wide breadth of habitat types, making it ideal to study biodiversity patterns and compare them with modern assemblages. Alpha diversity in the Cassian Formation is found to be comparable to Neogene assemblages (Kowalewski et al. 2006), and gamma diversity is also known to be unusually high for the Mesozoic (Nützel and Kaim 2014). This thesis aims to find out whether beta diversity is similarly high and to uncover its drivers. Another research question regards the source of the high gamma diversity in the Cassian Formation: Is it driven by a high primary diversity, or is taphonomy the key factor? Partitioning the biodiversity of the Cassian Formation and comparing it with other fossil assemblages and particularly modern faunas can help to reveal whether complex marine communities have undergone large changes through time, or whether basic principles of diversity patterns uphold the test of time. Quantifying beta diversity, uncovering its drivers, and finding differences in beta diversity patterns between fossil and modern assemblages will bring us a step closer to understanding community assembly mechanisms, and perhaps even contribute to conservation science.

Fig. 1: Marine beta diversity through the Phanerozoic. Beta diversity is calculated as multiplicative beta diversity (see Different measures) based on genera in collections. Figure from Aberhan and Kiessling (2012).

Beta diversity

Beta diversity – the difference in diversity among a set of samples, quadrats, areas, or communities – quantifies environmental changes and disturbances, spatial and temporal turnover, and biogeographical patterns of diversity (e.g., Jurasinski et al. 2009 and references therein). Discerning these patterns and the drivers behind them can provide insight into biotic and abiotic influences on life in the past and present. Especially important is the role of beta diversity in disentangling the principles of community assembly (e.g., Chase and Myers 2011, Segre et al. 2014) and in conservation science (e.g., Legendre et al. 2005, Soininen 2010). Some of the most problematic issues with beta diversity are the different definitions and uses of the term, and the many measures used for its calculation, some of which are reviewed here. Although this makes comparisons from different studies difficult, it remains an important tool in modern and fossil biodiversity research.

Different measures Similarity in community composition can be expressed in many ways, the debate surrounding useful indices dating back to the beginning of the 20th century (e.g., Gleason 1920, Jaccard 1901, Kulczyński 1928). The term beta diversity was only applied decades later, and its precise definition is still under debate (Jurasinski et al. 2009, Tuomisto 2010a, b). Roger H. Whittaker (1960) studied vegetation patterns in the Siskiyou Mountains, discerning how changes in vegetation relate to environmental gradients. He applied different measures of beta diversity and discussed the characteristics and usage of each – from the coefficient of community (Jaccard 1901) and percentage similarity (Bray and Curtis 1957), to ecological distance (Whittaker 1952, 1956) and multiplicative (first introduced in his work) and additive beta diversity (MacArthur et al. 1966). This broad characterization is summarized as The extent of change of community composition, or degree of community differentiation, in relation to a complex gradient of environment, or a pattern of environments, which may be designated secondary or "beta" diversity (Whittaker 1960, p. 320). Beta diversity can be analyzed using different types of data, such as taxonomic (e.g., Vellend 2001), phylogenetic (e.g., Vellend et al. 2011), or functional diversity (e.g., Petchey and Gaston 2002). Here the focus is on taxonomic diversity, with specimen counts or occurrences of species or genera comprising the data. Taxonomic diversity can also be expressed as biomass, vegetation or coral cover (e.g., using line transects or quadrats) (Krebs 1999). There is a large variety of ways to calculate beta diversity, and the terminology has not been used consistently throughout scientific studies (Jurasinski et al. 2009). Comprehensive reviews of the many ways of measuring beta diversity and their merits also reflect the ongoing debate on preferred indices and terminology (Anderson 2006, Jost et al. 2011, Jurasinski et al. 2009, Koleff et al. 2003, Tuomisto 2010a, b, Vellend 2001). A short overview is provided here.

Hierarchical measures Hierarchical measures of beta diversity take the entire diversity of the region or set of samples into account, called regional diversity or gamma diversity. Alpha diversity is the diversity of a smaller area, a single sample, community, or quadrat. Alpha and gamma diversity can be expressed in several ways, the most common being the Shannon-Wiener index, Simpson index (Veech et al. 2002) or species richness (Vellend 2001). They are also known as “inventory diversity” (Whittaker 1977). Beta diversity expresses the relationship between alpha and gamma diversity, and has been referred to as “differentiation diversity” by Whittaker (1972). Jurasinski et al. (2009) use the term “differentiation 3 diversity” only for beta diversity based on compositional dissimilarity, and reserve the term “proportional diversity” for multiplicative and additive beta diversity. Ricotta (2005) found that additive and multiplicative beta diversity are related through logarithmic transformation and are very similar in their nature. Multiplicative beta diversity Whittaker (1960) introduced multiplicative beta diversity, which is gamma diversity divided by mean alpha diversity, βm = γ/α. But since α and γ are measured at different spatial scales, βm is dependent on spatial grain (Vellend 2001). According to Tuomisto (2010b), multiplicative beta diversity is “true beta diversity”, and it counts the number of compositional units. Each compositional unit contains the mean effective species diversity of the dataset and is compositionally distinct (see Other measures). Another measure of multiplicative beta diversity is the regional-to-local diversity ratio, which has the same value as “true beta diversity” but no units. It expresses how many times more species-rich the complete dataset is than one compositional unit (Tuomisto 2010b). Additive beta diversity To express turnover along a gradient, additive beta diversity can be applied. Additive beta diversity is the number of species that change among the individual sites and is expressed as βa = γ – α (Lande 1996, MacArthur et al. 1966, Whittaker 1972). It is also known as diversity excess (Chao et al. 2012). Veech et al. (2002) suggest that additive beta diversity is the “most operational definition” of beta diversity, since gamma diversity can be partitioned to analyze any driver of species diversity. Since sample size affects additive beta diversity, Olszewski (2004) has suggested an assessment of beta diversity through the difference in the rarefaction curve and the collector’s curve of the gamma diversity of a dataset.

Heterogeneity measures Abundance-based measures Marion et al. (2017) recommend the use of pairwise measures (heterogeneity measures) as opposed to set-wise measures (hierarchical measures), because estimates of set-wise measures are strongly dependent on the size of the dataset and cannot be interpreted as change in community composition from one area or sample to the next. Kulczyński (1928)’s coefficient calculates similarity between two sites using raw abundance data, by averaging the minima of abundance of each species at both sites. A better known index for similarity used with raw abundances counts double the sum of the minimum abundance of each species between the two sites divided by the sums of abundances of both sites (Legendre and Legendre 2012, Motyka 1947). When relative species abundances or vegetation coverage are used, the measure becomes more linear and is reduced to the sum of the minima of relative scores (Bray and Curtis 1957). The one-complement of this index of similarity is the Bray- Curtis dissimilarity index, often called percentage dissimilarity, and herein referred to as pairwise proportional dissimilarity (PPD):

PPD = 1 – ∑min(xij, xik) , with xij and xik being the proportions of species abundance in each sample. The PPD can be averaged to find the overall beta diversity of a set of samples or a larger region, although this cannot express any spatial arrangement (Vellend 2001). Roden et al. (2018, publication #1) found that dominant species drive proportional dissimilarity by showing that mean PPD of a dataset is depicted similarly well when only the five or ten most abundant species per sample are counted, as opposed to including the entire dataset (Fig. 2). The results appear to hold true for pairwise comparisons and are not a result of averaging (Roden et al. 2018, supporting information, publication #1). Pairwise or mean proportional

4 dissimilarity is an intuitive measure and relatively independent of the number and size of units sampled (Krebs 1999, Marion et al. 2017). It was developed Bray and Curtis (1957) and other authors more or less concurrently, and is a modified version of the Sørensen index based on abundance data (also known as the Sørensen abundance index; Magurran 2004).

Fig. 2: Mean pairwise proportional dissimilarity (PPD) among samples. Points depict the mean PPD for certain percentiles of specimens (bottom axis) of the most abundant species from each sample included in the species composition matrix. Triangles depict the mean PPD for the most abundant species from each sample included in the species composition matrix (top axis). Lines depict the mean PPD of the complete datasets. Gray boxes indicate the bootstrapped standard error of PPD of the complete matrix. For the Cassian Formation (highlighted), including more than 5 species per samples yields a mean PPD within the standard error of the complete matrix. Figure and figure caption adapted from Roden et al. (2018, publication #1).

Wolda (1981) recommends the widely applied Morisita–Horn index to measure dissimilarity and examines many several other well-known dissimilarity indices. A large number of other abundance- based indices have been developed and are presented and discussed in Legendre and Legendre (2012). Incidence-based measures For incidence-based (presence/absence) data, beta diversity is based on the change in taxon identities. There is also a wide array of indices available, reviewed and performance-tested in Koleff et al. (2003). They found the Simpson dissimilarity index (Lennon et al. 2001, Simpson 1943) to perform best among the eight indices tested. The Simpson dissimilarity index (symmetric version, Lennon et al. 2001) counts species presences of one and both sites or samples but disregards joint absences:

SIM = 1 – , β ( , ) 𝑎𝑎 where a is the number of shared species between themin two𝑏𝑏 𝑐𝑐sites,+𝑎𝑎 and b and c occur in one site and not the other. The similarity indices are the one-complement of the respective dissimilarity indices. The Jaccard dissimilarity index, also known as the coefficient of community (Jaccard 1901), is

J = 1 – = . β 𝑎𝑎 𝑏𝑏 + 𝑐𝑐 The Sørensen dissimilarity index, also called the𝑎𝑎 +coincidence𝑏𝑏 + 𝑐𝑐 𝑎𝑎+𝑏𝑏+𝑐𝑐 index (Czekanowski 1909, Sørensen 1948) is

βSØR = 1 – = , 2𝑎𝑎 𝑏𝑏 + 𝑐𝑐 The Jaccard and Sørensen indices are among the2𝑎𝑎+𝑏𝑏+ most𝑐𝑐 widely2𝑎𝑎+𝑏𝑏+ used𝑐𝑐 classic indices of (dis)similarity (Chao et al. 2005). Beta diversity can describe a directional change from one sample to another along a gradient (directional turnover) or refer to the variation among a set of samples (non-directional variation) (Anderson 2006, Anderson et al. 2011, Vellend 2001). To understand drivers of beta diversity, pairwise dissimilarities between samples or sites can be correlated with environmental gradients or distance (Vellend 2001). To express the change in beta diversity along an environmental gradient or with distance, several measures can be used, such as compositional turnover rate or rate of change in pairwise compositional turnover with distance (Tuomisto 2010b).

Multiple-site measures Even when multiple sites are studied, dissimilarity measures are restricted to pairwise comparisons, as they are usually simply averaged to calculate overall beta diversity in a larger region. Taxa shared across several sites are not reflected in mean pairwise measures. Diserud and Ødegaard (2007) developed a multiple-site similarity index, an extension of the Sørensen similarity index:

C = 1 – (ST iai) – ( / ∑ ) , T T S where T is the number of sites, ai is the numberT 1 of species in a site, and ST is ∑iai – ∑i

Baselga et al. (2007) therefore developed a new multiple-site similarity index from the Simpson index which is independent of variation in richness:

MSim = (∑ Si - ST) / (∑ min (bij,bji) + ∑ Si – ST) , where Si is the number of species in a site, ST is the total number of species, and bij and bji are the number of species exclusive of both sites. Baselga (2010) developed multiple-site indices that separately express turnover (Simpson dissimilarity index) and nestedness. Since the Sørensen dissimilarity index expresses species turnover and nestedness, nestedness is calculated by subtracting Simpson dissimilarity (true species turnover) from Sørensen dissimilarity.

Other measures Whittaker (1960) introduced several measures of beta diversity, also including the slope of the distance-decay relationship. Community similarity tends to decrease with increasing spatial distance, and the slope of this relationship is an expression of beta diversity (also Jurasinski et al. 2009). When drivers of beta diversity are being analyzed, Legendre et al. (2005) recommend partitioning spatial variation of community composition using canonical partitioning. Beta diversity is expressed as variance of a community composition table and calculated using its sum-of-squares and then compared with other datasets, such as environmental or spatial data. A framework for diversity measures which estimates the effective number of species was developed (Hill 1973). These are now known as numbers equivalents or Hill’s numbers, and can be used in hierarchical measures of beta diversity. Jost (2007) transforms the components of multiplicative diversity with Hill’s numbers to derive a new beta diversity measure that yields the effective number of distinct communities. Other forms of transformations of these indices are presented and discussed in Tuomisto (2010b) and Chao et al. (2012).

Ecological significance Along with the wide array of metrics and applications of beta diversity comes a plethora of assertions of its ecological meaning. Hierarchical measures of beta diversity express differences in species richness in a region. They are used to evaluate how much of the diversity originates at the assemblage level and how much is attributed to the differences between assemblages (Veech et al. 2002). In other words, they "assess the proportion of the total diversity (γ) found in different habitats, landscapes, or regions" (Crist et al. 2003, p. 1). Veech et al. (2002) recommend the use of diversity partitioning in conservation studies to address issues relating to the relationship between regional and local diversity. Diversity partitioning has also been applied to assess changes in ecosystems over geological time (Hautmann 2014, 2015, Hofmann et al. 2016). However, to reflect differences in community composition between samples, heterogeneity measures should be applied. They can be used to assess the effect of environmental disturbances, such as fishing or pollution, on assemblages, or seasonal differences by comparing community composition between different points in time (e.g., Hily et al. 2008, Johnson and Angeler 2014, Lamy et al. 2015). For example, beta diversity measured as change in species composition of communities over the last several decades has been found to increase, while alpha diversity has remained constant (Dornelas et al. 2014). Spatial distribution of species, particularly along environmental gradients, has been the focus of many studies, often finding changes in species composition correlated with environmental factors (e.g., Fitzpatrick et al. 2013, Jankowski et al. 2009, Melo et al. 2009). Several studies have used a combination of temporal and spatial beta diversity, e.g., to assess differences in temporal turnover of mollusc assemblages along an environmental gradient using heterogeneity measures 7

(Tomašových et al. 2014) or finding differences in temporal turnover in different habitats for Hymenoptera using additive partitioning (Tylianakis et al. 2005). Particularly the differentiation between spatial species turnover (Simpson dissimilarity index) and species loss (nestedness) is important, as these represent different ecological drivers (Baselga 2010, Roden et al. 2019, publication #2, Tomašových et al. 2016). Beta diversity has often been applied to disentangle community assembly mechanisms (e.g., Myers et al. 2013, Segre et al. 2014, Siefert et al. 2013). Perhaps most important, however, at least for neontologists, is the role of beta diversity in conservation studies. Determining patterns of diversity, either as hierarchical beta diversity or as heterogeneity, can help determine beneficial sites, sizes, and spatial arrangements of protected areas (Socolar et al. 2016, Wiersma and Urban 2005).

Problems (and some solutions) In addition to issues regarding terminology as well as the wide array of concepts and measures (Anderson et al. 2011), the application of beta diversity can face a multitude of problems. One issue mentioned quite frequently in the literature is the effect of differing sample sizes, which can bias beta diversity estimates (Magurran 2004, Veech et al. 2002). Specifically, there is a higher number of rare species in larger sample sizes (Maurer and McGill 2011). Particularly hierarchical beta diversity measures are subject to the same biases that affect alpha and gamma diversity, whether species richness, Shannon or the Simpson index are used (e.g., Kraft et al. 2011, Lande 1996). In addition, additive and multiplicative beta diversity are strongly dependent on spatial scale (Marion et al. 2017, Soininen 2010). There is no definition of a local (alpha-level) community, and the division between alpha and gamma diversity is arbitrary, yielding different values of beta diversity for the same dataset (Loreau 2000). Tuomisto (2010b) recommends using the same number of sampling units when comparing multiplicative beta diversity in different regions. Incidence-based dissimilarity measures, such as the Simpson, Jaccard, and Sørensen dissimilarity indices discussed above, are biased when richness in the samples varies and/or sampling is incomplete (Magurran 2004, Wolda 1981). Abundance-based measures of heterogeneity, however, are less problematic. Proportional dissimilarity, or the Bray-Curtis coefficient, is a popular and robust beta diversity index used in many ecological studies (Bloom 1981, Faith et al. 1987, Legendre and Legendre 2012). While proportional dissimilarity has been shown to be relatively unaffected by uneven sample sizes (Krebs 1999), impoverished and completely empty samples lead to inconsistent behavior of this dissimilarity measure (Smith 2017), particularly in ordinations (Clarke et al. 2006, De'ath 1999). Clarke et al. (2006) proposed an adjustment to the Bray-Curtis index, and De'ath (1999) uses “extended dissimilarities” to produce meaningful multi-dimensional scaling displays in cases of very high beta diversity. Chao et al. (2005) argue that proportional dissimilarity is also affected by sampling bias, and have developed an adjustment to estimate the number of unsampled species and incorporate them into beta diversity. However, Roden et al. (2018, publication #1) show that the effect of rare species on proportional dissimilarity is negligible, and that incomplete sampling still yields reliable beta diversity estimates. This result not only makes beta diversity studies less time-consuming, as only a limited number of taxa need to be identified, but also shows proportional dissimilarity is robust to incorrect taxon identifications of rarer species. Beta diversity of an area is often calculated by averaging pairwise differences. However, this disregards species shared across more than two sites (Diserud and Ødegaard 2007). To avoid this, multiple-site indices have been developed that include information on species shared by more than two sites (Baselga et al. 2007, Diserud and Ødegaard 2007). While these express overall dissimilarity in a region, nothing is known about the spatial arrangement of diversity. To convey changes in community

8 composition along gradients, the rate and magnitude of compositional changes along a gradient should be measured (Vellend 2001). However, as environmental gradients change with spatial distance, it can be difficult to disentangle the effects of dispersal or randomness in species distribution from correlation with environmental factors (Harrison et al. 1992). In addition to the increase in environmental heterogeneity with increasing geographic distance, there are multiple other factors that can contribute to beta diversity. Stegen et al. (2013) test how stochastic and deterministic factors influence temporal and spatial turnover. To test how much of the calculated beta diversity is attributable to random distribution of the overall (gamma) diversity of a region into local (alpha-level) plots or assemblages, a statistical null model should be applied (Anderson et al. 2011). This can offer insights into the source of beta diversity, quantifying how much is controlled by stochastic as opposed to deterministic ecological processes (Stegen et al. 2013). For the Cassian Formation, beta diversity calculated from a null model (mean PPD: 0.24 ± 0.0004) was significantly lower than from the true dataset (0.91 ± 0.02), leading to the conclusion that stochasticity is not the main driver of beta diversity in this case (Roden et al., in review, publication #3). Unfortunately, many studies do not include null models (Anderson et al. 2011). It is important for studies to explicitly state which measure of beta diversity is being used to avoid confusion and increase replicability. Applying multiple measures of beta diversity in a study to address different ecological aspects and questions as well as comparing results with null models is recommended (Anderson et al. 2011).

Common and rare species While few species in ecological communities comprise most of the relative abundance, most species are very rare (e.g., Hannisdal et al. 2017, Magurran and Henderson 2003). Rarity can be defined in various ways, usually referring to small geographic distributions or low abundance (Gaston 1994). Bouchet et al. (2002) differentiate between ecological rarity – the number of species collected at single stations – and biological rarity – the number of species represented by five specimens or less, or by a single specimen only. Using the quartile definition of rarity, species in the first quartile of a species abundance distribution (or distribution of range sizes) are considered rare (Gaston 1994). Reddin et al. (2015), who define commonness and rarity based on range size, found common species to drive similarity in the marine realm. As discussed above, the number of rare species is dependent on sampling (e.g., Coddington et al. 2009). This directly affects various measures of beta diversity (i.e., hierarchical measures and incidence-based dissimilarity). Much of ecosystem functioning is generally ascribed to common species (Magurran and Henderson 2011, Smith and Knapp 2003). Depending on the research question, focusing on common species can be useful and intuitive. For alpha diversity measures, the Berger-Parker dominance index (Berger and Parker 1970), which only provides the proportion of the most abundant species in the sample, has been shown to correlate well with other alpha diversity indices (Kowalewski et al. 2006). Like the Berger- Parker dominance index, mean proportional dissimilarity can also be applied with a focus on only the most abundant species (Roden et al. 2018, publication #1). It is a useful measure of beta diversity, as it is comparable across datasets that differ in size, sampling completeness, heterogeneity, and environmental setting (Marion et al. 2017, Roden et al. 2018, publication #1).

Beta diversity in different environments There are many beta diversity studies in the terrestrial realm, such as on vegetation (e.g., Baldeck and Asner 2013, Felfili et al. 2004, Tuomisto et al. 2003), birds (e.g., Mac Nally et al. 2004, Melo et al. 2009, Veech and Crist 2007), insects (e.g., Brehm et al. 2003, Novotny et al. 2007, Ødegaard 2006), and many other groups. For the marine realm, though, studies remain few (Ellingsen 2002). Beta diversity studies on coral reef or soft-bottom benthic assemblages rarely provide comparable values of beta diversity. Instead, they focus on relationships between community composition and/or beta diversity with, e.g., distance, water depth, or grain size, and do not provide the actual values of beta diversity. They figure pairwise dissimilarity values as points (Becking et al. 2006, de Voogd et al. 2006, Pandolfi 2002), ordination plots (Henry et al. 2010, Pandolfi 2002, Pandolfi and Jackson 2001), provide correlation values between beta diversity and other variables (de Voogd et al. 2006, Pandolfi and Jackson 2001), but rarely are values given. There are several exceptions, however. Using species abundances based on counts of coral colonies along line transects, Dornelas et al. (2006) found dissimilarity in coral reefs to be much higher than predicted from the null model. Mean pairwise proportional dissimilarity (PPD) ranges between 0.54 in island slope assemblages and 0.83 among flat assemblages. In a study of a continental shelf soft- bottom macrobenthic fauna, including large ranges of water depth and variability in grain size, Ellingsen (2002) found PPD to range between 0.26 and 0.86. She found different drivers of beta diversity for the different faunal groups studied. Specifically, beta diversity in molluscs is related to depth and median grain size of the sediment. Roden et al. (2018, publication #1) calculated alpha, beta, and gamma diversity indices of four fossil and two modern marine datasets with species counts of molluscs and, in part, other fauna. Mean PPD ranges between 0.76 for recent samples from the Northern Adriatic Sea and 0.94 for the Triassic Cassian fauna, and large variability is seen in pairwise differences in four of the datasets. While PPD is comparable among datasets of varying size and sampling intensity (see sections above), the lack of comparable datasets makes it difficult to assess large-scale differences in beta diversity among very different habitats.

The Cassian Formation Geology The Middle to Late Triassic Cassian Formation is exposed in the Dolomites, Southern Alps, northern Italy, which was situated along the Western Tethys. Toward the end of the Ladinian, the Dolomites are influenced by an intensive phase of volcanic activity, leading to tectonic uplift, followed by a phase of erosion, depositing sediment in the oceanic basins between volcanic islands (Bosellini 1998). The coarse-grained sediments deposited proximally are known as Marmolata Conglomerate; finer-grained sediments like sand and clay deposited distally are now known as the Wengen Formation (Bosellini 1998; Fig. 3). In the Anisian and Ladinian, the carbonate platforms – today the Schlern Dolomite and the Marmolata Limestone – grow vertically and laterally, and as the previously prevailing subsidence slows down, the platforms continue to prograde (Bosellini 1998, Keim et al. 2001). A new generation of reefs are formed, as algae, sponges, and corals begin colonizing the elevated parts of the oceanic basins, such as old Ladinian reefs or volcanic hills (Bosellini 1998). These originally fringing reefs continue prograding and are now known as the Cassian Dolomite, and the sediments deposited between the reefs in the Late Ladinian and the Carnian comprise the Cassian Formation (Bosellini 1998; Fig. 4; see also Stratigraphy). The Cassian sediments begin filling deep basins that lie between the prograding carbonate platforms and reefs (Keim et al. 2001). The material is mostly fine-grained sediments remaining from the last erosion phase mixed with calcareous particles from the new platforms (Bosellini 1998). They mostly consist of argillaceous sediments, with marls and marlstones, mudrocks, micritic limestones, calcarenites, and carbonate breccias (Fürsich and Wendt 1977, Keim et al. 2006). With tectonic uplift in the Late Carnian, the extent and depth of basins is reduced. Several isolated basins remain in the eastern part of the Dolomites that are eventually filled with carbonate mud. They now form the Dürrenstein Dolomite that partly overlies the Cassian reefs. The Late Carnian Raibl Formation, made up of various types of sedimentary rocks, overlies the Cassian Dolomite and Dürrenstein Dolomite (paragraph based on Bosellini 1998; see Fig. 3). The Cassian Formation covers a total area of over 500 km2 (Roden et al. 2019, publication #2; Fig. 5), and, in some parts, the basin sediments are up to 300 m thick (Fürsich and Wendt 1977). A very large number of well-preserved fossils have been found in the marls, compiled from the literature and own field work in Roden et al. (2019, publication #2). Fossils have been reported from more than 30 localities (Table 1). After 185 years of research (Münster 1834) and more than 150 publications, the Cassian Formation is a thoroughly researched and intensively sampled assemblage. Several museums host large collections of material, e. g. the Natural History Museum Vienna, the Geological Survey of Austria, the Bavarian State Collection for Palaeontology in Munich, the Naturmuseum Südtirol in Bolzano.

Fig. 3: Stratigraphy of the Dolomites. The Cassian Formation (SC) was deposited in the reef basins coeval with the carbonate platforms and reefs that now make up the Cassian Dolomite (DC). Figure from Bosellini (1998), modified.

Fig. 4: Several outcrops at Stuores with soft basin sediments are in the foreground. The former carbonate platforms now forming the Dolomites are seen in the background.

Fig. 5: Map of reported localities in the Cassian Formation (dots) and major settlements (stars). Figure from Roden et al. (2019, publication #2).

Table 1: Cassian localities with fossil finds reported in the literature, their stratigraphic age and depositional environment. Table adapted from Roden et al. (2019, publication #2).

Locality Environment Source Ammonite biozone References transported from Campo allochtonous probably austriacum own observations shallow reef area Carbonin Cianzopé late aonoides Urlichs (2017) Cason dei Caài Ciòu del Conte shallow water, soft- autoch- Fürsich and Wendt (1977), Urlichs Costalaresc austriacum bottom thonous (2017) Forcella Col Duro shallow water, very autoch- Forcella Giau aonoides HH; MU; F. Fürsich field notes proximal thonous Lago Antorno basin, soft-bottom probably austriacum own observations Milieres / Dibona aonoides & austriacum Bizzarini et al. (1986), Urlichs (2012) predomi- probably austriacum Keim et al. (2006), Nützel et al. covers various Misurina Skilift nately alloch- (?aonides), partly (2010), Urlichs (2012), Wendt and environments thonous Heiligkreuz Fm. Fürsich (1980) predomi- probably austriacum Bizzarini and Laghi (2005, loc. 4); Misurina Landslide nately autoch- (?aonides), partly Hausmann et al. (accepted, thonous Heiligkreuz Fm. publication #4) Pocol aonoides Bizzarini et al. (1986) very proximal (back Rumerlo allochtonous aonoides Urlichs (2012) reef) Sasso di Stria aonoides & aon Urlichs (2017) deep subtidal shelf; Staolin austriacum F. Fürsich field notes; Urlichs (2017) also input from reef Fürsich and Wendt (1977), Nützel and shallow basin, soft- autoch- Settsass probably aon Kaim (2014), Urlichs (1994); own bottom thonous observations very shallow water, predomi- austriacum (possibly Fürsich and Wendt (1977), Russo et al. Alpe di Specie back-reef, soft- nately autoch- upper) (1991), Urlichs (2017) bottom thonous Bizzarini et al. (1986), Fürsich and aonoides & aon (& basin, ?slope & Wendt (1977), Hausmann and Nützel Stuores mixed canadensis & carbonate platform (2015), Mietto et al. (2008), Urlichs regoledanus) (2017) Tamarin austriacum Urlichs (2017) Vervei aonoides Urlichs (2012) Pescol Base Punta Gusella Ruones youngest aon Urlichs (2017); MU Picolbach aon Urlichs (2000, 2017) Rio Stueres aonoides & aon Urlichs (2012) Rio di Foves aonoides Urlichs (2012) Urlichs (2012); (Mietto et al. 2008: Piz Lavarella deep neritic zone aonoides canadensis) Masareis aonoides Urlichs (2017) Saverie aonoides Urlichs (2017) Pedraces Kristan-Tollmann (1960) *Substages based on Urlichs (2017)

Stratigraphy The Cassian Formation sensu lato, which includes all Ladinian-Carnian sediments deposited in the basins between the carbonate platforms of the Dolomites, comprises six ammonite biozones (Roden et al. 2019, Urlichs 2017, Table 2). Most occurrences of diverse benthic fauna range from the aon to the austriacum ammonite zones, approximately 236-231 Ma (Gradstein et al. 2012). The Cassian Formation as well as the coeval reefs and platforms used to be considered to be only of Carnian age, until recently parts of the formation as well as parts of the reefs (e.g., Sella) were found to be of Late Ladinian age (Bosellini 1998). The Cassian Formation is considered to be the counterpart to the platforms of the Cassian Dolomite, but the base of the formation at its border with the Wengen Formation is vague and the two formations are partially intercalating (Bosellini 1998).

Table 2: Stratigraphy of the Cassian Formation with ammonite zonation. The Cassian Formation sensu stricto comprises the late regoledanus, canadensis, aon, and aonoides ammonite biozones. The austriacum and dilleri ammonite biozones are now regarded as belonging to the Heiligkreuz Formation. Studied samples from marked ammonite biozones. Table from Roden et al. (in review, publication #3).

Tuvalian dilleri zone

Heiligkreuz Formation austriacum zone Julian aonoides zone

Carnian Cassian Cassian Formation aon zone Late Triassic Late Formation sensu lato "Cordevolian" sensu stricto canadensis zone

Longobardian regoledanus zone nian

Ladi-

Environment

In the late Triassic, the climate was warm and arid, with average global temperatures c. 6° C warmer than today (Sellwood and Valdes 2006). Paleocoordinates based on today's position are estimated at c. 13° N, 20° E (Paleobiology Database, paleobiodb.org). The extensive carbonate platforms and reefs, the paleoposition, and isotope ratios all indicate warm, tropical conditions (Nützel et al. 2010). Evidence for seasonal fluctuations and fresh water influx is shown in oxygen and carbon isotopes (Nützel et al. 2010).

The Cassian Formation includes shallow and deeper water sediments from the reef basin and the nearshore area as well as material from the carbonate platform (Fürsich and Wendt 1977). Volcanic islands and submarine volcanic mounds are probably the source of proximal sandstones as well as turbidites; an extensive lagoonal area with patch reefs, with locally occurring proximal back-reef areas, grades into the carbonate platform; the reef basin has relatively shallow areas, a slope, and deeper parts of the central basin (Fürsich and Wendt 1976; Fig. 6). Table 1 gives an overview of the different environments of localities for which this has been interpreted. In Roden et al. (in review,

15 publication #3), relative water depth of eight Cassian localities is inferred from the ratio of suspension and deposit feeders, the ratio of carnivores and grazers, bivalve articulation, gastropod abundance and diversity, encrustation, and the quantity of coral, sponge, and echinoderm fragments (Fig. 7). Water depth ranges from very shallow, as in Forcella Giau, Rumerlo, and Alpe di Specie, to very deep parts of the basin, as in Piz Lavarella, Staolin, and some localities of the Misurina Skilift area (Table 1).

Fig. 6: Depositional environments of the Cassian Formation. Figure from Fürsich and Wendt (1976).

Fig. 7: Depth-related attributes of studied samples (a); change of sample characteristics with relative depth (b). Figure from Roden et al. (in review, publication #3).

Preservation

The large number of fossils found and species described from the Cassian Formation is most likely due to low lithification, owing to low-grade diagenesis of the marls (Roden et al. 2019, publication #2). Low diagenetic alteration is probably due to low permeability of the marly sediments and early cementation (Roden et al. 2019, publication #2, Russo et al. 1991, Scherer 1977). Due to this excellent preservation – which includes the preservation of aragonite – and the softness of the sediment, fossils are easy to extract and minute details are often preserved (Fig. 8). However, some recrystallization does occur.

The large number of gastropod species found in the Cassian Formation (552 vs. 1421 total invertebrate species) are presumably a taphonomic phenomenon due to the preservation of many very small gastropod species and preservation of their larval shells, which aids in identification (Roden et al. 2019, publication #2). Comparable assemblages from the same environment and climate and close stratigraphic ages yield fewer gastropods due to lithification of the host rock: The Ladinian to Early Carnian Wetterstein Formation and the Late Anisian to Late Ladinian Marmolata Limestone have a much lower proportion of molluscs and especially gastropods (Friesenbichler et al. 2019, Roden et al. 2019, publication #2). This has led Roden et al. (2019, publication #2) to coin the term 'liberation lagerstätten' for lagerstätten with a high diversity and easy extractability of fossils. Liberation lagerstätten may be the key to revealing biodiversity patterns in ancient ecosystems, as the widely discussed loss of diversity through aragonite dissolution, particularly of molluscs, may have distorted diversity estimates (Bush and Bambach 2004, Cherns and Wright 2000, Wright et al. 2003). Fig. 9 shows how strongly the proportion of molluscs and gastropods in the Cassian Formation deviates from the total Carnian proportion and that the proportions are close to those of the Cenozoic.

Fig. 8: Examples of very small gastropods with minute details preserved: (a) Stuorilda cassiana Bandel, 1995 from Rumerlo cliff, (b) Domerionina stuorense (Bandel, 1994) from Costalaresc, (c) Ptychostoma sanctaecrucis (Wissmann, 1841 in Münster) from Costalaresc, (d) & (e) Dicosmos maculosus (Klipstein, 1843) from Costalaresc. SEM images.

Fig. 9: Proportions of benthic mollusc, gastropod and bivalve genera among all marine invertebrates by stage. Values from the Cassian literature compilation added for comparison. Figure from Roden et al. (2019, publication #2).

The biota

The biota reported from the Cassian Formation includes (in descending order of number of species) gastropods, bivalves, echinoderms, brachiopods, porifera, cnidaria, cephalopods, foraminifers, ostracods, polychaetes, polyplacophores, and scaphopods; less frequent are bryozoans, cyanobacteria, chlorophytes, rhodophytes, dinoflagellates, tunicates, vertebrates, ichnofossils, and problematica (references in supplementary information of Roden et al. 2019, publication #2). These include Cipit boulders that stem from the reef platform, from which mostly sponges and microencrusters have been reported (e.g., Sánchez-Beristain and Reitner 2012, Sánchez-Beristain and Reitner 2018). Apart from the noteworthy quantitative paleoecological study by Fürsich and Wendt (1977), most publications on the Cassian fauna are of taxonomic nature. Specifically, the large monographs by Münster and Wissmann (1841), Laube (1865a, 1865b, 1868, 1869a, 1869b), and Kittl (1891, 1892, 1894) as well as numerous publications by Bandel (e.g., 1991, 1992, 1993, 2007) and Nützel (e.g., 2006, 2007, 2013, 2018) have contributed greatly to our knowledge on the composition of the fossil biota. A few remarkable discoveries have been made from Cassian assemblages, such as the first tunicate with a calcareous exoskeleton (Wendt 2018) or the youngest ophiocistioid, previously only known from the Paleozoic (Reich et al. 2018). Much of the ammonite fauna has been reported for stratigraphy (e.g., Urlichs 1994, Urlichs 2017).

Alpha diversity

There are several highly diverse assemblages in the Cassian Formation. Including all 30 localities from which species have been reported, the mean species richness per locality is 96 (Roden et al. 2019, publication #2), and there are nine localities with more than 100 reported species (Roden et al. 2019, publication #2, supplementary information) using the compilation from the literature. One of the most diverse localities are the Stuores Wiesen, or Prati di Stuores (Fig. 4). While they represent a larger area with several study sites (Fig. 5), 171 species are reported from a quantitative study on a single outcrop (Hausmann and Nützel 2015). The vicinity of Misurina has also yielded high diversity, one study site recording 57 species (Hausmann et al. accepted, publication #4), and more than 60 species are reported from Settsass (Nützel and Kaim 2014). Rarefaction curves from different assemblages suggest that more species will likely be found with further exploration (Hausmann and Nützel 2015, Hausmann et al. accepted, publication #4). Studying individual assemblages with regard to alpha diversity and paleoenvironment is crucial to compiling a larger dataset with which to assess beta diversity patterns and how these change with environment.

Beta diversity

While differences in faunal composition have been noted (e.g., Fürsich and Wendt 1977, Nützel and Kaim 2014), only recently studies have attempted quantifying beta diversity in the Cassian Formation (Hausmann et al. accepted, publication #4, Roden et al. 2018, publication #1, Roden et al. 2019, publication #2, Roden et al. in review, publication #3). Using a dataset of species occurrences compiled from the literature and own field work in the Cassian Formation, Roden et al. (2019, publication #2) found very high beta diversity using the mean Jaccard dissimilarity index (βJ = 0.95). Beta diversity was calculated as spatial turnover using the multiple-site Simpson dissimilarity index

(MSim = 0.84) and species loss, or nestedness (multiple-site nestedness = 0.12). This led to the conclusion that differences in community composition are mostly driven by spatial turnover and not by species loss in this ecosystem. Applying an abundance-based measure to a quantitative dataset from Fürsich and Wendt (1977) from the Cassian Formation, Roden et al. (2018, publication #1) found a mean PPD of 0.94, the highest value among six different recent and fossil datasets studied. However, when using multiplicative beta diversity, the Cassian dataset only ranks third highest. This may be due to uneven sample sizes and/or more rare species in the other two datasets and may not be of ecological significance. Beta diversity was again explored in another study, in which Roden et al. (in review, publication #3) calculated mean PPD on a set of samples from the Cassian Formation and compared it with a recent dataset from the Bay of Safaga, Red Sea, Egypt (Zuschin and Hohenegger 1998, Zuschin and Oliver 2005) to determine drivers of beta diversity and find out whether change in faunal composition is directional (e.g., changes with water depth). Overall beta diversity is again found to be very high for the Cassian Formation (mean PPD: 0.91 ± 0.02), similar to the recent dataset (mean PPD: 0.89 ± 0.04) and much higher than predicted from the null model (mean PPD: 0.24 ± 0.0004). Beta diversity of the studied samples does not decrease with depth (Fig. 10) as authors originally hypothesized. Ordination of the Cassian samples shows no apparent association between samples from a similar inferred water depth (Fig. 11 a). And while there is temporal turnover in the Cassian Formation, time is not the main reason for dissimilarity among communities (Roden et al. in review, publication #3, Fig. 11 b). Results show minor effects of water depth, sediment structure, and stochasticity on beta diversity, and the assumption is made that priority effects play a key role in driving beta diversity.

Beta diversity of known liberation lagerstätten (Roden et al. 2019, publication #2) for which data was available in the Paleobiology Database (paleobiodb.org) as well as two modern assemblages for comparison was calculated as mean PPD based on genera (Fig. 12). Beta diversity is very high and relatively similar in the five fossil assemblages and slightly lower in the two modern ones. Alpha and gamma diversity vary strongly, but since no sample size standardization was applied, only beta diversity estimates provide a reliable comparison among assemblages. More data is needed to fill the large gaps, and liberation lagerstätten provide a relatively unbiased window into past ecosystems.

Fig. 10: Inferred relative water depth of several Cassian localities. Mean pairwise proportional dissimilarity (PPD) of each sample with other samples and mean PPD among samples grouped by depth. Figure from Roden et al. (in review, publication #3).

Fig. 11: Non-metric multidimensional scaling of the Cassian samples, color-coded by (a) depth and by (b) ammonite biozone (darker colors represent older strata). There are no distinct associations among localities from similar depths or from the same ammonite biozone. Figure modified from Roden et al. (in review, publication #3).

alpha is mean number of pergenera

lagerstätten for data availablewhich were

y the ten y abundant most speciesper sample

fossil data: fossil Paleobiology Database

schin andschin Hohenegger (1998), and Zuschin

not to not scale; position barsof Upper in

Oliver (2005).Oliver

(paleobiodb.org);sources modern data: Sawyer and Zuschin (2010), Zu

yield very yield very similar results (average difference in PPD:mean 0.02). Source

Cretaceous adjusted for visualization. Calculations of mean PPDonl using

collection or sample. Error represent bars standard error. barsof Width

Fig. 12:Fig. Mean pairwise proportional dissimilarity (PPD) liberation known of and two modern assemblages. calculations All based on counts genera.of Mean

Outlook

Changes in beta diversity probably drive global diversity patterns at some scale (Holland 2010). The wide breadth of ecological literature as well as several paleontological studies on beta diversity patterns in different environments, regions, and periods of time provide a foundation on which to base further research. However, variations in sampling intensity, taphonomy, and dataset size, and different measures of beta diversity and methods of standardization make comparisons difficult. With the Cassian Formation and other liberation lagerstätten as well as modern assemblages, taphonomic bias can be reduced, providing more insights into biodiversity patterns of soft-bottom reef-associated faunal assemblages. In a next step, datasets and measurements should be standardized and compared.

Jablonski and Sepkoski Jr (1996) find each marine evolutionary fauna to show different characteristics of diversity: the Cambrian Fauna shows low levels of alpha and beta diversity, the Paleozoic fauna has intermediate values, and the Modern Fauna yields very high diversities. This can be explained by a much larger proportion of ecologically complex communities in the Mesozoic and Cenozoic than in the Paleozoic (Wagner et al. 2006). To corroborate these findings, more well-preserved fossil assemblages, particularly from the Triassic – a time of during which ecosystems seem to have undergone major changes – need to be studied with regard to alpha, beta, and gamma diversity. In addition, they can help us answer the question of how taxon proportions, specifically mollusc and gastropod proportions, have changed through time. Whereas Early Triassic assemblages have yielded low values of beta diversity (e.g., Hofmann et al. 2014), the Cassian Formation has shown that high values of beta diversity can be found in the Middle to Late Triassic (Roden et al. 2019, publication #2; Roden et al. in review, publication #3). The Phanerozoic beta diversity curve shows another drop from the Triassic to the Jurassic and subsequent increase until the later Cretaceous; the Cenozoic yields intermediate values of beta diversity after another large drop at the end-Cretaceous. (Aberhan and Kiessling 2012; Fig. 1).

To reveal whether these global patterns are robust at varying scales and habitats, future research should be based on a larger number of fossil and recent datasets from different environments and regions. This will help infer drivers of beta diversity and overall biodiversity patterns. Applying the concept of dominant species driving beta diversity (Roden et al. 2018, publication #1), it is now possible to create more community composition data for beta diversity analyses, spending less time on taxon identification and counting. Specifically, more liberation lagerstätten should be studied, as only they can be directly compared with modern datasets with regard to diversity and taxon proportions. This would greatly contribute to revealing change in ecosystems through space and time. In particular, the understudied soft-bottom reef-adjacent habitats have great potential in uncovering patterns of community assembly. In comparison with reef diversity, future research can provide insights into the interaction and influence these adjacent habitats have on one another regarding diversity patterns. Results from this thesis and future studies will contribute to encouraging (paleo)ecological research and perhaps even conservation science.

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List of manuscripts and declaration of own contribution to manuscripts

#1 Roden V. J., Kocsis, Á., Zuschin, M. & Kießling, W. 2018. Reliable estimates of beta diversity with incomplete sampling. Ecology 99: 1051-1062. https://doi.org/10.1002/ecy.2201. and the supplementary data package available with the online version of the article

Contributions Data compilation, analysis, and figures: 90 % Writing: 70 % Concept and discussion: 50 %

#2 Roden, V. J., Hausmann, I. M., Nützel, A., Seuss, B., Reich, M., Urlichs, M., Hagdorn, H. & Kiessling, W. 2019. Fossil liberation: A model to explain high biodiversity in the Triassic Cassian Formation. Palaeontology. https://doi.org/10.1111/pala.12441. and the supplementary data package: Roden, V. J., Hausmann, I. M., Nützel, A., Seuss, B., Reich, M., Urlichs, M., Hagdorn, H. & Kiessling, W. 2019. Data from: Fossil liberation: a model to explain high biodiversity in the Triassic Cassian Formation. Dryad Digital Repository. https://doi.org/10.5061/dryad.6s5651k.

Contributions Data compilation, analysis, and figures: 60 % Writing: 70 % Concept and discussion: 50 %

#3 Roden, V. J., Zuschin, M., Nützel, A., Hausmann, I. M. & Kiessling, W. Drivers of beta diversity in modern and ancient reef-associated soft-bottom environments. PeerJ. In review. and the supplementary data package

Contributions Field work: 40 % Data compilation, analysis, and figures: 70 % Writing: 80 % Concept and discussion: 70 %

#4 Hausmann, I. M., Nützel, A., Roden, V. J. & Reich, M. 2019. Diversity and palaeoecology of Late Triassic invertebrate assemblages from the tropical marine basins near Lake Misurina (Dolomites, Italy). Acta Palaeontological Polonica. Accepted pending revisions.

Contributions Field work: 40 % Data compilation, analysis, and figures: 10 % Writing: 10 % Concept and discussion: 10 %

Publication #1

Roden V. J., Kocsis, Á., Zuschin, M. & Kießling, W. 2018. Reliable estimates of beta diversity with incomplete sampling. Ecology 99: 1051-1062. https://doi.org/10.1002/ecy.2201. and the supplementary data package available with the online version of the article reproduced with permission

Reliable estimates of beta diversity with incomplete sampling

1,3 1 2 1 VANESSA JULIE RODEN, ADAM T. KOCSIS, MARTIN ZUSCHIN, AND WOLFGANG KIESSLING 1GeoZentrum Nordbayern, Section Palaeobiology, University Erlangen-Nurnberg,€ Loewenichstraße 28, 91054 Erlangen, Germany 2Department of Palaeontology, University of Vienna, Althanstraße 14, 1090 Vienna, Austria

Abstract. Beta diversity, the compositional variation among communities or assemblages, is crucial to understanding the principles of diversity assembly. The mean pairwise proportional dissimilarity expresses overall heterogeneity of samples in a data set and is among the most widely used and most robust measures of beta diversity. Obtaining a complete list of taxa and their abundances requires substantial taxonomic expertise and is time consuming. In addition, the information is generally incomplete due to sampling biases. Based on the concept of the ecological significance of dominant taxa, we explore whether determining proportional dissimilarity can be simplified based on dominant species. Using simulations and six case studies, we assess the correlation between complete community compositional data and reduced subsets of a varying number of dominant species. We find that gross beta diversity is usually depicted accurately when only the 80th percentile or five of the most abundant species of each site is considered. In data sets with very high evenness, at least the 10 most abundant species should be included. Focusing on dominant species also maintains the rank-order of beta diversity among sites. Our new approach will allow ecologists and paleobiologists to produce a far greater amount of data on diversity patterns with less time and effort, supporting conservation studies and basic science. Key words: beta diversity; Bray-Curtis dissimilarity; community composition; distance matrices; dominant species; heterogeneity; proportional dissimilarity; sampling.

Rosenzweig 1998), or environmental gradients (e.g., Fenton INTRODUCTION et al. 2016, Tomasovych et al. 2016), and apply the Bray- Understanding the principles of diversity assembly and Curtis dissimilarity index to quantify the compositional diversity partitioning is important to improve our knowl- variations. edge of past and current changes in biodiversity. Beta diver- Beta diversity is driven by various biotic and abiotic fac- sity, the variation of community composition, is crucial to tors (Soininen 2010), which trigger habitat differentiation characterize diversity partitioning at multiple scales. Since and associated temporal and spatial turnover (Melo et al. the term was coined (Whittaker 1960), beta diversity has 2009, Soininen 2010, Stegen et al. 2013, Astorga et al. been defined and applied in various ways (Jurasinski et al. 2014). Understanding the spatiotemporal patterns of beta 2009, Tuomisto 2010a, b, Anderson et al. 2011). Diversity diversity may provide insights into the mechanisms of com- of a larger region or a set of assemblages, gamma diversity, munity assembly (e.g., Vellend 2010) and even the processes is partitioned into its alpha and beta components (Whit- of evolutionary diversifications (Hautmann 2015). In con- taker 1960, Olszewski 2010). Alpha diversity is the commu- servation science, changes in beta diversity can indicate nity diversity in a small geographic location (usually a local whether an ecosystem is stressed, and may facilitate conser- sample) and beta diversity the variation in species among vation planning (Wiersma and Urban 2005, Socolar et al. these communities. Beta diversity is often assessed indirectly 2016). either by the ratio of gamma to mean alpha diversity (multi- Diversity indices can reflect different aspects of diversity, plicative beta diversity; Whittaker 1960), or alternatively by such as dominance, evenness, taxon richness, or a combina- subtracting mean alpha from gamma diversity (additive beta tion of these. For most diversity indices, a complete list of diversity; MacArthur et al. 1966, Lande 1996). Measures of taxa needs to be obtained for each sample. For abundance- ecological dissimilarity between samples using multivariate based indices, the number of specimens in each sample is dispersion in ordination space and various (dis)similarity also required. For example, Shannon entropy is a widely measures are potentially more informative than additive or used abundance-based diversity index that incorporates multiplicative beta diversity (e.g., Legendre and Legendre both species richness and evenness (e.g., Sanders 1968). Sim- 2012, see also Methods). Beta diversity can be directional, plified diversity indices have been developed for alpha diver- expressing changes along a gradient, or non-directional, sity that require less information. For example, the Margalef expressing heterogeneity among a set of samples (e.g., index (Margalef 1958) only requires the total number of spe- Anderson et al. 2011). Many studies seek to infer diversity cies and specimens in a community, assuming a log-series changes along temporal (e.g., Mannion et al. 2014, rank-abundance distribution. The most simple alpha diver- Tomasovych et al. 2014a), spatial (e.g., Davidowitz and sity index is probably the Berger-Parker dominance index, which is the proportion of the single most abundant species in a community (Berger and Parker 1970). In spite of its sim- Manuscript received 29 January 2018; accepted 9 February 2018. Corresponding Editor: Conrad C. Labandeira. plicity, this metric correlates well (albeit negatively) with 3E-mail: [email protected] other diversity indices that incorporate more information

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TABLE 1. Parameter ranges of 30,778 simulated data sets. targeted. We find that the dominant species determine the community structure more than rare species or any random Parameter Range selection of individuals. Total species richness (gamma) 2–600 Number of sites 10–150 DATA Total number of specimens in data set 100–676,690 Mean species-level richness 1–600 We simulated >30,000 sites-by-species matrices. Simu- Mean PPD 0–0.98 lated communities cover a wide range of diversity indices Mean sample-level Shannon entropy 0–6.3 (alpha and beta diversity), number of specimens, sam- Gamma Shannon entropy 0–6.3 pling units and number of species as well as evenness Total evenness 0–1 values (Table 1). The generation of these data sets is Mean sample-level evenness 0–1 described in Methods. Note: PPD, pairwise proportional dissimilarity. In addition, we assess six empirical marine data sets, four fossil and two modern, which contain (but are not limited to) species counts of molluscs. Molluscs have a good fossil (Kowalewski et al. 2006) but does not require identification record, are common today, and are well suited for biodiver- and counting of all species in a community. The Berger-Par- sity assessments (Flessa and Jablonski 1996, Wells 1998, ker index emphasizes dominance, and dominant species are Bouchet et al. 2002, Zuschin and Oliver 2005, Tyler and widely recognized to control community structure and Kowalewski 2017). The empirical data sets also cover a large ecosystem functioning in modern (Caruso et al. 2007) and range of ecological indices, although not as extreme as the fossil communities (Hannisdal et al. 2017). Another aspect simulated data (Table 2). We filtered the empirical data sets that supports our emphasis on the important role of abun- to only include count data of distinguishable species. The dant species is the volatility of species richness with respect two recent data sets comprise molluscan death assemblages to sampling technique and intensity. Rare species can give a of standardized bulk samples from two shallow-water shelf misleading ecological signal by increasing the value of alpha areas. (1) One data set is from the Gulf of Trieste, Northern diversity indices that factor in species richness although the Adriatic Sea (AS). Standardized bulk sampling in soft sub- rare species play a smaller role in ecological functioning strata was conducted at eight sites down to 15 m water (Reddin et al. 2015). depth, two on tidal flats and six in the sublittoral zone (Saw- Unfortunately, no simplified measure of dissimilarity- yer and Zuschin 2010). (2) Another data set is from the based beta diversity is currently at hand. Determining beta Northern Bay of Safaga, Red Sea, Egypt (SB). Standardized diversity requires substantial effort in identification and bulk sampling in soft substrates was conducted at 13 sites, counting of taxa, and in practice, the information is always from shallow subtidal down to 40 m water depth (Zuschin incomplete. Based on the concept of the ecological signifi- and Hohenegger 1998, Zuschin and Oliver 2005). cance of dominant taxa, we explore whether the measure of The four fossil data sets represent different time periods beta diversity can be simplified in a similar fashion as the and sampling strategies. Two data sets were collected for a Berger-Parker index using simulated community composi- study of onshore–offshore gradients (Tomasovych et al. tion data sets as well as empirical data sets. 2014a) and include bulk samples of molluscs from (3), a Previous analyses focused on the minimum number of warm-temperate Plio-Pleistocene environment from Piacen- individuals to achieve robust results (Forcino 2012, Forcino zian age deposits of the Lower Arno basins and Piacenzian- et al. 2015) or emphasized the impact of rare species (e.g., Gelasian age deposits of the Piedmont-Padan basins, Gotelli and Colwell 2001, Chao et al. 2005). Here we show Northern Apennines (PPM); and (4), a tropical Eocene envi- that incomplete sampling can yield accurate estimates of ronment from Ypresian age deposits from the Pyrenean beta diversity, when just the most abundant species are Foreland and Aquitaine Basin as well as Lutetian age

TABLE 2. Attributes of empirical data sets.

PPD No. No. No. Mean no. species Data set species specimens sites ac per site Evenness Multiplicative beta Mean SE AS 152 47,606 8 2.53 3.55 62 0.71 1.40 0.76 0.080 SB 639 23,190 13 3.26 4.40 124 0.68 1.35 0.80 0.050 PPM 381 103,641 48 2.33 3.29 37 0.55 1.41 0.74 0.028 EM 560 43,670 104 1.65 4.71 17 0.74 2.86 0.84 0.015 KB 216 24,219 218 1.34 3.92 10 0.73 2.92 0.90 0.008 CF 274 3,958 46 1.85 4.26 16 0.76 2.31 0.94 0.011

Notes: AS, Adriatic Sea, Mediterranean, Recent; SB, Safaga Bay, Red Sea, Recent; PPM, Plio-Pleistocene molluscs, Italy; EM, Eocene molluscs, France; KB, Kachchh Basin, India, Jurassic; CF, Cassian Formation, Italy, Triassic. The mean sample-level alpha (a) diversity and gamma (c) diversity are calculated as Shannon entropy, the multiplicative beta diversity as the ratio of c to a, the mean pairwise proportional dissimilarity (PPD) based on the raw community composition matrix, and the bootstrapped standard error of mean PPD. May 2018 ESTIMATES OF BETA DIVERSITY 1053

FIG. 1. Mean pairwise proportional dissimilarity (PPD) among samples in each empirical data set using abundance data. Points depict the mean PPD for certain percentiles of specimens (bottom axis) of the most abundant species from each sample included in the species composition matrix. Triangles depict the mean PPD for the s most abundant species from each sample included in the species composition matrix (top axis). Lines depict the mean PPD of the complete species composition matrix. Gray boxes indicate the bootstrapped standard error of PPD of the complete matrix. Abbreviations as in Table 2.

deposits from the Paris Basin (EM). The PPM and EM in the Paleobiology Database (available online).4 (6) The assemblages were assigned to different depths, two onshore Cassian Formation, Middle to Late Triassic, located in the and two offshore habitats. The data are available through Dolomites in northeastern Italy (CF), was deposited in Dryad (Tomasovych et al. 2014b). (5) Samples from the inter-reef basins and back-reef areas (Fursich€ and Wendt Kachchh Basin in western India, Washtawa Formation, 1977). The samples represent various reef and basinal envi- Middle Jurassic (KB), stem from an offshore environment ronments. The Cassian Formation is known for its high and were gathered for paleoecological analysis using bulk diversity and excellent preservation. We use the data of sampling and field collection. The unpublished data was assembled by F. Fursich€ from 1988 to 2004 and is available 4 paleobiodb.org 1054 VANESSA JULIE RODEN ET AL. Ecology, Vol. 99, No. 5

TABLE 3. Mean correlation coefficients between the dissimilarity Bray-Curtis dissimilarity index because it is a widely used, matrices calculated including only the s most abundant species robust, and intuitive method of expressing differences in and the complete dissimilarity matrices, across all and a subset of the simulated data sets. community composition (Bloom 1981, Faith et al. 1987, Legendre and Legendre 2012). All data sets Data sets with evenness ≤ 0.6 We generated simulated sites-by-species matrices repre- s Correlation coefficient SD Correlation coefficient SD senting community compositions with all possible values of PPD, total and mean sample-level Pielou’s evenness, varying 1 0.61 0.29 0.77 0.17 degrees of overall and sample-level richness, as well as differ- 2 0.65 0.30 0.80 0.20 ent numbers of specimens and sampling units (Table 1). 3 0.69 0.30 0.84 0.20 A total of 4,500 species pools were randomly created with a 4 0.72 0.30 0.87 0.18 5 0.75 0.29 0.90 0.16 lognormal distribution function expressing a mean log of 2 6 0.77 0.28 0.91 0.15 and a standard deviation of between 0.2 and 25. This 7 0.78 0.28 0.92 0.14 resulted in various types of abundance distributions and val- 8 0.80 0.27 0.94 0.13 ues of evenness. From each of these species pools, varying 9 0.81 0.27 0.95 0.12 proportions of specimens were randomly selected to create 10 0.82 0.26 0.95 0.11 sampling sites. Accordingly, seven community composition 15 0.86 0.23 0.98 0.07 matrices were created from each species pool. In total, 20 0.89 0.21 0.99 0.05 31,500 data sets were generated. After removing data sets with a non-calculable evenness (NaN), 30,717 data sets remained for further analysis. While the simulated data Fursich€ and Wendt (1977), which are publicly available in sets cover all theoretically possible scenarios, only a few of the Paleobiology Database. these are likely to be realized in nature. We therefore focus on the empirical data sets to test the effects of incomplete sampling. METHODS We apply simple correlation tests between the dissimilarity To measure beta diversity, we focus on dissimilarities matrices of the complete and reduced data sets, in which in taxonomic composition among sampling units only the s most abundant species as well as certain per- expressed as proportional dissimilarity. The pairwise pro- centiles of specimens belonging to the most abundant spe- portional dissimilarities (PPD) between the samples are cies from each site are included. The mean PPD is averaged to express the overall dissimilarity among a set calculated for the complete and reduced data sets. We tabu- of samples. This mean PPD is the measure of beta late the number of species, specimens, and sites, the mean diversity used in this study. As the PPD always ranges and total species richness, the evenness, the mean PPD, and, between 0 (identical community composition) and 1 (no for comparison, multiplicative beta diversity for each empir- common elements), it can be compared across different ical data set. Correlation tests refer to Pearson’s product- regions and between various studies. This is not the case moment correlation. Standard errors are assessed with boot- for the traditional multiplicative beta diversity, which has strap resampling (1,000 iterations). an undefined maximum and is dependent on the number To assess the importance of count data, the approach of samples and the size of the studied area (see Discus- is repeated after converting abundance to presence- sion). absence data for the empirical data sets. Abundance data Proportional dissimilarity is relatively insensitive to are used to determine the most abundant species, but unequal sample sizes (Krebs 1989) and is calculated as the dissimilarity is then calculated using binary data reduced to the s most abundant species of each site. ø djk ¼ 1 À X minðxij; xikÞ; (1) Here, the S rensen dissimilarity was applied, which is the binary equivalent of the Bray-Curtis index (Bray and with xij and xik being the proportions of taxon abundance in Curtis 1957, Magurran 2004). each assemblage. This metric is identical to relative Bray- To establish whether the results of mean PPDs are repro- Curtis dissimilarity (Bray and Curtis 1957). We focus on the ducible for single PPDs or are only acquired through

TABLE 4. Correlations between reduced dissimilarity matrices and the complete dissimilarity matrix for empirical data sets.

Data set s = 3 s = 4 s = 5 s = 10 Percentile for which R ≥ 0.90 s for which R ≥ 0.90 ps p1 AS 0.82 0.95 0.97 0.98 93 4 0.60 0.27 SB 0.92 0.96 0.97 0.99 98 3 0.45 0.24 PPM 0.91 0.94 0.96 0.9869 92 3 0.63 0.41 EM 0.95 0.97 0.99 0.999 80 3 0.57 0.31 KB 0.95 0.97 0.98 0.998 85 2 0.71 0.55 CF 0.92 0.95 0.96 0.99 82 3 0.63 0.34

Notes: Correlation coefficients between dissimilarity matrices generated from complete community composition data and dissimilarity matrix generated from reduced community composition matrix (using s most abundant species of each sample). All correlation values are highly significant (P < 0.001); ps provides the proportion of specimens that is comprised by the s most abundant species; p1 provides the proportion of specimens belonging to the most abundant species. Abbreviations of data sets as in Table 2. May 2018 ESTIMATES OF BETA DIVERSITY 1055

FIG. 2. Correlation coefficients between the dissimilarity matrix generated from complete community composition data and the matrix generated from reduced data using the empirical data sets. Percentiles (points, bottom axis) and number of species (triangles, top axis) are shown. All values are highly significant (P < 0.001). Abbreviations as in Table 2. averaging, sites of different PPD are selected from the data To test which factors affect the accuracy of the reduced sets and tested in the same way. The selected examples dissimilarity estimates, we tabulated the correlation values include sites with the highest and lowest dissimilarity values against ecological indices such as diversity for the simulated as well as randomly selected samples from each data set. and the empirical data sets. To increase the number of Ordination plots of the empirical data sets were created empirical data sets and the range of diversity values, we using non-metric multidimensional scaling based on Bray- divided each data set into subsets of similar communities Curtis dissimilarity. These were recreated using reduced data using cluster analysis and performed our calculations on sets that include only the 20, 10, and 5 most abundant spe- these subsets in addition to the original data sets. For the cies per site. Correlation tests were performed between the cluster analyses, the Ward error sum of squares hierarchical Euclidian ordination distances among the sites. clustering method was applied (Murtagh and Legendre 1056 VANESSA JULIE RODEN ET AL. Ecology, Vol. 99, No. 5

2014). Correlation tests between the parameters (total and TABLE 6. Factors influencing the correlation strength between the sample-level species richness, number of samples and speci- raw and reduced species composition matrices for the simulated data. mens, total and sample-level evenness, mean PPD) and the = correlation coefficient at s 5 most abundant species and at Parameter R (s = 5) the 90th percentile were performed to assess which factors influence the strength of the correlation between the reduced Total species richness (gamma) À0.80 Mean sample-level species richness (alpha) À0.68 and complete matrices. Calculations were performed using Number of samples 0 R Version 3.3.2 (R Core Team 2016) and the vegan (Oksa- Number of specimens À0.18 nen et al. 2016) and MASS packages (Venables and Ripley Total evenness À0.74 2002). Mean sample-level evenness À0.76 Mean proportional dissimilarity À0.33 RESULTS Notes: Correlation tests between the correlation coefficient at s = 5 and each of the parameters of the data sets. All correlations Beta diversity changes in a systematic fashion with are highly significant. increasing amounts of information in the empirical data sets (Fig. 1). The curve flattens rapidly and reaches the standard TABLE 7. Factors influencing the correlation strength between the = raw and reduced species composition matrices for the empirical error of the complete dissimilarity matrix between s 2 and data sets and their subsets. s = 10. The correlation coefficients between the reduced and Parameter R (s = 5) complete dissimilarity matrices show a systematic relation- Total species richness (gamma) À0.24 ship with the number of the most abundant species included Mean sample-level species richness (alpha) À0.06 in the reduced data sets, both in the simulated (Table 3) and Number of samples 0.05 the empirical (Table 4) data sets. In the simulated data sets, Number of specimens À0.09 > a correlation coefficient of 0.8 is reached when on average Total evenness À0.39 the eight most abundant species are included in the reduced Mean sample-level evenness À0.32 matrix. For the empirical data sets, a correlation coefficient Mean proportional dissimilarity À0.20 of >0.8 is reached when including just the three most abundant species. Correlation coefficients >0.9 are reached when Notes: Correlation tests between the correlation coefficient at s = 5 and each of the parameters of the data sets. Only total even- 2–4 species are included, representing the 80th to 98th per- ness has a significant correlation with R. centile of the empirical data sets (Fig. 2, Table 4). The 80th percentile represents an average of 2 (KB) to 24 (SB) domi- values are reached at s = 3(Fig.4).Intheempiricaldatasets, nant species per site. The correlations are all highly signifi- high correlation values are reached for all values of evenness, cant, even with only the single most abundant species although higher evenness also yields slightly lower correlation considered in each sample (s = 1). The simulated data sets show a moderately high mean correlation coefficient of 0.66 when species in the 70th percentile are included (Table 5). Several ecological parameters significantly influence the performance of the approach that considers dominant species, especially in the simulated data (Table 6). For example, a high species richness or high evenness dampens the correlation between the reduced and complete matrices. Total and sample-level evenness affect the strength of the correlation among the 31 empirical data sets (six original data sets and 25 subsets; Table 7), but only total evenness has a significant influence. The simulated data yield high correlation values when evenness is smaller than 0.6 (Fig. 3). Higher evenness values require a larger number of dominant species to be included. For a total species richness <50, high correlation

TABLE 5. Mean correlation coefficient between the dissimilarity matrices calculated including only a certain percentile of the specimens belonging to the most abundant species and the complete dissimilarity matrices, across all simulated data sets.

Percentile Correlation coefficient SD 97.5 0.32 0.18 95 0.37 0.21 90 0.44 0.23 85 0.50 0.24 80 0.57 0.24 FIG. 3. Mean correlation coefficients using the simulated data 70 0.66 0.25 sets for different numbers of dominant species (s) binned by total evenness. May 2018 ESTIMATES OF BETA DIVERSITY 1057

TABLE 8. Factors influencing the correlation strength between the raw and reduced species composition matrices for the simulated data.

Parameter R (at 90th percentile) Total species richness (gamma) 0.08 Mean sample-level species richness (alpha) À0.02 Number of samples À0.05 Number of specimens 0.02 Total evenness À0.02 Mean sample-level evenness À0.05 Mean proportional dissimilarity 0.08

Notes: Correlation tests between the correlation coefficient at the 90th percentile and each of the parameters of the data sets. There are no notable correlations (although all values are statistically significant).

correlation coefficients: including the five most abundant species results in a mean correlation coefficient of 0.9 (Table 3). The pairwise comparisons are very similar to those using averaged dissimilarity (Appendix S1: Figs. S1, S2). The results of our method using only the most abundant species are therefore robust and are not an effect of averaging. The effect of most ecological parameters is minimized when using species that comprise a certain percentile of specimens at sites (Table 8). For example, percentiles reduce FIG. 4. Mean correlation coefficients using the simulated data the effect of evenness and richness. sets for different numbers of dominant species (s) binned by total Presence–absence data yield less conclusive results. In the number of species in the data sets. empirical data sets, the dissimilarity of the reduced matrices lies within one standard error of the complete matrix for values between s = 4 (PPM) and s = 23 (SB). However, in the AS data set, none of the mean Sørensen dissimilarity values reach the standard error range (Appendix S1: Fig. S3). The correlation coefficient shows a similar pattern for presence– absence data (Appendix S1: Fig. S4) as for abundance data, although more species are required to yield high correlation values (Appendix S1: Table S1). Just as the correlations of raw distances among sites (Appendix S1: Fig. S5), the correlations are also strong for distances of sites in ordination space. The Euclidian distances of site coordinates in a two-dimensional nonmetric multidimensional scaling analysis are strongly cross-correlated between the full and reduced data sets, when even just the five most abundant species are considered (Table 9, Fig. 6). For the CF data set, the ordination plots of the complete matrix and one reduced to 20 abundant species show a similar pattern (Fig. 7). The same holds true for the

TABLE 9. Correlation values between the ordination distances using NMDS among all sites of the complete data set and a reduced data set.

Data set R (s = 20) R (s = 10) R (s = 5) AS 0.78 0.79 0.69 SB 0.91 0.93 0.76 FIG. 5. Mean correlation coefficients using the empirical data PPM 0.85 0.77 0.63 sets and their subsets for different numbers of dominant species (s) EM 0.73 0.59 0.59 binned by total evenness. KB 0.997 0.98 0.78 CF 0.96 0.78 0.48 values (Fig. 5). Species richness does not have a significant < influence in the empirical data sets. Subsetting the simulated Notes: All correlation values are highly significant (P 0.001). For s = 5 and s = 10 in the EM and AS data sets and s = 5 in the data sets to those with an evenness ≤0.6 yields higher mean SB data set, data is insufficient for NMDS. 1058 VANESSA JULIE RODEN ET AL. Ecology, Vol. 99, No. 5

FIG. 6. Euclidian ordination distances among sites using the complete data sets and those including only the five most abundant species per sample. Abbreviations as in Table 2. other data sets (Appendix S1: Figs. S6–S10). The EM data obvious differences that distinguish these data sets except set, while also showing a good correlation, shows common for the low number of sites, although further testing has complete dissimilarities in the reduced data set, which pro- shown no correlation between the number of samples and duces an odd plot (Fig. 6d). the correlation strength. Samples were taken to cover the The dissimilarity values in the empirical data sets exhibit a habitat variability of the region, but the number of replicates left-skewed distribution (Fig. 8). The CF and KB data sets per habitat is low. The ordination plots and frequency contain few values under 0.9. The other four empirical data distributions of dissimilarity values support the interpreta- sets show a wider range of pairwise dissimilarity values, tion that within-habitat sampling is important (Fig. 8, whereas the PPM data set shows the largest variation of values. Appendix S1: Figs. S6a–S10a). The small number of domi- Our approach is therefore applied to data sets with variable nant species needed to reach the error range of the complete distributions of PPD values, although high PPD values dissimilarity matrix is due to the much higher standard dominate. error, which might be ascribed to the low number of sites. The dissimilarity of the reduced matrices in the recent AS and SB data sets shows unusual patterns compared with the DISCUSSION fossil data sets. The two recent data sets also yield slightly lower correlation results between the two measures of alpha Our analysis of alpha diversity supports the conclusion diversity (Appendix S1: Table S2, Fig. S11). There are no of a previous study (Kowalewski et al. 2006) that the May 2018 ESTIMATES OF BETA DIVERSITY 1059

FIG. 7. Ordination plots of the CF data set using varying numbers of abundant species (for other data sets, see Appendix S1). Colors denote matching sites. The axes were adjusted in panel c for easier comparison.

Berger-Parker dominance index is strongly correlated with While evenness and species richness show a strong nega- Shannon entropy. Knowing the proportion of the relative tive relationship with the quality of the correlation, all abundance of just the most abundant species in a commu- parameters except the number of sites have some influence. nity can be sufficient to characterize its diversity. Of course, these parameters are not independent. In general, We find that beta diversity can be depicted similarly well we can say that with a low to moderate evenness, including if only a small fraction of the species in a community is con- only five of the dominant species yields very good estimates sidered. Although looking at just the single most abundant of beta diversity. When using data sets with a very high even- species tends to inflate beta diversity estimates, the estimates ness (≥0.8), we recommend considering the ten most abun- quickly become more robust with a few more species dant taxa. In general, including only the 80th percentile of assessed. Beta diversity estimates and ordinated distances specimens from the most abundant species is sufficient to based on five species are usually statistically indistinguish- depict the beta diversity of a data set. able from the estimate of the full community. In the empiri- Measures of beta diversity with a fixed maximum tend to cal data, we observe a flattening curve between 5 and 10 fail when high dissimilarity values abound. Data sets includ- dominant species. This is similar to rarefaction curves, ing many pairwise dissimilarities >0.9, such as the EM data which level off when the sample size is large enough. set, may require an adjustment developed by De’ath (1999) Regarding the top percentiles, the curve generally flattens to yield valid ordination results. However, our simplification between the 90th and 80th percentiles. yields robust results even for data sets dominated by high The simulated data sets show lower average correlation val- dissimilarities. ues between full and reduced data sets when compared to the Although species abundance information is more accu- empirical data sets. This is likely due to their large coverage rate, presence–absence data can also provide a good depic- of ecological metrics. Many of these metrics are unlikely to tion of beta diversity for most data sets when considering co-occur in local and regional habitats. Nevertheless, even in only the most abundant species. To attain a good depiction the simulated data, including only the 20 most abundant spe- of dissimilarity without including abundance counts, the 20 cies yields results that are statistically indistinguishable from most abundant taxa should be identified per sample before the full data. Although the number of species that need to be calculating the Sørensen dissimilarity. Of course, it is still included for accurate results varies with evenness, the neces- necessary to know which species are most abundant. There- sary number of species can be estimated using percentiles. fore, our method cannot be applied to existing data sets that 1060 VANESSA JULIE RODEN ET AL. Ecology, Vol. 99, No. 5

FIG. 8. Distribution of pairwise proportional dissimilarity values within empirical data sets. Variation of beta diversity is strongly left skewed. only give information on the presence or absence of taxa. multiplicative beta diversity is based on alpha and The classical, presence–absence-based similarity measures gamma diversity measures, such as species richness, Shan- often underestimate similarity between assemblages and are non entropy, or the Simpson index, it is susceptible to not robust to differing sample sizes (e.g., Wolda 1981). the same biases as those measures, which can be substan- Indices that do not take species frequency into account are tial (e.g., Lande 1996). Methods have been developed to strongly biased by sampling intensity and strategy, taphon- acquire a beta diversity estimate independent of alpha omy (the post-mortem fate of organisms), and species split- diversity (Jost 2007), or to account for the effects of ting and are not ecologically meaningful (Jost 2007). biases on alpha and gamma diversity (Lande 1996, Chao Pairwise dissimilarity characterizes differences in com- et al. 2005). However, mean pairwise dissimilarity is still munity composition better than other beta diversity more comparable across data sets that vary in size and indices and should be favored as a beta diversity measure sampling design (Marion et al. 2017). in ecological studies for several reasons. Multiplicative as As proportional similarities are also subject to sam- well as additive beta diversity are dependent on gamma pling bias, Chao et al. (2005) have proposed an adjust- diversity (Kraft et al. 2011) and the number and size of ment by incorporating the estimated number of rare sampling units (Soininen 2010, Marion et al. 2017). Since unsampled species. Their indices are “better suited than May 2018 ESTIMATES OF BETA DIVERSITY 1061 the corresponding classic indices for assessing composi- Berger, W. H., and F. L. Parker. 1970. Diversity of planktonic fora- tional similarity between samples that differ in size, are minifera in deep-sea sediments. Science 168:1345–1347. known or suspected to be undersampled, or are likely to Bloom, S. A. 1981. Similarity indices in community studies: potential pitfalls. Marine Ecology Progress Series 5:125–128. contain numerous rare species” (p. 158). However, it is Bouchet, P., P. Lozouet, P. Maestrati, and V. Heros. 2002. Assessing shown here that rare species have a statistically minor the magnitude of species richness in tropical marine environ- effect on diversity partitioning. ments: exceptionally high numbers of molluscs at a New Caledo- Sample-size standardization, such as rarefaction, extrapo- nia site. Biological Journal of the Linnean Society 75:421–436. lation (Chao et al. 2014), shareholder quorum subsampling Bray, J. R., and J. T. Curtis. 1957. An ordination of the upland forest (Alroy 2010), or equal coverage (Chao and Jost 2012), is communities of southern Wisconsin. Ecological Monographs necessary for diversity metrics like species richness or pres- 27:325–349. Bush, A. M., M. J. Markey, and C. R. Marshall. 2004. Removing ence–absence-based similarity indices. Standardization is bias from diversity curves: the effects of spatially organized biodi- not always an accurate method, as it is sensitive to the spa- versity on sampling-standardization. Paleobiology 30:666–686. tial characteristics of diversity (Bush et al. 2004). To limit Caruso, T., G. Pigino, F. Bernini, R. Bargagli, and M. Migliorini. the effects of sample size on beta diversity, a new type of rar- 2007. The Berger–Parker index as an effective tool for monitoring efaction has been suggested (Stier et al. 2016). Nevertheless, the biodiversity of disturbed soils: a case study on Mediterranean we find that the mean proportional dissimilarity and the dis- oribatid (Acari: Oribatida) assemblages. Biodiversity and Conser- vation 16:3277–3285. similarity among sites are driven by dominant species. Chao, A., and L. Jost. 2012. Coverage-based rarefaction and extrap- The empirical data sets differ in environmental setting, olation: standardizing samples by completeness rather than size. habitat heterogeneity, sample size, and sampling method. Ecology 93:2533–2547. This variability leads us to postulate that our method can be Chao, A., R. L. Chazdon, R. K. Colwell, and T. J. Shen. 2005. A applied to many types of quantitative community composi- new statistical approach for assessing similarity of species compo- tion data. Our simplification will facilitate the characteriza- sition with incidence and abundance data. Ecology Letters 8: 148–159. tion of diversity partitioning in large data sets and yield less Chao, A., N. J. Gotelli, T. Hsieh, E. L. Sander, K. Ma, R. K. Col- biased results. For example, our approach is less prone to well, and A. M. Ellison. 2014. Rarefaction and extrapolation with sampling and identification bias, as only a few common spe- Hill numbers: a framework for sampling and estimation in species cies need to be identified, especially in cases in which the diversity studies. Ecological Monographs 84:45–67. sampling and processing are performed by students or, for Davidowitz, G., and M. L. Rosenzweig. 1998. The latitudinal gradi- instance, in carrying out a census for ecological studies, by a ent of species diversity among North American grasshoppers layperson. Our method also requires less time spent on (Acrididae) within a single habitat: a test of the spatial heterogeneity hypothesis. Journal of Biogeography 25:553–560. taxon identification, as most researchers can identify the De’ath, G. 1999. Extended dissimilarity: a method of robust estima- common species from their respective fields with little effort, tion of ecological distances from high beta diversity data. Plant and a large part of their work is put into identifying rare Ecology, 144:191–199. species. In paleocommunity data sets, species that were rare Faith, D. P., P. R. Minchin, and L. Belbin. 1987. Compositional dis- in the living assemblage are often filtered out through similarity as a robust measure of ecological distance. Vegetatio preservation bias. Fossil and recent data sets are therefore 69:57–68. Fenton, I. 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SUPPORTING INFORMATION Additional supporting information may be found in the online version of this article at http://onlinelibrary.wiley.com/doi/10.1002/ecy. 2201/suppinfo Reliable estimates of beta diversity with incomplete sampling. Vanessa Julie Roden, Ádám T. Kocsis, Martin Zuschin, and Wolfgang Kiessling. Ecology. 2018.

Appendix S1

Tables

Table S1: Correlations between degraded dissimilarity matrices and complete dissimilarity matrix using presence-absence data for empirical datasets.

Dataset Sørensen standard n=3 n=4 n=5 n=10 n=20 dissimilarity error AS 0.53 0.073 0.34 0.43* 0.49** 0.71*** 0.81*** SB 0.72 0.040 0.60*** 0.68*** 0.82*** 0.87*** 0.88*** PPM 0.77 0.016 0.42*** 0.48*** 0.56*** 0.71*** 0.87*** EM 0.77 0.019 0.59*** 0.70*** 0.78*** 0.96*** 0.994*** KB 0.83 0.012 0.58*** 0.67*** 0.73*** 0.94*** 0.996*** CF 0.91 0.014 0.51*** 0.57*** 0.62*** 0.82*** 0.96***

Correlation coefficients using presence-absence data. The mean pairwise proportional dissimilarity using presence-absence data (Sørensen dissimilarity) is based on the presence-absence community composition matrix and calculated as the ratio of the number of mismatches of species presence to the total number of presences in both samples. All data were converted to binary data after determining the most abundant species. AS = Adriatic Sea, Mediterranean, recent; SB = Safaga Bay, Red Sea, recent; PPM = Plio-Pleistocene molluscs, Italy; EM = Eocene molluscs, France; KB = Kachchh Basin, India, Jurassic; CF = Cassian Formation, Italy, Triassic.

Table S2: Correlations between the Berger-Parker dominance index and the Shannon entropy in empirical datasets.

Dataset Correlation p-value coefficient AS -0.83 0.01 SB -0.76 0.003 PPM -0.89 <0.0001 EM -0.87 <0.0001 KB -0.95 <0.0001 CF -0.92 <0.0001

The Berger-Parker dominance index and the Shannon entropy were calculated for each sample. The correlation coefficient and p- value are given for each dataset. Abbreviations of datasets as in Table 2. The mean Berger-Parker dominance index and mean Shannon entropy of the simulated datasets are also tightly correlated (R = -0.93, p < 0.0001).

1 Figures Figure S1. Pairwise proportional dissimilarity (PPD) from various selected (very low and high PPD) and random samples from empirical dataset AS. Points depict the PPD for the s most abundant species from each sample included in the matrix. Lines depict PPD from complete matrix.

Figure S2. Pairwise proportional dissimilarity (PPD) from various selected (very low and high PPD) and random samples from empirical dataset CF. Points depict the PPD for the s most abundant species from each sample included in the matrix. Lines depict PPD from complete matrix.

Figure S3. Dissimilarity using presence-absence data (Sørensen dissimilarity). Points depict the mean PPD for the s most abundant species from each sample included in the species composition matrix. Lines depict dissimilarity of the complete species composition matrix. Grey boxes indicate the bootstrapped standard error of dissimilarity of the complete matrix. AS = Adriatic Sea, Mediterranean, recent; SB = Safaga Bay, Red Sea, recent; PPM = Plio-Pleistocene molluscs, Italy; EM = Eocene molluscs, France; KB = Kachchh Basin, India, Jurassic; CF = Cassian Formation, Italy, Triassic.

Figure S4. Correlation coefficient between binary dissimilarity (Sørensen) matrix generated from complete community composition data and matrix generated from degraded data, using the s most abundant species of each sample. Black points depict significant values (p-value < 0.05).

Figure S5. Pairwise proportional dissimilarities (PPD) among sites using the complete datasets and those including only the 5 most abundant species per sample. Abbreviations as in Fig. S3.

Figures S6-S10. Ordination plots of the empirical datasets using varying numbers of abundant species. Colors denote matching sites. Abbreviations as in Fig. S3.

Figure S6

Figure S7

Figure S8

Figure S9

Figure S10

Figure S11. Correlation between Shannon entropy and the Berger-Parker dominance index of samples within datasets. Abbreviations as in Fig. S3.

Publication #2

Roden, V. J., Hausmann, I. M., Nützel, A., Seuss, B., Reich, M., Urlichs, M., Hagdorn, H. & Kiessling, W. 2019. Fossil liberation: A model to explain high biodiversity in the Triassic Cassian Formation. Palaeontology. https://doi.org/10.1111/pala.12441. and the supplementary data package: Roden, V. J., Hausmann, I. M., Nützel, A., Seuss, B., Reich, M., Urlichs, M., Hagdorn, H. & Kiessling, W. 2019. Data from: Fossil liberation: a model to explain high biodiversity in the Triassic Cassian Formation. Dryad Digital Repository. https://doi.org/10.5061/dryad.6s5651k. reproduced with permission

[Palaeontology, 2019, pp. 1–18]

FOSSIL LIBERATION: A MODEL TO EXPLAIN HIGH BIODIVERSITY IN THE TRIASSIC CASSIAN FORMATION by VANESSA JULIE RODEN1 , IMELDA M. HAUSMANN2,3, ALEXANDER NUTZEL€ 2,3,4 , BARBARA SEUSS1 ,MIKEREICH2,3,4 , MAX URLICHS5, HANS HAGDORN6 and WOLFGANG KIESSLING1 1GeoZentrum Nordbayern, Section Palaeobiology, University Erlangen-Nurnberg,€ Loewenichstr. 28, 91054 Erlangen, Germany; [email protected], [email protected], [email protected] 2SNSB – Bayerische Staatssammlung fur€ Pal€aontologie und Geologie, Richard-Wagner-Str. 10, 80333 Munchen,€ Germany 3Department of Earth & Environmental Sciences, Ludwig-Maximilians-Universit€at Munchen,€ Richard-Wagner-Str. 10, 80333 Munchen,€ Germany 4GeoBio-Center, Ludwig-Maximilians-Universit€at Munchen,€ Richard-Wagner-Str. 10, 80333 Munchen,€ Germany 5Staatliches Museum fur€ Naturkunde, Rosenstein 1, 70191 Stuttgart, Germany; [email protected] 6Muschelkalkmuseum Ingelfingen, Schlossstraße 11, 74653 Ingelfingen, Germany; encrinus@hagdorn-ingelfingen.de

Typescript received 8 January 2019; accepted in revised form 8 May 2019

Abstract: With 1429 animal species, the Triassic Cassian contrast to conservation Lagerst€atten, liberation Lagerst€atten Formation in the Dolomites, Southern Alps (Italy), yields like the Cassian Formation originate from normal marine the highest species richness reported from any spatially con- conditions but low-grade diagenesis. Molluscs contribute strained pre-Quaternary formation known to science. The substantially to species richness, comprising 67% of all inver- high preserved diversity is partly attributable to a high pri- tebrate species in the Cassian Formation. The gastropod mary diversity governed by the tropical setting, increasing dominance (39% of all species) is nearly as great as in alpha diversity, and the breadth of habitats spurring beta Recent tropical settings, contradicting the concept of a sub- diversity. More important is the excellent preservation of stantial Cenozoic rise. fossils and the ease with which they can be extracted from the poorly lithiﬁed sediments. We propose the term ‘libera- Key words: diversity, Cassian Formation, gastropod domi- tion Lagerst€atten’ to capture this preservational window. In nance, aragonite preservation, fossil Lagerst€atten.

H IGH diversity in an ecosystem is often equated with true biological diversity in ancient ecosystems (Alroy ecosystem complexity and stability (McCann 2000). Com- 2010b). paring diversity among ecosystems and sites is difﬁcult Excluding samples from poorly or unlithiﬁed rocks and even in modern environments, and the fossil record yields those with aragonite preservation might be appropriate many more challenges for the assessment of true biodiver- when comparing diversity through time in order to cor- sity. Variations in sampling intensity, differences in rect for taphonomic biases (Alroy et al. 2008). However, preservation, and the availability of fossil-bearing rocks targeting such samples explicitly may allow for a better are some of the problems palaeontologists face when comparison of biodiversity in ancient ecosystems. This studying diversity across time and space (Raup 1972; approach was previously taken by Bambach (1977) to Koch & Sohl 1983; Smith & McGowan 2011). Other track marine community diversity in different settings issues in the comparison of diversity patterns are time over time. In light of new data, we revisit Bambach’s averaging and spatial and temporal extent of fossil depos- approach, focusing on peak diversities in fossil Lagerst€at- its (Tomasovych & Kidwell 2010; Kidwell & Tomasovych ten and well-sampled formations. Fossil Lagerst€atten pro- 2013). Subsampling techniques have provided opportuni- vide snapshots of what may be closest to true diversity in ties to reduce the effects of sampling biases related to dif- different points in time (Nudds & Selden 2008). ferences in sample size (Alroy et al. 2001, 2008; Bush Whereas fossil Lagerst€atten may represent a good proxy et al. 2004; Alroy 2010a, 2015). However, although sub- for the true biodiversity in a particular palaeoenviron- sampling accounts for sampling or preservation-induced ment, they vary in preservational mode, fossil abundance, variation of biodiversity, it is not suitable for assessing and spatial and temporal extent. Simply compiling raw

© The Palaeontological Association doi: 10.1111/pala.12441 1 2 PALAEONTOLOGY species richness of fossil Lagerst€atten may thus be mis- late Ladinian and early Carnian (Urlichs 2017). Histori- leading. Conservation Lagerst€atten are defined by excel- cally, the terms ‘Cassian Formation’ and ‘Cassian Beds’ lent preservation, especially of articulated multi-element have also been used to describe sediments from the aus- skeletons and often including soft-part preservation, triacum and dilleri zones in what is now called the Hei- whereas concentration Lagerst€atten represent accumula- ligkreuz Formation. We apply the definition Cassian tions of more or less disarticulated fossils (Seilacher Formation sensu lato herein, that is, in a traditional sense 1970). Some fossil Lagerst€atten cannot be categorized into for all clayey and marly, Ladinian–Carnian sediments either of these two types, as they feature a high number deposited in the interplatform basins of the Dolomites. of fossils and good preservation, primarily due to a low The Cassian Formation therefore includes some fossil grade of lithification of the source sediments, while being localities in the Cortina basin (e.g. the highly diverse deposited under normal marine conditions. We refer to occurrences of Misurina and Alpe di Specie) that are these Lagerst€atten as ‘liberation Lagerst€atten’ and present reported as belonging or being equivalent to the Heiligk- the Triassic Cassian Formation as a prime example of this reuz Formation today (Bizzarini & Laghi 2005; Keim new Lagerst€atten type. et al. 2006; Urlichs 2017; Nose et al. 2018). The vast Scientific study started with Munster€ (1834), and since majority of occurrences representing diverse benthic then numerous publications have dealt with palaeontolog- assemblages of the Cassian Formation sensu lato range ical aspects of the Cassian Formation. Close to 1800 from the aon to the austriacum Zone. According to Grad- animal species have been named from this tropical stein et al. (2012), the base of the aon Zone is at 236 Ma reef-to-basin setting, making it the most diverse Mesozoic and the top of the austriacum zone is at 231 Ma. Earlier formation. To discern the reasons for the high preserved occurrences are largely restricted to ammonites, ossicles diversity, we first provide estimates of alpha, beta and of planktonic crinoids, and microfossils. gamma diversity using taxonomically revised occurrence data. The assessment of preservational bias and a Phanerozoic-scale comparison of well-studied Lagerst€atten Diagenesis and formations leads us to reveal the role of liberation Lagerst€atten in the assessment of ancient biodiversity pat- Scherer (1977) and Russo et al. (1991) interpreted the terns in normal marine ecosystems. low diagenetic alteration of corals and calcareous sponges and erratic boulders from Alpe di Specie and Settsass as a result of sealing of the carbonate bodies by marly sedi- GEOLOGICAL SETTING ments and early cementation. This sealing reduced the permeability to a minimum (hindering pore fluid circula- The Middle to Late Triassic (Ladinian–Carnian) Cassian tion) and facilitated preservation of aragonite. Low lithifi- Formation is exposed in the Dolomites, Southern Alps, cation of the marly sediments of the Cassian Formation is northern Italy (Fig. 1). It consists of up to 300 m thick, undoubtedly also a result of low-grade diagenetic alter- predominantly argillaceous basin sediments and is dis- ation. The low-grade diagenesis of skeletal material from tributed over an area of c. 500 km2. The Cassian Forma- the Cassian Formation is well established. Based on XRD- tion comprises shallow and deeper water sediments, analysis, Nutzel€ et al. (2010) reported aragonitic shells of deposited between carbonate platforms that now form the megalodontoid bivalves from Misurina (Fig. 1). Original Cassian and Schlern Dolomite (e.g. Fursich€ & Wendt skeletal microstructures of sponges, corals and molluscs 1977; Bosellini 1998; Hausmann & Nutzel€ 2015). These (such as nacre and crossed lamellar microstructures) are prograding platforms grew during the Middle and Late preserved (e.g. Wendt 1974; Senowbari-Daryan 1989; Triassic and shaped the environment in which the basin Bandel 1992, 2007; Hautmann 2001; Fryda et al. 2009; sediments were deposited (Keim et al. 2001). The tropical Nutzel€ & Kaim 2014; Hausmann & Nutzel€ 2015). Exam- setting in the Western Tethys offered warm water temper- ples for the high quality of preservation are shown in Fig- atures with seasonality and fresh water influx comparable ure 2. Because fossils from the Cassian Formation are to modern tropical environments (Nutzel€ et al. 2010). commonly very well preserved, many more taxonomic Several depositional environments are recorded in the characters can be evaluated, and more taxa were Cassian Formation: a nearshore back-reef area with patch described. However, many fossils are less well-preserved, reefs and the sediments intercalated between these; the and encrustation and recrystallization do occur (Fig. 2D carbonate platform; and the basin, which includes shallow shows aragonitic crossed lamellar shell beginning transfor- areas, the slope and the central basin (Fursich€ & Wendt mation to blocky calcite). 1977; Table 1). The softness of the marls facilitates weathering as well The Cassian Formation comprises the late regoledanus, as easy disaggregation of samples in the laboratory with canadensis, aon and aonoides ammonite biozones in the water, hydrogen peroxide or tensides, making an RODEN ET AL.: BIODIVERSITY IN LIBERATION LAGERSTAT€ T E N 3 unproblematic fossil extraction by wet-sieving possible. However, in the older literature, concise information on Due to these factors, small metazoan fossils are unusually the localities is often lacking, reporting only ʻCassian common. Morphological details, such as intricate orna- Bedsʼ. We researched which species are confined to the mental patterns, are usually preserved, allowing to distin- Cassian (‘formation singletons’) and which have also been guish a high number of species. reported from other localities. To put our results in context, several other well-known and highly diverse fossil Lagerst€atten were assessed based MATERIAL AND METHOD on published (and one unpublished) literature compilations and the Paleobiology Database (PBDB; https://paleo We assessed 150 publications on the Cassian Formation, biodb.org). The effect of preservation on Cassian diversity comprising original taxonomic descriptions, biostrati- was assessed by comparison with other tropical sites of graphical studies, literature compilations and quantitative the same age. palaeoecological analyses. In many cases, we critically At the level of named formations, we compared the evaluated the taxon descriptions and added results from number of species from all formations with more than our own samples to compile a list of valid species (see 500 species using only data from the PBDB. So as to not Roden et al. (2019) for the species list (appendix S1), ref- bias diversity estimates in favour of our focal Lagerst€atte, erences and explanatory notes (appendix S2)) reported no additional information has been entered into the from the Cassian. In addition to taxonomic information PBDB within the scope of this work. The Margalef diver- and suprageneric (class, subphylum) attribution, we col- sity index was computed for all formations, using the lected information on shell mineralogy. As far as possible, equation D = (S À 1)/ln (n), where S is the number of we also tried to assign localities to species records. species and n the number of specimens or occurrences

FIG. 1. Map of reported localities in the Cassian Formation (dots) and cities (stars). Stuores encompasses several collection sites over a larger area (grey). Colour online. 4 PALAEONTOLOGY

TABLE 1. Stratigraphical age and depositional environment of localities in the Cassian Formation used in literature compilation. Locality Environment Source Ammonite Substage* References Comments biozone

Campo Transported Allochthonous Probably Julian Pers. obs. from shallow austriacum reef area Carbonin Cianzope Late aonoides Julian Urlichs (2017) Cason dei Caai Ciou del Conte Costalaresc Shallow water, Autochthonous Austriacum Julian Fursich€ & Wendt Wave base, above storm soft-bottom (1977), Urlichs wave base (2017), pers. obs. Forcella Col Duro Forcella di Shallow water, Autochthonous Aonoides Julian HH; MU; F. Fursich€ Giau very ﬁeld notes proximal Lago Basin, soft- Probably Julian Pers. obs. Antorno bottom austriacum Milieres/ Aonoides & Julian Bizzarini et al. (1986), Dibona austriacum Urlichs (2012) Misurina Covers various Predominately Probably Julian Wendt & Fursich€ Probably transported skilift environments allochthonous austriacum (1980), Keim et al. from a patch reef, with (literature (?aonides), (2006), Nutzel€ et al. some autochthonous mostly partly (2010), Urlichs basin deposits; shallow refers to Heiligkreuz (2012) and deep-water deposits this Fm. (AN); upper subtidal or locality) at least within the photic zone (Wendt & Fursich€ 1980); deeper water depths, reaching 100 m and more (Urlichs 2012) Misurina Predominately Probably Julian Bizzarini & Laghi landslide autochthonous austriacum (2005, loc. 4), pers. (?aonides), obs. partly Heiligkreuz Fm. Pocol Aonoides Julian Bizzarini et al. (1986) Rumerlo Very proximal Allochthonous Aonoides Julian Urlichs (2012), (back reef) pers. obs. Sasso di Aonoides & Julian & Urlichs (2017) Stria aon ʻCordevolianʼ Staolin Deep subtidal Austriacum Julian F. Fursich€ ﬁeld notes; shelf; also Urlichs (2017) input from reef Settsass Shallow basin, Autochthonous Probably aon ʻCordevolianʼ Fursich€ & Wendt Also a shell bed from reef soft-bottom (1977), Urlichs front or fore-reef area; (1994), Nutzel€ & mixed with parts from Kaim (2014), pers. carbonate platform; obs. <200 m depth

(continued) RODEN ET AL.: BIODIVERSITY IN LIBERATION LAGERSTAT€ T E N 5

TABLE 1. (Continued) Locality Environment Source Ammonite Substage* References Comments biozone

Alpe di Very shallow Predominately Austriacum Julian Fursich€ & Wendt Some transported Specie water, back- autochthonous (possibly (1977), Russo et al. elements reef, soft- upper) (1991), Urlichs bottom (2017) Stuores Basin, ?slope Mixed Aonoides & Julian & Fursich€ & Wendt Community from shallow & carbonate aon (& ʻCordevolianʼ (1977), Bizzarini water carbonate platform canadensis (& et al. (1986), Mietto platform (probably & Langobardian) et al. (2008), lagoon settings), regoledanus) Hausmann & Nutzel€ transported into basin; (2015), Urlichs mixing of platform biota (2017) with slope or basin assemblages also possible Tamarin Austriacum Julian Urlichs (2017) Vervei Aonoides Julian Urlichs (2012) Pescol Base Punta Gusella Ruones Youngest ʻCordevolianʼ Urlichs (2017); MU aon Picolbach Aon ʻCordevolianʼ Urlichs (2000, 2017) Rio Stueres Aonoides & Julian & Urlichs (2012) aon ʻCordevolianʼ Rio di Aonoides Julian Urlichs (2012) Foves Piz Deep neritic Aonoides Julian Urlichs (2012); Below 100 m water depth Lavarella zone (Mietto et al. 2008: canadensis) Masareis Aonoides Julian Urlichs (2017) Saverie Aonoides Julian Urlichs (2017) Pedraces ʻCordevolianʼ Kristan-Tollmann (1960)

*Substages based on Urlichs 2017.

(Margalef 1958). Although the underlying assumption of multiple-site dissimilarity indices, which are derived from a log-series distribution is often not veriﬁed, the Margalef the respective pairwise dissimilarity indices. A randomized index provides a suitable comparative framework of species accumulation curve is generated using 1000 permu- diversity when individual species abundance data are not tations. Due to the large number of studies from various at hand (Magurran 1988; Kiessling 2002). ﬁelds and on different taxonomic groups, and due to the Using data from the PBDB, the sampled-in-bin genus many sites that have undergone intensive study, it is likely richness of all marine invertebrate taxa was counted, and that we acquire a good representation of the true commu- the proportions of benthic molluscs (all molluscs exclud- nity composition and diversity patterns. The results pro- ing cephalopods), gastropods and bivalves were calculated vide a baseline of the distribution of diversity in the for the Phanerozoic, binned by geological stages. Using Cassian Formation. Calculations were performed using R proportions avoids some of the biases that arise when v.3.5.0 (R Core Team 2016) and the vegan (Oksanen et al. comparing taxon richness values (Madin et al. 2006). 2016) and divDyn packages (Kocsis et al. 2019). Based on our compilation of Cassian species, we calculate and discuss alpha, beta and gamma diversity. Beta diversity is partitioned into spatial species turnover (Simp- RESULTS son dissimilarity index) and a nestedness component (Simpson dissimilarity index subtracted from Sørensen A total of 1517 species are considered to be valid in the dissimilarity index), calculated using Baselga’s (2010) Cassian Formation (Roden et al. 2019, appendix S1). This 6 PALAEONTOLOGY

FIG. 2. Examples of exceptional preservation. A–B, ossicles of free-swimming crinoid Axicrinus sp. from Misurina skilift, Cassian Fm., with well-preserved stereom structure. C, Ampezzopleura hybridopsis as an example of a well-preserved microgastropod from Misurina landslide, Cassian Fm., with protoconch representing a larval shell of the planktotophic type (ﬁrst four whorls). D, aragonitic crossed lamellar shell microstructure of a neritimorph gastropod from Costalaresc, Cassian Fm.; diagenetic calcite rhombohedra are growing on the inside of the specimen (lower part). Scale bars represent: 10 lm (A); 50 lm (B, D); 100 lm (C). number includes protists and species with uncertain recorded from Alpe di Specie, Stuores, Misurina, Campo genus attributions but excludes synonyms and nomina and Costalaresc (Roden et al. 2019, appendix S2, table dubia. A total of 3263 species occurrences are known S1). We count 1429 species of animals, of which 1421 are from the Cassian, 2867 of which can be attributed to invertebrates and 8 are chordates. Molluscs comprise 67% speciﬁc localities. The highest numbers of species are of all invertebrates, with gastropods being the most RODEN ET AL.: BIODIVERSITY IN LIBERATION LAGERSTAT€ T E N 7

TABLE 2. Species per clade from the Cassian Formation based on the literature compilation. Phylum Class/Subphylum Species Proportion of Proportion of total species invertebrates

Mollusca Total molluscs 950 0.63 0.67 Gastropoda 552 0.36 0.39 Bivalvia 300 0.20 0.21 Cephalopoda 87 0.06 0.06 Polyplacophora 6 <0.01 <0.01 Scaphopoda 5 <0.01 <0.01 Echinodermata 131 0.09 0.09 Brachiopoda 103 0.07 0.07 Cnidaria 93 0.06 0.07 Porifera 100 0.07 0.07 Foraminifera 73 0.05 – Bryozoa 5 <0.01 <0.01 Cyanobacteria 2 <0.01 – Chlorophyta 1 <0.01 – Arthropoda Ostracoda 28 0.02 0.02 Annelida Polychaeta 11 0.01 0.01 Rhodophyta Rhodophyceae 3 <0.01 – Dinoﬂagellata Dinophycea 4 <0.01 – Chordata Tunicata 5 <0.01 – Vertebrata 3 <0.01 – Other Ichnofossil 3* <0.01 – Problematica 5 <0.01 – Total species 1517 Total animal species 1429 Total invertebrate species 1421 Total benthic invertebrate species 1334

*Not counted in total species. strongly represented class by far (39%), and bivalves Hunsruck€ Slate), with the exception of the Pennsylvanian (21%) in second place (Table 2). Echinoderms, bra- Finis Shale, which deviates strongly from the other data- chiopods, cnidarians and poriferans are also well-repre- sets with a singleton proportion of 0.08 (Table 5). PBDB sented phyla. data yields a proportion of 0.68 for the Cassian Forma- Comparing the richness of animal species among sev- tion. Excluding formation singletons, the most species- eral fossil Lagerst€atten known for their high diversity, rich fossil Lagerst€atten by far are the Cassian Formation good preservation and long record of study, the Cassian and the Finis Shale. is the most diverse (Table 3). The second most species Molluscs have always contributed to assemblage biodi- rich formation is the Late Jurassic Solnhofen Limestone, versity after the Cambrian, but mollusc and speciﬁcally with 861 animal species, closely followed by the Late Cre- gastropod dominance become more prevalent in the taceous White Chalk of Rugen€ with 853. Cenozoic (Fig. 4). The proportion of gastropod genera Comparing the species richness among all named for- among all marine invertebrate genera assessed globally for mations with over 500 species in the PBDB, two forma- each stage remained between 0.07 and 0.20 throughout tions are statistical outliers: 957 species are reported from most of the Phanerozoic, only increasing in the Creta- the late Permian Changxing Formation and 951 from the ceous and Cenozoic. The Cassian proportion of gas- Late Triassic Cassian Formation (Fig. 3). The Cassian tropods is outstanding relative to all Carnian sites as Formation has the highest Margalef diversity index computed from the PBDB (0.32 and 0.18, respectively). (121.9; Table 4) followed by the Changxing Formation With respect to skeletal mineralogy, 60% of inverte- (114.0), the Plio-Pleistocene Caloosahatchee Formation in brate species of the Cassian fauna were originally arago- Florida (100.3), and the Miocene Termofoura Formation nitic, 20% calcitic and 19% bimineralic (Fig. 5A). When of Italy (98.3). only formation singletons are considered, the proportions The proportion of formation singletons ranges between of shell mineralogy remain the same. The basic results are 0.57 (Burgess Shale) and 0.93 (Mazon Creek fauna and also robust when comparing the clade proportions 8 PALAEONTOLOGY

TABLE 3. Diversity comparison of selected, thoroughly studied fossil Lagerst€atten. Fossil Lagerst€atte Age Species Species of Type of Lagerst€atte Source animals

Chengjiang biota ʻEarlyʼ Cambrian (Series 2, Stage 3) 228 203 Conservation Zhao et al. (2010) Lagerst€atte Burgess Shale ʻMiddleʼ Cambrian (Miaolingian, 172 149 Conservation Briggs et al. (1994), Caron Wuliuan) Lagerst€atte & Jackson (2008) Hunsruck€ Slate Early Devonian (Emsian) >275 233 Conservation Bartels et al. (1998) Lagerst€atte Mazon Creek Late Carboniferous (Moscovian) >815 >465 Conservation Nitecki (1979), Clements fauna Lagerst€atte et al. (2018) Finis Shale Late Carboniferous (Kasimovian/ 292 259 Impregnation Literature compilation* Gzhelian) Lagerst€atte (a type of conservation Lagerst€atte), grading into liberation Lagerst€atte Cassian Late Triassic (Ladinian/Carnian) 1517 1429 Liberation Lagerst€atte Literature compilation* Formation Solnhofen Late Jurassic (Kimmeridgian/ 1544 861 Conservation Schultze (2015) Limestone Tithonian) Lagerst€atte White Chalk of Late Cretaceous (Maastrichtian) 1348† 853† Liberation Lagerst€atte Reich et al. (2018) Rugen€ London Clay Eocene (Ypresian) >584 334 Partly conservation Collinson (1984), Clouter Lagerst€atte, partly (2018) liberation Lagerst€atte

*Literature compiled by the authors. †Includes subspecies.

between the complete dataset of invertebrate species and calculated with Fursich€ and Wendt’s quantitative dataset one only including formation singletons (Fig. 5B). from the Cassian Formation (Roden et al. 2018). Beta Using a dataset reduced to the 1124 species from the diversity is mostly ascribed to spatial turnover (Simpson Cassian Formation that remain after removing occur- dissimilarity index: 0.84) and only in small part to nest- rences that lack locality information, we investigate the edness, or species loss (0.12). species accumulation curve with new sites randomly Testing whether the high beta diversity is related to added and re-sampled. The curve flattens at larger site poor sampling in many localities, we filtered out all local- numbers but is far from saturation (Fig. 6). This suggests ities with fewer than 10 species occurrences, finding a that, in spite of the long scientific scrutiny, new species mean Jaccard dissimilarity of 0.92 among the remaining are likely to be found when new sites are discovered in ones. Including only the 10 most species-rich and there- the Cassian Formation. Alpha diversity varies, ranging fore presumably very well-sampled localities yields a dis- from 534 species from Alpe di Specie and 463 species similarity of 0.85 (see Table 6). from Stuores to sites with only one reported species Information on the depositional environment, taphon- (Roden et al. 2019, table S1). The by-locality median is omy and stratigraphy is provided wherever possible 45 species. Within-sample diversities (alpha diversity) of (Table 1). The Jaccard dissimilarity between all shallow approximately 200 species have been reported from and all deep-water settings is 0.94. With 0.85, there is still washed bulk samples from Stuores Wiesen (Hausmann & a high mean dissimilarity among all localities with known Nutzel€ 2015). High values of beta diversity contribute to shallow depositional environment. Temporal turnover is the high gamma diversity of the Cassian Formation high between the aon and the aonoides ammonite bio- (Table 6). The mean dissimilarity between sites using the zones, with a Jaccard dissimilarity of 0.84. A slightly lower Jaccard index is 0.95, expressing distinct community temporal turnover of 0.77 takes place with the transition compositions among sites, with pairwise dissimilarities from the aonoides to the austriacum biozones. Comparing ranging from 0.66 to 1. High beta diversity is corrobo- the localities within each ammonite biozone, we find a rated by the high mean proportional dissimilarity of 0.94 value of 0.91 for the austriacum, 0.94 for the aonoides, RODEN ET AL.: BIODIVERSITY IN LIBERATION LAGERSTAT€ T E N 9

4 5 Dominant lithology Sandstone Limestone Marl 14 Marl & limestone Siliciclastic 9 15 Mixed 8 11 1212 16 Conglomerate 1 3 10 2 6 7 1313 Tropical setting Species Non-tropical setting 200 400 600 800 1000

500 400 300 200 100 0 Start age (Ma)

FIG. 3. Comparison of raw species richness among all formations with more than 500 species. Species data includes nominal species. Data is exclusively from the Paleobiology Database; our new data is not included. Formations: 1, Kopanina; 2, Qixia; 3, Road Canyon; 4, Changxing; 5, Cassian; 6, Lower Greensand; 7, Ripley; 8, Selsey; 9, Termofoura; 10, Chipola; 11, Shoal River; 12, Gatun; 13, York- town; 14, Caloosahatchee; 15, Bowden; 16, Bermont. See Table 4 for details.

TABLE 4. Formations with more than 500 species, the number of occurrences, and their Margalef index. Formation Species Occurrences Age Margalef diversity Dominant lithology index

Changxing 957 4379 Late Permian (Lopingian) 114.0 Limestone Cassian 951 2426 Late Triassic (Ladinian/Carnian) 121.9 Marl + limestone Caloosahatchee 747 1698 Plio-Pleistocene 100.3 Marl + sandstone Termofoura 674 942 Miocene 98.3 Conglomerate Gatun 612 4107 Miocene 73.4 Sandstone + siltstone Bowden 607 1176 Pliocene 85.7 Marl Selsey 586 946 Eocene 85.4 Sandstone + claystone Chipola 554 2491 Miocene 70.7 Marl Kopanina 542 1059 Late Silurian (Ludlow) 77.7 Limestone Bermont 540 741 Pleistocene 81.6 Marl, sandstone + mudstone Road Canyon 537 2338 Permian (Cisuralian/ 69.1 Limestone Guadalupian) Shoal River 531 1706 Miocene 71.2 Marl Qixia 522 1167 Permian (Cisuralian/ 73.8 Limestone Guadalupian) Lower 520 1133 Early Cretaceous 73.8 Sandstone + shale Greensand Yorktown 519 1200 Miocene/Pliocene 73.1 Sandstone Ripley 518 1319 Late Cretaceous 72.0 Sandstone

Data from the Paleobiology Database. See also Figure 3. 10 PALAEONTOLOGY

TABLE 5. Proportion of formation singletons in each of the community composition and, especially, the excellent selected fossil Lagerst€atten, using data from the Paleobiology preservation of fossils. Database (PBDB) and literature compilations. Fossil Species Proportion Species Source Lagerst€atte of single- excluding Ecological causes of the Cassian diversity peak tons singletons All fossil Lagerst€atten included in this study have been Chengjiang 145 0.70 44 PBDB sampled and researched extensively. Good preservation biota goes along with a high proportion of stratigraphic single- Burgess 77 0.57 33 PBDB tons, which may bias diversity estimates over time (Alroy Shale Hunsruck€ 54 0.93 4 PBDB 1998; Foote 2000). While omitting formation singletons Slate from diversity studies would neglect a large part of Trias- Mazon 267 0.93 19 PBDB sic diversity, the Cassian Formation would still yield Creek almost 600 species and the same taxon proportions, fauna including a pronounced mollusc dominance. Finis Shale* 292 0.08 269 Literature Tropical systems are known to exhibit a higher diver- compilation sity than temperate latitudes (e.g. Roy et al. 2000; Bush & Cassian 1517 0.61 591 Literature Bambach 2004). The tropical setting of the Cassian thus Formation compilation suggests that a high primary diversity formed the founda- Cassian 951 0.68 304 PBDB tion of the high preserved diversity. Increased species Formation interactions in Mesozoic marine ecosystems may have Solnhofen 230 0.89 25 PBDB Limestone contributed to the high diversity values, driving species White 77 0.21 63 PBDB richness at local sites (alpha diversity), which in turn gen- Chalk of erates a high overall (gamma) diversity (Hofmann et al. Rugen€ † 2019). In addition to high gamma and alpha diversity, London 293 0.62 111 PBDB very high dissimilarity among sites (beta diversity) is a Clay main component of diversity and is signiﬁcant in discerning the sources of diversity. A large number of different Number of species differ from Table 3 as only data from the environments contribute to the high dissimilarity among PBDB is used in 5 of these 7 fossil Lagerst€atten. *Finis Shale only has 8 species entries in the PBDB and therefore faunal assemblages and thus high species richness in the only data from the literature compilation was used here. Cassian Formation. They represent various depositional †White Chalk of Rugen€ only has 77 species entries in the PBDB, settings, including the shallow subtidal basin, slope, dee- a small fraction of species reported acc. to the literature compi- per basin, back-reef areas, as well as transported frag- lation by Reich et al. (2018). Singleton proportions may there- ments of the carbonate platforms (i.e. Cipit boulders) fore not be representative. (Fursich€ & Wendt 1977; Nutzel€ & Kaim 2014; Hausmann &Nutzel€ 2015). This highly structured environment yields a high spatial turnover even within ammonite bio- and 0.90 for the aon zones. Therefore, community com- zones, which is greater than the temporal turnover across position differs more strongly within than among time biozones. Roden et al. (2018) reported a higher beta intervals. diversity using abundance data from the Cassian Forma- tion (from Fursich€ & Wendt 1977) than several other fossil and Recent assemblages covering a similar breadth of DISCUSSION environments. While we hypothesize that spatial heterogeneity and environmental breadth is crucial for the high The Cassian Formation is the most diverse pre-Cenozoic beta diversity in the Cassian, more work is required to marine ecosystem known to science. The species richness understand the relationship between environmental and is very high, even when compared with other fossil temporal components. Heterogeneous sampling probably Lagerst€atten known for their outstanding preservation contributes to the high beta diversity as well, but remov- and/or diversity. There are several factors contributing to ing localities with lower species richness from the dataset this biodiversity: the high primary diversity in the living still yields a high mean dissimilarity. This points to eco- communities, the long history of research, the accessibility logical reasons for the high beta diversity in this Middle of localities in the centre of Europe, the moderately large to Late Triassic ecosystem. Cassian beta diversity can area over which this formation crops out, the high num- partly be explained by evolutionary diversity partitioning ber of collection sites with a high dissimilarity in models (Hautmann 2014; Hofmann et al. 2014). The RODEN ET AL.: BIODIVERSITY IN LIBERATION LAGERSTAT€ T E N 11

Molluscs Gastropods Bivalves

Cassian Fm.: 61 %

Cassian Fm.: 39 % Proportion richness genus

0.0Cm 0.2 O 0.4 S 0.6 D 0.8 C 1.0 P Tr J K Pg Ng

500 400 300 200 100 Age (Ma)

FIG. 4. Proportions of benthic mollusc (molluscs excluding cephalopods), gastropod and bivalve genera among all marine invertebrate genera by stage throughout the Phanerozoic. Values from Cassian dataset added for comparison. Colour online.

AB 700

0.60 Complete dataset 0.39 Formation singletons 800 1000 500 600

0.60 0.39

0.21 400 600 Invertebrate species 0.20 0.21

0.22 0.09 0.12 0.12 0.07 0.07 0.07 0.06 0.12 0.07 0.07 0.07 0.05 0.05 0.06 0.02 0.01 0.01 0.02 0.010.01 0.01 0.01 0 200 0 100 200 300 400 a ri

Calcite orifera Bivalvia P Cc/Arag Arag/Cc Cnida Aragonite Spon/Silic olychaeta OstracodaP Gastropoda rachiopoda B Cephalopoda Echinodermata Polyplacophora

FIG. 5. Proportions of shell mineralogy (A) and clades/phyla (B) among valid Cassian invertebrate species. Values calculated from the complete dataset (dark) are compared with values calculated using only formation singletons (light). Proportions are very similar while species numbers vary. Spon/Silic refers to spicules consisting of spongin and/or silica. 12 PALAEONTOLOGY Species 400 600 800 1000 1200

0 Observed species richness 1124 0 Bootstrap richness estimator 1350 First-order jackknife estimator 1641 02

0 5 10 15 20 25 30

Sites

FIG. 6. Species accumulation curve of Cassian occurrence data with 1000 random permutations. Dataset reduced to species with information on localities (1124 species). Grey bars show 95% confidence intervals. post-extinction faunas of the Early Triassic would repre- In contrast, the Cassian Formation crops out over a sent the niche overlap phase with low beta diversity. The larger area than, for example, the White Chalk of Rugen€ high beta diversity in the Cassian Formation points to (Reich et al. 2018), which also covers fewer environments, increased competition in the Middle Triassic, reflecting less geological time, and has a much lower proportion of decreasing environmental breadth in the habitat contrac- originally aragonitic fossils than the Cassian. At this tion phase. point, we can only speculate about the true skeletal biodiversity of Rugen€ over the same spatio-temporal extent as the Cassian. The much lower proportion of gastropods Taphonomic, spatial and temporal biases (11% of molluscs) in Rugen€ is probably due to preservation, as the warm and humid climate would have been The late Permian Changxing Formation of South China suitable for a high gastropod diversity (Herrig et al. 1996; yields a greater species richness than the Cassian Forma- Reich et al. 2018). tion according to the PBDB, albeit not if our list of spe- The largest effect on the preserved diversity of Cassian cies from the Cassian Formation is used. Being from a fossils is probably the taphonomic bias. Quantifying this tropical setting (Wang et al. 2011), a high primary diver- effect is difficult because of the many confounding vari- sity for the Changxing (also Changxiang, Changhsing) ables. The best-suited environments for comparison are Formation is plausible. The reasons for the high reported those that are identical in all primary attributes but differ biodiversity are probably its vast spatial extent and its in preservation quality. The Wetterstein Formation, or intense study in the context of end-Permian mass extinc- Wettersteinkalk, represents such an example. Like the tion. While the stratigraphical range and thickness of the Cassian, the Wetterstein represents a tropical carbonate Changxing are similar to those of the Cassian (Shen et al. platform with reefs and lagoonal environments and is of 1998; Jin et al. 2006; Chen et al. 2009), the former covers Ladinian to early Carnian age (Zeeh 1994). The Wetter- an area approximately 2000 times greater, such that stein is similarly well studied as the Cassian. Differences species–area effects (Preston 1960; Raup 1976) may be are the larger spatial extent (known from four countries), substantial. The intense study of the Changxing is sup- the lack of deeper-water environments, and especially ported by a simple search on Google Scholar (March strong lithification and recrystallization in the Wetterstein 2019) providing c. 2700 references, compared to c. 700 (Zeeh et al. 1995). Only using PBDB data, we find 484 for the Cassian Formation and c. 300 for the White Chalk species of animals in the reef and shallow basin areas of of Rugen.€ We may thus describe the Changxing Forma- the Cassian Formation, but only 106 species in the Wet- tion as an ‘exploitation Lagerst€atte’. terstein. Thus, the liberation effect on total diversity is RODEN ET AL.: BIODIVERSITY IN LIBERATION LAGERSTAT€ T E N 13

TABLE 6. Diversity metrics of Cassian dataset (valid species thus brings preserved biodiversity at least in the same only; see Roden et al. 2019, appendix S1). range as modern marine biodiversity in the tropics and Gamma Total species 1517 subtropics. diversity Margalef diversity index* 121.9 Alpha diversity Mean number of species per 96 locality† A new type of fossil Lagerst€atte: liberation Lagerst€atten Median number of species per 45 locality‡ Chengjiang, Burgess Shale, Mazon Creek, Hunsruck€ Slate, Beta diversity† Mean Jaccard dissimilarity 0.95 Solnhofen Limestone and parts of the London Clay (the Multiple-site Simpson 0.84 concretions) are conservation Lagerst€atten (Allison 1988a, dissimilarity index b; Nudds & Selden 2008; Forchielli 2014). In many cases Nestedness component 0.12 € Number of localities 30 of excellent preservation in conservation Lagerstatten, the environmental conditions responsible for the preservation Mean Jaccard n z are not favourable for high primary diversity (hypersalin- dissimilarity ity, anoxia or restricted oxygen ﬂow etc.; Allison 1988a; Nudds & Selden 2008). Beta diversity† including only the n 0.85 10 71 The Cassian Formation, White Chalk of Rugen€ and most species-rich localities, excl. all 0.88 15 49 Finis Shale also exhibit very good preservation, but they localities with

Lagerst€atte in which aragonitic shells are preserved due spatial heterogeneity. Taking the species counts at face to early diagenetic impregnation by hydrocarbons (im- value would suggest that gastropod diversity has pregnation Lagerst€atte; Seuß et al. 2009). Impregnation increased more than threefold in similar settings since Lagerst€atten are a special type of conservation Lagerst€at- the Triassic. However, rather than representing a genuine ten and grade into liberation Lagerst€atten. diversity rise, the increase may also be governed by dif- Liberation Lagerst€atten typify a Cenozoic-style preser- ferences in the preservation potential, for example due to vation, which is especially supportive of mollusc preser- the contribution of gastropods with delicate or reduced vation, including small gastropods that are usually either shells in the New Caledonia survey: At least 20% of mol- destroyed or cannot be isolated from their host rock lusc species from the survey are from families completely (Hendy 2011). In the Cassian Formation, the low lithifi- or mostly comprised of very small gastropods, and 9% cation facilitates bulk sampling and obtaining fossils by are opisthobranchs, most of which have reduced or are wet sieving, which is the most effective method to lacking shells. The proportion of gastropod species in retrieve small fossils. Studying Cenozoic assemblages, the respective faunas may be less affected by this remain- Sessa et al. (2009) showed that lithified assemblages ing bias. The proportion of gastropods among molluscs appear less diverse (on average, unlithified samples have is 0.58 in the Cassian, such that the proportion of the 2.4 times the diversity) and have less even abundance New Caledonian site is just 1.4 times greater (or 1.2 distributions than coeval unlithified samples (see also times, if we exclude the opisthobranchs). We suggest Hawkins et al. 2018). Therefore, a preservational bias that the genuine diversity increase of gastropods from may contribute to the often high number of species the Triassic to today is somewhere between these two found in this Lagerst€atten-type. While liberation values and perhaps closer to the lower estimate. Lagerst€atten provide a nearly complete picture of the The loss of mollusc diversity through aragonite dissolu- diversity of skeletal organisms, they do not allow soft- tion in the Palaeozoic and Mesozoic has been widely dis- part preservation, one disadvantage compared to conser- cussed (Cherns & Wright 2000; Wright et al. 2003; Bush & vation Lagerst€atten. Bambach 2004; Seuß et al. 2009). Some reports from well- preserved Palaeozoic assemblages also show high gastropod proportions, such as the Buckhorn Asphalt Quarry, with Mollusc diversity through time 33% of the invertebrate fauna being gastropods (Seuß et al. 2009). The fauna of the Cassian Formation clearly A pronounced mollusc dominance is present in the fauna supports the assumption that the scarcity of tiny gas- of the Cassian Formation, and gastropod species outnum- tropods in many fossil biota and their apparent rise ber bivalves by far. Mollusc dominance is also known through time are largely a taphonomic phenomenon that from Early Triassic biota, but here bivalves usually out- can only be overcome by the study of liberation Lagerst€at- number gastropods (e.g. Hofmann et al. 2014, 2015; ten. Only liberation Lagerst€atten are suitable for compar- Foster et al. 2018). Several Middle to Late Triassic tropi- isons with modern ecosystems, as they combine excellent cal settings show a similar contribution of gastropods to preservation and favourable marine conditions. The win- total diversity as we find in the Cassian (Friesenbichler dow into diversity provided by the Cassian Formation as et al. 2019). This is surprising because we attribute the well as other fossil Lagerst€atten with exceptional preserva- Cassian gastropod richness to the liberation effect, tion contradicts the widely held view of gastropod domi- whereas most of the other faunas listed by Friesenbichler nance being a Cenozoic phenomenon (e.g. Crame 2001). et al. (2019) are not of liberation type. Monographic bias is the most likely explanation. Molluscs are known to dominate modern shallow- CONCLUSIONS marine ecosystems (e.g. Gosliner et al. 1996). The Ceno- zoic increase in tropical species-rich groups, such as The high diversity in the Cassian Formation is ascribed to molluscs, has been ascribed to the process of escalation ecological and preservational factors. Ecological reasons through biotic interactions (Vermeij 1993; Crame 2001), for the high species richness are a favourable environmen- increased diversification in groups that fertilize through tal setting in the tropics and a strongly structured habitat. direct sperm transfer, allowing smaller population sizes The stratigraphical and spatial extent may also be con- (Bush et al. 2016), or an evolutionary shift facilitated by tributing factors. However, taphonomic bias is most phytoplankton radiations (Knoll & Follows 2016). A important, raising preserved richness by a factor of 4.5 comprehensive survey of molluscs in New Caledonia relative to non-liberation style preservation. Only libera- yielded 2738 species, 80% of which were gastropods tion Lagerst€atten such as the Cassian are able to provide (Bouchet et al. 2002). Similar to the Cassian fauna, the a glimpse into what the true skeletal diversity of an study was conducted in a tropical reef habitat of high ecosystem may have been. RODEN ET AL.: BIODIVERSITY IN LIBERATION LAGERSTAT€ T E N 15

€ Acknowledgements. The authors appreciate the many construc- -ABERHAN, M., BOTTJER, D. J., FOOTE, M., FUR- tive comments made by M. Hautmann, M. Aberhan, and an SICH, F. T., HARRIES, P. J., HENDY, A. J., HOLLAND, anonymous reviewer. We also thank Evelyn Kustatscher, Bolzano S. M., IVANY, L. C., KIESSLING, W., KOSNIK, M. A., (Italy), for attaining permits and aiding in fieldwork. This work MARSHALL, C. R., McGOWAN, A. J., MILLER, A. I., was supported by the Deutsche Forschungsgemeinschaft (KI OLSZEWSKI, T. D., PATZKOWSKY, M. E., PETERS, S. 806/14-1, NU 96/13-1, SE 2283/2-1). The authors thank all con- E., VILLIER, L., WAGNER, P. J., BONUSO, N., BOR- tributors to the Paleobiology Database. This is Paleobiology KOW, P. S., BRENNEIS, B., CLAPHAM, M. E., FALL, Database Publication No. 339. L. M., FERGUSON, C. A., HANSON, V. L., KRUG, A. Z., LAYOU, K. M., LECKEY, E. H., NURNBERG, S., POW- ERS, C. M., SESSA, J. A., SIMPSON, C., TOMASO- AUTHOR CONTRIBUTIONS VYCH, A. and VISAGGI, C. C. 2008. Phanerozoic trends in the global diversity of marine invertebrates. Science, 321,97– VJR, IMH and AN compiled the Cassian dataset, with 100. BAMBACH, R. K. 1977. Species richness in marine benthic support from MR, MU and HH. The Finis Shale dataset habitats through the Phanerozoic. Paleobiology, 3, 152–167. was compiled by BS. The concept was developed by VJR, BANDEL, K. 1992. Uber€ Caenogastropoden der Cassianer AN and WK. Analysis was done by VJR and WK. The Schichten (Obertrias) der Dolomiten (Italien) und ihre tax- manuscript was written by VJR, WK and AN, with addi- onomische Bewertung. Mitteilungen aus dem Geologisch- tions by BS and MR. Pal€aontologischen Institut der Universit€at Hamburg, 73,37–97. -2007. Description and classification of Late Triassic Neriti- morpha (Gastropoda, Mollusca) from the St Cassian Forma- DATA ARCHIVING STATEMENT tion, Italian Alps. Bulletin of Geosciences, 82, 215–274. -and DOCKERY, D. T. III 2012. 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Appendix S1: Species list, Cassian Formation

A list of species described from the Late Triassic Cassian Formation, Dolomites, Northern Italy, was compiled by the authors of the accompanying publication. This list is used for analysis in the main text. It is intended to facilitate comparisons with other fossil lagerstätten not only in terms of taxonomic richness but also in terms of clade proportions and the distribution of primary shell mineralogy. It is available on Dryad: https://datadryad.org/stash/dataset/doi:10.5061/dryad.6s5651k.

Appendix S2: Explanatory notes and references

Appendix S2 provides details on the compiled list of species from the Cassian Formation (Appendix S1), including information on the localities and methods. It lists the references used for the literature compilation.

A list of 1517 valid nominal species (exclusive synonyms; Appendix S1) was compiled by the authors. This list is used for analysis in the main text. The species have been reported from 30 known localities of the Late Triassic Cassian Formation.

This list presents an overview of how many species have been described from the Cassian Fm. until now. It is intended to facilitate comparisons with other fossil lagerstätten not only in terms of taxonomic richness but also in terms of clade proportions and the distribution of primary shell mineralogy.

The list summarises the literature and, to a minor degree, taxonomic work by the authors of the present contribution (initials provided). In total, 150 publications have been reviewed, comprising monographs or other articles with taxonomic descriptions, quantitative studies, studies on facies and environment, stratigraphic work, and other reports including observations on taxa from the Cassian Fm. In addition, for gastropods, bivalves, and brachiopods – and hence for most of the species from the Cassian Formation – the Fossilium Catalogus was used as a reference (Diener 1920, 1923, 1926; Kutassy 1931, 1940). In general, the opinion of the last revising author has been followed. The primary description of the species was not checked in all cases, especially if subsequent revisions are available. Other entries are based on subsequent reports of the occurrences of this species in the Cassian Fm. (e.g., Fürsich and Wendt 1977). We have also added occurrences of species from our own field work. If yet unpublished, we use the term "field work" in the references. Field work not done collectively is commented with initials of authors of this work.

Many of the generic assignments are outdated, such as Turbo or Pecten. However, we assume that a large majority of described species are still valid.

In the Comments section of our lists, synonymies and chresonomies (differing genus attributions) are included for many species. In addition, discussions and opinions about the taxonomy and other

1 relevant information are also provided in many cases. Orthographic variants of species and genus names are also reported in the Comments section.

The primary shell mineralogy of each species is given according to its higher assignment at the superfamily, family, and, rarely, the genus level (e.g., Taylor et al. 1969; Carter 1990; Paleobiology Database). We also provide the information which species only occur in the Cassian Fm. and mark them with "y" (formation singletons). Those species that occur in other geological strata and/or other geographic regions are marked with "n". Class or (sub)phylum attribution is included but other suprageneric categories are not used.

The present list is a working list and certainly not entirely accurate or complete. However, it will be revised and completed continuously as more information is gathered. We estimate that the present list includes more than 95 % of the valid species reported from the Cassian Formation.

Localities

During the history of its research, the term Cassian Formation has often been used in a broader sense. We therefore apply the definition Cassian Formation sensu lato herein to comprise the Cassian Formation sensu stricto (the current definition) in addition to localities within the Cortina basin that are assigned to the Heiligkreuz Formation today (e.g., Nose et al. 2018). In the older literature, only the term "Cassian Beds" is usually provided as locality information, and it was not differentiated between the Heiligkreuz and Cassian Formations, nor were individual localities clearly named, mapped or described in many cases.

Species from the following localities belonging to the Cassian Fm. are listed: Campo, Carbonin, Cianzopé (Cian Zoppè), Cason dei Caài, Ciòu del Conte, Costalaresc (Costalares), Forcella Col Duro, Forcella Giau, Lago Antorno, Milieres/Dibona, Misurina (this includes Valle di Rimbianco, acc. to Sanchez-Beristain 2018a), Pocol/Son dei Prade (the town; not to be confused with Rio Pocol), Rumerlo (Romerlo), Sasso di Stria, Staolin (Staulin), Settsass (Settsass-Scharte, Forcella di Settsass), Alpe di Specie (Seelandalpe, Plätzwiese), Stuores (Prati di Stuores, Stuoreswiesen, includes Bosco di Stuores and Pralongiá), Tamarin, Vervei, Pescol, Base Punta Gusella, Ruones (Prati di Ruones, Ruones-Wiesen, Incisa), Rio Pocol (Picolbach), Rio Stuéres (acc. to Urlichs 2012; Rio Stuores), Rio di Foves, Piz Lavarella (Piz Lavarela), Masareis (Masarei), Pedraces (includes Col da Oj), and Saverie (Appendix S3). Details on some of the localities can be found in the cited literature (e.g., Zardini 1978, Urlichs 2012, 2017). These localities vary strongly in their expanse and species richness (Table S1).

The "Pachycardientuff" fauna, including the Seiser Alm (Alpe de Suisi), is not included in this list, as it is uncertain to which formation these beds belong (e.g., Fürsich and Wendt 1977). According to Urlichs (2017), the allodapic limestone beds at the Seiser Alm are now considered belonging to the Marmolada Conglomerate.

Table S1: Number of (valid) species reported from each locality and those reported from the Cassian Formation without specifying a locality ("unspecified"). Based on Appendix S1.

Total Animal Invertebrate species species species Alpe di Specie 533 513 509 Stuores 461 440 438 Misurina 331 307 307 Campo 258 258 258 Costalaresc 173 173 173 Rumerlo 150 150 150 Settsass 139 132 132 Milieres/Dibona 118 118 118 Tamarin 117 89 89 Forcella Giau 71 71 70 Cianzopé 70 70 70 Staolin 65 64 64 Picolbach 64 60 60 Sasso di Stria 55 55 55 Pocol 49 49 49 Vervei 40 40 40 Ruones 39 34 34 Cason dei Caài 26 26 26 Pedraces 22 9 9 Carbonin 17 17 17 Lago Antorno 16 16 16 Ciòu del Conte 11 11 11 Pescol 8 8 8 Rio di Foves 8 8 8 Rio Stueres 7 7 7 Forcella Col Duro 5 5 5 Base Punta Gusella 5 5 5 Saverie 3 3 3 Piz Lavarella 2 2 2 Masareis 1 1 1 unspecified 404 393 391 Total 1517 1429 1421

Another list includes species in open nomenclature as additional information. It is used as a working list by the authors and currently comprises 2177 entries. This list can be requested from the corresponding author.

References in Appendices

References reviewed for species list:

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CARTER, J. G. 1990. Skeletal Biomineralization: Patterns, Processes and Evolutionary Trends Volume I. 671 pp. DIENER, C. 1920. Brachiopoda triadica. Fossilium Catalogus (I: Animalia), 10, 1–109. --- 1923. Lamellibranchiata triadica. Fossilium Catalogus (I: Animalia), 19, 1–259. --- 1926. Glossophora triadica. Fossilium Catalogus (I: Animalia), 34, 1–242. FÜRSICH, F. T. and WENDT, J. 1977. Biostratinomy and palaeoecology of the Cassian Formation (Triassic) of the Southern Alps. Palaeogeography, Palaeoclimatology, Palaeoecology, 22, 257–323. KUTASSY, A. 1931. Lamellibranchiata triadica II. Fossilium Catalogus (I: Animalia), 51, 261–477. --- 1940. Glossophora triadica II. Fossilium Catalogus (I: Animalia), 81, 243–477. NOSE, M., SCHLAGINTWEIT, F. and NÜTZEL, A. 2018. New Record of Halimedacean Algaa from the Upper Triassic of the Southern Alps (Dolomites, Italy). Rivista Italiana di Paleontologia e Stratigrafia (Research In Paleontology and Stratigraphy), 124, 421–431. TAYLOR, J. D., KENNEDY, W. J. and HALL, A. 1969. The Shell Structure and Mineralogy of the Bivalvia. Bulletin of the British Museum (Natural History) Zoology, Supplement 3, 1–183. URLICHS, M. 2012. Stunting in some invertebrates from the Cassian Formation (Late Triassic, Carnian) of the Dolomites (Italy). Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen, 265, 1–25.

--- 2017. Revision of some stratigraphically relevant ammonoids from the Cassian Formation (latest Ladinian-Early Carnian, Triassic) of St. Cassian (Dolomites, Italy). Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen, 283, 173–204. ZARDINI, R. 1978. Fossili Cassiani (Trias Medio-Superiore): Atlante dei gasteropodi della formazione di S. Cassiano raccolti nella regione Dolomitica attorno a Cortina d'Ampezzo. Edizioni Ghedina, Cortina d'Ampezzo, 144 pp.

Publication #3

Roden, V. J., Zuschin, M., Nützel, A., Hausmann, I. M. & Kiessling, W. Drivers of beta diversity in modern and ancient reef-associated soft-bottom environments. PeerJ. In review. and the supplementary data package

Drivers of beta diversity in modern and ancient reef- associated soft-bottom environments

Vanessa Julie Roden1, Martin Zuschin2, Alexander Nützel3,4,5, Imelda M. Hausmann3,4, Wolfgang Kiessling1

1GeoZentrum Nordbayern, Section Paleobiology, University Erlangen-Nürnberg, Erlangen, Germany 2Department of Palaeontology, University of Vienna, Vienna, Austria 3SNSB – Bayerische Staatssammlung für Paläontologie und Geologie, München, Germany 4Department of Earth & Environmental Sciences, Ludwig-Maximilians-Universität München, München, Germany 5GeoBio-Center, Ludwig-Maximilians-Universität München, München, Germany

Corresponding author: Vanessa Julie Roden1 GeoZentrum Nordbayern, Loewenichstr. 28, 91054 Erlangen, Germany Email address: [email protected]

Abstract

Beta diversity – differences in community composition – are often associated with environmental gradients. Other drivers of beta diversity include stochastic processes, priority effects, predation, or competitive exclusion. Temporal turnover may also explain differences in faunal composition between fossil assemblages. To assess the drivers of beta diversity in reef-associated soft-bottom environments, we investigate community patterns in a Middle to Late Triassic reef basin assemblage from the Cassian Formation in the Dolomites, Northern Italy, and compare results with a Recent reef basin assemblage from the Northern Bay of Safaga, Red Sea, Egypt. We evaluate beta diversity with regard to age, water depth, and geographic distance and compare the results with a null model to evaluate the stochasticity of these differences. Using pairwise proportional dissimilarity, we find very beta diversity for the Cassian Formation (0.91 ± 0.02) and slightly lower beta diversity for the Bay of Safaga (0.89 ± 0.04). Null models yield very low beta diversity for both datasets and show that stochasticity only plays a minor role in determining faunal differences. Spatial distance is also irrelevant. Both datasets show no apparent trend of beta diversity with water depth. Samples from deeper parts of the reef basin have slightly higher beta diversity than shallower areas, whereas intermediate depths yield the

1 highest values. Although water depth has frequently been found to be a key factor in determining beta diversity, we find that it is not the major driver. We postulate that priority effects – the order in which organisms settle in an ecosystem – are the main driver of beta diversity in the studied reef-related soft-bottom habitats.

Introduction

Disentangling the drivers of beta diversity in various habitats has been the aim of many biodiversity studies, most often ascribing variation in community composition to environmental factors and/or spatial distance (e.g., Melo et al. 2009; Qian & Ricklefs 2007; Svenning et al. 2011, Pitacco et al. 2019). In some cases, topographic complexity plays a key role in community dissimilarity (Al‐Shami et al. 2013; Ellingsen & Gray 2002). Particularly in reefs, which are known for their topographic complexity, environmental heterogeneity or gradients have been established as the most important drivers of beta diversity (Becking et al. 2006; Carlos‐Júnior et al. 2019; Pandolfi 1996; Pandolfi 1999; Pandolfi & Jackson 2006). However, studies have shown large variation in faunal composition in very uniform habitats, such as the continental shelf (e.g., Ellingsen 2001). While it is clear that environmental factors are a strong driver of beta diversity, regional diversity in connection with stochastic processes (Stegen et al. 2013), biotic interactions, such as predation (e.g., Huntley & Kowalewski 2007; Klompmaker & Finnegan 2018; Stanley 2008), and intrinsic factors related to organism characteristics (Soininen 2010) may also play an important role. This can obscure identification of determinants, and additional complication factors abound. For example, large-scale patterns in modern settings can result from regional-historical processes ("priority effects") as well as environmental gradients (Rex et al. 1997). In a large quantitative study of the Cassian fauna, Fürsich & Wendt (1977) describe autochthonous assemblages that are thought to represent communities. These contain recurring sets of species, which favors the idea of community- assembly processes and dynamics determining faunal heterogeneity (Drake 1991). Several studies have found differences in beta diversity in soft-bottom mollusk assemblages with depth, but patterns vary among climatic regions (Aldea et al. 2009; Benkendorfer & Soares- Gomes 2009; Koulouri et al. 2006). Variability in community composition also depends on spatial scale and grain (e.g., Barton et al. 2013; Ellingsen 2001; Mac Nally et al. 2004; Pandolfi 2002), making it difficult to compare beta diversity between different studies and environments. Pandolfi’s (2002) three-phase model demonstrates high faunal variability in coral reefs at small spatial and temporal scales and relatively high on large, but lowest at intermediate scales. Using simple pairwise measures of dissimilarity decreases the influence of spatial scale and grain (Marion et al. 2017; Soininen 2010). Gamma diversity – related to the size of the dataset and overall diversity in the region – and uneven sampling can influence measured beta diversity, which can be assessed by applying a null model derived through random sampling from the entire species pool (e.g., Astorga et al. 2014; Kraft et al. 2011; Segre et al. 2014).

2 Here we address whether water depth is the main driver of beta diversity in soft-bottom reef- associated assemblages, or if stochastic processes, temporal changes, or priority effects are more likely to drive differences in community composition. Soft-bottom reef basin habitats are well- suited to explore this question due to their lack in complex topography and easier assessment of environmental variables, although there can be strong habitat variability in these environments. We investigate beta diversity patterns in a Triassic reef basin assemblage from the Cassian Formation in the Dolomites and compare results with a Recent reef basin assemblage from the Northern Bay of Safaga, Red Sea (Zuschin & Hohenegger 1998; Zuschin & Oliver 2005). To help discern the factors contributing to differences in community composition, we evaluate beta diversity with regard to known variables: age, water depth, and geographic distance. We then compare the results with a null model to evaluate the stochasticity of these differences. Determining the drivers of faunal heterogeneity has long been one of the central question in ecology – how communities assemble in an ecosystem (Remmer et al. 2019; Stegen et al. 2013). However, more data in the form of standardized and therefore comparable datasets is needed to help disentangle the drivers of beta diversity (Keil & Chase 2019). With the ancient Cassian and the modern Safaga communities sharing several patterns of beta diversity, our results help provide a better understanding of diversity patterns in warm-water reef-associated faunas.

Materials & Methods

Triassic data The Cassian Formation in the Dolomites, Southern Alps, northern Italy, preserves Middle to Late Triassic (Ladinian–Carnian) tropical reef to basin environments with exceptional fossil preservation (Roden et al. 2019). The Cassian Formation comprises deposits with considerable differences in depth, from back-reef and lagoonal settings as well as shallow and deeper water deposits from the reef basin (e.g., Bosellini 1998; Fürsich & Wendt 1977). The predominantly argillaceous basin sediments were deposited between prograding carbonate platforms that now form the Cassian and Schlern Dolomite (Bosellini 1998; Hausmann & Nützel 2015; Keim et al. 2001) and can reach a thickness of over 300 m (Fürsich & Wendt 1977). The Cassian Formation sensu lato includes all marly or clayey Ladinian–Carnian sediments deposited in the interplatform basins of the Dolomites (supplementary information, part I). Deposition took place in the Western Tethys in a setting comparable to recent tropical environments, with warm water temperatures, seasonality, and fresh water influx (Nützel et al. 2010). Diagenetic alteration and lithification were low and fossil extraction is easy, yielding many well-preserved fossils with original skeletal microstructures and aragonite preservation (Roden et al. 2019). Although most of the strata of the Cassian Formation are not fossiliferous, many localities from this reef-basin assemblage have yielded abundant fossils, ideal for assessments of diversity patterns and paleoecological studies. Various factors contribute to the high diversity and, particularly, the high variation in community composition: a high primary diversity favored by the tropical setting, a wide breadth of habitats, and very good preservation of fossils (Fürsich & Wendt 1977;

3 Nützel et al. 2010; Roden et al. 2019). The Cassian Formation is ideal for the assessment of ecological patterns in the fossil record, allowing comparisons with recent assemblages due to their Cenozoic-style preservation. Surface and bulk samples from the Cassian Formation were taken in field campaigns conducted in 2015 and 2016 (Fig. 1). Studied samples belong to the aon, aonoides, and austriacum zones, the time span that covers the vast majority of diverse benthic assemblages of the Cassian Formation sensu lato (Table S1), equivalent to approximately 5 myr. The entire formation is distributed over an area of c. 500 km2. Quantitative faunal data of samples from the localities Costalaresc, Picolbach, Rumerlo cliff and Rumerlo ski slope are first reported herein. This dataset was supplemented with data from Settsass (Nützel & Kaim 2014), Stuores (Hausmann & Nützel 2015), and the two localities Lago Antorno and Misurina landslide (Hausmann et al. accepted), covering various environments (Table 1).

Bulk samples were disaggregated in a 7% H2O2 solution and wet-sieved with mesh sizes of 2, 1, 0.5, 0.25, and 0.125 mm. Only size fractions > 0.5 mm from bulk samples are included in this study. Samples were picked and sorted using a light microscope. Roden et al. (2018) found that beta diversity calculated as mean proportional dissimilarity is depicted accurately when only the most abundant taxa in each sample are counted. Whereas the five most abundant species are usually sufficient, we identified and conservatively counted the ten most abundant species. Using SEM photographs, samples were identified to species level whenever possible. All animal taxa were included, providing comparability with previously published data. In disarticulated bivalves, the few incomplete specimens were each counted as single specimens, since valves were of differing shapes and sizes. We inferred paleo-depth following the criteria of Fürsich & Wendt (1977). Inference is based on the ratio of suspension and deposit feeders, the ratio of carnivores and grazers, the proportion of articulated bivalves, the abundance and diversity of gastropods, the encrustation of specimens, and the presence of coral, sponge, and echinoderm fragments (Fig. 2). Modern data The Recent samples are from a shallow-water area in the Northern Bay of Safaga in the Red Sea, Egypt (Zuschin & Hohenegger 1998), representing a coral-dominated, subtropical setting with warm water temperatures and seasonality, high salinity, and a highly structured bottom topography reaching down to more than 50 m water depth (Piller & Pervesler 1989; Titschack et al. 2010). The tidal range is < 1 m, but water temperature and salinity are without any obvious depth gradient due to complete water mixing (Piller & Pervesler 1989). Terrigenous input along with nutrients occurs mainly along the coast and is due to fluvial transport during flash floods, local erosion of impure carbonate rocks, and aeolian transport by the prevailing northerly winds (Piller & Mansour 1994). Water energy is relatively weak, but a complex current pattern influences facies development (Piller & Pervesler 1989).

4 Standardized bulk sampling in soft substrates was conducted at 13 sites, from shallow subtidal down to 40 m water depth (Table 2), covering an area of approximately 75 km². The dataset consists only of mollusks. Whole shells > 1mm were considered and disarticulated valves were counted as individuals (Zuschin & Hohenegger 1998; Zuschin & Oliver 2005). For comparability, the Safaga dataset was reduced to the ten most abundant species per sample. To test whether results are robust, the complete dataset was analyzed and results are provided in the supplementary information (part II). Samples taken from the same environment, site, and depth (only several meters apart) were combined to create a by-site dataset comparable to that from the Cassian Formation. Results from the by-sample dataset are provided in the supplementary information (part III). Diversity estimates We assess beta diversity patterns in the Triassic Cassian Formation based on 8 bulk samples and compare the results with those from the Red Sea samples. For both datasets, we use pairwise proportional dissimilarity (relative Bray-Curtis) to compare samples because it is a measure of beta diversity relatively insensitive to uneven sample sizes (Krebs 1989). Proportional dissimilarity is calculated as djk = 1 – ∑min(xij, xik), with xij and xik being the proportions of species abundance in each sample. Ordination plots using non-metric multidimensional scaling are also based on pairwise proportional dissimilarity. Calculations and visualization were implemented using R Version 3.5.0 (R Core Team 2016) and the vegan (Oksanen et al. 2016), sads (Prado et al. 2014), and visreg (Breheny & Burchett 2013) packages. A null model for each dataset was created by randomly sampling the gamma species pool until the number of specimens and number of sampling sites of the original datasets were obtained. Mean proportional dissimilarity was calculated for each simulated dataset in 1000 iterations. Alpha-level community diversity is deduced from rank-abundance distributions of the 10 most abundant species per sample as well as the Berger-Parker dominance index (the proportion of the most abundant species) and Pielou's evenness (J = H/log(s), where H is the Shannon index and s is the number of species) (Berger & Parker 1970; Krebs 1989; Pielou 1966).

Results

Environments and alpha diversity Faunal composition of the four new samples (Costalaresc, Picolbach, Rumerlo cliff and Rumerlo ski slope) are provided in Table 3. After excluding foraminifers from one sample (Rumerlo ski slope, 11 specimens of Pragsoconulus robustus), the dataset only contains mollusks. All occurrences of brachiopods, sponges, corals, and echinoderms were not among the 10 most abundant species. The samples are arranged along a shallow reefal to basinal transect (Fig. 3). The bathymetric partitioning among the Cassian localities is relative, rendering a comparison with recent settings difficult. There were no apparent differences in the sediment matrix among

5 samples. Due to the high proportion of grazers and high gastropod abundance and diversity, we describe Costalaresc as originating from a relatively shallow environment, but – with a high proportion of deposit feeders and all specimens of bivalves being articulated – we interpret a slightly deeper setting than for the Rumerlo localities. Rumerlo ski slope is interpreted as very proximal, possibly a back reef setting, due to the large number of fragments of corals, sponges, and echinoids, among other factors. Picolbach probably stems from a deeper setting, as interpreted from mode of life of reported specimens and articulated bivalves. Evenness values, Berger-Parker dominance index (Table 1), and rank-abundance distributions (Fig. S8, supplementary information part IV) demonstrate relatively diverse assemblages, with the exception of Costalaresc. Low alpha diversity in Costalaresc is probably due to the extremely high abundance of the gastropod Ptychostoma sanctaecrucis (Wissmann, 1841). Specimens attributed to Ptychostoma sanctaecrucis may belong to closely related species. There is no significant correlation between depth and alpha diversity measured as dominance or evenness in the Cassian samples. Environments and depth from which the Safaga samples were taken are recorded and alpha diversity calculated (Table 2). Samples from the reef slope and from sand between coral patches show lowest dominance and highest evenness. There is no significant correlation between alpha diversity and depth in the Safaga samples. The range of evenness is slightly higher than in the Cassian samples. Beta diversity As shown previously, overall beta diversity is high in the Cassian Formation (mean PPD: 0.91 ± 0.02, ± is standard error; range: 0.52-1; Table 4). In the by-site dataset from Safaga, we measure a beta diversity of 0.89 ± 0.04 (range: 0.35-1.00; Table 5). Null models created for each dataset from the gamma species pool yield much lower beta diversity, with a mean of 0.24 ± 0.0004 for the Cassian dataset (Fig. 4a) and 0.10 ± 0.0002 for the by-site Safaga dataset (Fig. 4b). There is no significant correlation between geographical distance and dissimilarity neither in the Cassian samples (Spearman's rank correlation rho: 0.27, p-value: 0.17; Fig. 5a) nor the by-site Safaga dataset (rho: 0.01, p-value: 0.95; Fig. 5b). Grouping Cassian samples from similar environments (according to inferred depth) yields a dissimilarity of 0.83 between the four shallower (very shallow and shallow, Table 1) and the four deeper (intermediate and deep, Table 1) localities. Using three depth categories (the four shallowest localities, two intermediate and two deeper localities), we find the following dissimilarities: very shallow/intermediate: PPD = 0.81, intermediate/deeper: PPD = 0.86, very shallow/deeper: PPD = 0.93). Dissimilarity between the two localities from deeper environments is lower than among the shallower localities (Fig. 3). Temporal turnover is also very high and dissimilarity within the ammonite biozones strongly varies (supplementary information, part I). At Safaga, there is no clear relationship between beta diversity and water depth (Fig. 7). Samples taken from deep, muddy settings exhibit the highest mean beta diversity relative to other samples (0.98 ± 0.02). Otherwise, there is no relationship between sedimentary attributes and mean

6 dissimilarity. By grouping the samples into depth ranges, we cover several environments for each. We generally find that samples from shallower environments have a more similar community composition than samples from deeper environments (Figs. 7, 8). There is no correlation of water depth with mean PPD of each site (rho = 0.02, p = 0.98). Dissimilarity between the four shallower and the four deeper samples is 0.77 and therefore lower than other values measured within depth ranges. Using three depth categories (the four shallowest localities, two intermediate and two deeper localities), we find the following dissimilarities: very shallow/intermediate: PPD = 0.79, intermediate/deeper: PPD = 0.60, very shallow/deeper: PPD = 0.77).

Discussion

Environment There are no distinct trends in alpha diversity with depth in either dataset, whereas patterns in the literature are conflicting (e.g., Brown & Thatje 2014; Gray et al. 1997; Holte et al. 2004; Martins et al. 2013). Measures of evenness and dominance show relatively high alpha diversity for most samples in both datasets, from all environments and depths. Low dominance is corroborated by another study on soft-bottom taxa in the central Red Sea (Alsaffar et al. 2019). Beta diversity has not been studied extensively in soft-bottom habitats, with only a few studies in non-reefal soft-bottom settings (e.g., Aldea et al. 2009; Ellingsen 2002; Koulouri et al. 2006). This study shows high beta diversity in two reef-associated soft-bottom assemblages from warm- water settings. We find only minor contributions of water depth, spatial distance, and stochastic processes to beta diversity. There is also no influence of age in the Cassian samples. The high beta diversity in the Cassian Formation is remarkable, considering that all samples stem from soft-bottom habitats adjacent to reefs – most likely a more uniform habitat than the reef structure. Although diversity in studies of coral reefs may not be directly comparable to other marine studies due to differences in taphonomy and sampling strategy (Pandolfi & Minchin 1995), we can compare different reef-adjacent soft-bottom assemblages. The slightly lower beta diversity of modern Safaga compared with ancient Cassian is surprising considering that certain environments such as mangrove and seagrass, which contribute to beta diversity at Safaga, did not yet exist in the Triassic period. In addition, the bottom topography of Safaga is highly structured for a soft-bottom habitat (Zuschin & Oliver 2005). Of course, the comparison is slightly hampered as the temporal ranges are quite different between the two datasets (5 myr vs. < 1000 years, respectively). However, time averaging generally lowers beta diversity in an assemblage (Tomašových & Kidwell 2009) and therefore does not explain higher beta diversity in the Cassian Formation (see also supplementary information). Results from grouping the Cassian localities by inferred depth are ambiguous: Dissimilarity between depth categories does not differ much from dissimilarity within depth groups. While dissimilarity between the two localities from deeper environments is lower than most other

7 values, data are too limited to allow robust conclusions on beta diversity vs. depth. However, the Safaga samples – with a larger number of sampling sites and specific recorded depths – yield slightly higher beta diversity in deeper habitats. In addition, dissimilarity between two depth categories (four shallower samples vs. four deeper samples) is lower than within depth categories for both datasets. The high beta diversity at both Cassian and Safaga may partly driven by the great range of environments included. Specifically, beta diversity has been shown to increase with the variance of depths, due to the larger range of communities included in the study (Harborne et al. 2006). Change in faunal composition with depth is usually linked to variations in environmental factors, such as temperature, salinity, oxygenation, or sediment characteristics (Durden et al. 2015; Ellingsen & Gray 2002; Holte et al. 2004; Laine 2003). Due to water mixing in the Bay of Safaga, however, there is probably no depth gradient regarding water conditions (Zuschin & Oliver 2005). Differences in sedimentary attributes are also not related to faunal dissimilarity. While samples from a muddy environment have the highest mean dissimilarity with the other samples from Safaga (see also ordination in Zuschin & Hohenegger 1998, fig. 11a), this may be related to other factors, as there is no trend in beta diversity from sand to muddy sand to mud. Muddy habitat is common in the Red Sea in deeper waters and occurs in a shallower setting here due to a protected depression. Differences in sedimentary attributes were not noted in the Cassian Formation, leading us to assume that other factors may play a larger role in determining faunal composition. Especially the very high dissimilarity between samples from similar depths at Safaga contradicts findings by Ellingsen and Gray (2002) that samples from similar depths show higher similarity. While depth is often found to be an important driver of beta diversity (Ellingsen & Gray 2002; Harborne et al. 2006), we find no changes in beta diversity with depth in our sites. However, depth can determine faunal composition through depth-range restriction of species (Rex and Etter 2010), which may explain why beta diversity is highest between samples from the reef slope in Safaga. Comparing dissimilarity among different datasets is made more difficult by the fact that spatial grain influences beta diversity. Small spatial scales yield higher beta diversity than larger scales in coral reefs and rain forests, as the heterogeneity of environments is limited (Pandolfi 2002). However, studies on the effects of spatial scale on beta diversity reach differing conclusions (Lennon et al. 2001). Specifically, small-scale environmental differences – often created by the biota itself – can increase faunal variability. These small-scale differences can in turn increase beta diversity at a larger scale (e.g., Thrush et al. 2005). Applying Pandolfi's (2002) three-phase model of variability to the reef-adjacent soft bottoms of the Cassian Formation and the Bay of Safaga, we find that variance in community composition is expected to be lower at the observed geographical extent of both datasets (and temporal extent for the Safaga dataset) than at smaller or larger scales. In addition, temporal mixing in the Cassian Formation would yield lower variance. We therefore conclude that the high values of beta diversity are genuine and not due to spatial scale.

Stochasticity and distance decay The lack of correlation between geographic distance and community dissimilarity in the two sites lets us assume that there is no noteworthy distance decay over the limited spatial extent covered by the fossil and modern datasets. Studying a very environmentally homogeneous soft-bottom habitat on the Norwegian continental shelf, Ellingsen (2002) also found a weak relationship between spatial distance and dissimilarity. In addition, beta diversity in both study sites is much higher than predicted from the null models. Therefore, the spatial patterns of community composition among the study sites are not random and probably not constrained by dispersal. Since the two datasets differ in size (the Safaga dataset contains a higher number of samples, specimens, and species over a smaller area), the higher beta diversity in the Cassian null model is probably due to increased randomness by sampling fewer specimens and species from a slightly smaller species pool. With a beta diversity of 0.91 for the Cassian Formation despite the small species pool, stochasticity is clearly not the main driver of beta diversity. With the lack of stochasticity on top of the lack of a spatial pattern related to distance, other factors must have a stronger control on beta diversity. Community assembly Competitive interactions are probably not the main factor in determining faunal assemblages in shallow soft-bottom habitats. Klompmaker & Finnegan (2018) hypothesize predation to be an important factor in structuring modern and fossil soft-bottom communities, supporting earlier assessments (Stanley 2008). However, predation has increased since the Triassic (Huntley & Kowalewski 2007), therefore the Cassian fauna was probably less affected by predation than the Safaga fauna. In addition, physical disturbances, such as storms, have a large impact on benthic communities, especially in shallower settings where they are more prevalent. Low competition is attributed to high predation and disturbance limiting diversity. In greater depths, competition may be a stronger driving force due to less prevalent disturbances and predation (Harper & Peck 2016; Klompmaker & Finnegan 2018). Environmental heterogeneity is often considered the main driver of faunal heterogeneity (e.g., Carlos‐Júnior et al. 2019; Ellingsen 2002; Pandolfi & Jackson 2001; Stegen et al. 2013), with more uniform environments generally yielding a more homogeneous fauna (e.g., Clarke & Lidgard 2000; Ellingsen & Gray 2002; Fagerstrom 1983; Shin & Ellingsen 2004). However, it is often ignored that the environment can be structured by the biota itself. Organisms with hard parts that live on the sediment are found to directly contribute to environmental heterogeneity and in turn to faunal heterogeneity (Hewitt et al. 2005). The studied assemblages include both epifauna and infauna, which may directly contribute to high beta diversity through an increase in diversity driven by the combination of higher sediment stability in infaunal assemblages and biotic interactions in epifaunal assemblages (van der Zee et al. 2015).

9 We presume priority effects as one of the main drivers of beta diversity in the modern and ancient reef-related soft-bottom habitats. While there are many mechanisms that lead to differences in community composition, the order in which organisms settle in a habitat directly affects the community that subsequently assembles (Drake 1991; Fukami 2015; Thrush et al. 2005). Priority effects influence community composition at smaller sites by affecting the regional species pool as well as local population dynamics (Fukami 2015). In addition, the first species to arrive may even gain an evolutionary advantage, as they adapt to environmental conditions sooner than subsequent arrivals (De Meester et al. 2016).

Conclusions

Large variations in community composition are evident in reef-associated soft-bottom assemblages such as the Triassic Cassian Formation and the modern Bay of Safaga. Our original hypothesis that beta diversity decreases with depth is not supported by our analyses. We find depth, sediment structure, and stochastic effects to play minor roles in determining beta diversity. Through exclusion of other drivers, we presume priority effects to play a key role in determining community structure, through biotic interactions and increasing environmental heterogeneity on a small scale. Future research should clarify whether this pattern is contrained to relatively shallow reef-associated faunas or whether it is a general principle in marine environments.

Acknowledgements

The authors thank Evelyn Kustatscher, Bolzano (Italy), for attaining permits and Hans Hagdorn (Ingelfingen) and Max Urlichs (Stuttgart) for help in the field and interesting discussions on the Cassian fauna. VR thanks student assistants Jule Jung, Christian Ringkewitz, and George William Harrison for help in wet-sieving and picking samples and Christian Schulbert for assisting at the SEM. This work was supported by the Deutsche Forschungsgemeinschaft (KI 806/14-1, NU 96/13-1).

Author contributions. VR processed and identified the four new Cassian samples, with support in identification by AN. The Safaga dataset was compiled by MZ. Analyses and figures were done by VR. The manuscript was written by VR, MZ and WK. VR, IH, AN & WK participated in field work.

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15 Tables Table 1: Age, locality, size, and diversity of studied samples from the Cassian Formation. Samples from Lago Antorno, Misurina landslide, Settsass, and Stuores are from previous studies (Hausmann et al. submitted, APP; Nützel and Kaim 2014; Hausmann and Nützel 2015). See Material and Methods for applied measures. Indices based on 10 most abundant species per sample. PPD = pairwise proportional dissimilarity. Mean PPD with regard to other samples.

Stratigraphic age Berger-Parker Inferred Sample Even- Locality (ammonite biozone, Coordinates No. of specimens dominance Mean PPD relative weight ness substage) index depth

Costalaresc austriacum, Julian 46.53995 N 12.16390 E 4540 g 315 0.73 0.28 0.92 ± 0.03 intermediate

probably austriacum, Lago Antorno 46.59438 N 12.26100 E 5 – 10 kg 216 0.31 0.51 0.91 ± 0.06 shallow Julian Misurina probably austriacum, 46.59490 N 12.25962 E 5 – 10 kg 558 0.30 0.49 0.90 ± 0.06 intermediate landslide Julian

Picolbach aon, Julian 46.53427 N 11.92253 E 2840 g 222 0.24 0.55 0.89 ± 0.04 deep

probably aonoides, Rumerlo cliff 46.53375 N 12.09882 E 3313 g 235 0.21 0.55 0.86 ± 0.06 shallow Julian Rumerlo ski aonoides, Julian 46.53684 N 12.10214 E 3805 g 33 0.21 0.59 0.89 ± 0.06 shallow slope

Settsass aon, "Cordevolian" 46.51733 N 11.95846 E > 7 kg 296 0.24 0.50 0.94 ± 0.03 deep

Stuores aon, "Cordevolian" 46.52872 N 11.93672 E 16.5 kg 1026 0.33 0.53 0.95 ± 0.02 very shallow

16 Table 2: Environment, locality, and diversity of studied samples from the Bay of Safaga. See Material and Methods for applied measures. Indices based on 10 most abundant species per sample. PPD = pairwise proportional dissimilarity. Mean PPD with regard to other samples.

No. of Berger-Parker Locality Environment Depth Coordinates Evenness Mean PPD specimens Dominance Index

94-1-a Sand between coral patches 10 26.81417 N 33.97683 E 901 0.17 0.54 0.67 ± 0.11 94-1-b Sand between coral patches 10 26.81417 N 33.97683 E 778 0.16 0.55 0.66 ± 0.11 94-1-c Sand between coral patches 10 26.81417 N 33.97683 E 785 0.18 0.53 0.66 ± 0.11 94-1-d Sand between coral patches 10 26.81417 N 33.97683 E 729 0.17 0.54 0.66 ± 0.12 94-3-a Muddy sand 23 26.79117 N 33.94667 E 510 0.45 0.41 0.74 ± 0.10 94-3-b Muddy sand 23 26.79117 N 33.94667 E 624 0.45 0.39 0.74 ± 0.10 94-4-a Mud 39 26.81417 N 33.96533 E 2140 0.22 0.50 0.83 ± 0.10 94-4-b Mud 39 26.81417 N 33.96533 E 1647 0.23 0.50 0.83 ± 0.10 94-5 Reef slope 19 26.84733 N 34.00483 E 416 0.31 0.51 0.91 ± 0.10 94-6 Mangrove-channel <1 26.76750 N 33.96283 E 481 0.44 0.45 0.86 ± 0.08 95-31 Reef slope 12 26.82933 N 33.98483 E 1187 0.49 0.43 0.85 ± 0.07 B-5-8 Sandy seagrass 6 26.82683 N 33.95383 E 2161 0.43 0.47 0.68 ± 0.08 C-1-3 Muddy sand with seagrass 40 26.83000 N 33.98683 E 3969 0.44 0.43 0.75 ± 0.09

17 Table 3: Faunal composition of the four new samples from the Cassian Formation. Information on the localities provided in Table 2. We differentiate between Domerionina scalaris sensu Bandel 1994 and Domerionina scalaris sensu Kittl 1894 as they may belong to different species. Palaeonucula strigilata var. 2 differs from Palaeonucula strigilata and is treated as a different species here. The same applies to Prostylifer paludinaris var. 2.

Rumerlo ski slope Costalaresc Picolbach Rumerlo cliff

Species Specimens Species Specimens Species Specimens Species Specimens Ptychostoma Camposcala biserta 7 230 Domerionina stuorense 54 Camposcala biserta 50 sanctaecrucis Ptychostoma Zygopleura campoensis Dicosmos maculosus Dicosmos maculosus 5 28 pleurotomoides 30 48 Domerionina scalaris Domerionina Domerionina scalaris 4 Domerionina stuorense 16 25 38 sensu Kittl 1894 pralongiana sensu Kittl 1894 Palaeonucula strigilata Promathildia decorata 3 10 Plagioglypta undulata 24 Stuorilda cassiana 30 var. 2 Dicosmos maculosus 3 Plagioglypta undulata 9 Palaeonucula strigilata 23 Zygopleura depressa 20 Kittliconcha Ampezzopleura Ptychostoma Tirolthilda seelandica obliquecostata 2 hybridopsis 7 sanctaecrucis 20 9 Domerionina scalaris Zygopleura hybridissima 2 Atorcula anoptychopsis 5 17 Mathilda biserta 9 sensu Bandel 1994 Zygopleura depressa 2 Ampezzopleura bandeli 4 Dicosmos maculosus 12 Domerionina scalaris 9 Colubrellopsis Domerionina scalaris 2 3 Stuorilda cassiana 10 Prostylifer paludinaris 7 acutecostata sensu Bandel 1994 Popenella misurina, Palaeonucula strigilata Prostylifer paludinaris Stuorilda tichyi, Spirostylus brevior 1 3 7 6 Rinaldoconchus bieleri* var. 2 var. 2

*Each represented with one specimen. Rumerlo ski slope yielded a very low number of specimens

18 Table 4: Pairwise proportional dissimilarity (PPD) of the studied samples from the Cassian Formation. Information on the localities provided in Table 2. PPD based on 10 most abundant species per sample.

Lago Misurina Rumerlo Rumerlo ski Costalaresc Picolbach Settsass Stuores Antorno landslide cliff slope

Costalaresc 0.98 0.97 0.74 0.89 0.91 0.96 1.00

Lago Antorno 0.52 1.00 0.97 1.00 0.97 0.95

Misurina 0.98 0.95 1.00 0.96 0.95 landslide

Picolbach 0.83 0.95 0.76 1.00

Rumerlo cliff 0.52 0.97 0.92

Rumerlo ski 1.00 0.86 slope

Settsass 0.97

Stuores

19 Table 5: Pairwise proportional dissimilarity (PPD) of the studied samples from the Bay of Safaga. Samples taken from same site (only several meters apart) were combined (94-1-a to -d: 94-1, 94-3-a and -b: 94-3, 94-4-a and -b: 94-4-a). Information on the localities provided in Table 3. PPD based on 10 most abundant species per sample.

94-1 94-3 94-4 94-5 94-6 95-31 B-5-8 C-1-3 Sand Muddy between Muddy Mangrove Sandy Mud Reef slope Reef slope sand with coral sand channel seagrass seagrass patches 94-1 Sand between 0.97 1.00 1.00 0.86 0.83 0.70 0.91 coral patches 94-3 Muddy 0.88 1.00 0.97 0.99 0.44 0.42 sand 94-4 Mud 1.00 1.00 1.00 1.00 1.00

94-5 Reef slope 1.00 0.89 1.00 1.00

94-6 Mangrove 0.96 0.86 0.97 channel 95-31 Reef slope 0.89 0.97

B-5-8 Sandy 0.35 seagrass C-1-3 Muddy sand with seagrass

20 Figures

Fig. 1: Map of reported localities in the Cassian Formation (dots) and major settlements (stars).

Fig. 2: Depth-related attributes of the studied samples from the Cassian Formation (left). Change of sample characteristics with depth (right).

Fig. 3: Inferred relative depth of the Cassian samples. Mean pairwise proportional dissimilarity (PPD) of each sample with other samples and mean PPD among samples grouped by depth are depicted.

Fig. 4: Null model of mean beta diversity of the Cassian dataset (left) and the by-site Safaga dataset (right). Beta diversity was calculated as mean proportional dissimilarity over 1000 iterations.

Fig. 5: Correlation between geographical distance and pairwise proportional dissimilarity in the Cassian dataset (a) and the by-site Safaga dataset (b). Distance decay is non- significant for the Cassian (Spearman's rank correlation rho: 0.27, p-value: 0.17) and the Safaga dataset (rho: 0.01, p-value: 0.95).

Fig. 6: Non-metric multidimensional scaling of the Cassian samples, color-coded by depth. There are no distinct associations among localities from similar depths.

Fig. 7: Mean PPD among samples and depth categories for the by-site Safaga dataset.

Fig. 8: Non-metric multidimensional scaling of the Safaga samples, color-coded by depth. As in the Cassian (Fig. 6), there are no distinct associations between localities from similar depths.

24 Supplementary information to Roden VJ, Zuschin M, Nützel A, Hausmann IM and Kiessling W. Drivers of beta diversity in modern and ancient reef-associated soft-bottom environments. PeerJ [subm.].

Part I: Temporal changes Herein, we apply the definition of the Cassian Formation as sensu lato, in a traditional sense, including all marly or clayey Ladinian–Carnian sediments deposited in the interplatform basins of the Dolomites (Table S3) (Bizzarini & Laghi 2005; Keim et al. 2006; Nose et al. 2018; Urlichs 2017). Studied samples are from the aon, aonoides, and austriacum zones. The base of the aon Zone is at 236 Ma and the top of the austriacum zone is at 231 Ma (Gradstein et al. 2012), covering a temporal range of approximately 5 Ma.

Temporal turnover, calculated by pooling the faunal communities of each ammonite biozone, is also relatively high (PPD austriacum/aonoides zones: 0.93, aonoides/aon zones: 0.88). Dissimilarity between the two localities from the aonoides zone is much lower (PPD: 0.52) than among austriacum (mean PPD: 0.82 ± 0.15) localities and aon (mean PPD: 0.91 ± 0.08) localities. A visualization of community dissimilarity using NMDS does not show strong relationships among localities from similar depths or the same ammonite biozones (Fig. S6). While we do report temporal turnover in the Cassian Formation, beta diversity within two of the three ammonite biozones is similarly high. Therefore, time is unlikely to play a major role in the observed community dissimilarities.

Table S1: Stratigraphy of the Cassian Formation with ammonite zonation. Studied samples from marked ammonite biozones. The Cassian Formation sensu stricto comprises the late regoledanus, canadensis, aon, and aonoides ammonite biozones. The austriacum and dilleri ammonite biozones are now regarded as belonging to the Heiligkreuz Formation.

Heiligkreuz Tuvalian dilleri zone Formation austriacum zone Julian aonoides zone

Carnian Cassian Formation Cassian aon zone

Late Triassic Triassic Late sensu lato Formation "Cordevolian" sensu stricto canadensis zone

regoledanus Longobardian zone

Ladinian

Rumerlo skipiste Stuores

Rumerlo cliff

NMDS2 Picolbach Costalaresc Lago Antorno Misurina landslide

austriacum

-0.4 -0.2 0.0 0.2 0.4 aonoides Settsass aon

-0.4 -0.2 0.0 0.2 0.4

NMDS1

Fig. S1: Non-metric multidimensional scaling of the Cassian samples, color-coded by ammonite biozone (darker colors represent older strata). No strong relationships among localities from the same ammonite biozone are seen.

Part II: Reduced versus complete dataset, Bay of Safaga

The Safaga dataset was reduced to the ten most abundant species for comparability with the Cassian dataset. To test whether results are robust, the analyses using the complete Safaga dataset are provided here.

RESULTS Environments Environments and depth from which the Safaga samples were taken are recorded and alpha diversity calculated (Table S1). Samples from the reef slope and from sand between coral patches show highest evenness; samples from sand between coral patches show lowest dominance. There is also no significant correlation between alpha diversity, either measured as dominance or evenness, and depth in the Safaga samples. The range of evenness is slightly higher than in the Cassian samples. Beta diversity Overall beta diversity of the modern Safaga dataset is lower (0.80 ± 0.03; range: 0.09-0.99; Table S2) than in the Triassic Cassian Formation. When samples taken from the same site in Safaga Bay are pooled, we measure a beta diversity of 0.85 ± 0.03. Null models created for each dataset from the gamma species pool yield much lower beta diversity, with a mean of 0.18 ± 0.0001 for the pooled Safaga dataset (8 samples) and 0.20 ± 0.0001 for the unpooled dataset (13 samples) (Fig. S1). The Safaga dataset shows no distance decay (rho: 0.13, p-value: 0.49; Fig. S2a) when samples taken from the same sites are pooled. Without pooling, there is a low correlation (rho: 0.28, p-value: 0.013; Fig. S2b) in the Safaga samples. At Safaga, there is no clear pattern of beta diversity related to depth (Fig. S3). Samples taken from the same environment, locality, and depth (only several meters apart) are very similar. Samples taken from deep, muddy settings exhibit the highest mean beta diversity (0.95 ± 0.02). Otherwise there is no relationship between sedimentary attributes and mean dissimilarity. By grouping the samples into depth ranges, we cover several environments for each range. Grouping the localities into two, three, or four depth ranges, we generally find that samples from shallower environments have a more similar community composition than samples from deeper environments (Figs. S3, S4). Dissimilarity between the four shallower and the four deeper samples is 0.72 and therefore lower than other values measured within depth ranges.

CONCLUSIONS Overall beta diversity of the complete dataset (0.80 unpooled, 0.85 pooled) is slightly lower than beta diversity for the dataset containing only the ten most abundant species per sample (0.82 unpooled, 0.89 pooled). This corroborates results from Roden et al. (2018), who found beta diversity estimates based on the five or ten most abundant species per sample to be statistically indistinguishable from estimates using the complete dataset. Beta diversity for most datasets – including the same dataset from the Bay of Safaga – is only slightly higher when only abundant species are included. Null models yield higher beta diversity for the complete dataset. Since the two Safaga datasets differ in size (the complete dataset contains 23 190 specimens and 639 species, the reduced dataset contains 16 328 specimens and 59 species), the higher beta diversity in the Cassian null model (2901 specimens and 50 species) is probably due to increased randomness by sampling fewer specimens from a smaller species pool. Other results (distance decay, mean PPD vs. depth, NMDS) are very close to results from the reduced dataset. Therefore, overall results are robust.

Table S2: Environment, locality, and diversity of studied samples from the Bay of Safaga. See Material and Methods for applied measures. PPD = pairwise proportional dissimilarity. Mean PPD with regard to other samples.

Berger- Evenness Mean PPD Coordinates No. of Parker Locality Environment Depth specimens Dominance Index

Sand between 0.61 0.70 ± 0.08 94-1-a 10 26.81417 N 33.97683 E 1637 0.09 coral patches

Sand between 0.62 0.70 ± 0.08 94-1-b 10 26.81417 N 33.97683 E 1454 0.09 coral patches

Sand between 0.57 0.71 ± 0.08 94-1-c 10 26.81417 N 33.97683 E 1283 0.11 coral patches

94-1-d Sand between 0.60 0.70 ± 0.08 10 26.81417 N 33.97683 E 1311 0.10 coral patches

94-3-a Muddy sand 23 26.79117 N 33.94667 E 651 0.35 0.41 0.79 ± 0.07

94-3-b Muddy sand 23 26.79117 N 33.94667 E 767 0.36 0.38 0.78 ± 0.07

94-4-a Mud 39 26.81417 N 33.96533 E 2353 0.20 0.38 0.87 ± 0.07

94-4-b Mud 39 26.81417 N 33.96533 E 1901 0.20 0.41 0.87 ± 0.07

94-5 Reef slope 19 26.84733 N 34.00483 E 877 0.15 0.63 0.93 ± 0.03

94-6 Mangrove- 0.42 0.90 ± 0.02 <1 26.76750 N 33.96283 E 611 0.35 channel

95-31 Reef slope 12 26.82933 N 33.98483 E 2301 0.25 0.59 0.86 ± 0.03

B-5-8 Sandy seagrass 6 26.82683 N 33.95383 E 3108 0.30 0.50 0.73 ± 0.05

C-1-3 Muddy sand 0.42 0.80 ± 0.06 40 26.83000 N 33.98683 E 4936 0.35 with seagrass

Fig. S2: Null model of mean beta diversity of the Safaga dataset with samples pooled (a) and unpooled (b). Null model created by randomly sampling the gamma species pool until the number of specimens and number of sampling sites of the original datasets were obtained. Beta diversity was calculated as mean proportional dissimilarity over 1000 iterations.

Fig. S3: Correlation between geographical distance and pairwise proportional dissimilarity in the Safaga dataset with samples pooled (a), and unpooled (b). Distance decay is non- significant for the pooled dataset and low for unpooled samples.

Table S3: Pairwise proportional dissimilarity (PPD) of the studied samples from the Bay of Safaga. Samples taken from same site (only several meters apart) are pooled; their composition is very similar (mean PPD samples 94-1-a to -d: 0.23 ± 0.01, PPD samples 94-3-a and -b: 0.22, PPD samples 94-4-a and -b: 0.09).

94-1 94-3 94-4 94-5 94-6 95-31 B-5-8 C-1-3 Sand Muddy Mud Reef Mangrove Reef Sandy Muddy between sand slope channel slope seagrass sand coral with patches seagrass 94-1 Sand 0.90 0.96 0.90 0.81 0.75 0.64 0.84 between coral patches 94-3 Muddy 0.83 0.98 0.94 0.96 0.54 0.46 sand 94-4 Mud 0.99 0.98 0.99 0.96 0.95

94-5 Reef 0.96 0.66 0.96 0.98 slope 94-6 Mangrove 0.92 0.85 0.95 channel 95-31 Reef 0.88 0.93 slope B-5-8 Sandy 0.45 seagrass C-1-3 Muddy sand with seagrass

Fig. S4: Mean PPD among samples and depth categories for the Safaga dataset with samples pooled.

C-1-3 94-3-a 95-31 B-5-8 94-3-b 0 294-1-a 4

NMDS2 94-5 94-1-b 94-1-d 94-4-a 94-1-c 94-4-b

94-6

very shallow shallow deeper

-4 -2

-4 -3 -2 -1 0 1 2 3

NMDS1

Fig. S5: Non-metric multidimensional scaling of the Safaga samples (unpooled), color-coded by depth. No strong relationships among localities from similar depths are seen.

Part III: Results from Safaga dataset, by sample When samples from the same site are not combined, overall beta diversity of the Safaga dataset is lower (0.82 ± 0.04; range: 0.05-1.00) than in the by-site dataset. A null model created from the gamma species pool of the by-sample dataset yields much lower beta diversity, with a mean of 0.12 ± 0.0001 (Fig. S7). Samples taken from same site (only several meters apart) are pooled in the by-site dataset (main text); their composition is very similar (mean PPD samples 94-1-a to -d: 0.12 ± 0.01, PPD samples 94-3-a and -b: 0.16, PPD samples 94-4-a and -b: 0.06). There is a low correlation (rho: 0.25, p-value: 0.02; Fig. S8) in the by-sample Safaga dataset, but this is attributed to very high similarities between samples from the same site.

Mean PPDMean

0.105 0.115 0.125

Fig. S6: Null model of mean beta diversity of the Safaga dataset with samples unpooled. Beta diversity was calculated as mean proportional dissimilarity over 1000 iterations. The dataset was reduced to the ten most abundant species.

1.0

Mean PPD Mean

0.5

0.0 0.0 2.5 5.0 7.5 Distance (km)

Fig. S7: Correlation between geographical distance and pairwise proportional dissimilarity in the Safaga dataset with samples unpooled. Distance decay is low (Spearman's rank correlation rho: 0.25, p-value: 0.02). The dataset was reduced to the ten most abundant species.

Part IV: Alpha diversity

0.0 0.5 1.0 1.5 2.0 2.5 0.0 0.5 1.0 1.5 2.0 2.5 0.0 0.5 1.0 1.5 2.0 2.5 0.0 0.5 1.0 1.5 2.0 2.5 1 3 5 7 9 1 3 5 7 9 1 3 5 7 9 1 3 5 7 9

Costalaresc Lago Antorno Misurina landslide Picolbach

0.0 0.5 1.0 1.5 2.0 2.5 0.0 0.5 1.0 1.5 2.0 2.5 0.0 0.5 1.0 1.5 2.0 2.5 0.0 0.5 1.0 1.5 2.0 2.5 1 3 5 7 9 11 13 1 3 5 7 9 11 1 3 5 7 9 1 3 5 7 9

Rumerlo cliff Rumerlo ski slope Settsass Stuores

Fig. S8: Rank-abundance distributions of the 10 most abundant species in Cassian samples. Abundances logged (base 10).

REFERENCES Bizzarini F, and Laghi GF. 2005. La successione "Cassiana" nell’area a nord di Misurina (Trias, Dolomiti). Lavori Società Veneziana Scienze Naturali 30:127-143. Gradstein FM, Ogg JG, Schmitz M, and Ogg G. 2012. The Geologic Time Scale 2012. Amsterdam: Elsevier. Keim L, Spötl C, and Brandner R. 2006. The aftermath of the Carnian carbonate platform demise: a basinal perspective (Dolomites, Southern Alps). Sedimentology 53:361-386. Nose M, Schlagintweit F, and Nützel A. 2018. New Record of Halimedacean Algaa from the Upper Triassic of the Southern Alps (Dolomites, Italy). Rivista Italiana di Paleontologia e Stratigrafia (Research In Paleontology and Stratigraphy) 124:421-431. Roden VJ, Kocsis ÁT, Zuschin M, and Kiessling W. 2018. Reliable estimates of beta diversity with incomplete sampling. Ecology 99:1051-1062. Urlichs M. 2017. Revision of some stratigraphically relevant ammonoids from the Cassian Formation (latest Ladinian-Early Carnian, Triassic) of St. Cassian (Dolomites, Italy). Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen 283:173-204.

Publication #4

Hausmann, I. M., Nützel, A., Roden, V. J. & Reich, M. 2019. Diversity and palaeoecology of Late Triassic invertebrate assemblages from the tropical marine basins near Lake Misurina (Dolomites, Italy). Acta Palaeontologica Polonica. Accepted pending revisions.

Diversity and palaeoecology of Late Triassic invertebrate assemblages from the tropical marine basins near Lake Misurina (Dolomites, Italy)

IMELDA M. HAUSMANN, ALEXANDER NÜTZEL, VANESSA JULIE RODEN, and MIKE REICH

Imelda M. Hausmann [[email protected]], SNSB – Bavarian State Collection of Palaeontology and Geology, Richard-Wagner-Str. 10, 80333 München, Germany; Department of Earth and Environmental Sciences, Palaeontology & Geobiology, Ludwig-Maximilians-Universität München, Richard-Wagner-Str. 10, 80333 München, Germany. Alexander Nützel [[email protected]], SNSB – Bavarian State Collection of Palaeontology and Geology, Richard-Wagner-Str. 10, 80333 München, Germany; Department of Earth and Environmental Sciences, Palaeontology & Geobiology, Ludwig-Maximilians-Universität München, Richard-Wagner-Str. 10, 80333 München, Germany; GeoBio-Center LMU, Richard-Wagner-Str. 10, 80333 München, Germany. Vanessa Julie Roden [[email protected]], GeoZentrum Nordbayern, Section Paleobiology, University Erlangen-Nürnberg, Loewenichstr. 28, 91054 Erlangen, Germany. Mike Reich [[email protected]], SNSB – Bavarian State Collection of Palaeontology and Geology, Richard- Wagner-Str. 10, 80333 München, Germany; Department of Earth and Environmental Sciences, Palaeontology & Geobiology, Ludwig-Maximilians-Universität München, Richard-Wagner-Str. 10, 80333 München, Germany; GeoBio-Center LMU, Richard-Wagner-Str. 10, 80333 München, Germany.

Keywords. Mollusca; Echinodermata; diversity; palaeoecology; Cassian Formation; small body size

Abstract

Two marine invertebrate fossil assemblages from the Late Triassic Cassian Formation (North Italy, Dolomites) were examined regarding diversity and palaeoecology. Surface and bulk samples from the localities Misurina and Lago Antorno were taken and analysed separately. Both benthic assemblages are relatively similar in taxonomic composition. Mollusc dominance is pronounced in both samples. Gastropods are the most abundant and diverse group, followed by bivalves. Disarticulated echinoderm ossicles are also common in the bulk sample from Misurina Landslide, but they are rare at Lago Antorno. The gastropod species Coelostylina conica (Münster, 1841), Prostylifer paludinaris (Münster, 1841) and Ampezzopleura hybridopsis Nützel, 1998 are characteristic elements of both assemblages. However, the gastropod Jurilda elongata (Leonardi and Fiscon, 1959) is the most abundant species at Misurina, whereas the gastropod species Dentineritaria neritina (Münster) sensu Bandel (2007) dominates the assemblage from Lago Antorno. Newly described gastropod species are Angulatella bizzarinii Nützel & Hausmann sp. nov., Bandellina compacta Nützel & Hausmann sp. nov. and Ampezzogyra angulata Nützel & Hausmann sp. nov. In total, 57 invertebrate species were found in the Misurina bulk sample and 26 species in the bulk sample from Lago Antorno. However, sample size from Lago Antorno was much smaller than that from Misurina. Diversity indices show approximately the same moderate diversity in both assemblages. Rarefaction curves and rank- abundance distributions also point to a very similar diversity and ecological structure of the fossil assemblages. Both assemblages are autochthonous or parautochthonous, stemming from basinal, soft- bottom habitats. Their taxonomic composition differs significantly from that of other faunas known from the Cassian Formation. This shows that few species are shared between outcrops and that different species are dominating (high beta diversity). The tropical marine Cassian palaeoecosystem was highly complex and its diversity is far from being fully explored.

Introduction

The Late Triassic Cassian Formation sensu lato has yielded by far the most diverse marine invertebrate fauna known from the early Mesozoic. 1421 invertebrate species have been described up to now, with molluscs (950 species) being the most diverse phylum (Roden et al. 2019 accepted). The main reason for this very high diversity is a high primary diversity and the fact that the poorly lithified marls qualify the cassian Formation as a Liberation Fossil-lagerstätte i.e., well-preserved specimens can be extracted easily. The vast majority of the literature on Cassian fossils treats taxonomic or stratigraphic questions and in most cases refers to particular fossil groups. In contrast, few quantitative datasets about entire invertebrate assemblages have been provided including relative abundances (Fürsich and Wendt 1977; Nützel and Kaim 2014; Hausmann and Nützel 2015). However, abundance data are needed for sample standardisation methods used in biodiversity estimations and palaeoecological questions. It is therefore desirable to provide such data sets of high quality, i.e., descriptions, counts and discussion of the taxa present in a sample or in a fauna. Ideally, such data sets should be illustrated so that they are easily verifiable. Moreover, it should be stated how many specimens were collected in the field and how many were obtained by bulk sampling and sieving because these different methods produce different assemblage compositions. A large variety of fossil assemblages has been found in the Cassian Formation, ranging from very high-diverse reef dwellers from shallow water to various low-diverse soft-bottom assemblages. In addition to differences in diversity, rank-abundance distributions and taxonomic composition differ considerably between the studied assemblages (Fürsich and Wendt 1977; Nützel and Kaim 2014; Hausmann and Nützel 2015; Roden et al. 2019 accepted). The previous quantitative datasets suggest that the entire complex tropical marine ecosystem of the Cassian Formation is far from being fully explored (Fürsich and Wendt 1977; Nützel and Kaim 2014; Hausmann and Nützel 2015). Therefore, the present contribution quantitatively and systematically investigated the Late Triassic hitherto unknown invertebrate fossil assemblages from two outcrops near Lake Misurina (Dolomites, N Italy). The studied assemblages are strongly dominated by molluscs and especially by gastropods as is usual for the Cassian Formation (e.g., Roden et al. 2019 accepted). The taxonomy of the gastropods is intricate because of a complex history of research. Therefore, we also focus on the systematic description and illustration of the gastropod fauna from our samples. This establishes falsifiability and facilitates species identification for future work. The study of the exceptionally preserved Cassian biota helps to understand the evolution of diversity at a large scale i.e. anwering the question whether early Mesozoic tropical marine ecosystems were as diverse as modern ones.

Geological setting

Surface and bulk samples were taken near Lago Antorno at a landslide scar (GPS 46°35'39.8"N / 12°15'39.6"E). In addition, several samples were taken at another landslide scar near the locality Misurina (named here Misurina Landslide; GPS 46°35'41.6"N / 12°15'34.6"E) (Fig. 1). The latter sampling site corresponds to outcrop number 4 of Bizzarini and Laghi (2005). The section exposed in the scar is in situ and consists largely of marls and claystones with a few marlylimestone beds (Fig. 1D). In the upper part of this landslide area, a relatively thick marly limestone bed is exposed, situated a few metres above our sampling spot (Fig. 1C). Both sites, Lago Antorno and Misurina Landslide, expose greyish to brownish claystones, which are poorly lithified. They belong to the sediments of the Cassian Formation (s. l.) as is indicated by several typical invertebrate species (see below), which has a Late Ladinian to Middle Carnian age.

During the Late Triassic, the Cassian Formation was positioned in the northern tropics (at about 16°N) as part of the western Tethys region (Broglio Loriga et al. 1999; Keim et al. 2006). Sea surface temperatures were comparable to modern tropical seas; however, it was shown that seasonal fluctuations were pronounced (Nützel et al. 2010a).

Material and methods

Samples from the landslide scar near Lago Antorno stem from sampling campaigns conducted in the years 2008, 2010 and 2016. Samples from Misurina Landslide were collected in the upper part of the landslide scar in June 2016. A marly limestone bed is located near this sampling locality. Samples were taken from unconsolidated marls. One bulk and three surface samples from Lago Antorno and two bulk and four surface samples from Misurina Landslide comprising 5-10 kg were taken.

The marly bulk samples were treated with a 7 % H2O2 solution and wet-sieved with mesh sizes of 5, 0.5 and 0.11 mm. For the Lago Antorno bulk sample, a 0.4 mm instead of a 0.5 mm mesh was used. Residues were picked completely. The finest fraction, 0.11 to 0.5/0.4 mm, was analysed only qualitatively and was therefore excluded from the statistical analyses. Nevertheless, the fossil content inside this size fraction is briefly discussed herein. The fossil material from bulk (> 0.5/0.4 mm) and surface samples was quantified and identified to species level. SEM images were made of the most common and of problematic species to facilitate identification. To account for the best possible estimation of the abundance of fossils with more than one shell part (i.e., bivalves, brachiopods, ostracods, echinoderms), we calculated the estimated number of specimens as follows: In bivalves, brachiopods and ostracods, the estimated number of specimens was calculated as articulated fossils plus higher number of left/right or ventral/dorsal valves. Regarding echinoderms, each species was counted as being represented by one specimen as long as the number of hard parts did not exceed the number present in one specimen (see also Fürsich and Wendt 1977; Nützel and Kaim 2014; Hausmann and Nützel 2015). All shells were additionally investigated for predatory drill holes irrespective of complete or incomplete drilling. Alpha diversity was estimated using the diversity indices Shannon, Simpson and Berger-Parker, which were calculated in PAST version 3.20 (Hammer et al. 2001). Rarefaction curves were performed with PAST and R version 3.5.3 (R Core Team 2019) using the package vegan (Oksanen et al. 2019). Best model fit for rank-abundance distributions, using AIC values, was calculated with the vegan package (Oksanen et al. 2019). The R package sads (Prado et al. 2018) was used for plotting rank-abundance distributions. Beta diversity was calculated based on dissimilarities in community composition among samples from this study and previous work (Nützel & Kaim 2014, Hausmann & Nützel 2015) using identified species. It is expressed as pairwise proportional dissimilarity (PPD), which is relatively insensitive to unequal sample sizes (Krebs 1989) and is calculated as djk = 1 ∑min(xij, xik), with xij and xik being the proportions of species abundance in each sample. Beta diversity calculations were performed using R version 3.5.0 (R Core Team 2016) and the vegan package (Oksanen et al. 2016).

Results

Taxonomic composition 57 species were found in the bulk sample from Misurina Landslide and 26 species from Lago Antorno. Fossil assemblages at both sites are strongly dominated by gastropods (Tables 1 and 2, Fig. 2). 20 gastropod species and 567 specimens were contained in the Misurina Landslide bulk collection. In comparison, 17 species and 230 specimens of gastropods were found at Lago Antorno. Vetigastropods are almost completely absent, represented by only two species and two specimens. Bivalves made up

3 the second most abundant and species-rich group. Scaphopods and ostracods were rare. Cephalopods and brachiopods were only found at one sampling site, respectively. Twenty-one echinoderm species were retrieved from Misurina Landslide, with echinoids and holothurians being the most diverse groups. Lago Antorno was much less diverse regarding echinoderms, since only two species were found in the bulk sample. Many skeletal elements, most of them belonging to echinoids, were contained in the bulk samples from Misurina Landslide, whereas only 5 elements could be retrieved from Lago Antorno. Reef-building organisms were no characteristic elements of the fossil assemblages; in fact, only one tiny sponge piece was found in the surface samples from Misurina Landslide and only one small fragment of a presumably hydrozoan taxon in the Lago Antorno sample. In the surface samples, gastropods again made up the most species-rich and abundant group, followed by bivalves. 14 and 11 gastropod species were found at Misurina Landslide and Lago Antorno, respectively, comprising 89 and 136 shells (Table 1). Eight species and 24 specimens of bivalves were contained in the surface samples from Misurina Landslide in comparison to 5 species and 10 specimens from Lago Antorno. Scaphopods were also rare and cephalopods, brachiopods, and ostracods are completely missing in the surface samples. No echinoderms were contained in the surface samples from both localities, except one skeletal element of a cidaroid echinoid, which was found at Misurina Landslide. In addition, one small sponge fragment was found at Misurina Landslide. The most abundant species in the bulk sample from Misurina Landslide is Jurilda elongata (Leonardi and Fiscon, 1959), which is only rarely found at Lago Antorno. In contrast, the most abundant species in the Lago Antorno bulk sample is the gastropod Dentineritaria neritina (Münster) sensu Bandel (2007), which is also abundant in the bulk sample from Misurina Landslide but less frequent than at Lago Antorno (Table 1). The gastropod Neritaria mandelslohi (Klipstein, 1843) sensu Bandel (2007) is also very abundant at Lago Antorno, but rare at Misurina Landslide. However, the caenogastropods Coelostylina conica (Münster, 1841), Prostylifer paludinaris (Münster, 1841) and Ampezzopleura hybridopsis Nützel, 1998 are characteristic faunal components at both locations. Regardless of some differences in species abundances and composition, both fossil assemblages from Lago Antorno and Misurina Landslide are similar, indicating that they derive from a similar palaeoenvironment.

Diversity All three calculated diversity indices Simpson, Shannon and Berger-Parker indicate that diversity is approximately the same between the bulk collections of Lago Antorno and Misurina Landslide (Table 3). Simpson and Shannon indices suggest a moderate diversity of both fossil assemblages. However, dominance is not very pronounced, as indicated by the Berger-Parker index. Diversity indices of the surface collections show that diversity is even lower and dominance is much more pronounced in comparison to the bulk samples. The Lago Antorno surface collection is less diverse than the surface sample from Misurina Landslide. Rarefaction curves suggest that the bulk collections from both Cassian localities are similar in diversity (Fig. 3). In addition, the surface samples show high similarities with the corresponding bulk samples. All rarefaction curves are not saturated but are still rising. Therefore, it can be expected that additional species would be found with larger sample sizes. Rank-abundance distributions of Lago Antorno and Misurina Landslide bulk samples best fit the Zipf- Mandelbrot model (Table 4, Fig. 4). This indicates that both assemblages have the same ecological complexity, since they follow the same distribution.

Drilling predation Some molluscan shells from Misurina Landslide and Lago Antorno showed drill holes similar to recent naticid borings. In most cases, gastropods were drilled, for instance Coelostylina conica (Münster, 1841), Ampezzopleura hybridopsis Nützel, 1998, Ampezzogyra angulata Nützel &

Hausmann sp. nov. and Angulatella bizzarinii Nützel & Hausmann sp. nov. However, only a small portion of the species was drilled, pointing to a certain prey preference. When considering both, fossil locations and bulk as well as surface samples, only about 15 molluscan species showed drill holes. In addition, only a comparatively small number of shells was drilled in total (c. 60 shells). All drilled species that were found simultaneously in both bulk and surface samples were considerably more frequently drilled in the corresponding surface samples, regardless of the fossil locality. In several cases, shells showed more than one drill hole.

Fossil size The fossils from Lago Antorno and Misurina Landslide are small, often only a few millimetres in size. The marly limestone bed situated near the sampling spot at Misurina Landslide (Fig. 1C) also contained fossils, mostly gastropods of the genus Coelostylina Kittl, 1894 and the bivalves Nuculana Link, 1807 and Cassianella Beyrich, 1862. The largest fossil found there was a specimen of Cassianella with a height of 32 mm and a width of 27 mm. We assume that the fossil assemblage embedded in the marly limestone bed is also of autochthonous origin. However, fossils of the size of the Cassianella specimen were not found in the unconsolidated marls. Instead, they were much smaller in these samples.

Repository

All illustrated specimens will be stored in the Naturmuseum Südtirol (PZO).

Systematic palaeontology

Foraminifera

Foraminiferids are abundant in the bulk samples from Misurina Landslide, with the most abundant groups being the genus Glomospira Rzehak, 1888 and encrusting forms of unknown identity. The fine fraction (< 0.5 mm) from both localities was not analysed for this study but yields an abundant micro- fauna of foraminiferids. Variostoma exile Kristan-Tollmann, 1960 was also found with several specimens in the bulk sample from Lago Antorno.

Sponges/hydrozoans

Reef-building organisms such as colonial corals, massive calcareous sponges or algae are absent in the studied assemblages from Lago Antorno and Misurina Landslide. Only one small sponge fragment was found in the surface collection from Misurina Landslide. A small fragment of a presumably hydrozoan representative was contained in the bulk sample from Lago Antorno.

Class Gastropoda Phylum Mollusca Class Gastropoda Subclass Vetigastropoda Salvini-Plawén, 1980 Family Wortheniellidae Bandel, 2009 Genus Wortheniella Schwardt, 1992

Type species. Worthenia coralliophila Kittl, 1891, Carnian, Cassian Formation.

A single specimen representing slit-band gastropods is present in the studied collection from Lago Antorno. It represents the genus Wortheniella Schwardt, 1992 and seems to be closest to Wortheniella canalifera (Münster, 1841) from the Cassian Formation.

Wortheniella cf. canalifera (Münster, 1841) Fig. 5. cf. 1841 Pleurotomaria canalifera n. sp.; Münster 1841: 111, pl. 12: 4. cf. 1891 Worthenia canalifera (Münster); Kittl 1891: 188, pl. 2: 23–26. non 1986 Worthenia cf. canalifera (Münster); Batten & Stokes 1986: 6, fig. 4. cf. 1992 Wortheniella canalifera (Münster): Schwardt 1992: 46, pl. 8: 2–3. cf. 2009 Wortheniella canalifera (Münster) – Bandel: 17.

Additional synonymy in Diener (1926) and Kutassy (1940).

Material. One specimen, from Lago Antorno, PZO YYY.

Description. Shell trochoid, comprising five whorls (apical whorls missing), 5.2 mm high, 4.4 mm wide; whorl face angulated at about mid-whorl with selenizone situated on angulation; whorl-face above angulation forming oblique, somewhat concave ramp; whorl-face below angulation approximately parallel to shell axis, concave; base convex joining whorl face at distinct angular edge at suture; whorl-face and base covered with numerous spiral threads and enhanced growth lines; at least six spiral threads on whorl face each, above and below median angulation; base with one or two weak angulations; whorls adpressed with subsutural bulge; this bulge, the median and the basal angulation form three prominent spiral ribs; growth lines opisthocyrt between adapical suture and median angulation and rather straight, almost opisthocline below median angulation; growth lines curve back abruptly and sharply at median angulation forming narrow, almost invisible selenizone; minute pits present on median and basal angulations; aperture elongated, oblique.

Remarks. The selenizone of the present specimen is not well visible and was probably extremely narrow. It is not nodular or very pronounced. The specimen lacks a subsutural row of nodes. Such a nodular row has been reported for Wortheniella canalifera (Münster 1841; Kittl 1891; Schwardt 1992) and is also present in Münster’s (1841) type specimen although it is relatively weak. Moreover, the present specimen differs from W. canalifera in the growth line pattern and in having a very narrow selenizone. The angulation lies in a median position and not submedian as is the case in W. canalifera. Wortheniella canalifera has much stronger spiral ribs on the base whereas the spiral ornament of the whorl face is much weaker. Thus, species identity of the specimen from the Lago Antorno location with W. canalifera is unlikely although Wortheniella canalifera is closest to the present specimen. The small pits on the spiral angulations of W. cf. canalifera are remarkable and suggest the presence of periostracal hair. To our knowledge this feature has not been described from Worthenia-like gastropods so far. It is remarkable that this specimen is the only representative of Pleurotomariida and one of the few vetigastropods in this collection. In other Cassian locations e.g., at Alpe di Specie location (= Seelandalpe = Plätzwiesen) vetigastropods are much more diverse and abundant. Worthenia cf. canalifera as illustrated by Batten & Stokes (1986, fig. 4) from the Early Triassic (Smithian) of the Sinbad Limestone (Utah, U.S.A.) certainly does not represent this species; its spiral ribs are much stronger and it has a much stouter shape. Batten & Stokes (1986) mentioned that their specimen probably represents a new species and we agree with this view.

? Family Turbinidae

“Turbo” sp. Fig. 6.

Material. One specimen from Misurina Landslide, surface; PZO YYY.

Description. Shell turbiniform, comprising ca. 6 whorls 5.4 mm high, ca. 4.4 wide (specimen slightly compressed, appearing wider); whorl embracing at mid-whorl periphery; last whorl distinctly higher than spire; whorl face moderately convex with shoulder giving spira gradate appearance; whorls ornamented with strengthened prosocline and slightly prosocyrt growth-lines; base evenly convex, seemingly anomphalous.

Remarks. Turbiniform shape and prosocline ornament of strengthened growth lines suggest that this specimen represents a turbinid vetigastropod species. The specimen from Misurina that was figured by Zardini (1978, pl. 12, fig. 7 and 1985, pl. 10, fig. 2) as Solarioconulus nudus (Münster, 1841) is probably conspecific with the present specimen. However, S. nudus is much broader with a greater apical angle according to the figures provided by Münster (1841) and Kittl (1892). Moreover, it lacks the strengthened growth lines and is smooth according to Kittl (1892). Trochus lissochilus Kittl, 1892 is similar but lacks a shoulder and the transition to the base is rounded angular. Turbo? vixcarinatus Münster, 1841 resembles the present specimen but lacks a shoulder and according to Kittl (1892) the growth lines are straight. We think that the present specimen represents an undescribed species but more material is necessary to characterize it sufficiently.

Subclass Neritimorpha Koken, 1896 Family Naticopsidae Waagen, 1880 Genus Hologyra Koken, 1892

Type species. Hologyra alpina Koken, 1892, SD Kittl, 1899, Carnian, Cassian Formation.

Hologyra? expansa (Laube, 1869) Fig. 7.

1869 Naticopsis expansa; Laube 1869: 11, pl. 22: 5. 1892 Naticopsis expansa; Kittl 1892: 82, pl. 7: 22–24. pars 1978 Hologyra expansa; Zardini 1978: pl. 19: 6–12, 23, 24.

Material. One specimen from the surface collections of Lago Antorno; PZO YYY.

Description. Shell bulbous, consisting of about four rapidly expanding whorls, 3.6 mm wide, 3.9 mm high; spire slightly elevated; whorls markedly convex, with broad subsutural shelf; whorl embracing somewhat above periphery; whorls smooth except for distinct, prosocline, prosocyrt growth lines; aperture with outer lip broken off, with pronounced callus on parietal lip.

Remarks. This specimen differs from the other neritimorphs in the studied samples, Neritaria mandelslohi and Dentineritaria neritina, by having a low but nevertheless distinctly elevated spire. It is much larger than the specimens representing these species in our samples that are only present with small juveniles. It agrees well with the illustrations of H. expansa given by Kittl (1892) who also

8 figured Laube’s (1869) type specimens. It is also close to the specimens that were illustrated by Zardini (1978) as H. expansa however, not to all of them. Species identity is not entirely beyond doubt because this specimen is not fully grown and large parts of the aperture are broken off. The placement of this species in Hologyra is doubtful because the type species of Hologyra has a blunt and not an elevated spire.

Family Neritariidae Wenz, 1938 Genus Neritaria Koken, 1892

Type species. According to Bandel (2007) Natica mandelslohi Klipstein, 1843, Late Triassic (Carnian) Cassian Formation, northern Italy.

Neritaria mandelslohi (Klipstein, 1843) sensu Bandel (2007) Fig. 8.

2007 Neritaria mandelslohi (Klipstein, 1843); Bandel 2007: 261, fig. 11N–P, fig. 12A–H.

Material. Twenty-nine specimens from the bulk collection of Lago Antorno; five specimens from the bulk sample of Misurina landslide; 34 specimens in total; PZO YYY.

Description. Shell egg-shaped, low-spired with rapidly increasing whorls; illustrated specimen with about three whorls, 0.7 mm wide and high; initial whorl corroded but seemingly convolute, smooth; larval shell largely smooth, only with faint reticulate ornament on adapical portion of whorls; reticulate ornament consists of somewhat strengthened growth lines and spiral lirae which diverge somewhat in an apertural direction; base smooth, evenly rounded; larval shell with diameter of about 0.5 mm, ends at simple, faint suture; only small part of teleoconch present, seemingly smooth.

Remarks. Only isolated larval shells or juvenile specimens with a small teleoconch portion are at hand. They do not exceed a maximum size of 1 mm. However, this species reaches a size of several millimetres at others locations (Kittl 1892; Bandel 2007). This could indicate that the studied specimens represent mortal larval fall or that specimens died at or shortly after metamorphosis. The larval shell is rather characteristic and resembles that of Neritaria mandelslohi as reported by Bandel (2007, fig. 11 N–P).

Genus Dentineritaria Bandel, 2007

Type species. Natica neritina Münster, 1841, Late Triassic (Carnian) Cassian Formation, northern Italy.

Dentineritaria neritina (Münster) sensu Bandel (2007) Fig. 9.

2007 Dentineritaria neritina (Münster); Bandel 2007: 265, fig. 13A–H.

Material. Sixty-eight specimens from Lago Antorno bulk; 38 specimens from Misurina landslide bulk; 106 specimens in total; PZO YYY.

Description. Shell egg-shaped, low-spired with rapidly increasing whorls; illustrated specimen (Fig. 9A) with about three whorls, 0.9 mm wide, 0.8 mm high; protoconch consists of about three smooth whorls, 0.43 mm wide; initial whorls corroded but seemingly convolute; last larval whorl with distinct adapical suture; larval shell ends at simple, faint suture; somewhat less than one teleoconch whorl preserved; early teleoconch with subsutural bulge and initially with weak axial ribs (strengthened growth lines) which are restricted to adapical portion of whorls; axial ribs fade after half whorl so that remaining teleoconch is entirely smooth; base smooth, evenly rounded; aperture higher than wide with evenly arched outer lip; inner lip reflexed, forming columellar callus; first illustrated specimen from Misurina Landslide (Fig. 9B) is 0.8 mm wide and 0.7 mm high; consists of about three whorls; second specimen (Fig. 9C) 0.7 mm wide, with about two whorls; both illustrated specimens from Misurina Landslide less well preserved than illustrated shell from Lago Antorno.

Remarks. As in Neritaria mandelslohi, only isolated larval shell or specimens with a small teleoconch portion are at hand. Thus even this neritimorph species did not find suitable living conditions in the sampled area. The present specimens resemble early growth stages of Dentinerita neritina as reported by Bandel (2007). Bandel (2007) interpreted the axial ribbed shell as a part of the larval shell which according to him has a diameter of 0.8 mm. However, the present material suggests that the larval shell is much smaller (0.4 mm wide) and that the axially ribbed shell represents the early teleoconch.

Subclass Caenogastropoda Cox, 1960 Family Coelostylinidae Cossmann, 1909 Genus Coelostylina Kittl, 1894

Type species. Melania conica Münster, 1841

Emended diagnosis. Shell acute conical, medium-sized; last whorl higher than spire; whorls moderately convex with narrow shoulder; sutures distinctly impressed; whorls smooth or with very faint spiral ornament including spirally arranged micro-pits and furrows; growth lines slightly opisthocyrt to orthocline; base convex, not demarcated from whorl face; base minutely phaneromphalous; aperture higher than wide, with straight columellar lip and convex outer lip; protoconch conical, orthostrophic, smooth; protoconch whorls convex, without shoulder, demarcated from teleoconch by a distinct sinusigera.

Discussion. The re-investigation of Münster’s (1841) type specimen and the well-preserved material at hand allow a sharper diagnosis of the genus Coelostylina which has been used as a trash can for many years.

Coelostylina conica (Münster, 1841) Figs. 10, 11.

1841 Melania conica n. sp.; Münster 1841: 28, pl. 23: 20. 1894 Coelostylina conica (Münster, 1841); Kittl 1894: 181, pl. 14: 1–7. 1959 Coelostylina conica (Münster, 1841); Leonardi & Fiscon 1959: 54, pl. 5: 20. 1978 Coelostylina conica (Münster, 1841); Zardini 1978: 44–45, pl. 28: 12–14, pl. 29: 1–3. pars 1992 Coelostylina conica (Münster, 1841); Bandel 1992: 55, pl. 6: 6, pl. 7: 1, 2, 6, non 5 non 2006, pl. 12: 10–12. 1996 Carboninia valvatiformis n. sp.; Bandel 1996: 55, figs. 17a–h, 18a.

Material. Lectotype here designated, the specimen illustrated by Münster (1841, pl. 23, fig. 20) BSPG AS VII 504. Twenty-nine specimens were found in the bulk sample and 26 in the surface samples from Lago Antorno near Misurina PZO YYY. 53 specimens were contained in the Misurina Landslide bulk sample and 19 in the corresponding surface samples. Description. Shell acutely conical; apical angle about 45°; lectotype comprises about eight whorls, 13.4 mm high, 6.7 mm wide (Fig. 10A); last whorl higher than spire; whorls moderately convex with narrow shoulder; sutures distinctly impressed; whorls smooth or with rows of minute pits (seen on lectotype) or very faint spiral grooves which are only visible in oblique light; growth lines slightly opisthocyrt to orthocline; base convex, not demarcated from whorls face; base minutely phaneromphalous; aperture higher than wide, with straight columellar lip and convex outer lip; protoconch conical, more low-spired than teleoconch, apical angle 70–80°; protoconch orthostrophic, smooth, consisting of about 3.5 whorls 0.35–0.45 mm high, 0.38–0.50 mm wide; protoconch whorls convex, without shoulder (in contrast to teleoconch); protoconch demarcated from teleoconch by opisthocyrt ledge; initial whorl flattened, almost planispiral to immersed, with diameter of 0.11–0.13 mm.

Discussion. The present material from Lago Antorno and Misurina Landslide closely resembles Münster’s (1841) type specimen (lectotype) from the Stuores Wiesen and is obviously conspecific with it. The specimens illustrated by Bandel (1992, pl. 6, fig. 6, pl. 7, figs 1, 2, 6) also agree well with the present material. However, the protoconchs illustrated by Bandel (1992, pl. 7, fig. 5; 2006, pl. 12, figs 10–12) and assigned by him to C. conica differ significantly from the protoconchs reported here. According Bandel’s (1992) illustration and description, the protoconch of Coelostylina conica is about 0.25 mm high and wide, consists of about 2.5 whorls, and has an ornament of minute tubercles. In contrast, the protoconchs reported here consist of 3.5 whorls, are much larger (twice the size) and lack any ornament. The juvenile specimens identified by Bandel (2006, pl. 12, figs 10–12) has a larval shell with numerous spirally arranges tubercles. This specimen which has only one teleoconch whorl preserved does not represent C. conica but another species and genus. Carboninia valvatiformis Bandel, 1996, type species of Carboninia Bandel, 1996 is conspecific with our material and hence represents a synonym of Coelostylina conica and therefore Carboninia is a synonym of Coelostylina. Bandel (1996) interpreted the immersed initial whorl to represent larval heterostrophy with a protoconch of 1.8 whorls but our better preserved material shows that this species has a caenogastropod larval shell of 3.5 whorls which can also be seen in Bandel’s (1996 fig. 17e) illustration of Carboninia valvatiformis.

Coelostylina sp. 1 Fig. 12B.

Material. One specimen from Misurina Landslide bulk sample; PZO YYY.

Remarks. A single small shell is present with a height of about 1 mm. It consists of about two teleoconch whorl which are smooth and bulbous and a poorly preserved mammilated larval shell. Species identification is impossible, but the specimen resembles the genus Coelostylina or Prostylifer to some degree.

Coelostylina sp. 2 Fig.12C.

Material. One specimen from the Misurina Landslide surface collections; PZO YYY.

Remarks. This fusiform shell consists of about four whorls (apex missing), has largely smooth, convex whorls with almost straight orthocline growth lines and a faint spiral micro-striation. It resembles Coelostylina species, for instance Coelostylina (Pseudochrysalis) stotteri (Klipstein, 1843) (see Zardini 1978, pl. 30, fig. 6), to some degree but an umbilical chink seems to be absent. Genus Coelochrysalis Kittl, 1894

Type species. Melania pupaeformis Münster, 1841

Coelochrysalis pupaeformis (Münster, 1841) Fig.12E, F.

1894 Euchrysalis (Coelochrysalis) pupaeformis; Kittl 1894: 225, pl. 6: 15–20.

Material. Two specimens from the Misurina Landslide surface samples; PZO YYY.

Remarks. Two specimens show the characteristic pupoid shape of this species that is produced by the constriction of the body whorl. The whorls are low; the larger specimen is 18 mm high. Both specimens lack the early whorls and are compressed. Fürsich & Wendt (1977) reported a single specimen from their Ampullina association.

Unidentified caenogastropod Fig. 12A.

Material. Two specimens from Lago Antorno surface; PZO YYY.

Remarks. Two small fragments of a smooth shelled high-spired gastropod species that may represent Caenogastropoda are at hand.

Genus Helenostylina Kaim, Jurkovšek & Kolar-Jurkovšek, 2006

Type species. Helenostylina mezicaensis Kaim, Jurkovšek & Kolar-Jurkovšek, 2006

Helenostylina convexa Nützel & Kaim, 2014 Fig. 13, 14.

1992 Ptychostoma sanctaecrucis (Laube, 1868); Bandel 1992: 52, pl. 6: 4, 5. 1994 Ptychostoma sanctaecrucis (Laube, 1868); Bandel 1994: pl. 4: 8. 2014 Helenostylina convexa n. sp.; Nützel & Kaim 2014: 418, fig. 7e–h.

Material. Six specimens from Lago Antorno bulk; four specimens from Lago Antorno surface; one specimen from Misurina landslide bulk; two from Misurina landslide surface; 13 specimens in total; PZO YYY.

Description. Shell turbiniform, conical; apical angle about 70°; illustrated specimen from Misurina Landslide (Fig. 14D) with about seven whorls, 4 mm high, 2.8 mm wide; last whorl higher than spire; teleoconch whorls smooth, convex, without shoulder; base flatly convex with two spiral ribs and furrows surmounting the centre of the base; aperture as high as wide; protoconch comprising about 3.5

12 to 4 whorls, 0.4–0.5 mm high and wide, with about same apical angle as teleoconch (70°–80°); initial whorl smooth with a diameter of about 0.14 mm; larval whorls convex, somewhat angulated at lower third; larval whorls with subsutural row of tubercles, followed by a smooth zone below extending to the whorl angulation; lower zone between angulation and abapical suture ornamented with five to six rows of fine tubercles; larval shell ends abruptly.

Discussion. This species has a very characteristic larval shell of rows of small tubercles below the suture and on the lower third of the larval whorls separated by a wide smooth zone. Our materials resembles the more juvenile type specimens as reported by Nützel & Kaim (2014) from the Settsass Scharte – one of their figured specimens (fig. 7e) shows the tubercular ornament on the larval shell although it was not mentioned in the description. The same species and larval shell was reported by Bandel (1992, 1994) who assigned it to Ptychostoma sanctaecrucis (Wissmann, 1841 in Münster) [erroneously cited as Ptychostoma sanctaecrucis (Laube, 1968)]. However, Bandel’s (1992, 1994) illustrated specimen from the locality Campo near Cortina d’Ampezzo does not represent P. sanctaecrucis. Ptychostoma sanctaecrucis was first described from the type location of the Heiligkreuz Formation which overlies the Cassian Formation. This species lacks the spiral ornament on the base and is larger. Moreover, Ptychostoma sanctaecrucis has a smaller larval shell which is ornamented by spiral crests, the same type that is present in Prostylifer (own observation on material from the type locality). Helenostylina mezicaensis Kaim, Jurkovšek & Kolar-Jurkovšek, 2006, the type species of Helenostylina resembles H. convexa in shape and in having a spiral ornament around the umbilicus. However, this species has a subsutural ramp and the protoconch is seemingly smooth. Omphaloptycha muensteri (Wissmann, 1841) in Münster is similar. However the type specimen (SNSB-BSPG AS VII 1676) lacks circumumbilical spiral ribs and furrows and its whorls are higher. The type is larger (height 7 mm) than the specimens assigned to Helenostylina convexa by Nützel & Kaim (2014) and herein. The possibility that Omphaloptycha muensteri has basal spiral ribs and furrows only in the middle whorls but not on a more mature growth stage as present in the type specimen cannot be ruled out. If this is the case, Helenostylina convexa could represent a synonym of Omphaloptycha muensteri but this is seen as unlikely.

Family Prostyliferidae Bandel, 1992 Genus Prostylifer Koken, 1889

Type species. Melania paludinaris Münster, 1841

Prostylifer paludinaris (Münster, 1841) Fig. 15.

1841 Melania paludinaris n. sp.; Münster 1841: 97, pl. 9: 50. 1992 Prostylifer paludinaris (Münster, 1841); Bandel 1992: 50, pl. 5: 3–6. 1993 Prostylifer paludinaris; Bandel 1993: 50, pl. 6: 1. 1994 Prostylifer paludinaris (Münster, 1841); Bandel 1994: 143, pl. 4: 10.

Material. Lectotype here designated, the specimen illustrated by Münster (1841, pl. 23, fig. 20) BSPG AS ; 24 specimens from Lago Antorno bulk and 81 specimens from Lago Antorno surface near Misurina; 128 specimens from Misurina landslide bulk; 50 specimens from Misurina landslide surface; 283 specimens in total; PZO YYY.

Description. Shell littoriniform to turbiniform, bulbous; spire conical, acute; shell with eight whorls (including protoconch), 5.0 mm high, 3.8 mm wide (Fig. 15A); last whorl much higher than spire; whorls strongly convex; sutures distinct; teleoconch whorls smooth; base rounded, evenly convex, not demarcated from whorl face, cryptomphalous; aperture oblique teardrop-shaped; inner lip oblique, evenly arched; columellar lip strengthened, somewhat reflexed; protoconch orthostrophic, mammilate, in general more slender than teleoconch; protoconch consisting of about 3.1–3.2 whorls, 0.33–0.40 mm high, 0.42–0.45 mm wide; initial whorl smooth, with diameter of 0.14–0.15 mm; protoconch whorls convex, ornamented with up to six sharp, narrow spiral crests; spiral crests evenly spaced, separated by wide concave interspaces; spiral crests crenulated with fine tubercles; abapical crest emerges at lower suture; additional crests present on convex base of the larval whorls; larval shell terminates abruptly with a distinct sinusigera; larval projection largely covered by succeeding teleoconch whorls; illustrated specimen from Misurina Landslide (Fig. 15D) comprising about seven whorls; last whorl broken; shell 2.1 mm high, 1.7 mm wide; protoconch 0.43 mm high and 0.4 wide.

Discussion. This material from Lago Antorno and Misurina Landslide agrees well with the specimens illustrated by Bandel (1992, pl. 5, figs 3–6) which were reported from the localities Misurina, Alpe di Specie, and Costalaresc by this author. It also agrees with Münster’s (1841) type specimens at the Bavarian State Collection. One of the specimens illustrated by Bandel (1992: pl. 5, fig. 5) has shouldered teleoconch whorls; Bandel (1992) mentioned also a great variation in the course of the growth line from slightly opisthocyrt to specimens which have an apertural sinus in the upper part of the whorls. Moreover, he mentioned the presence of a fine spiral striation on some specimens. This character was not observed in the present material. The larval shells documented by Bandel (1992) agree well with those in the present material.

Angulatella Nützel & Hausmann gen. nov.

Type species. Angulatella bizzarinii Nützel & Hausmann sp. nov.

Diagnosis. High-spired shell, spiral keels on teleoconch; upper keel angulates whorl profile in early teleoconch whorls, with a steep ramp between adapical suture and keel; whorl profile concave, parallel to shell axis between upper and lower keels; later whorl more or less convex with weaker angulations base convex, anomphalous; protoconch orthostrophic; larval whorls ornamented with two strong spiral keels; third spiral keel present on third protoconch whorls; spiral keels angulate larval whorls; spiral keels ornamented with minute tubercles; protoconch ends abruptly at sinusigera; sinus strengthened with a varix.

Remarks. The carinate, small larval shell of Angulatella closely resembles larval shells of many Recent and fossil Cerithioidea. The teleoconch resembles that of some Mathildoidea. However, Mathildoidea have a heterostrophic protoconch. The finding of Angulatella is further evidence for an early radiation of Cerithioidea.

Angulatella bizzarinii Nützel & Hausmann sp. nov. Fig. 16.

1993 Protuba winkleri (Klipstein, 1894) in Kittl; Bandel 1993: pl. 4: 3.

Etymology. After the palaeontologist Fabrizio Bizzarini for his work on the fauna of the Cassian Formation.

Material. Five specimens from Lago Antorno bulk (including holotype); three specimens from Misurina landslide bulk; eight specimens in total; PZO YYY.

Diagnosis. High-spired, conical shell; teleoconch with two spiral keels on whorl face; upper keel at about mid-whorl; lower keel emerging at abapical suture; upper keel angulates whorl profile with a steep ramp between adapical suture and keel; shell axis of orthostrophic protoconch somewhat oblique to teleoconch axis; larval whorls with spiral keels which angulate larval whorls; spiral keels ornamented with minute tubercles.

Stratum typicum. Cassian Formation; Late Triassic, Early Carnian.

Type Locality. Misurina, close to the Lago Atorno, near Cortina d’Ampezzo, N Italy.

Description. Shell high-spired, conical; apical angle about 45°; shell with 6.5 whorls about 1.4 mm high, 0.8 mm wide (Fig. 16A); teleoconch with two spiral keels on whorl face of earliest teleoconch whorls; upper keel at about mid-whorl; lower keel emerging at abapical suture; upper keel angulates whorl profile with a steep ramp between adapical suture and keel; ramp slightly convex to straight; whorl profile concave, parallel to shell axis between upper and lower keels; in later whorl the abapical spiral keel moves in an adapical direction; the latest preserved whorl has a rounded convex appearance with only slight angulations (Fig. 16B); base convex, anomphalous ornamented with several weak spiral ribs; protoconch orthostrophic, consisting of about three whorls, 0.25 mm high, 0.22 mm wide; shell axis of protoconch somewhat oblique to teleoconch axis; initial whorl without visible ornament, with diameter of 0.12 mm; first larval whorl ornamented with two strong spiral keels; third spiral keel present on third protoconch whorls; spiral keels angulate larval whorls; spiral keels ornamented with minute tubercles; protoconch ends abruptly at sinusigera; sinus strengthened with a varix.

Remarks. Bandel (1993, pl. 4, fig. 3) illustrated a protoconch obviously representing Angulatella bizzarinii Nützel & Hausmann sp. nov. and identified it as “Protuba winkleri (Klipstein, 1843)”. However, Protuba Cossmann, 1912 is a monotypic genus holding P. intermittens Kittl, 1894 from the Cassian Formation. Bandel (1993) probably meant Promathildia winkleri Klipstein, 1894 in Kittl. Promathildia winkleri is known from relatively large teleoconch fragments – its protoconch is unknown. It has a much stronger median spiral angulation and the whorls do not become more or less rounded convex in mature whorls so that species identity with our material can be excluded.

Family Protorculidae Bandel, 1991 Genus Atorcula Nützel, 1998

Type species Melania canalifera Münster, 1841 sensu Kittl (1894), Cassian Formation.

Atorcula sp. Fig. 17A, B.

Material. Three teleoconch fragments in total from Lago Antorno surface; PZO YYY.

Description. Shell high-spired; one fragment (apex missing) comprises five whorls, is 13.4 mm high and 7.0 mm wide (Fig. 17A); whorls moderately convex; sutures distinct; shell smooth; growth lines parasigmoidal with shallow opisthocyrt sinus below suture and opisthocline on remaining part of

15 whorl face; base moderately convex, smooth with growth lines only; transition from whorl face to base a rounded edge; protoconch unknown; illustrated specimens A and B of Fig. 17 show circular borings; one specimen with two borings, one unsuccessful; other specimen with a single boring.

Remarks. The high-spired shape, the smooth shell and the parasigmoidal course of the growth lines on the base suggest that the present specimens represent the genus Atorcula. However, Atorcula is also characterized by an axially ribbed larval shell but the protoconch of the present material is unknown. Moreover, Atorcula has spiral furrows on the base whereas the base of the present specimens lacks spiral furrows. Atorcula canalifera also has a less convex, almost straight whorl face. This species was obviously a preferred target for a boring predator. At least some of the specimens that were illustrated by Zardini (1978, pl. 27, figs 6–13) as Anoptychia canalifera (Münster, 1841) are probably conspecific with the present specimens. These specimens are mainly from the location Costalaresc. As in the present specimens, several of Zardini’s (1978) specimens have drill holes.

Atorcula canalifera (Münster, 1841) sensu Kittl (1894) Fig. 17C, D, E.

Material. One specimen from Lago Antorno bulk and 6 shells from Lago Antorno surface; 1 specimen from Misurina bulk; 4 specimens from Misurina Landslide surface; 12 specimens in total; PZO YYY.

Description. Shell high-spired slender, acutely conical; teleoconch fragment of 6 whorls 14.9 mm high, 6.3 mm wide; whorl face straight to very slightly convex; whorls smooth or with faint spiral striation; suture distinct; base flatly convex with several spiral furrows. Juvenile specimen (Fig. 17E) with relatively large larval shell with distinct axial ribs and a single smooth teleoconch whorl is preserved.

Remarks. The material at hand is very close to Kittl’s (1894 pl. 4, figs 45, 46) type material of Atorcula canalifera (see Nützel 1998).

Family Zygopleuridae Wenz, 1938 Subfamily Ampezzopleurinae Nützel, 1998 Genus Ampezzopleura Bandel, 1991

Type species. Ampezzopleura tenuis Nützel, 1998 (see Bouchet et al. 2017)

Ampezzopleura hybridopsis Nützel, 1998 Fig. 18A–G.

Material. Thirty-eight specimens from Lago Antorno (29 from bulk, nine from surface). 96 specimens from Misurina Landslide (95 from bulk, one from surface); 134 specimens in total; PZO YYY.

Description. Shell high-spired, slender; largest specimen from Lago Antorno comprises 8–9 whorls, 1.9 mm high, 0.8 mm wide; protoconch 4.5 to 5 whorls, 0.94 mm high, 0.54 mm wide; protoconch whorls somewhat convex; initial whorls almost flat; remaining larval shell high-spired; first two whorls smooth; remaining larval whorls with strong somewhat opisthocyrt axial ribs numbering 15 to 20 per whorl; axial ribs rather sharp, much narrower than interspaces between them; larval axial ribs curve strongly forward just above lower suture, becoming thinner at the same time and fusing to a sharp, suprasutural spiral thread which forms angular edge between base and whorl face of larval

16 whorls; base of larval whorls flat to slightly convex; larval ribs do not continue onto base; axial ribs reduced to subsutural row of nodules in last half whorl of larval shell; larval shell ends at wide opisthocyrt arc which is poorly demarcated and not strengthened by a varix; teleoconch whorls slightly convex with broad, wave-like axial ribs numbering about ten per whorl; sutures distinct; base rather flat to slightly convex, joining whorl face at an angle; ribs do not continue onto base; base flat to slightly convex; base and whorls face meet at rounded edge.

Remarks. The specimens at hand are very close to the type material from Campo near Cortina (type locality) and Alpe di Specie as illustrated and described in Nützel (1998). The reduction of the larval ribs on the last larval whorl to a subsutural row of nodules was interpreted by Nützel (1998) as evidence for a close phylogenetic relationship between Ampezzopleurinae (with axial ribs on larval shell) and Zygopleuridae with a subsutural row of nodules or riblets on larval whorls.

Ampezzopleura bandeli Nützel, 1998 Fig. 18H.

Material. Twenty-one specimens from the bulk sample and three specimens from the surface collections sampled at Misurina Landslide; 24 specimens in total; PZO YYY.

Remarks. The illustrated specimen (Fig. 18H) from Misurina Landslide is deformed over its entire shell length (shell 1.6 mm high; protoconch about 0.3 mm high). It has preserved its small, bulbous larval shell that is typical of that species (Nützel 1998).

Axially ribbed larval shell

Material. One specimen from Misurina Landslide bulk.

Remarks. An isolated globular protoconch with strong axial ribs, about 0.5 mm; such larval shells are found in the genus Striazyga Nützel, 1998 or in Ampezzopleura bandeli.

Genus Zygopleura Koken, 1892

Type species. Zygopleura hybridissima (Münster, 1841)

Zygopleura sp. Fig. 19.

Material. One specimen from Lago Antorno bulk; one specimen from Misurina Landslide bulk; two specimens in total; PZO YYY.

Description. Broadly conical larval shells with immersed initial whorls; whorls smooth except of sub- and suprasutural rows of minute nodules; specimen from Lago Antorno (Fig. 19A) broken; 0.67 mm high, 0.57 mm wide; specimen from Misurina Landslide (Fig. 19B) 1.02 mm high, 0.85 mm wide.

Remarks. The larval shells at hand are typical of zygopleurid protoconchs (Bandel 1991; Nützel 1998).

Family Settsassiidae Bandel, 1992 Genus Kittliconcha Bonarelli, 1927

Kittliconcha aonis (Kittl, 1894) Comb. nov. Fig. 20 A–C.

1894 Pseudomelania? aonis n. sp.; Kittl 1894: 194, pl. 6: 32–34, pl. 8: 19. 1978 Pseudomelania? aonis; Zardini 1978: 46, pl. 41: 3.

Material. Four specimens, all from surface collections; two from Lago Antorno and two specimens from Misurina Landslide; PZO YYY.

Description. High-spired shell with very low, convex whorls that are ornamented with orthocline, broad irregular axial ribs; ribs are as wide as interspaces, irregular in strength, number and spacing; growth lines orthocline, distinct, irregular; axial ribs tending to be reduced on last preserved whorls; suture distinct; base convex with traces of spiral lirae and umbilical chink.

Remarks. The present specimens closely resemble Kittl’s (1894) type specimens and those illustrated by Zardini (1978, pl. 41, fig 3). Kittl (1894) placed this species tentatively in the genus Pseudomelania. However, Pseudomelania is based on Cretaceous steinkerns and is therefore problematic. We place Pseudomelania? aonis in Kittliconcha, which has a similar gross morphology and axial ribbing (see Nützel 2010). The type species Kittliconcha obliquecostata has higher whorls and oblique axial ribs. The Palaeozoic genus Palaeostylus Mansuy, 1914 is also similar. The species Kittliconcha aonis is insufficiently known i.e., its protoconch is unknown and its aperture is insufficiently know. Therefore, its systematic placement may change in the future.

Genus Tyrsoceus Kittl, 1892

Type species. Tyrsoceus cassiani Cox 1960, Carnian, Cassian Formation.

The genus Tyrsoceus is problematic because it was based on Turritella compressa Münster, 1841 (Tyrsoceus cassiani Cox, 1960 is a replacement name) which was based on a poorly illustrated teleoconch fragment. According to Kittl (1894), the type specimen is lost.

Tyrsoceus zeuschneri (Klipstein, 1843) Fig. 20D, E.

1843 Turritella zeuschneri n. sp.; Klipstein 1843: 178, pl. 11: 24. 1849 Loxonema zeuschneri (Klipstein); Orbigny 1849: 187. 1894 Coronaria? zeuschneri (Klipstein); Kittl 1894: 167. ?1894 Coronaria subcompressa n. sp.; Kittl 1894: 166, pl. 4: 31, 32. 1909 Tyrsoceus zeuschneri (Klipstein); Cossmann 1909: 35. 1926 Stephanocosmia? zeuschneri (Klipstein); Diener 1926: 199. 1940 Stephanocosmia (Tyrsoceus) zeuschneri (Klipstein); Kutassy 1940: 369. Non 1978 cfr. Coronaria zeuschneri (Klipstein); Zardini 1978: 41, pl. 26: 25.

Material. One specimen from the Lago Antorno surface, PZO YYYY; the type material of Klipstein (1843) is housed in the Natural History Museum in London including figured type specimen (number 35421 [33 G 43]).

Description. Shell high-spired, present specimen from Lago Atorno is a teleoconch fragment of four whorls, 8.9 mm high, 4.6 mm wide specimen (flattened by compaction; 5.3 and 3.9 mm wide); the holotype from the Klipstein collection comprises c. six whorls, is 16.2 mm high, 7.0 mm wide; whorls low, stout, slightly adpressed; sutures distinct; whorls convex with slight median angulation which bears a faint spiral rib; additional faint spiral present; whorl with relatively weak axial ribs (12–14 per whorl) which do not reach sutures and are strongest at mid-whorl; whorl with faint, mostly obscured micro-striation; base flatly convex, without prominent ornament.

Remarks. Tyrsoceus zeuschneri seems to be a rare species. Since its initial description, only a single specimen was assigned to this species as “cfr. Coronaria zeuschneri“ from Misurina (table caption) or Alpe di Specie (tabulation) (Zardini 1978). However, Bandel (1995) listed Zardini’s (1978) specimen in the synonymy list of the mathildoid species Camponaxis lateplicata (Klipstein, 1843). Indeed, Zardini’s (1978) specimen is not very close to Klipstein’s (1843) illustration and type specimen. This illustration is inaccurate; it overemphasizes the axial ribs and does not show the slight median angulation. The type specimen housed in the Natural History Museum in London (number 35421 [33 G 43]) agrees well with the specimen from the present collection. Tyrsoceus subcompressus (Kittl, 1894) is close to T. zeuschneri and could represent a synonym.

Family Ladinulidae Bandel, 1992 Genus Flemmingia Kittl, 1891 sensu Bandel (1992)

Remarks. Kittl (1891) emendated Flemingia de Koninck, 1881 that has a Carboniferous type species to Flemmingia – an unjustified emendation. Flemingia is, however, a junior homonym and was replaced with Flemingella by Knight (1936). Knight et al. (1960) treated Flemingella as junior synonym of Pseudophorus Meek, 1873 that has a Devonian type species. The species from the Cassian Formation that have been assigned to Flemmingia respectively Flemingia do not represent the mentioned Palaeozoic taxa. However, at present we follow Bandel’s (1992) conception of this genus.

Flemmingia bistriata (Münster, 1841) Fig. 12D.

1841 Trochus bistriatus n. sp.; Münster 1841: 108, pl. 11: 16. 1891 Flemmingia bistriata; Kittl 1891: 253, pl. 7: 14–16. 1992 Flemmingia bistriata; Bandel 1992: 47, pl. 4: 4, 5. See Diener (1926), Kutassy (1940) and Bandel (1992) for additional synonymy.

Material. One specimen from Misurina Landslide surface; PZO YYY.

Remarks. This shell that is about 8 mm high, closely resembles the specimens illustrated by Kittl (1891) and Bandel (1992). There are several other Cassian species that have been assigned to Flemmingia. Flemmingia bicarinata (Klipstein, 1843) as reported by Kittl (1891) is very similar to our specimen. However, this species has been considered a synonym of Flemmingia bistriata by Bandel (1992).

Subclass Heterobranchia Family Mathildidae Dall, 1889 Genus Jurilda Gründel, 1973

Type species. Mathilda (Jurilda) crasova Gründel, 1973; OD; according to Gründel (1997) a synonym of Promathildia (Teretrina) concava Walther, 1951, Middle Jurassic, Germany, Poland.

Remarks. The type species of Tirolthilda Bandel, 1995, Tirolthilda seelandica Bandel, 1995 closely resembles the type species of Jurilda and therefore we consider Tirolthilda to represent a subjective junior synonym of Jurilda.

Jurilda elongata (Leonardi and Fiscon, 1959) Comb. nov. Fig. 21

*1959 Promathildia (?) peracuta n. var. elongate; Leonardi-Fiscon 1959: pl. 9: 14, 15, 20. Pars 1978 Promathildia peracuta f. elongata (Leonardi-Fiscon); Zardini 1978: pl. 35: 24, 25, non 23. 1995 Tirolthilda seelandica n. sp.; Bandel 1995: 13, pl. 5: 6, 8–10.

Material. Five specimens from Lago Antorno bulk; one specimen from Misurina Landslide surface; 166 specimens from Misurina Landslide bulk; 170 specimens in total; PZO YYY.

Description. Shell high-spired, slender, largest illustrated specimen 3.7 mm high, 1.4 mm wide (apex broken off); two prominent spiral cords present immediately after protoconch; spiral cords relatively close to each other on early whorls and widely separated on later whorl; whorl angulated at spiral cord so that whorl face is bevelled towards sutures; whorl straight to slightly concave between spiral cords; whorl angulated with fine axial threads which are much weaker than spiral cords; axial threads straight between spiral cords, prosocline above adapical spiral cord and opisthocline below abapical spiral cord; number of axial threads increases to up to more than 30 per mature teleoconch whorls; bordering spiral cord emerges at suture and is fully exposed on base.

Remarks. Leonardi & Fiscon (1959) described this species from Costalaresc as variety of Flemingia bicarinata Kittl, 1891 (placed tentatively in Promathildia by them) – a species from the Middle Triassic Esino Limestone. Since this variety was published before 1961 it has subspecific rank (ICZN Article 45.6.4.). Leonardi & Fiscon (1959) discussed several characters separating Flemingia bicarinata from their new variety. Therefore, they clearly had the intention to describe a new taxon and not an infrasubspecific name as becomes obvious from the synonymy list provided by him. Bandel (1995) was aware that his material is conspecific with the variety described by Leonardi & Fiscon (1959) but nevertheless described the species as new (Tirolthilda seelandica). We raise Promathildia (?) peracuta n. var. elongata to species rank – there is no doubt that the morphological differences mentioned by Leonardi & Fiscon (1959) (ribbing, shape) are sufficient to raise it from subspecies rank. Tirolthilda seelandica Bandel falls in synonymy of Jurilda elongata.

The Middle Jurassic type species of Jurilda as reported by Walther (1951), Gründel (1973, 1997) and Kaim (2004) closely resembles Jurilda elongata from the Cassian Formation. The only major difference is that the apical carination is stronger and thus the whorl face above it is oblique instead of parallel to the shell axis. Gründel and Nützel (2013) gave an emendated diagnosis of Jurilda which fits the present material well. Especially the ornament with two primary spiral cords close to the sutures which are crossed by fine axial threads is similar. Thus placement of Jurilda seelandica in Jurilda and the synonymisation of Jurilda and Tirolthilda are justified. It is the first report of this genus from the Triassic.

Bandel (1995) reported about 40 specimens from the type locality Alpe di Specie (Seelandalpe) and three specimens from Misurina. Zardini (1978) reported that it is very abundant at Misurina, abundant at Alpe di Species and rare at Costalaresc and Campo. Here it is one of the most abundant species at Misurina Landslide but very rare at Lago Antorno.

Genus Promathildia Andreae, 1887

Type species. Mathilda janeti Cossmann, 1885; SD Gründel and Nützel, 2013; Jurassic, Europe.

Promathildia cf. milierensis Zardini, 1980 Fig. 22C–H.

Material. Nineteen specimens from Misurina Landslide bulk; one specimen from Misurina Landslide surface; 20 specimens in total; PZO YYY.

Remarks. Shell high-spired, slender; whorl face distinctly angulated low on the whorls; whorl ornamented with two spiral cords and ca. 10 axial ribs per whorl; adapical spiral cord weak to absent, in subsutural position; abapical spiral cord strong, forming angulation and periphery, somewhat above abapical suture but higher on whorl face in earlier whorls; nodes at intersections of spiral cords and axial ribs, strong on abapical spiral cord, weak on adapical cord; whorl face with fine spiral threads; protoconch consisting of somewhat more than one whorl with a diameter of the first whorl 0.24 mm; protoconch smotth except a very fine spiral striation; first teleoconch whorls angulated but without distinct ornament; teleoconch ornament develops from the third teleoconch whorl onward; base flat with spiral ornament and a spiral cord at angulation at border to whorl face.

Remarks. The main characteristic of this species is the pronounced carina with strong, almost spiny nodules low on the whorls and a much weaker subsutural spiral cord. The protoconch with only about one whorl and a relatively large diameter suggest that this species had non-planktotrophic larval development. The specimens are more or less encrusted or fragmented making an identification difficult. They resemble Promathildia milierensis as illustrated by Zardini (1980, pl. 5, figs. 12, 14, 15 but not 13) and Hausmann & Nützel (2015; fig. 8I) but these specimens have the knobby angulation higher on the whorls. Tofanella cancellata Bandel, 1995 is similar but has more spiral cords and it lacks strong to almost spine-like nodes on the lower spirals. Promathildia colon (Münster, 1841) and P. pygmaea (Münster, 1841) as illustrated by Kittl (1894) and Zardini (1978) are similar but examination of Münster’s type specimens of these species showed that they are probably not conspecific with our specimens.

Promathildia cf. decorata (Klipstein, 1843) Fig. 22A.

Material. 2 specimens from Misurina Landslide bulk; PZO YYY.

Description. Two juvenile specimens with preserved protoconch show strongly angulated whorls; spiral carina below mid-whorl, additional spiral cord present below suture; additional spiral cords on base; protoconch coaxial heterostrophic with radial fold at the end of larval shell; axial ornament either weak or absent, obscured due to preservation.

Remarks. These two juvenile specimens resemble the early whorls of Promathildia decorata (Klipstein, 1843) as reported by Bandel (1995) who also reported the same type of coaxial protoconch with folds. In addition Bandel’s (1995) specimens have axial threads as teleoconch ornament which might be obscured due to preservation in our specimens.

Promathildia subnodosa (Münster, 1841) Fig. 22B.

1841 Fusus subnodosus n. sp.; Münster 1841: 124, pl. 13: 51. 1894 Promathildia subnodosa; Kittl 1894: 243, pl. 9: 36–45. 1978 Promathildia subnodosa; Zardini 1978: 50–51, pl. 35: 4–9. ?1995 Promathildia subnodosa; Bandel 1995: 8, pl. 2: 5, 7, pl. 3: 1–4, 6, 7. 2015 Promathildia subnodosa; Hausmann & Nützel 2015: fig. 8H.

Material. One specimen from Misurina Landslide, surface collection; PZO YYY.

Description. A single teleoconch fragment consisting of about 5 whorls, 12 mm high, 4.7 mm wide; whorls convex with median angulation; growth lines distinct, sometimes thread-like, orthocline below suture and then curving forward so that they become markedly opisthocline in the two thirds of whorls; two prominent spiral cords, one at mid-whorl angulation, the other half way between mid- whorl and abapical suture; both main spiral cords undulating to nodular at intersections with opisthocline axial ribs, numbering 10 to 14 per whorl; a third faint spiral cord somewhat below suture; base convex, with two distinct spiral cords and additional spiral lirae.

Remarks. This is a rather variable species; the specimen at hand is close to some of the specimens illustrated by Kittl (1894) and Zardini (1978) as P. subnodosa. The identity of the specimens illustrated by Bandel (1995) is doubtful because they represent early juvenile shell portions only.

Family Tofanellidae Bandel, 1995 Genus Camponaxis Bandel, 1995

Type species. Cerithium (?) lateplicatum Klipstein, 1843

Camponaxis lateplicata (Klipstein, 1843) sensu Bandel (1995) Fig. 22I.

Material. One specimen from Misurina Landslide bulk sample; PZO YYY.

Description. Shell high-spired; whorls convex with slight angulation high on the whorls; whorl ornamented with axial ribs and spiral cords of about same strength with intersection not or only slightly nodular; axial ribs, straight orthocline, rounded, separated by wide interspaces, numbering up to 20 per whorl; spiral cords of variable strength and irregularly species; two adapical spiral cords particularly weak.

Remarks. This specimen resembles Bandel's (1995) illustrations of Camponaxis lateplicata (Bandel 1995, pl. 13, fig. 9; pl. 14, figs. 1–5) and is probably conspecific. However, it is questionable whether Bandel’s (1995) material is conspecific with Klipstein’s (1843) type specimen which AN has examined at the Museum of Natural History in London. This type specimen is relatively large,

22 fusiforme and has fewer but stronger axial ribs. It is therefore likely that Camponaxis has a misidentified type species.

Family Cornirostridae Ponder, 1990 Genus Bandellina Schröder, 1995

Type species. Bandellina laevissima Schröder, 1995

Remarks. The genus was discussed by Bandel (1996) and Kaim (2004) who pointed out its resemblance to the modern sunken wood and hot vent species Hyalogyra Marshall, 1988. Kaim (2004) did not follow Bandel’s assignment to the family Cornirostridae but left the family assignment open.

Bandellina compacta Nützel & Hausmann sp. nov. Fig. 23.

Material. Two specimens from Lago Antorno bulk sample; holotype PZO YYY, paratype PZO YYY.

Type locality. Lago Antorno near Misurina (see Fig. 1B).

Age. Cassian Formation, Early Carnian.

Description. Shell low-spired, turbiniform; specimen comprises 3.6 whorls (two larval), 0.9 mm wide, 0.7 mm high; protoconch blunt, comprising about two whorls; initial whorl sinistral, sunken, smooth; second protoconch whorl dextral, round, convex with axial subsutural rib character of strengthened growth lines; protoconch clearly demarcated from teleoconch by a suture; teleoconch smooth, with evenly convex whorls embracing somewhat above periphery; base evenly convex; minutely phaneromphalous, covered with numerous fine spiral ribs.

Remarks. Bandellina compatca differs from B. cassiana and B. laevissima in being more high-spired and in having a narrower umbilicus. Moreover, B. cassiana and B. laevissima lack spiral ribs on the base and axial riblets on the last larval whorl.

Family Hyalogyrinidae Warén & Bouchet, 1993 Genus Alexogyra Bandel, 1996

Type species. Alexogyra marshalli Bandel, 1996, Late Triassic, Cassian Formation.

Remarks. Kaim (2004) considered Alexogyra to represent a synonym of Bandellina Schröder, 1995. However, Alexogyra is almost planispiral whereas Bandellina is distinctly helicoidal and more massive. Therefore, a possible synonymy is considered here as unlikely although both genera are probably closely related.

Alexogyra marshalli Bandel, 1996 Fig. 24.

Material. Seven specimens from Lago Antorno bulk; PZO YYY.

Description. Shell almost planispiral with very slightly elevated spire; teleoconch flatly dextral; with about three whorls, 1.0 mm wide, 0.5 mm high; protoconch flat, comprising about 1.5 whorls, diameter 0.26 mm; initial whorls dipping, sinistral; remaining protoconch flatly dextral; protoconch smooth, with convex whorls; protoconch demarcated from teleoconch by a distinct suture and a bulge; teleoconch whorls smooth, convex, circular in transverse section; suture distinct; base distinctly phaneromphalous.

Remarks. The present specimens agree well with Bandel’s (1996) type specimens from the type locality Misurina.

Family Stuoraxidae Bandel, 1996 Genus Ampezzogyra Bandel, 1996

Type species. Ampezzogyra schroederi Bandel, 1996, Late Triassic, Cassian Formation.

Ampezzogyra angulata Nützel & Hausmann sp. nov. Figs. 25, 26.

Material. Nine specimens from Lago Antorno bulk; 14 specimens from Misurina Landslide bulk; 23 specimens in total; holotype PZO YYY, paratypes PZO YYY.

Type locality. Lago Antorno near Misurina (see Fig. 1B).

Age. Cassian Formation, Early Carnian.

Description. Shell planispiral with somewhat depressed upper side (assuming dextral teleoconch) and somewhat deeper, widely phaneromphalous umbilicus; shell with about 3.4 whorls, 0.9 mm wide, 0.3 mm high; protoconch flat, comprising about 1.5 whorls, diameter 0.16-0.18 mm; initial whorls dipping, sinistral; protoconch smooth, with convex whorls; protoconch demarcated from teleoconch by a distinct suture and a bulge; teleoconch whorls convex at periphery, ornamented with seven to eight distinct spiral ribs which angulate the whorls somewhat especially at transition from periphery to upper side; axial ribs having character of strengthened growth lines; intersections of weak axial ribs and upper spiral rib somewhat pronounced, node-like, especially in early portions of teleoconch; teleoconch covered with micro-ornament of fine tubercles; shell structure crossed lamellar.

Remarks. Ampezzogyra angulata n. sp. resembles the type species A. schroederi Bandel, 1996 from the Cassian Formation. However, A. schroederi has strong axial ribs and only subordinate, weak numerous spiral threads at which the whorls are not angulated so that the whorls are circular in transverse section. Moreover, the larval whorls have axial folds in A. schroederi while those of A. angulata are entirely smooth. Sloeudaronia karavankensis Kaim, Jurkovšek & Kolar-Jurkovšek, 2006. from the Carnian of Slovenia is similar but has widely spaced distinct axial ribs and fewer, more distinct spiral ribs on the whorls. Kaim et al. (2006) placed Sloeudaronia in Vetigastropoda based on the poorly preserved protoconch which they interpreted consisting of one whorl and as being of the vetigastropod type. However, if this protoconch turns out to be heterostrophic, Sloeudaronia and Ampezzogyra could be considered synonyms. The genus Rinaldoconchus Bandel, 1996 from the Cassian Formation (R. bieleri and R. ampezzanus) is similar but has an elevated spire.

Family Tubiferidae Cossmann, 1895 Genus Sinuarbullina Gründel, 1997

Type species. Sinuarbullina ansorgi Gründel, 1997

Sinuarbullina sp. 1 Fig. 27A, D.

Material. Ten specimens from Lago Antorno bulk; 14 specimens from Misurina Landslide bulk; 24 specimens in total; PZO YYY.

Description. Shell slender, fusiforme with last whorl larger than spire, embracing above mid-whorl; illustrated specimens with about 2.5 teleoconch whorls; whorls smooth, evenly convex with narrow subsutural ramp which is demarcated from whorls sides by an angular edge and a weak spiral furrow; aperture elongated much higher than wide, narrow posteriorly, wide and rounded anteriorly; protoconch heterostrophic sinistral, transaxial, consisting of about two smooth whorls, 0.28 mm wide (Fig. 27A); illustrated specimen from Lago Antorno (Fig. 27A) 0.7 mm wide, 1.2 mmm high; illustrated specimen from Misurina Landslide (Fig. 27D) 0.5 mm wide, 0.9 mm high.

Remarks. This is a typical representative of a group of “shelled opisthobranchs” which occurs in the Early Triassic (Batten & Stokes 1986; Nützel 2005; Nützel & Schulbert 2005) and ranges into the Cretaceous (Kaim 2004).

Sinuarbullina sp. 2 Fig. 27E.

Material. Two specimens from Lago Antorno bulk; two specimens from Misurina Landslide bulk; four specimens in total; PZO YYY.

Description. Illustrated specimen from Misurina Landslide 0.5 mm wide, 0.9 mm high.

Remarks. Sinuarbullina sp. 2 differs from Sinuarbullina sp. 1 by the having a lower spire. The protoconch size of both species is more or less the same.

Sinuarbullina sp. 3 Fig. 27B, C.

Material. Two specimens from Lago Antorno bulk; PZO YYY.

Description. Shell slender, 0.4 mm wide, 1.1 mm high (Fig. 27B).

Remarks. This species is distinct from the two Sinuarbullina species in being more slender und having higher whorls and more oblique sutures. Moreover, the protoconch is smaller than in the other Sinuarbullina species.

Gastropoda indet. sp. 1

Material. One specimen from Misurina Landslide bulk.

Remarks. The specimen at hand is poorly preserved. The shell is heavily encrusted and compressed. It resembles the genus Camposcala biserta (Münster, 1841) to some degree, but the encrustation does not allow a clear assignment to this genus.

Gastropoda indet. sp. 2

Material. One specimen from Lago Antorno bulk.

Remarks. The shell is smooth, high-spired with low whorls; the apex is missing. Although distinct in this collection, this specimen cannot be identified.

Class Bivalvia Linnaeus, 1758 Family Nuculidae Gray, 1824 Genus Palaeonucula Quenstedt, 1930

Type species. Nucula hammeri Defrance, 1825

Palaeonucula strigilata (Goldfuss, 1837) Fig. 28C, D.

1837 Nucula strigilata n. sp.; Goldfuss 1837: 153, pl. 124: 18a, b. 1841 Nucula strigilata Goldf.; Münster 1841: 83, pl. 8: 10a, b. 1865 Nucula strigilata Goldf.; Laube 1865: 65, pl. 19: 2. 1895 Nucula strigilata Goldf.; Bittner 1895: 137-138, pl. 17: 1–17. 1977 Palaeonucula strigilata (Goldfuss); Fürsich & Wendt 1977: fig. 11. 1981 Palaeonucula strigilata (Goldfuss); Zardini 1981: pl. 1: 1–14, pl. 39: 11. 1988 Palaeonucula strigilata Goldfuss; Zardini 1988: pl. 1: 3, 4. 2012 Palaeonucula strigilata (Goldfuss, 1837); Urlichs 2012: 5, pl. 1: 3.1–3.3, 4, 8. 2014 Palaeonucula strigilata (Goldfuss 1837); Nützel & Kaim 2014: 422, figs. 10a, d.

More synonyms are listed in Diener (1923) and Urlichs (2012).

Material. Two specimens from Lago Antorno bulk; 10 specimens from Misurina Landslide bulk; eight specimens from Misurina Landslide surface; 20 specimens in total; PZO YYY.

Remarks. All found specimens are double-valved and the shells are often diagenetically compressed. In many cases, the co-marginal ribs are concealed by encrustation. Palaeonucula strigilata (Goldfuss, 1837) is a very common bivalve in Cassian deposits and was therefore also found at many other Cassian localities, including Costalaresc, Piz Stuores, Pralongia, Rio Pocol, Settsass Scharte and Stuores Wiesen (Fürsich and Wendt 1977; Urlichs 2012; Nützel and Kaim 2014). This species constitutes the second most abundant taxon in the Rhaphistomella radians/Palaeonucula strigilata association and even the most abundant species of the Palaeonucula strigilata/Dentalium undulatum association described by Fürsich and Wendt (1977).

Family Nuculanidae Adams & Adams, 1858 Genus Nuculana Link, 1807

Type species. Arca rostrata Chemnitz, 1784

Nuculana sulcellata (Wissmann, 1841) Fig. 28A, E.

1841 Nucula sulcellata Wissm.; Münster 1841: 85, pl. 8: 15. 1843 Nucula sulcellata Wissm.; Klipstein 1843: 263, pl 17: 19. 1857 Nucula sulcellata Wissm.; Hauer 1857: 558, pl. 2: 11, 12. 1865 Leda sulcellata Wissmann sp.; Laube 1865: 68-69, pl. 19: 5. 1895 Leda sulcellata Wissm. sp. (emend.); Bittner 1895: 147-148, pl. 18: 10. 1981 Naculana sulcellata (Muenster) [sic]; Zardini 1981: pl. 3: 4, 6–13. 1988 Nuculana sulcellata Muenster; Zardini 1988: pl. 4: 34.

Material. Two specimens from Lago Antorno surface; three specimens from Misurina Landslide bulk; five specimens from Misurina Landslide surface; 10 specimens in total; PZO YYY.

Remarks. Specimens with single- and double-valved shells occur in the samples. The characteristic long rostrum at the posterior end is broken in all specimens. Nevertheless, the shells fit best to Bittner's (1895), Laube's (1865) and Zardini's (1981) illustrated specimens of this species, which are however, erroneously written Naculana sulcellata in Zardini's (1981) description of pl. 3. This bivalve species is relatively common in the Cassian Formation and was also found at the localities Costalaresc, Rumerlo, Alpe di Specie and Stuores Wiesen (see Roden et al. (2019 accepted) and references therein). Bittner (1895) mentioned that Münster's (1841) type specimen of this species is not conspecific and therefore named it Leda Wissmanniana n. sp. He also emphasised that there are doubts if the type specimen really comes from the Cassian Formation.

Family Malletiidae Adams & Adams, 1858 Genus Palaeoneilo Hall & Whitfield, 1869

Palaeoneilo distincta f. laubei (Bittner, 1895)

1895 Leda (?) distincta n. sp.; Bittner 1895: 150-152, pl. 16: 38, 39. 1981 Palaeoneilo distincta f. laubei (Bittner); Zardini 1981: pl. 3: 14, 15.

Material. Two specimens from Lago Antorno bulk; two specimens from Misurina Landslide bulk; four specimens in total.

Remarks. All specimens show only a weak sculpture, similar to Bittner´s (1895) and Zardini´s (1981) illustrations of Palaeoneilo distincta f. laubei (Bittner, 1895). The shell outline also fit best to Bittner´s (1895) and Zardini´s (1981) illustrations. The umbo is centred regarding anterior and posterior position, the shell outline round to oval-shaped. The specimens studied herein also resemble Bittner´s (1895) Leda (?) Zelima d´Orbigny to some degree, however, this species is more oval than our shells. All four specimens are double-valved.

Palaeoneilo elliptica (Goldfuss, 1837) Fig. 28B.

1837 Nucula elliptica sp. nov.; Goldfuss 1837: 153, pl. 124: 16 (pars).

1841 Nucula elliptica Goldf.; Münster 1841: 83, pl. 8: 8. 1843 Nucula tenuis ?; Klipstein 1843: 263, pl. 17: 17. 1848 Leda elliptica; Deshayes 1848: 278. 1849 Leda elliptica; d´Orbigny 1849: 197. 1852 Nucula Münsteri; Giebel 1852: 389 (pars.). 1864 Nucula elliptica; Alberti 1864: 102. 1864 Leda elliptica; Laube 1864: 407. 1865 Leda elliptica Goldf. sp.; Laube 1865: 67–68, pl. 19: 6. 1895 Palaeoneilo elliptica Goldf. spec.; Bittner 1895: 142–143, pl. 16: 26–31. 1981 Palaeoneilo elliptica (Goldfuss); Zardini 1981: pl. 2: 12–14, pl. 3: 1, 2.

Material. One specimen from Lago Antorno surface; two specimens from Misurina Landslide surface; three specimens in total; PZO YYY.

Remarks. All specimens from Lago Antorno and Misurina Landslide are double-valved. They fit best to Zardini's (1981) illustrated shells of Palaeoneilo elliptica (Goldfuss, 1837). Also Bittner´s (1895) illustrated specimens are similar in shape to our specimens.

Family Mytilidae Rafinesque, 1815 Genus Modiolus Lamarck, 1799

Type species Mytilus modiolus Linnaeus, 1758

Modiolus paronai Bittner, 1895

1895 Modiola Paronai nov. spec.; Bittner 1895: 48, pl. 5: 19, 20. 1981 Modiolus paronai (Bittner); Zardini 1981: pl. 6: 16, 17, pl. 7: 1, 2. 2015 Modiolus paronai; Hausmann and Nützel 2015: fig. 9G.

Material. One specimen from Misurina Landslide bulk.

Remarks. The single-valved specimen at hand is heavily encrusted and, with a length of c. 1 mm, very small. However, it closely resembles Zardini's (1981) illustrated specimens of Modiolus paronai Bittner, 1895. M. paronai Bittner, 1895 was also found at the Cassian locality Stuores Wiesen, where it was represented by 15 specimens (Hausmann and Nützel 2015).

Family Bakevelliidae King, 1850 Genus Gervillia Defrance, 1820 Subgenus Cultriopsis Cossmann, 1904

Type species Gervillia (Cultriopsis) falciformis Cossmann, 1904

Gervillia (Cultriopsis) sp.

Material. Three specimens from Misurina Landslide bulk; one specimen from Misurina Landslide surface; four specimens in total.

Remarks. Only fragments were found in the samples from Misurina Landslide. Four of them were single-valved (to account for an estimation of the real number of bivalve individuals, this number was divided by two), two were double-valved. Our specimens were compared with Gervillia (Cultriopsis) species from Bittner (1895) (who spelled this genus Gervilleia throughout his monograph), Zardini (1981) and Hautmann (2001). Because of their fragmented nature, a species identification was not possible. Nevertheless, the characteristic shell features assign the Misurina Landslide specimens to this genus.

Pteroida Family Antijaniridae Hautmann, 2011 (in Carter et al. 2011) Genus Antijanira Bittner, 1901

Type species. Pecten hungaricus Bittner, 1901

Antijanira auristriata (Münster, 1841)

1841 Pecten auristriatus; Münster 1841: 73, pl. 6: 35. 1865 Pecten Nerei Münster; Laube 1865: 70–71, pl. 20: 3, 5. 1895 Pecten cfr. auristriatus Münst.; Bittner 1895: 165–166, pl. 19: 23–26. 1981 Antijanira auristriata (Muenster); Zardini 1981: pl. 17: 15–23, pl. 18: figs. 1–3, 6.

Material. One specimen from Misurina Landslide bulk.

Remarks. Only the anterior auricle is preserved, but the specimen was assigned to Antijanira auristriata (Münster, 1841) because it resembles the illustrated shells of Zardini (1981). Unfortunately, the auricle region was not depicted distinctly enough in Bittner (1895) to differentiate between species shown in his monograph.

Family Cassianellidae Ichikawa, 1958 Genus Cassianella Beyrich, 1862

Type species. Avicula gryphaeata Münster, 1836

Remarks. Cassianella is very diverse in the Cassian Formation. Bittner (1895) listed 10 species from the Cassian beds. The genus ranges from the Middle to the Upper Triassic.

Cassianella beyrichi Bittner, 1895 Fig. 29B, C.

Pars 1838 Avicula gryphaeata Münst.; Goldfuss 1838: 127 pl. 106: 10 e (nec fig. 10 a–d). Pars 1841 Avicula gryphaeata; Münster 1841: 75–76 (exclus. fig.). Pars 1865 Cassianella gryphaeata Münst. sp.; Laube 1865: 46–47, pl. 17: 1a–h. 1895 Cassianella Beyrichii nov. spec.; Bittner 1895: 54–55, pl. 6: 16–21. 1977 Cassianella beyrichii; Fürsich and Wendt 1977: 288, fig. 13(6). 1981 Cassianella beyrichi (Bittner); Zardini 1981: pl. 13: 3, 4.

Material. Three specimens from Lago Antorno surface; one specimen from Misurina Landslide bulk; three specimens from Misurina Landslide surface; seven specimens in total; PZO YYY.

Remarks. Only the characteristic left valves are preserved. They were identified according to Zardini (1981). This Cassianella species, together with C. ampezzana Bittner, 1895, belongs to the trophic nucleus of Fürsich and Wendt´s (1977) Ampullina association, which is very similar in taxonomic composition to the Misurina Landslide and Lago Antorno assemblages studied herein.

Cassianella sp. 1

Material. One left valve found in the surface samples from Misurina Landslide.

Remarks. The specimen is diagenetically compressed. The smooth surface distinguishes this species from both other Cassianella species found at Lago Antorno and Misurina Landslide. A species comparable to Cassianella sp. 1 was not found in the literature. Therefore, using open nomenclature was the best solution in the case of this single specimen.

Cassianella sp. 2

Material. Two left valves from Lago Antorno surface.

Remarks. This species is ornamented with distinct, densely packed co-marginal ribs, between which radially arranged densely spaced threads are visible.

Family Hunanopectinidae Yin, 1985 Genus Leptochondria Bittner, 1891 Type species – Pecten aeolicus Bittner, 1891

Leptochondria monilifera (Braun in Münster 1841)

1841 Pecten moniliferus Braun; Münster 1841: 72–73, pl. 7: 4. 1865 Pecten subalternans d´Orb.; Laube 1865: 69–70, pl. 20: 4. 1895 Pecten moniliferus Münst.; Bittner 1895: 157, pl. 18: 29, 30. 1981 Leptochondria monilifera (Bittner) (sic!); Zardini 1981: pl. 18: 21, pl. 19: 1, 2.

Material. One specimen from Lago Antorno bulk; one specimen from Misurina Landslide bulk; two specimens in total.

Remarks. Only fragments were found in both bulk samples. However, since they showed the characteristic ornamentation of Leptochondria monilifera depicted in Zardini (1981), they were assigned to this species.

Family Lucinidae Fleming, 1828 Genus Schafhaeutlia Cossmann, 1897

Type species Gonodon schafhaeutli Salomon, 1895

Schafhaeutlia cf. astartiformis

2015 Schafhaeutlia cf. astartiformis; Hausmann and Nützel 2015: fig. 10J.

Material. One specimen from Misurina Landslide surface.

Remarks. The single specimen is double-valved and partly fragmented. It is the same species as depicted in Hausmann and Nützel (2015). However, the illustrated specimen in Hausmann and Nützel (2015) is heavily encrusted whereas the individual studied herein shows no incrustations.

Family Cardiidae Lamarck, 1809 Genus Septocardia Hall & Whitfield, 1877

Septocardia pichleri (Bittner, 1895) Fig. 30.

1895 Cardita Pichleri nov. spec.; Bittner 1895: 38–39, pl. 24: 8–10. 1895 Cardita cf. Pichleri nov. spec.; Bittner 1895: 38–39, pl. 4: 17. 1981 Palaeocardita pichleri; Zardini 1981: pl. 31: 3–11. 2001 Septocardia pichleri; Schneider & Carter 2001: fig. 3, 4.

Palaeocardita Conrad, 1867

Material. Two specimens from Lago Antorno surface; two specimens from Misurina Landslide bulk; three specimens from Misurina Landslide surface; seven specimens in total; PZO YYY.

Description. Septocardia pichleri (Bittner, 1895) is ornamented with strongly denticulated and locally slightly reflected co-marginal flanges; shell highly inflated; single- and double-valved specimens occur.

Remarks. The present material agrees well with the type specimens illustrated by Bittner (1895) from the localities Issberg-Gehänge and Bergangerl near Hall in Northern Tyrol, Austria (N Alps). Bittner (1895, pl. 4, fig. 17) also illustrated an articulated specimen from the Cassian Formation of the Seelandalpe. Bittner stated that he could not study the hinge of the material from the South Alps but that it shows no external morphological differences to the type material from the Northern Alps. The present specimens are relatively small. The specimen from Alpe di Specie illustrated by Schneider & Carter (2001) closely resembles the present specimens and is of approximately the same size.

Bivalvia indet. sp. 1

Material. Eleven specimens from Lago Antorno bulk; eight specimens from Misurina Landslide bulk; in total 19 specimens.

Remarks. Most specimens are single-valved. Nevertheless, assignment to a species or genus was not possible.

Bivalvia indet. sp. 2

Material. Only one specimen from Misurina Landslide bulk.

Remarks. The single specimen consists of only one valve and is relatively thin-shelled. The fossil could not be determined properly, but an affiliation to the family Entoliidae is possible (M. Hautmann, pers. comm. 2017).

Class Scaphopoda Bronn, 1862 Family Dentaliidae Children, 1834 Genus Dentalium Linnaeus, 1758

Type species. Dentalium elephantinum Linnaeus, 1758

Dentalium klipsteini Kittl, 1891 Fig. 31.

1891 Dentalium Klipsteini Kittl; Kittl 1891: 172, pl. 1: 3. 1978 Dentalim klipsteini (Kittl) (sic!); Zardini 1978: 56, pl. 39: 14–17, 20, pl. 40: 7. 1978 Dentalium klipstein (Kittl) n. f. tenuistriatum (sic!); Zardini 1978: 56, pl. 39: 19, 22, 23, pl. 40: 13.

Material. Five specimens from Lago Antorno bulk; six specimens from Lago Antorno surface; two specimens from Misurina Landslide bulk; one specimen from Misurina Landslide surface; 14 specimens in total; PZO YYY.

Remarks. Only broken specimens were found. Characteristic of this species are the more or less oblique annulations in combination with variably strongly pronounced longitudinal ribs.

Genus Plagioglypta Pilsbry & Sharp, 1897

Plagioglypta undulata (Münster, 1841)

1841 Dentalium undulatum; Münster 1841: 91, pl. 9, fig. 6. 1844 Dentalium undulatum Münster; Goldfuss 1844: 3, pl. 166, fig. 8. 1891 Dentalium undulatum Münster; Kittl 1891: pl. 1, fig. 1. 1977 Dentalium undulatum; Fürsich and Wendt 1977: 268, fig. 12 (2). 1991 Pseudobactrites subundatus (Münster); Bizzarini & Gnoli 1991: 114, pl. 1, fig. 5a–b. 2012 Plagioglypta undulata (Münster, 1841); Urlichs 2012: figs. 3.11, 3.12. 2014 Plagioglypta undulata (zu Münster 1841); Nützel and Kaim 2014: fig. 11 e, f. 2015 Plagioglypta undulata; Hausmann and Nützel 2015: 246, fig. 10 K. Refer to Kittl (1891) and Stiller (2001, p. 624) for further synonyms.

Material. Two specimens from Misurina Landslide, one from the bulk sample and one from the surface collections.

Remarks. This taxon was the second most abundant species in Fürsich and Wendt's (1977) Palaeonucula strigilata/Dentalium undulatum association, which was found at Costalaresc. It is also a major component of the basinal soft-bottom fauna described from the Settsass Scharte (Nützel and Kaim 2014). In the allochthonous assemblage from Stuores Wiesen, P. undulata was only moderately represented (Hausmann and Nützel 2015).

Cephalopoda A single fragment of a trachycertid ammonite and four fragment of unidentified ammonites material is present from the Misurina Landslide bulk sample.

Brachiopoda There is a single very small brachiopod from the Lago Antorno bulk sample that presumably represents a juvenile. Therefore, species identification is not possible.

Crustaceans Crustaceans are present with two ostracods representing two species are in our samples. One of them was found in the bulk collection from Misurina Landslide, the other in the bulk sample from Lago Antorno. Both species were not determined to species level. Ostracods are much more abundant and diverse in the finer fraction (< 0.5 mm) which was not used for this analysis. Abundant crustacean coprolites were found in the Misurina Landslide bulk samples (Fig. 32; PZO YYY). They are oval in tranverse section and have longitudinal structures on the centre of both sides.

Phylum Echinodermata Bruguière, 1791 [ex Klein, 1734]

Crinoids.—One poorly preserved columnal (Fig. 33A) of isocrinid affinities only.

Asteroids and ophiuroids.—Asterozoan echinoderms (Fig. 33B–E) were mostly represented by a few ophiuroid species, undetermined yet, based on lateral arm plates, vertebrae and spines.

Ophiocistioids.—A single small linguaserrid goniodont was collected (Fig. 33F) and described recently by Reich et al. (2018) as a new species (Linguaserra triassica Reich in Reich et al., 2018), representing the stratigraphically youngest record of ophiocistioid teeth worldwide. Our Misurina material is important because it provides the only evidence of this ‘Palaeozoic’ echinoderm class known from Mesozoic strata. Ophiocistioids are exclusively benthic and were presumably active predators using their lantern and teeth to capture small benthic prey.

Echinoids.—Sea urchin ossicles and plates are the commonest in our material. As the Cassian Formation contains the largest and most important Triassic echinoid fauna worldwide (e.g. Kroh 2011), it is not suprising that even very rare, unexpected Palaeozoic-type forms can be found. Nützel and Kaim (2014: fig. 11p, q) figured an “Unknown echinoderm plate” from the Settsass Scharte which is, in fact, an ambulacral plate of a proterocidarid echinoid (refigured in part by Thuy et al. 2017a: fig. 1B). New investigations by the authors at Misurina Landslide revealed >100 disarticulated ambulacral and interambulacral plates of Pronechinus? sp. nov. (Fig. 33G–J). This proterocidarid material is also remarkable because it provides evidence for persistence of this ‘Palaeozoic’ echinoid stem group for at least 16 Ma after the P/T boundary. Misurina Landslide is the same locality from which a representative of another ‘Palaeozoic-type’ echinoderm group—the Ophiocistioidea—were recently described (Reich et al. 2018). These findings are in accordance with other proterocidarid echinoids recently reported from France (Hagdorn 2018) and China (Thuy et al. 2017a; Thompson et al. 2018). In addition, we have found well preserved and partly articulated test fragments (Fig. 33N) and spines (a few types; e.g. Fig. 33K–M) of cidaroid echinoids (including “Cidaris” cf. decoratissima Wöhrmann, 1889 and “Cidaris” cf. flexuosa Münster, 1841) at Misurina Landslide, which present the

33 majority of sea urchin material from the Cassian Formation (see also Vadet 1999a, 1999b; Kroh 2011). Regular echinoids, like in our material, are vagile benthos, moving by means of their spines over the sea floor and using their tube-feet to climb and grip hard substrata (Smith 2004). Proterocidarid species are presumably deposit feeders, using their oral tube-feet for detritus gathering.

Holothurians.—Sea cucumbers were represented by calcareous ring (CR) elements and body-wall ossicles of Apodida (Fig. 34A–E) and Synallactida (F–H) only (see Miller et al. 2017). A few apodid interradial and radial elements of the CR associated by different wheels (Chiridotidae/stem group Chiridotidae/stem group Myriotrochidae) were present. In addition, two species of stem group Synallactidae (Tetravirga spp.) were also found in the Misurina Landslide sample. Apodids were mainly infaunal deposit feeders, whereas synallactids were epibenthic deposit feeders (e.g. rake-feeder or sweeper) and capable of active swimming. Representatives of both groups are therefore active and important bioturbators of the sediment floor.

Discussion

Palaeoenvironment Different factors indicate that the assemblages stem from basinal soft-bottom settings: First, nuculids are characteristic representatives of the bivalve assemblages and are considered to be soft-bottom inhabitants (e.g., Fürsich and Wendt 1977). They almost always occur with conjoined valves. Second, ooids and oncoids, which are typical components of transported shallow-water assemblages from the Cassian Formation (Hausmann and Nützel 2015), are lacking. In addition, the marly clayey sediments yielding the fauna point to soft-bottom conditions. The large amount of double-valved shells indicate a predominantely autochthonous origin of both fossil assemblages. However, it is most likely that some transported elements from other palaeoenvironments are also present. For example, one calcareous sponge was found in a surface sample from Misurina Landslide and a small fragment of presumably hydrozoan origin was contained in the bulk sample from Lago Antorno, which may both stem from originally reefal environments. The presence of echinoderms, nuculid bivalves and clearly marine gastropods that had planktotrophic larval development (Nützel 2014) indicates fully marine conditions. Fürsich and Wendt (1977) described a variety of faunal assemblages from the Cassian Formation stemming from different palaeoenvironments, including, for example, patch reef faunas of partly allochthonous origin and several autochthonous basin associations. The fossil assemblages studied herein resemble the Ampullina association of Fürsich and Wendt (1977) from the Cortina basin, which includes the region of Misurina. This basinal, autochthonous, soft-bottom association is characterised mainly by the smooth-shelled, bulbous caenogastropod species Helenostylina convexa and Prostylifer paludinaris, which were called Ampullina sanctaecrucis and A. paludinaris in Fürsich and Wendt (1977) and Bizzarini and Laghi (2005). It is unclear which species the authors were referring to with Ampullina sanctaecrucis (=Ptychostoma sanctaecrucis) because no photographs were provided. Ptychostoma sanctaecrucis is a relatively large gastropod that resembles P. paludinaris. Ptychostoma sanctaecrucis is abundant at its type locality which is also the type locality of the Heiligkreuz Formation and is interpreted as brackish. Prostylifer paludinaris belongs to the most abundant species in our bulk samples and is by far the most abundant species in the surface samples, corresponding to the observations made by Fürsich and Wendt (1977) that this species is highly abundant in the Ampullina association. The fact that H. convexa is relatively rare in our samples, whereas it is the most abundant species in Fürsich and Wendt´s (1977) association, can be explained as follows: Helenostylina convexa and P. paludinaris look very similar with respect to the teleoconch and can

34 only be identified clearly when the protoconch is present and the base is well exposed. Since this is most often not the case, it makes species identification difficult and could have led to some misinterpretations in either Fürsich and Wendt´s (1977) or our own samples. Other similarities between Fürsich and Wendt´s (1977) Ampullina association and our studied assemblages are as follows: First, representatives of palaeonuculid, cassianellid and cardiid bivalves are also present in Fürsich and Wendt´s (1977) assemblage and the samples studied herein, even though they are relatively more abundant in Fürsich and Wendt´s (1977) dataset. This is probably due to the fact that these authors based their study on surface samples and not on washed bulk samples – since bivalve species are commonly larger than gastropod species, their proportion in surface samples is expected to be higher. And second, as in our samples, Fürsich and Wendt´s (1977) association contained a considerable amount of trace fossils resembling Planolites-shaped burrows (Fig. 32). The water depths of the palaeosettings, in which the faunal assemblages from Misurina Landslide and Lago Antorno lived, cannot be determined with certainty. According to Fürsich and Wendt (1977), the autochthonous soft-bottom faunas they described lived in shallow basins, whereas almost no autochthonous benthic assemblages are found in deep basins. Wendt and Fürsich (1980) suggested that the benthic soft-bottom assemblages lived in the upper subtidal or at least within the photic zone. However, Urlichs (2012) concluded that they stem from higher water depths, reaching 100 m and more. Diversity indices show that alpha diversity is approximately the same across bulk samples from both studied Cassian localities (Table 3). Similar evenness and ecological complexity as well as a relatively similar fossil content suggest an origin from similar palaeoenvironments.

Faunal composition Even though the overall faunal content is similar between Lago Antorno and Misurina Landslide, there are some differences in species composition and abundances (Table 1). This suggests that distinct Cassian assemblages may change gradually and that, even if faunas lie very close to each other or stem from the same facies, they can exhibit relatively large differences in faunal composition. For instance, the majority of the more abundant species is shared between the Lago Antorno and the Misurina Landslide localities (e.g., the gastropods Prostylifer paludinaris, Coelostylina conica, Ampezzopleura hybridopsis and Jurilda elongata. Jurilda elongata is the most abundant species at Misurina Landslide but has never been reported as a dominant species from elsewhere. It is rare at Lago Antorno. The rare species are commonly not shared between the studied sites but this is probably due to stochastic reasons. Although there is some similarity to the Ampullina assemblage sensu Fürsich & Wendt (1977), the assemblages from Misurina Landslide and Lago Antorno differ considerably in taxonomic composition from all other Cassian invertebrate assemblages described so far (Fürsich and Wendt 1977; Nützel and Kaim 2014; Hausmann and Nützel 2015). The most abundant species from Settsass Scharte (Goniospira armata, Schartia carinata, Helenostylina convexa, Plagioglypta undulata) are either absent or rare in the samples from Lago Antorno and Misurina Landslide. In contrast, all abundant species from the samples studied herein are absent at Settsass Scharte (except Coelostylina conica, which is, however, not very abundant at Settsass Scharte) (Nützel and Kaim 2014). The Rhaphistomella radians/Palaeonucula strigilata association (largely composed of the name- giving species as well the bivalve Prosoleptus lineatus), reported by Fürsich and Wendt (1977) from the Stuores Wiesen and the Pralongia, likewise represents an autochthonous basin association. The bivalve P. strigilata is rarer in the Lago Antorno and Misurina Landslide samples, and the gastropod character fossil Rhaphistomella radians is absent. Fürsich and Wendt (1977) based their analysis on surface collections and therefore did not consider the microgastropod fauna, which may partly explain the differences in faunal composition.

Alpha and beta diversity Both fossil assemblages from Lago Antorno and Misurina Landslide are characterised by a moderate to low diversity when compared to other Cassian faunas studied so far (Fürsich and Wendt 1977; Hausmann and Nützel 2015). A comparison of Misurina Landslide and Lago Antorno with the Cassian assemblage from Stuores Wiesen shows that, in addition to a difference in taxonomic composition, diversity is also profoundly different. The Stuores Wiesen diversity is very high (Shannon index of 4.01; Simpson index of 0.96), supported by rarefaction analyses (Fig. 35). The fossil assemblage found at this locality is thought to stem from a shallow water lagoonal palaeohabitat (Hausmann and Nützel 2015). In contrast, Misurina Landslide and Lago Antorno have a similar diversity as the basinal soft-bottom assemblage reported by Nützel and Kaim (2014) from the Settsass Scharte (Shannon index of 2.24; Simpson index of 0.85; Fig. 35) but differ also strongly in composition. Basinal soft-bottom assemblages from the Cassian Formation seem to share a similar moderate to low diversity, at least when comparing Misurina Landslide and Lago Antorno with Settsass Scharte (Nützel and Kaim 2014). A comparison of beta diversity based on dissimilarities across the quantitatively studied Cassian assemblages (Nützel and Kaim 2014; Hausmann and Nützel 2015) shows that all assemblages are highly dissimilar (values > 0.9), except for between Misurina Landslide and Lago Antorno (Table 5); a value of 0.52 indicates that both assemblages are quite similar to each other, confirming our previous results. Nevertheless, beta diversity is very high among the studied Cassian assemblages (Misurina Landslide, Lago Antorno, Settsass Scharte (Nützel and Kaim 2014), Stuores Wiesen (Hausmann and Nützel 2015)), with a mean dissimilarity value of 0.88.

Body size The fossil assemblages from Lago Antorno and Misurina Landslide are strongly dominated by molluscs, with gastropods being the most diverse and abundant group. In addition, the fossils are characterised by very small sizes. The size of most fossils does not exceed a few millimetres in length. The small size of fossils is a typical feature of Cassian assemblages, regardless of the palaeoenvironment from where they originally derive (e.g., Fürsich and Wendt 1977; Nützel and Kaim 2014; Hausmann and Nützel 2015). Taking into account that the majority of recent gastropods from marine tropical settings are also characterised by small to very small sizes (e.g., Bouchet et al. 2002; Bouchet 2009; Albano et al. 2011) and most fossils from Misurina Landslide and Lago Antorno and other Cassian locations are gastropods (e.g., Fürsich and Wendt 1977; Nützel and Kaim 2014; Hausmann and Nützel 2015), the small sizes are less remarkable than previously thought. Stunting due to unfavourable conditions has been proposed to explain the allegedly exceptionally small size of the Cassian fossils (e.g., Richthofen 1860; Leonardi and Fiscon 1959). However, as pointed out by Nützel et al. (2010b), the high overall diversity of the Cassian Formation argues against pronounced environmental stress, because such stress produces communities of low diversity and high dominance (see also Fuchs 1871). Stunting has been reported for some species at Stuores Wiesen and surrounding areas near San Cassiano (Urlichs 2012) but cannot be proposed for the Cassian fauna as a whole. On the other hand, the question arises why only a very small fraction or a complete lack of larger fossils characterises samples from the Cassian Formation. In allochthonous fossil assemblages, size sorting during transport could – at least in part – be responsible for the exclusively small sizes (Hausmann and Nützel 2015). However, since the samples from Misurina Landslide and Lago Antorno are of predominantely autochthonous origin, transport-induced size sorting cannot be a reason for the lack of fossils larger 10 mm. An explanation concerning surface samples could be the selective removal of large specimens by private collectors (e.g., Fürsich and Wendt 1977; Urlichs 2004, 2012). However, historical collections form the Cassian beds made during the last 180 years consist of a great majority

36 of specimens smaller than 15 mm. Regarding bulk samples, a comparison with modern (sub-)tropical marine sediment samples may help to understand the scarcity of large fossils, since modern benthic sediments typically consist of only a small number of large specimens (e.g., Bouchet et al. 2002; Bouchet 2009; own observations). Some larger Cassian fossils have been found, but in most cases they are fragmented or disarticulated (e.g., Hausmann and Nützel 2015; unpublished data). Molluscs, for example, can reach sizes of 40 mm and even more; however, as in recent (sub-)tropical marine sediment samples, members of these size classes are scarce (e.g., Bouchet et al. 2002; Bouchet 2009; unpublished data). In the samples studied herein, small adult as well as juvenile specimens were found. For example, heterobranch genera like Cylindrobullina and Sinuarbullina have a small adult size (see also Bandel 1994; Nützel and Kaim 2014; Hausmann and Nützel 2015). All specimens of the abundant neritimorph species Neritaria mandelslohi and Dentineritaria neritina were juveniles or isolated larval shells. This suggests that they were able to metamorphose but the palaeoenvironment was not suitable for them, leading to a high mortality. The small size of the species and the high mortality of the neritimorphs point to an environmental constraint. Most likely, fluctuating oxygen concentrations and the soft substrate limited body size in this case, as has also been proposed for other soft-bottom communities (e.g., for the Early Jurassic Nützel and Kiessling 1997; Nützel and Gründel 2015). Framboidal pyrite was observed in the crustacean coprolites from Misurina Landslide, and framboids were occasionally detected at Lago Antorno (Fig. 36). Many studies demonstrate that framboidal pyrite is characteristic of oxygen-deficient conditions in benthic habitats and that the size of framboidal structures indicate the severity of oxygen deficiency (e.g., Wilkin et al. 1996, 1997; Wignall and Newton 1998; Bond and Wignall 2010; Shen et al. 2007; Wignall et al. 2005). A lower oxygen content in the bottom waters of the palaeohabitats from the two sampling sites Lago Antorno and Misurina Landslide could argue for the relatively low biodiversity, but stunting at these localities has not been investigated so far.

Echinoderms A few invertebrate groups, including echinoderms, were apparently severely diminished during the Permian/Triassic mass extinction interval (e.g. Benton and Twitchett 2003; Twitchett and Oji 2005). However, existing paradigms that most of the echinoderm lineages are inferred to have gone extinct at the end of the Palaeozoic shifted recently due to the presence of ‘hangovers’ or ‘holdovers’ in Triassic strata (e.g. Thuy et al. 2017a, 2017b, 2017c; Thuy 2017; Blake 2017; Hunter and McNamara 2017; Salamon and Gorzelak 2017; Hagdorn 2018; Reich et al. 2018; Thompson et al. 2018). Due to the rapid post-mortem disarticulation of echinoderms, resulting in a relatively sparse articulated fossil record, the use of the disarticulated fossil record seemed rather more favourable (e.g. Kutscher and Reich 2004; Reich and Smith 2009; Thompson and Denayer 2017). Liberation lagerstätten (Roden et al. 2019 accepted), like the Cassian Formation, yield highly diverse echinoderm assemblages (e.g. Zardini 1973, 1988) with a large proportion of disarticulated material of Crinoidea, Asteroidea, Ophiuroidea, Echinoidea, and Holothuroidea (e.g. Gümbel 1869; Deflandre- Rigaud 1963; Kristan-Tollmann 1970; Janofske 1992; Bizzarini 1993, 1996; Broglio Loriga et al. 1999; Bizzarini and Laghi 2005; Gale 2011; Hagdorn 2011; Kroh 2011; Nützel and Kaim 2014; Hausmann and Nützel 2015). Cassian stem group echinoids (i.e., proterocidarids) were solely found in samples investigated herein and from the Settsass Scharte (Nützel and Kaim 2014) until now, all of which represent deeper water soft-bottom habitats. In the bulk collection from Misurina Landslide, the abundance of isolated proterocidarid plates was very high with 74 ossicles. Hagdorn (2018) stated that it is unclear whether stem group echinoids from the Triassic were inhabitants of shallow or deep water habitats. However,

37 results from Cassian assemblages studied so far suggest that they preferred deeper water settings (Nützel and Kaim 2014; Hausmann and Nützel 2015). The size fraction 0.11 – 0.5 mm of Misurina Landslide was additionally analysed, but in contrast to the other size fraction only qualitatively. One skeletal element (goniodont) was found, which belongs to the ophiocistioid Linguaserra triassica. Ophiocistioids were previously only found in Palaeozoic sediments and were therefore thought to have gone extinct at the end of the Palaeozoic. However, they survived much longer, at least up to the Late Triassic (Reich et al. 2018). The fact that proterocidarids and L. triassica from the Cassian Formation were until now solely found from basinal palaeohabitats (Nützel and Kaim 2014; Reich et al. 2018) suggests that the Late Triassic deep-water settings in this area may have acted as refugia for such hangover taxa, as also suggested by Thuy et al (2017c).

Predation Drill holes seem to be a characteristic component of autochthonous soft-sediment assemblages from the Cassian Formation (Klompmaker et al. 2016). In addition to the samples studied herein, drilling was also reported from a surface sample from the Stuores Wiesen, which contains a representative of the basinal Raphistomella radians/Palaeonucula strigilata association sensu Fürsich and Wendt (1977) (Klompmaker et al. 2016). However, drilling predation was not found in the basinal soft- bottom assemblage described from the Settsass Scharte by Nützel and Kaim (2014). It is unknown which organisms produced the drill holes found in the shells from the Late Triassic Cassian Formation (Klompmaker et al. 2016). Even though the shape of the drill holes resemble naticid borings, these predatory gastropods have to be excluded as potential drill hole producers since they originated much later in the Cretaceous (Bandel 1999; Klompmaker et al. 2016).

Preservation Low-grade lithification is a remarkable aspect of the Cassian Formation and points to the potential of these sediments to contain highly unbiased fossil assemblages with respect to taphonomic biases resulting from lithification (Kowalewski et al. 2006; Sessa et al. 2009). Kowalewski et al. (2006) found that bulk samples from the Cassian Formation are more similar to unlithified late Cenozoic than lithified Jurassic samples in several aspects, including diversity and higher taxonomic composition. Interestingly, gastropods are a major component of the late Cenozoic assemblages, whereas they play only a minor role in lithified Jurassic assemblages (Kowalewski et al. 2006). Kowalewski et al. (2006) and Sessa et al. (2009) suggest that differences in diversity and size distributions are at least partly due to diagenetic effects resulting from lithification and aragonite loss. The Cassian Formation offers the possibility to study fossil assemblages highly unaffected by taphonomic biases induced by lithification (Kowalewski et al. 2006; Sessa et al. 2009).

Diversification in the Triassic The new data from Misurina Landslide and Lago Antorno support Hautmann´s (2014) model of diversity partitioning. This model explains how diversification takes place after mass extinctions. It was found that the main recovery phase following the end-Permian mass extinction took place in the Middle Triassic (Hautmann 2007, Friesenbichler et al. 2019), which may have allowed early Late Triassic faunas from the Cassian Formation to further diversify with respect to alpha and beta diversity. Hautmann´s (2014) model recognises three phases during the full recovery process: (i) niche overlap phase, (ii) habitat contraction phase, and (iii) niche differentiation phase. During the first phase after a mass extinction, mainly alpha diversity rises since no or only low competition takes place. Therefore, the habitat width of individual species is not yet limited by competition across species. In the second phase, competition leads to a narrowing of the species' habitat width and, consequently, to a stagnation of alpha diversity but to a rise in beta diversity. In phase three, alpha

38 diversity may again be the main driver of diversity increase because of adaptive divergence (see Hofmann et al. 2013a, b, 2014 and Hautmann 2014 for further details). The high degree of variation in diversity and taxonomic composition between invertebrate assemblages in combination with a high diversity found in specific assemblages from the Cassian Formation (Fürsich and Wendt 1977; Nützel and Kaim 2014; Hausmann and Nützel 2015) indicate that faunal assemblages from the Late Triassic already reached the transition to the second phase of Hautmann´s (2014) model.

Conclusions

1. Basinal soft-bottom invertebrate assemblages from the Cassian Formation can be very different in taxonomic composition; however, previous data (Nützel and Kaim 2014) together with our dataset suggest that they have a similarily low alpha diversity in common. 2. The small size of Cassian invertebrate fossils is not as exceptional as previously thought but is very similar to recent tropical marine benthic assemblages (e.g., Bouchet et al. 2002; Bouchet 2009; Albano et al. 2011). 3. Soft-bottom basin habitats acted as refugia for echinoderm hangover taxa after the end-Permian mass extinction at least in the Cassian Formation (Nützel and Kaim 2014; Reich et al. 2018), but maybe also in a wider region of the western Tethyan border as proposed by Thuy et al (2017c). 4. This study confirms the need of analysing further Cassian assemblages to get a full picture of the complex Cassian palaeoecosystem.

Acknowledgements

We would like to thank Michael Hautmann (Zürich) for his help with species identifications. Special thanks go to Evelyn Kustatscher (Bozen) and the Naturmuseum Südtirol for supporting this study. Markus Moser (Munich) is acknowledged for his helpful comments on the manuscript. The research of IMH, VJR and AN were supported by the "Deutsche Forschungsgemeinschaft" (project number NU 96/13-1). MR acknowledges support from the "Bayerischer Pakt für Forschung und Innovation (BayPFI)" of the "Bayerisches Staatsministerium für Wissenschaft und Kunst (https://www.stmwk.bayern.de/)".

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Figures

Fig. 1. Map of northern Italy (Dolomites) showing the sampling localities Misurina Landslide and Lago Antorno, which are marked with asterisks. A. General overview of the map. B. Detailed view of the map. C. Upper part of Misurina Landslide where the samples were taken. D. Detailed view of the Misurina Landslide sediments.

Fig. 2. Species and specimen proportions within higher taxa of the bulk samples from Misurina Landslide and Lago Antorno.

Fig. 3. Rarefaction curves of surface and bulk samples from Misurina Landslide and Lago Antorno. A. Complete curves. B. Detailed view.

Fig. 4. Rank-abundance distributions of the bulk samples from Misurina Landslide and Lago Antorno.

Fig. 5. Wortheniella cf. canalifera (Münster, 1841) from Lago Antorno, Cassian Formation, northern Italy, Late Triassic. A–D. PZO YYY.

Fig. 6. “Turbo” sp. from Misurina Landslide Cassian Formation, northern Italy, Late Triassic. A–D. PZO YYY.

Fig. 7. Hologyra? expansa (Laube, 1869) from Lago Antorno, Cassian Formation, northern Italy, Late Triassic. PZO YYY.

Fig. 8. Neritaria mandelslohi (Klipstein, 1843) sensu Bandel (2007) from Lago Antorno,

Cassian Formation, northern Italy, Late Triassic. A. PZO YYY; A2, protoconch. B. PZO YYY.

Fig. 9. Dentineritaria neritina (Münster) sensu Bandel (2007) from Lago Antorno (A) and Misurina Landslide (B, C), Cassian Formation, northern Italy, Late Triassic. A. PZO YYY;

A3, protoconch. B. PZO YYY. C. PZO YYY.

Fig. 10. Coelostylina conica (Münster, 1841) from Lago Antorno (A–D) and Misurina Landslide (E, F), Cassian Formation, northern Italy, Late Triassic. A. PZO YYY. B. PZO

YYY. C. PZO YYY; C2, protoconch. D. PZO YYY; D2, protoconch; D3, drill holes. E. PZO YYY F. PZO YYY.

Fig.11. Coelostylina conica (Münster, 1841) from Lago Antorno (A–D) and Misurina

Landslide (E–G), Cassian Formation, northern Italy, Late Triassic. A. PZO YYY; A3, protoconch. B. PZO YYY. C. PZO YYY. D. PZO YYY. E. PZO YYY. F. PZO YYY; F4, protoconch. G. PZO YYY.

Fig. 12. Unidentified caenogastropod (A) from Lago Antorno, Coelostylina sp. 1 (B) from Misurina Landslide, Coelostylina sp. 2 (C) from Misurina Landslide, Flemmingia bistriata (Münster, 1841) (D) from Misurina Landslide and Coelochrysalis pupaeformis (Münster, 1841) (E, F) from Misurina Landslide, Cassian Formation, northern Italy, Late Triassic. A. PZO YYY. B. PZO YYY. C. PZO YYY. D. PZO YYY. E. PZO YYY. F. PZO YYY. 6

Fig.13. Helenostylina convexa (Nützel & Kaim, 2014) from Lago Antorno, Cassian Formation, northern Italy, Late Triassic. A–D. PZO YYY.

Fig. 14. Helenostylina convexa (Nützel & Kaim, 2014) from Lago Antorno (A,B), Misurina Skilift (C) and Misurina Landslide (D), Cassian Formation, northern Italy, Late Triassic. A.

PZO YYY; A3, protoconch. B. Protoconch, PZO YYY. C. PZO YYY; C3, protoconch, arrow shows end of larval shell; C4, protoconch; C5, arrow shows end of larval shell. D. PZO YYY;

D3, protoconch.

Fig. 15. Prostylifer paludinaris (Münster, 1841) from Lago Antorno (A–C) and Misurina Landslide (D), Cassian Formation, northern Italy, Late Triassic. A. PZO YYY. B. PZO YYY.

C. Protoconch, PZO YYY. D. PZO YYY; D2, protoconch.

Fig. 16. Angulatella bizzarinii Nützel & Hausmann sp. nov. from Lago Antorno (A, B) and

Misurina Landslide (C), Cassian Formation, northern Italy, Late Triassic. A. PZO YYY; A2-

A5, protoconch. B. PZO YYY. C. PZO YYY; C2, protoconch.

Fig. 17. Atorcula sp. (Kittl, 1894) (A, B) from Lago Antorno and Atorcula canalifera (Münster, 1841) sensu Kittl (1894) from Lago Antorno (C, D) and Misurina Landslide (E),

Cassian Formation, northern Italy, Late Triassic. A. PZO YYY; A2, drill holes. B. PZO YYY;

B2, drill hole. C. PZO YYY. D. PZO YYY. E. Protoconch, PZO YYY.

Fig. 18. Ampezzopleura hybridopsis Nützel, 1998 from Lago Antorno (A–C) and Misurina Landslide (D–G) and Ampezzopleura bandeli Nützel, 1998 (H) from Misurina Landslide,

Cassian Formation, northern Italy, Late Triassic. A. PZO YYY. B. PZO YYY; B3, protoconch.

C. Protoconch; PZO YYY. D. PZO YYY. E. Teleoconch; PZO YYY. F. PZO YYY; F2, F3, protoconch. G. PZO YYY. H. PZO YYY.

Fig. 19. Zygopleurid larval shells (Zygpleura sp.) from Lago Antorno (A) and Misurina Landslide (B), Cassian Formation, northern Italy, Late Triassic. A. PZO YYY. B. PZO YYY.

Fig. 20. Kittliconcha aonis (Kittl, 1894) from Lago Antorno (A, B) and Misurina Landslide (C) and Tyrsoceus zeuschneri (Klipstein 1843) from Lago Antorno (D), Cassian Formation, northern Italy, Late Triassic, in comparison to the holotype of Klipstein (1843) (E). A. PZO YYY. B. PZO YYY. C. PZO YYY. D. PZO YYY. E. Holotype.

Fig. 21. Jurilda elongata (Leonardi & Fiscon, 1959) from Misurina Landslide, Cassian Formation, northern Italy, Late Triassic. A. PZO YYY; A2, protoconch. B. PZO YYY; B2, protoconch. C. PZO YYY. D. PZO YYY. E. PZO YYY.

Fig. 22. Promathildia cf. decorata (Klipstein, 1843) (A), Promathildia subnodosa (Münster, 1841) (B), Promathildia cf. milierensis Zardini, 1980 (C, D, E, F, G, H) and Camponaxis lateplicata (Klipstein, 1843) sensu Bandel (1995) (I) from Misurina Cassian Formation, northern Italy, Late Triassic. A. PZO YYY; A2, protoconch. B. PZO YYY. C. PZO YYY; C2, C3, protoconch. D. PZO YYY. E. PZO YYY. F. PZO YYY. G. PZO YYY. H. PZO YYY. I. PZO YYY. 11

Fig. 23. Bandellina compacta Nützel & Hausmann sp. nov. from Lago Antorno, Cassian Formation, northern Italy, Late Triassic. A. PZO YYY. B. PZO YYY. C. Protoconch; PZO YYY. D. Protoconch; PZO YYY. E. PZO YYY.

Fig. 24. Alexogyra marshalli Bandel, 1996 from Lago Antorno, Cassian Formation, northern Italy, Late Triassic. A. PZO YYY. B. PZO YYY. C. Protoconch; PZO YYY .D. PZO YYY.

Fig. 25. Ampezzogyra angulata Nützel & Hausmann sp. nov. from Lago Antorno (A) and

Misurina Landslide (B), Cassian Formation, northern Italy, Late Triassic. A. PZO YYY; A4,

A5, protoconch. B. PZO YYY.

Fig. 26. Ampezzogyra angulata Nützel & Hausmann sp. nov. from Lago Antorno (A) and

Misurina Landslide (B), Cassian Formation, northern Italy, Late Triassic. A. PZO YYY; A6,

A7, protoconch. B. PZO YYY. 13

Fig. 27. Sinuarbullina sp. 1 (A) and Acteonoidea indet. sp. (B, C) from Lago Antorno and Sinuarbullina sp. 1 (D) and Sinuarbullina sp. 2 (E) from Misurina Landslide, Cassian Formation, northern Italy, Late Triassic. A. Sinuarbullina sp. 1; PZO YYY. B. Acteonoidea sp.; PZO YYY. C. Acteonoidea sp.; PZO YYY. D. Sinuarbullina sp. 1; PZO YYY. E. Sinuarbullina sp. 2; PZO YYY.

Fig. 28. Nuculid bivalves from Lago Antorno (A, B) and Misurina Landslide (C-E), Cassian Formation, northern Italy, Late Triassic. A. Nuculana sulcellata (Wissmann, 1841); PZO YYY. B. Palaeoneilo elliptica (Goldfuss, 1837); PZO YYY. C. Palaeonucula strigilata (Goldfuss, 1837); PZO YYY. D. Palaeonucula strigilata (Goldfuss, 1837); PZO YYY. E. Nuculana sulcellata (Wissmann, 1841); PZO YYY.

Fig. 29. Cassianella Beyrich, 1862 from Lago Antorno, Cassian Formation, northern Italy,

Late Triassic. A. Cassianella indet.; PZO YYY; A2, larval shell. B. Cassianella beyrichi Bittner, 1895; PZO YYY. C. Cassianella beyrichi Bittner, 1895; PZO YYY.

Fig. 30. Septocardia pichleri (Bittner, 1895) from Lago Antorno, Cassian Formation, northern Italy, Late Triassic. A-D. PZO YYY.

Fig. 31. Dentalium klipsteini Kittl 1891 from Lago Antorno, Cassian Formation, northern Italy, Late Triassic. A. PZO YYY. B. PZO YYY. C. PZO YYY.

Fig. 32. Coprolites from Misurina Landslide, Cassian Formation, northern Italy, Late Triassic. A. PZO YYY. B. PZO YYY. C. PZO YYY.

Fig. 33. Echinoderm plates, ossicles and elements (Crinoidea: A, ?Asteroidea: B, Ophiuroidea: C–E, Ophiocistioidea: F, Echinoidea: G–N) from Misurina Landslide, Cassian Formation, northern Italy; Carnian, Late Triassic. A. isocrinid? (sediment encrusted) columnal (PZO xxxxx). B. asteroid?/asterozoan spine, (PZO xxxxx). C. ophiuroid lateral arm plate, external view, showing the articulation for the attachment of spines (PZO xxxxx). D. ophiuroid arm vertebra, distal view, showing the muscle attachment area (PZO xxxxx). E. ophiuroid distal lateral arm plate, external view (PZO xxxxx). F. ophiocistioid goniodont Linguaserra triassica Reich in Reich et al., 2018, abaxial face, outer view (PZO 11827). G. ambulacral plate of Pronechinus? sp. nov. with peripodial ring and imperforate primary tubercle (PZO xxxxx). H–J. ambulacral plates of Pronechinus? sp. nov. with slightly developed peripodial ring surrounding pore pairs (PZO xxxxx, xxxxx, xxxxx). K–L. cidaroid? spines (partially broken) of unknown species (PZO xxxxx, xxxxx). M. broken cidaroid? spine fragment, showing the microstructure at the inner side of the cylinder (PZO xxxxx). N. Fragment of ambulacrum of unknown cidaroid? species (PZO xxxxx). All SEM images (A–N).

Fig. 34. Holothurian calcareous ring elements and body-wall ossicles from Misurina Landslide, Cassian Formation, northern Italy; Carnian, Late Triassic. A. radial calcareous ring element, Apodida gen. et sp. nov. 1, outer view (A1, A2), lateral oblique view from right (A3), inner view (A4) (PZO xxxxx). B. interradial calcareous ring element, Apodida gen. et sp. nov. 1, outer view (B1), lateral oblique view from left (B4), inner view (B2, B3) (PZO xxxxx). C. interradial calcareous ring element, Apodida gen. et sp. nov. 2, outer view (C1, C2), lateral oblique view from right (C3), inner view (C4) (PZO xxxxx). D. wheel Jumaraina sp., (interspoke areas filled with sediment), lower side (PZO xxxxx). E. wheel Theelia cf. multiplex Speckmann, 1968, (interspoke areas filled with sediment), lower side (PZO xxxxx). F. cross Tetravirga sp., (two arms and the central solid spire broken, perforated arm areas filled with sediment), upper side (PZO xxxxx). G. cross Tetravirga cf. perforata Mostler, 1968, (one arm and the central solid spire broken, perforated arm areas filled with sediment) upper side (PZO xxxxx). H. cross Tetravirga cf. perforata Mostler, 1968, (two arms and the central solid spire broken, perforated arm areas filled with sediment) upper side (PZO xxxxx). SEM (A2, B3, C2, D–H) and LM (A1, A3, A4, B1, B2, B4, C1, C3, C4) images.

Fig. 35. Rarefaction curves of Cassian assemblages from Misurina Landslide, Lago Antorno (assemblages studied herein), Settsass Scharte (Nützel and Kaim 2014) and Stuores Wiesen (Hausmann and Nützel 2015). Only bulk samples are used.

Fig. 36. Framboid from Lago Antorno, Cassian Formation, northern Italy, Late Triassic.

Table 1. Species and abundances lists of the bulk and surface collections from Misurina Landslide and Lago Antorno.

Taxa Species Misurina Landslide Bulk Misurina Landslide Surface Lago Antorno Bulk Lago Antorno Surface Porifera * Porifera indet. sp. * 1 Cnidaria * Hydrozoa ? indet. sp. * 1 Gastropoda Wortheniella cf. canalifera 1 Neritaria mandelslohi 5 29 Dentineritaria neritina 38 68 Hologyra? expansa 1 Coelostylina conica 53 19 29 26 Coelostylina sp. 1 1 Coelostylina sp. 2 1 Antornaia convexa 1 2 6 4 Turristylus cf. triadicus ??? 3 Atorcula canalifera sensu Kittl 1 4 1 6 Prostylifer paludinaris 128 50 24 81 Angulatella kustatscherae sp. nov. 3 5 Unidentified caenogastropod 2 Ampezzopleura bandeli 21 3 Ampezzopleura hybridopsis 95 1 29 9 Kittliconcha aonis 2 2 Zygopleura sp. 1 1 Axially ribbed larval shell 1 Tyrsoceus zeuschneri 1 Flemmingia bistriata 1 Coelochrysalis pupaeformis 2 Jurilda elongata 166 1 5 Promathildia cf. milierensis 19 1 Promathildia cf. decorata 2 Promathildia subnodosa 1 Camponaxis lateplicata 1 Bandellina compacta sp. nov. 2 Alexogyra marshalli 7 Ampezzogyra angulata sp. nov. 14 9 Sinuarbullina sp. 1 14 10 Sinuarbullina sp. 2 2 2 Acteonoidea indet. sp. 2 Gastropoda indet. sp. 1 1 Gastropoda indet. sp. 3 1 “Turbo” sp. 1 Bivalvia Palaeonucula strigilata 10 8 2 Nuculana sulcellata 3 5 2 Palaeoneilo distincta f. laubei 2 2 Palaeoneilo elliptica 2 1 Modiolus paronai 1 Gervillia (Cultriopsis) sp. 3 1 Antijanira auristriata 1 Cassianella beyrichi 1 3 3 Cassianella sp. 1 1 Cassianella sp. 2 2 Leptochondria monilifera 1 1 Schafhaeutlia cf. astartiformis 1 Septocardia pichleri 2 3 2 Bivalvia indet. sp. 1 8 11 Bivalvia indet. sp. 2 1 Scaphopoda Dentalium klipsteini 2 1 5 6 Plagioglypta undulata 1 1 Cephalopoda Trachyceratidae indet. sp. 1 Ammonoidea indet. sp. 4 Brachiopoda Brachiopoda indet. sp. 1 Ostracoda Ostracoda indet. sp. 1 1 Ostracoda indet. sp. 2 1 Echinodermata Echinodermata, inc. sed. 1 1 Crinoidea Isocrinus ? sp. 1 Crinoidea sp. inc. 1 Asteroidea Asteroidea sp. inc. 1 Ophiuroidea Ophiuroidea sp. indet. 1 1 Ophiuroidea sp. indet. 2 1 Ophiuroidea sp. indet. 3 1 Ophiuroidea sp. indet. 4 1 Ophiuroidea sp. inc. 2 Echinoidea “Cidaris” cf. decoratissima Wöhrmann 1 “Cidaris” cf. flexuosa Münster 1 Cidaroida sp. indet. 1 1 Pronechinus ? sp. 2 stem Cidaroida/Cidaroida sp. inc. 1 1 1 Echinoidea sp. inc. 2 Ophiocistioidea ** Linguaserra triassica sp. nov. ** 1 Holothuroidea Apodida , gen. et. sp. nov. 1 1 Apodida , gen. et. sp. nov. 2 1 Jumaraina sp. 1 Tetravirga cf. perforata 1 Tetravirga sp. 1 1 Theelia cf. multiplex 1

* Not included in statistical analyses because of allochthonous origin and therefore not being part of the original palaeocommunity. ** Not included in statistical analyses because size fraction was < 0.5 mm. Table 2. Number of species and specimens per higher taxa in the Misurina Landslide and Lago Antorno bulk samples.

Misurina Landslide Lago Antorno Taxa Species Specimens Species Specimens Gastropoda 20 567 17 230 Bivalvia 11 33 4 16 Scaphopoda 2 3 1 5 Cephalopoda 2 5 Brachiopoda 1 1 Ostracoda 1 1 1 1 Echinodermata 1 1 1 1 Echinodermata: Crinoidea 2 2 Echinodermata: Asteroidea 1 1 Echinodermata: Ophiuroidea 5 6 Echinodermata: Echinoidea 6 8 1 1 Echinodermata: Holothuroidea 6 6

Table 3. Diversity indices of bulk and surface samples from Misurina Landslide and Lago Antorno.

Misurina Landslide Misurina Landslide Lago Antorno Bulk Lago Antorno Surface Simpson 0.85 0.78 0.87 0.68 Shannon 2.47 2.19 2.48 1.73 Berger-Parker 0.26 0.43 0.27 0.53

Table 4. Best model fit for rank-abundance distributions of the Misurina Landslide and Lago Antorno bulk samples. Best fit is shown in bold.

AIC values Models Misurina Landslide Lago Antorno Brokenstick 861.32 145.82 Preemption 428.68 108.87 Log-normal 285.5 107.08 Zipf 270.89 122.81 Zipf-Mandelbrot 203.45 103.98

Table 5. Dissimilarity (using mean proportional dissimilarity) between Cassian assemblages from Misurina Landslide, Lago Antorno, Stuores Wiesen (Hausmann and Nützel 2015) and Settsass Scharte (Nützel and Kaim 2014). Only bulk samples were used.

Stuores Wiesen Misurina Landslide Lago Antorno Settsass Scharte Stuores Wiesen 0.959403835 0.963427948 0.931477911 Misurina Landslide 0.959403835 0.523447205 0.953156409 Lago Antorno 0.963427948 0.523447205 0.961850649 Settsass Scharte 0.931477911 0.953156409 0.961850649