Latest Triassic (Sevatian–Rhaetian) reef carbonates from the Northern Calcareous Alps (Austria), their mollusc dwellers, and their fate at the end-Triassic extinction event

A reef-associated mollusc fauna (gastropods and bivalves) and its facies context are described from latest Triassic (Sevatian–Rhaetian) reef carbonates of Austria (Rötelwand reef at Gaissau and Gosaukamm near Hallstatt). The studied carbonates from the Rötelwand reef consist of mollusc-rich rudstones, partly boundstones, which contain branched corals (Cycliphyllia and Retiophylia, Pinacophyllum), whereas coralline sponges are absent. The rich foraminiferid fauna that is associated with the reef builders consists of 11 genera; eight of these genera became extinct until the end of the Rhaetian. Associated with small patch reefs was a rich mollusc fauna with 19 gastropod species and 8 epifaunal bivalve species. The gastropod fauna is dominated by Microschiza rhaetica, Trochotoma praecursor, and the large growing Purpuroidea moosleitneri. Six gastropod species are new to science: Angulomphalus senowbarii sp. nov., Stuorella zapfei sp. nov., Hologyra callosa sp. nov., Microschiza rhaetica sp. nov., Angularia corallina sp. nov., and Purpuroidea moosleitneri sp. nov. Four Triassic gastropod species are placed in other genera (new combinations): Tylotrochus diversicostatus Wolff, 1967 and Eucycloscala epitoniformis Nützel and Senowbari-Daryan, 1999 are placed in Sadkia, Praelittorina sepkoskii Nützel and Erwin, 2004 in Microschiza, and Purpuroidea? minioi Leonardi, 1935 in Angularia Koken, 1892. Reversal of precedence is proposed for Angularia Koken, 1892 (Gastropoda) and Angularia Busk, 1881 (Bryozoa) under ICZN Art. 23.9. Although reefs suffered a catastrophic decline at the end of the Triassic, most of the studied reef-associated bivalve and gastropod genera survived into the Jurassic, indicating a considerable ecological plasticity of these groups. Only 12 out of 47 reef-associated mollusc genera became extinct (25.5%). This observation is at variance with earlier suggestions that taxa that were associated with reefs and carbonate substrata had a significantly higher extinction risk than level-bottom dwellers. However, extinction at the species level appears more severe; only three bivalve species but no gastropod species recorded in this fauna have records from the Jurassic.


Introduction
Tropical reefs belong to the most diverse marine ecosystems not so much because of the diversity of the reef builders but chiefly due to the high number of reef-associated species.
However, most fossil reefs of high geological age are strongly lithified and diagenetically altered, including aragonite dissolution (particularly relevant for molluscs), replacement by calcite and dolomitization. As a result, it is quite common that only few reef-associated species are reported in studies of fossil reefs. Typically, the presence of reefassociated molluscs is mentioned only cursory in such studies, and taxa are often listed in open nomenclature lacking species identification and commonly also illustrations. The present study reports fossiliferous reefal limestones including reef builders (corals) and associated benthic reef dwellers, especially molluscs (gastropods and bivalves), from the "Upper Rhaetian Reef Limestone" ("Oberrhät-Riffkalk") and the Sevatian-to-Rhaetian "Dachsteinkalk". The studied material comes from the Rötelwand Reef at Gaissau and the Gosaukamm in Austria (Figs. 1, 2). Gastropods are Fig. 1 Locality map of the Salzburg and Dachstein area, Austria. a, b Rötelwand reef complex near Gaissau, SE Salzburg, Austria. Geographically, the location is called "Looswand". The gastropod findings as well as the rock samples stem from the southern part of the reef complex marked with a black dot in b; see also Fig. 2; c Gosaukamm, mountain range west of Hoher Dachstein summit, SE Lake Hallstatt; fossils were collected from the scree of the steep NE slope, mostly at a height between 1500 and 1750 m a.s.l especially abundant in these coral-reef limestones and some species are rather large (especially Purpuroidea moosleitneri sp. nov., largest specimen ca. 90 mm high, 80 mm wide). The gastropod and bivalve fauna described herein is part of a mainly coarse-grained reefal debris facies with nearby intercalations of small patch reefs (in case of the Rötelwand locality), which are almost exclusively composed of large phaceloid coral colonies (Cycliphyllia cyclica). Gastropods and bivalves from the Upper Rhaetian Reef Limestone are present in various museum and private collections, but have not been studied in detail with the exception of the studies by Zapfe (1963Zapfe ( , 1967a. However, Zapfe's studies provided only illustrations of a few bivalve specimens, whereas most taxa were not illustrated, and many were described in open nomenclature only. In this context, the aims of our study are twofold: first, we document in detail the facies of the carbonate rocks and the biodiversity of the fauna. Second, we use these data to trace the fate of the reef-associated gastropod and bivalve taxa across the Triassic-Jurassic boundary, which coincided with one of the largest global mass extinction events including a major reef crisis (e.g., Hallam and Wignall 1997;Hautmann et al. 2008a;Hautmann 2021;Kiessling 2005;). Our main interest here is the question whether the reef-associated taxa suffered above average during this event as a consequence of the loss of their preferred habitats (reefs), as proposed by  and , or whether they were able to survive the crisis in alternative habitats due to their ecological flexibility.

Materials and methods
Material was obtained from museum, own, and private collections. Specimens were mechanically prepared and most illustrated specimens were coated with ammonium chloride for photography. Thin sections and polished slabs were prepared at the SNSB-BSPG. The studied material is reposited at the Naturhistorisches Museum Wien (NHMW) and the Bayerische Staatssammlung für Paläontologie und Geologie, München (SNSB-BSPG). A few studied gastropod specimens (non-type material) were given back to private collectors.

Geological setting and location
Initially, the present study comprised only the fossil occurrence of the Rötelwand Reef at Gaissau and its microfacies. A visit at the Naturhistorisches Museum Wien revealed that the same taxa of mollusc reef dwellers were present in collections from the slightly older (Sevatian and lower Rhaetian) Dachsteinkalk from the Gosaukamm (Gosau-Ridge). Bivalves and gastropods from this collection are included in this study. The microfacies analysis concerns only the fossiliferous Rötelwand Reef.
The Northern Calcareous Alps, a part of the Austroalpine nappe complex, are the northernmost overthrusted part of the eastern Alps. They form a W-to-E trending, 500-kmlong, and 20 to 50-km-wide thrust belt that extends from Bregenz in the west to Vienna in the east. The Calcareous Alps in the Salzburg region are characterized by the overthrust of the Staufen-Höllengebirgs-thrust system (Tirolikum) virtually up to the northern margin of the Northern Calcareous Alps (e.g., Tollmann 1985;Wagreich et al. 1996). The Tirolikum can be subdivided into several tectonic units (Osterhorn-Tirolikum, Sparber thrust sheet, Schafberg-Tirolikum) separated by faults (e.g., Plöchinger 1973Plöchinger , 1982Tollmann 1985;Wagreich et al. 1996). The sedimentological record of the Tirolikum encompasses Permian, thick Triassic Hauptdolomit and Dachstein limestones, in terms of facies strongly differentiated Jurassic and Lower Cretaceous deposits uncomformably overlain by Upper Cretaceous to Palaeogene sediments. Succeeding tectonic units comprise Hallstatt nappe sheets (Tiefjuvavikum) put in place in the Late Jurassic as well as the Berchtesgaden thrust sheet and the Dachstein thrust sheet (Hochjuvavikum; e.g., Plöchinger 1982;Tollmann 1985) all of which gain ground toward the east in the Salzkammergut. Also, the Berchtesgaden and Dachstein thrust sheets are unconformably overlain by Upper Cretaceous strata of the Gosau group (Wagreich et al. 1996).
Southeast of the Salzburg region, the Dachstein massif and the Gosaukamm near Hallstatt with their thick Upper Triassic platform carbonate succession (Dachstein limestone) belong to the Dachstein nappe, a major component of the Juvavikum thrust sheet complex (e.g., Mandl 2000;Krystyn et al. 2009).
In Late Triassic times, the Northern Calcareous Alps were part of a huge, up to 300-km-wide shelf at the passive continental margin of the northwestern Neotethys, located about 30º north of the equator. Tropical shallow-water conditions favored the formation of giant, up to 1200-m-thick carbonate platforms composed basically of Hauptdolomit and Dachstein Limestone. The southern and south-western, ocean-facing margins of the carbonate platforms (e.g., Hoher Göll, Hochkönig, and Gosaukamm) were characterized by the development of thick reefal carbonates formed by massive Dachstein Limestone. The transition into the pelagic realm of the Hallstatt basin is often formed by steep slopes. With the beginning of the Rhaetian, the Kössen Basin was formed in the northern part of the Hauptdolomit/Dachstein carbonate shelf. Patch reefs and reef-like structures ("Upper Rhaetian Reef Limestone") developed in ramp position, adjacent to the Dachstein platform (Steinplatte; Stanton and Flügel 1995), on the Dachstein platform (Adnet ;Schäfer 1979) as well as within the Kössen basin (e.g., Rötelwand, Feichtenstein, and Gruber reef structures ;Schäfer 1979;Senowbari-Daryan 1980;Flügel 1981;Stanton and Flügel 1987;cf. Bernecker 2005).
The Rötelwand Reef, yielding part of the gastropod fauna described herein, underlain and surrounded by Kössen beds, is about 100 m thick and shows both a lateral and a vertical facies zonation pattern. According to Schäfer (1979), the Rötelwand reef complex exhibits four developmental stages. It started with a preexisting relief in the Kössen beds formed by mechanical accumulation of sandy shoals (oolitic or bivalve shell beds) (Stage 1). In a deeper water stage, the formation of a carbonate mud-mound was caused by sporadic reef growth on the underlying shoals and by mechanical-biological baffling of lime mud between reef-building corals (Stage 2). Growing actively into the wave base, the mud-mound was capped by thick bivalve shell beds (Stage 3). Thus, the reef structure had developed into a shallowwater zone providing environmental conditions comparable to those of the Dachstein platform. Then, a small platform was formed in shallow water, with coral-coralline spongereef growth on its northern slope, and with the deposition of carbonate sands (oncolithic, algal-foraminiferal facies) with coral-reef patches under high-energy, wind exposed conditions in the south, which correspond with subtidal lagoonal facies types of the Dachstein platform (Stage 4). The gastropod mollusc fauna described herein stems from stage 4, the high-energy wind and current exposed shallow-water reef zone at the southern margin of the reef complex.

Molluscs from the Gosaukamm (Dachstein limestone)
The mollusc material from the Gosaukamm and also part of the material from the Rötelwand Reef studied herein comes from a collection present at the Naturhistorisches Museum Wien (NHMW) that was collected in the 1960s by Helmut Zapfe, Heinz Kollmann, Erik Flügel, and Herbert Summersberger (Zapfe 1967a). The material represents the same facies with the same corals and mollusc species as those present at the Rötelwand Reef. Like in the Rötelwand Reef, the diversity of the reef builders is high in the Gosaukamm reefs (Flügel 2002, fig. 21). According to Flügel (2002), the Dachstein Limestone of the Gosaukamm is slightly older (Sevatian-to-lower Rhaetian) than the Upper Rhaetian Reef Limestone ("Oberrhät-Riffkalk"), but, as said above, the faunal content is almost identical. Most molluscs studied herein are present in both complexes. The phenomenon of shared presence of species in the Dachstein Limestone and the Upper Rhaetian Reef Limestone was called mixed fauna ("Mischfaunen") by Zapfe (1967a), who noted that most species had a Norian (Sevatian) age but some are Rhaetian. Zapfe (1967a) noted that the fossils from the Gosaukamm were collected from the scree of the steep NE slope of the Gosaukamm, mostly at a height between 1,500 and 1,750 m. According to Krystyn et al. (2009), reef growth of the Dachstein limestone started in the Early Norian and reached a peak in the early Rhaetian.

General facies architecture and previous studies
The Rötelwand Reef complex that yielded part of the mollusc material studied herein was comprehensively investigated by Schäfer (1979Schäfer ( , 1984, Schäfer and Senowbari-Daryan (1981), and Stanton and Flügel (1987) in terms of faunal composition and facies development and in comparison with other well-known Rhaetian reef complexes (e.g., Gruber Reef, Adnet Reef, Feichtenstein Reef). Further studies focused on particular faunal aspects like the taxonomy and distribution of corals and foraminifers within the Rötelwand reef complex (Schäfer and Senowbari-Daryan 1978a, b). Flügel (2002, fig. 21) found that the diversity of reef builders in the Rötelwand Reef is among the highest of ones recorded from Triassic reefs.
The facies described here developed in the upper part of the Rötelwand reef complex corresponding to stage 4 of the overall sequential development of the reef complex. This stage of reef development exhibits a facies zonation in broad, interfingering ecologic belts. From north to south, a detrital mud facies, shell beds, and coral-sponge boundstone facies (i.e., the reef core facies) graded into a coarse-grained high-energy coral-reef debris facies followed by algal foraminifera facies and again detrital mud facies. According to Schäfer (1979), the zonation with a high-energy reefal debris zone at the southern margin of the reef is due to a southerly wind direction. This zone is inhabited by the mollusc fauna described herein (Fig. 3).

Fig. 3
Simplified facies model of the isolated Rötelwand patch reef complex with the facies zones defined by Schäfer (1979Schäfer ( , 1984 for the upper growth stage; slightly modified by own data. The new gastropod fauna lived in sheltered areas of the high-energy reef crest zone and the upper slope at the southern wind exposed margin of the patch reef complex. Robust phaceloid coral colonies of Cycliphyllia cyclica are capable of living in this high-energy zone Facies description and associated biota Figures 4,5,6,9, Table 1 Basically, we deal with a coarse-grained bioclast-intraclast-rudstone, with local transition to floatstone. Locally, autochthonous phaceloid coral boundstone patches occur, mainly composed of robust Cycliphyllia bafflestones. However, large, well-preserved gastropods (Purpuroidea and Microschiza) are the most prominent constituents in the rudstone/floatstone facies, contrasting the fragmented biota including branched corals (Cycliphyllia, Retiophylia, and Pinacophyllum), echinoderms, small molluscs, bryozoans, and porostromate cyanobacteria (e.g., Cayeuxia). Remarkably, coralline sponges, common in other reef zones of the Rötelwand reef complex, are completely missing at the studied site. Non-skeletal constituents include bioclastic or micritic intraclasts and lumps (mainly composed of Lithocodium and Bacinella). The groundmass is either micritic (matrix in the strict sense) or predominantly sparitic, and the latter composed of thick radial fibrous cement crusts.
Gravitational geopetal infillings include peloidal sediment, partly in stromatactoid cavities, as well as infiltrations of red mud probably derived from the Hallstatt basin with its red deeper water muddy sediments swept in by north directed currents (Schäfer 1979;Flügel 1963;Flügel and Flügel-Kahler 1963). These phenomena can be best seen in polished slabs (Fig. 4a-c). (Fig. 7).

Corals
The scleractinian coral fauna is solely composed of branched forms, with a dominance of robust Cycliphyllia cyclica (Schäfer and Senowbari-Daryan, 1978a). Cycliphyllia cyclica is typically characterized by large calice diameters of about 1 cm, distinct dissepimental rings within the calices as well as lack of costae ( Fig. 7a-c). Rarely, several calices arranged together in an almost cerioid pattern (Fig. 7h). Other branching scleractinians include various poorly preserved species of Retiophyllia spp. and rare Pinacophyllum sp. The retiophyllids exhibit calice diameters of 3-6 mm, costate epithecs with common pellicular coverings, endothecs with common dissepiments, as well as granulated septal flanges (Fig. 7b,. Pinacophyllum is typically characterized by thick walls and strongly reduced septal spines, diameter of the calices range between 3 and 4 mm (Fig. 7d).

Skeletal cyanobacteria
Small nodules of erect fan-like growing filaments lacking cross partitions can be attributed to the porostromate cyanobacteria Cayeuxia. Diameters of the filaments (lumen) range from 0.02 to 0.03 mm. Cayeuxia occurs scattered in the rudstone gastropod facies (Fig. 9b). (Fig. 8).
Tubiphytes sp. rarely occurs in the coral-rich debris facies. The sparite-filled internal cavity is surrounded by a conspicuous dense micritic envelope. Tubiphytes occurs isolated in the groundmass or attached to skeletal remains like coral septa. The systematic position of Tubiphytes is still a matter of debate. However, many authors (e.g., Schmid 1995;Senowbari-Daryan et al. 2008) suppose Tubiphytes to be a foraminifer or a combination of foraminifer, tubes of uncertain affinity, and cyanophyceans. For a review of interpretations and the systematic position of Triassic Tubiphytes, see Senowbari-Daryan (2013).
Lumps are also common constituents, mainly formed by Lithocodium sp. and Bacinella sp. Generally, they are small-to medium-sized (2-4 mm), although very largesized Lithocodium/Bacinella lumps of up to 10 cm were described by Schäfer (1979).
In our understanding, irregular crusts of Lithocodium/Bacinella or microbial coatings on larger bioclasts (mainly branching corals) cannot be classified as oncoids as Schäfer (1979) did. Pronounced irregularity as well as often minor thicknesses contradicts her interpretation. Many larger bioclasts even show destructive cortoid coatings.

Cementation
The bioclastic rudstones and partly boundstones exhibit thick early diagenetic gray and cloudy isopachous fringes of radiaxial fibrous cements (RFC) forming rims in intergranular pores. They are up to 3 mm thick, and are characterized by elongated calcite crystals with subcrystals and upward concave curvature of twin lamellae and cleavage (cf. Kendall 1985). Within each subcrystal that diverges from the substrate, an opposing pattern of distally convergent optic axes occurs, caused by the upward concave curvature of cleavage and twin lamellae. The early diagenetic or marine phreatic origin of the RFC cement crusts is evidenced by the following observations: RFC is the first cement generation, it developed in marine skeletal sands, it forms isopachous rims around pores, and it developed in uncompacted shelter pore cavities (cf. Flügel 2004). Current interpretations focus on neomorphic replacement by calcite of radiating bundles of acicular Mg-calcite that precipitated as early submarine   (Davies 1977;Davies and Nassichuk 1990). The remaining pore space is filled with late-diagenetic clear blocky calcite.

Facies interpretation
The facies described above developed within a high-energy regime subjected to strong currents in the front of the windward edge of the actual reef as evidenced by, e.g., the winnowed coarse-grained mainly rudstone fabric, the robust phaceloid corals, as well as the thick isopachous radial fibrous early diagenetic cements. The facies corresponds to the "oncolitic reef detritus facies (oncolitic facies)" described by Schäfer (1979), although she did not report the large gastropod fauna including purpuroids. However, she mentioned small pockets with gastropod accumulations within the Cycliphyllia cyclica dominated patch reefs ("Riffknospen"). According to Schäfer (1979), the coarse-grained bioclastic limestones can be correlated with facies zone 6 ("winnowed edge sands") of Wilson (1975). The common retiophyllid coral Cycliphyllia cyclica appeared to be well adapted to strong currents and high water energy by its thick-branched and thick-walled calices that are additionally stabilized by intracalical dissepimental rings. Cycliphyllia formed robust bafflestone patches of more than 1 m in height and width within the debris-rich facies zone (cf. Schäfer 1979).
The mostly unfragmented preservation of the wellpreserved large gastropods, especially of Purpuroidea and Microschiza, indicates that the shells were not transported very far and are more or less autochthonous. Most of them were probably associated with the small Cycliphyllia patch reefs and are still found in close association with these corals. Episodic storms together with erosion and resedimentation of dead gastropod shells might account for the fragmented bioclastic mollusc fraction of the rudstones (floatstones) as found in thin sections and polished slabs. The thick sculptured shells are indicative of an epifaunal lifestyle.

Systematic paleontology of gastropods and bivalves
Class Gastropoda Cuvier, 1795Subclass Vetigastropoda Salvini-Plawen, 1980 Family Symmetrocapulidae Wenz, 1938 Remarks. The family Symmetrocapulidae was placed in Neritimorpha (Neritopsoidea) by Bouchet et al. (2005Bouchet et al. ( , 2017 and Monari et al. (2018). However, the protoconch of the Middle Jurassic Symmetrocapulus cancellatina Gründel, 1998 is clearly of the vetigastropod type and unlike the protoconchs found in Neritimorpha (Gründel 1998(Gründel , 2000. The type species of Symmetrocapulus closely resembles Symmetrocapulus cancellatina in shape and in having a dextrally coiled early shell-therefore, the assumption that both are congeneric is justified at this point. However, the protoconch of the type species of Symmetrocapulus has to be studied in detail to corroborate this. According to the current state of knowledge, Symmetrocapulus is a limpet-shaped vetigastropod or a cocculiniform. The latter, however, have bilateral symmetrical protoconchs (e.g., McLean and Harasewych 1995) which seems not to be the case in Symmetrocapulus.
Description. Shell cap-shaped, bilateral symmetrical, longer than wide (28 mm long, 23 mm wide, 13 mm high) or approximately as long as wide; outline of peristome oval with apical portion narrower; apex median (lying on dorsal length axis), close to shell edge, distinctly bent; shell in lateral view with steep, concave outline at apical portion, evenly arched, convex outline in abapical portion; shell ornamented with fine, dense mesh-work of radial and co-marginal riblets.
Remarks. Limpet-shaped molluscs from the Triassic were placed in the genera Patella, Scurria, and Scurriopsis. Most of these species are poorly known, i.e., muscle scars are usually unknown and protoconchs of Triassic limpets have never been reported to our knowledge. Even the shell ornament is unknown or poorly known for many of the taxa. Without knowledge of the muscle scars, the orientation of limpets is unclear, i.e., whether the apex is situated anteriorly or posteriorly. The present shells differ from Scurriopsis Gemmellaro, 1879and Hennocquia Dacqué, 1934(in Gürich 1934 by having a distinctly bent apex and hence a concave posterior flank in lateral view. Order Pleurotomariida Knight, 1960 in Knight et al. 1960 Family Pleurotomariidae Swainson, 1840  Material. One specimen from Rötelwand Reef (Gaissau), Krispler collection.
Description. Shell turbiniform, low-spired, with gradate spire, about as high as wide; whorl face with bulge-like shoulder, approximately parallel to shell axis below shoulder, concave below shoulder, slightly convex at mid-whorl, concave below mid-whorl, with abapical spiral bulge forming transition to base; bulge-like shoulder ornamented with strong, broad, blunt, axially elongated nodes, numbering ca. 30 on last whorl; nodes separated by narrow interspaces; nodes crossed by at least 5 weaker spiral lirae; whorl face smooth or with very faint spiral ornamentation; two faint threads bordering smooth, convex area at mid-whorl, probably representing selenizone; base not exposed, seemingly flatly convex.
Remarks. The nodular shoulder with the spiral lirae characterizes this species. Stoppani's (1860) illustration is technically insufficient, but it seems to be likely that the present specimen belongs to the same species. The present specimen is probably also conspecific with the specimen from the Rhaetian Zlambach Marls of the Fischerwiese (Austria) illustrated by Zapfe (1967b, pl. 4, fig. 2) and also one of the specimens from the Fischerwiese that was illustrated by Koken (1897, pl. 7, fig. 1, not fig. 2) as Pleurotomaria marmoraea Koken, 1897. A selenizone is faintly visible in the studied specimen, and hence, its assignment to Pleurotomaria seems to be justified. Based on the studied specimen, an assignment to Sisenna (Osswald 1930) or Worthenia (Zapfe 1967b) can be rejected, because the whorl angulation clearly lacks a selenizone as would be the case in the mentioned genera (Karapunar and Nützel 2021). If the selenizone is really present at mid-whorl, below the angulation, Pleurotomaria? turbo would be the earliest certain representative of the genus Pleurotomaria in the Northwestern Tethys (Paleotethys). Begg and Grant-Mackie (2003) reported Pleurotomaria from the Norian of New Zealand and New Caledonia (Southeastern Tethys-Neotethys). Other assignments of Triassic species to Pleurotomaria are outdated.
Family Trochotomidae Cox, 1960  Remarks. Ferrari et al. (2015) gave an overview of trochotomids which encompass a considerable number of mainly Jurassic species representing the type genus Trochotoma. These species are mostly quite similar to each other. Ferrari et al. (2015) stated that Jurassic Trochotoma species are frequently related to reef environments of the Tethyan region (Europe, northern Africa). A few Triassic species representing Trochotoma have been reported, among it Trochotoma praecursor (Stoppani, 1860) that is present in the Rhaetian assemblages studied herein. Furthermore, T. carpathica Kollarova-Andrusova Microfacies. a Micritic rudstone rich in branching coral fragments, and b longitudinal sections of large phaceloid coral branches embedded in a bioclastic peloidal groundmass. Note porostromate cyanobacterial nodule (Cayeuxia) at the upper margin, c bioclastic floatstone with corals (co), echinods (e), molluscs (m); note Lithocodium crust (Li, lower left) and Thaumatoporella (th, lower right), d large intraclast (bioclastic floatstone) locally encrusted by foraminifers (cf. Planinvoluta sp.) and microbialites, e bioclast floatstone/ rudstone, note textulariid, duostominid and lenticulid foraminifers in the groundmass as well as chasmoendolithic Bacinella threads in interseptal spaces within coral branches, and f Lithocodium encrusting coral branches. Chasmoendoltihic Bacinella threads grown in interseptal space of corals (lower margin) render general entobian origin of Triassic Lithocodium supposed by Schlagintweit (2011) questionable. All scale bars = 1 mm. a SNSB-BSPG 2021 XVI 5, b, d SNSB-BSPG 2021 XVI 10, and c, e, f SNSB-BSPG 2021 XVI 7 and Kochanova, 1973 (Norian, Slovakia), T. fistulata Sachariewa-Kowatschewa, 1962 (Carnian, Bulgaria), T.? orbita Pan, 1982 (Early Triassic, China), and T. planoconvexa Yu, Pan and Wang, 1974 have been reported, all of which are doubtful members of Trochotoma according to Ferrari et al. (2015). Trochotoma carpatica is untypical for the genus in having a pronounced axial ornament on the ramp and a vertical outer whorl face instead of an inclining one; this species needs to be re-studied. Furthermore, Trochotoma sp. reported by Kollarova-Andrusova and Kochanova (1973) also has axial ribs. Trochotoma? orbita was only tentatively assigned to Trochotoma and seems to have evenly rounded whorls which is untypical for this genus. The type material of this species seems to be poorly preserved. Trochotoma fistulata as figured by Sachariewa-Kowatschewa (1962) seems to be correctly assigned to this genus. Trochotoma fallax (Kittl, 1891) from the early Carnian St. Cassian Formation is the oldest known representative of the genus (Karapunar and Nützel 2021). The fragmentary specimen reported by Nützel and Erwin (2004, fig. 12) from the Norian of Idaho as Tretospira sp. could represent a Trochotoma species.
Trochotoma praecursor (Stoppani, 1861)  Description. Shell trochiform with gradate spire; spire angle variable (70°-90°); whorl face angulated at one-third to onefifth of whorl face of spire whorls below adapical suture; ramp straight-to-slightly concave, weakly inclined; whorl face below angulation more strongly inclined, straightto-slightly concave, with more or less developed bulge at transition to base which forms whorl periphery; whorl face ornamented with spiral cords of variable strength and at variable distance to each other; up to 14 spiral cords below angulation, up to 4 on ramp; spiral cords strongest at middle of whorl face, weaker on ramp, near angulations and near abapical suture; whorls ornamented with strengthened growth lines, prososcline prososcyrt below angulation and Table 1 Stratigraphic ranges of mollusc and associated taxa in the Rhaetian reef limestones of Gaissau (Rötelwand reef) and Gosaukamm, Austria; references for gastropod ranges are given in the systematic section; FAD Cosmetodon (Hautmann 2001); FAD Cassianella (Ciriacks 1963); FAD Chlamys Anisian according to Allasinaz (1972), but records before the Ladinian are questionable; scleractinians according to Lathuilière and Marshall (2009) Carnian Rhaetian on ramp but more oblique on ramp; growth lines curving backward toward angulation where selenizone lies (no trema was observed); selenizone narrow, with sharp lunulae, bordered by spiral cords, upper one forming whorl angulation; base excavate, concave, ornamented with spiral cords in the same way as on whorl face.
Remarks. The present material is quite variable in spiral ornamentation and apical angle. It agrees generally well with the illustration of the type specimen of T. praecursor from the Rhaetian of Lombardy (beds with Rhaetavicula contorta, accordingly frequent near l 'Azzaròla, N Italy) given by Stoppani (1860) regarding general shape, spiral ornamentation and the excavate, funnel-like base. However, the ramp and the whorl face below the carination are seemingly slightly convex instead of straight to concave as in the present material. Although the species identity of our material seems to be correct, a study of Stoppani's (1860) type material is needed for corroboration. Stoppani (1860) provided no information about the growth-line pattern and the selenizone. He stated that he had no specimen that was well enough preserved to show the trema and the same is also true for the present material (see also Zapfe 1963). A trema is only formed in the last part of the last whorl and thus is not preserved if this part is broken off. If T. praecursor lacks a trema, it could represent a different genus, for instance Bathrotomaria, but this genus does not have a funnel-like base. Zapfe (1963) reported this species from Adnet-Kirchholz (Deißlbruch, Austria); he gave a short description but no illustration. This author pointed out that Pleurotomaria scansilis Ammon, 1893 is very similar or identical with T. praecursor and that Ammon (1893) erroneously gave an Early Jurassic age for Pleurotomaria scansilis which actually is from the Rhaetian reef limestone. We examined the holotype of Pleurotomaria scansilis (SNSB-BSPG 1929 XI 623). It is clearly conspecific with our material and has exactly the same color and type of preservation. An old label says "Pleurotomaria? Dachsteinkalk aus dem Adneter Tropfmarmorbruch" and therefore Zapfe's (1963) assumption that this taxon is Rhaetian is correct.
Remarks. Well-preserved specimens representing the type species of the Carboniferous genus Trepospira Ulrich in Ulrich and Scofield (1897) were studied by Karapunar et al. (2022). There seem to be no major differences of Trepospira (family Eotomariidae) and the Jurassic genera Angulomphalus Gründel, 2011 andPtychomphalus (family Ptychomphalidae Wenz, 1938). Angulomphalus differs from Ptychomphalus in having an angular periphery instead of having a rounded one. As to whether this slight difference is sufficient to separate these genera or whether they are synonymous needs further study. This is the first report of the genus Angulomphalus from the Triassic.
Description. Shell low-spired, sublenticular; largest specimen 27 mm wide, 19 mm high; spire low but clearly elevated; whorls convex, angulated at borders of selenizone at periphery; whorls with subsutural shoulder followed by nodular bulge; whorl face between nodular bulge and selenizone concave; nodes axially elongated, prosocline; selenizone concave bordered by spiral cords; adapical spiral cord with numerous nodes; selenizone covered by succeeding whorls, only exposed in last whorls when whorl is deflected downward; base convex, anomphalous with callus in umbilical region; whorls covered with fine spiral striation (commonly obscured by preservation).
Remarks. Angulomphalus senowbarii sp. nov. has a much wider selenizone than the other known members of the family Ptychomphalidae. In this respect, it resembles the Carboniferous genus Trepospira. However, Trepospira does not develop a convex subsutural bulge and concave ramp near the selenizone. This feature is known from the type species Angulomphalus expansus. The presence of an umbilical callus and the slightly elevated selenizone with distinct borders also suggest a placement in Angulomphalus. Angulomphalus wehenkeli (Terquem and Piette 1865) from the Early Jurassic (Upper Hettangian) of Brouch, Luxembourg, is very similar (Monari et al. 2011;alias Ptychomphalus caepa in Meier and Meiers 1988;Gründel 2011), but the selenizone of the mature whorls is not bordered by spiral cords, it lacks a spiral striation, and the subsutural knobs are not as elongated.
Remarks. Apart from two occurrences of Stuorella from Jurassic deposits of Sicily (Szabó et al. 2021) (but see Karapunar and Nützel 2021) and Cretaceous deposits of Spain , the family is restricted to the Triassic. An Anisian reference to Stuorella (Schnetzer 1934) seems to be doubtful. The oldest certain members of Stuorella have a Ladinian age (Kittl 1894). Range. Ladinian (Kittl 1894)-Campanian .
Etymology. After Helmut Zapfe for his work on the Late Triassic faunas of the Alps.
Description. Shell trochiform, conical, with straight flanks; apical angle ca. 60°; whorls very low, largely smooth with weak spiral striation of threads and furrows; whorl face straight, slightly imbricate, narrowly exposing basal edge; basal edge forms slightly nodular bulge; possible selenizone low on whorls, covered by spiral striae, flush with whorl face; transition to base at angular edge; base flat, slightly concave, with remains of spiral striation.
Remarks. This species likely has a selenizone low on the whorls which is, however, obscured by preservation. It is placed in the slit-band gastropod genus Stuorella. If it had no selenizone, a placement in the trochoid genus Epulotrochus Cossmann, 1918 would be possible. For instance, Epulotrochus strobiliformis (Hoernes) from the Norian Hallstätterkalke of Austria and Timor is similar but lacks a selenizone, spiral striation is weaker or absent, and it has a lower apical angle (see . Stuorella tofanae Leonardi and Fiscon, 1959 from the St. Cassian Formation is the most similar species. This species has a distinct axial ornament on its early whorls that is later reduced. It differs from Stuorella zapfei in having distinct lunulae on the selenizone and a weaker spiral striation (Karapunar and Nützel 2021).
Some species of the Jurassic genus Pyrgotrochus P. Fischer, 1880 closely resemble the present species for instance P. punctatus (Sowerby, 1818) (Monari et al. 2018) or P. elongatus (Sowerby, 1818) (Lindström and Peel 2010). However, the Early Jurassic (Pliensbachian) type species P. bitorquatus (Eudes-Deslongchamps 1849) has a median selenizone and strong nodes at both sutures according to the diagnosis and illustration given by Wenz (1938, p. 147, fig. 213). Nevertheless, Knight et al. (1960) and Harasewych and Kiel (2007, Table1) gave a submedian selenizone as diagnostic. In contrast to the type species of Pyrgotrochus, Stuorella zapfei has the selenizone low on the whorls and lacks a strong nodular ornament. However, many other species assigned to Pyrgotrochus also have a submedian selenizone and only a weak ornamentation. Those species are close to Stuorella zapfei, but taken together, this species is closer to the type species of Stuorella than to that of Pyrgotrochus, especially regarding the very low whorls and the submedian position of the selenizone. The genera Pyrgotrochus and Stuorella are closely related according to Harasewych (2002, fig. 9) who treated them a sister groups. However, this proposal needs corroboration. According to Monari (written communication 2021), Pyrgotrochus has an early shell with sharply reticulate ornament which is typical of the family Pleurotomariidae (Szabó et al. 2021;Karapunar and Nützel 2021) whereas in Stuorella, the spiral ornament is dominant. Although poorly preserved, the early whorls of the present new species seem to lack this ornament pattern.
Stuorella pappi Kutassy, 1937 (Norian, Hungary) is similar but the selenizone is bordered by distinct spiral cords and the whorls lack a spiral striation.
Description. Shell planispiral, widely phaneromphalous, 31 mm wide, 11 mm high; whorls convex with rounded periphery; whorls ornamented with broad, wavy radial ribs separated by wide interspaces, ca. 10-12 ribs per whorl; ribs do not continue onto periphery; whorls with traces of weak spiral cords obscured by preservation; selenizone on periphery also obscured by preservation.
Remarks. This is a typical but rather large representative of the Middle and Late Triassic genus Kokenella. The preservation is too poor for identification or characterization of a new taxon. The present specimens closely resembles the K. costata (Münster, 1841) from the Late Triassic (Carnian) St. Cassian Formation (see Karapunar and Nützel 2021) that has also been reported from the Rhaetian of Iran (Nützel and Senowbari-Daryan 1999).
Cassianopsis sp. Figure 16a, b Description. Shell neritiform with rapidly increasing whorls, broader than high, 20 mm wide, 16 mm high; spire small, gradate; whorls convex with periphery at about mid-whorl; whorls ornamented with pronounced, straight to prosocyrt, prosocline axial ribs separated by wide interspaces; whorls ornamented with numerous spiral cords, much weaker than axial ribs, forming weak nodes at shoulder of whorls; base convex, axial ribs seem to continue onto base.
Etymology. Latin for the callous aperture.
Description. Shell globular, 28 mm wide, 24 mm high, with flat-to-slightly immersed spire; whorls evenly rounded, strongly embracing each other, so that the spire whorls can only be seen in small area encircled by the last preserved whorl; sutures shallow; whorls smooth; aperture with strong parietal and columellar callus also covering umbilical area, with callous bulge on columellar part; inner lip oblique, slightly arched. (Kittl, 1892) from the Carnian St. Cassian Formation is similar, especially regarding the morphology of the apex. However, Hologyra involuta lacks the callous bulge on the columellar lip and its spire is slightly more elevated. Hologyra alpina Koken, 1892 is broader, and the spire is somewhat more elevated and lacks the callous bulge on the columellar lip. Hologyra timorensis (Krumbeck, 1924) from the Norian of Timor is similar, but is not as broad, lacks a callous bulge on the columellar lip and a greater portion of the apical whorls is exposed than in Hologyra involuta. Species of the genus Marmolatella are evolute instead of involute. Most other neritimorphs of the Triassic have a more elevated spire.
Description. Shell neritiform, low-spired, with rapidly increasing whorls, 29 mm high, 24 mm wide; whorls with  (Wolff, 1967 Etymology. After the Rhaetian stage. Description. Shell littoriniform, higher than wide; largest specimen 44 mm high, 33 mm wide; last whorl distinctly higher than spire; whorls embrace at periphery of evenly rounded, convex whorls; sutures shallow, whorls ornamented with alternating weak and strong spiral cords; up to ca. ten spiral cords present on whorl face; ornament indistinct in early whorls (probably due to preservation), strong spiral cords nodular, weak spiral cords not nodular; base convex, with evenly rounded transition from whorl face, covered with spiral cords; aperture oblique, higher than wide; inner lip almost straight with parietal inductura, outer lip evenly arched; aperture with posterior siphonal canal and anterior outlet.
? Etymology. In honor of Gero Mossleitner who shared his deep knowledge of the paleontology of the Austrian Alps with us and helped us during field work.
Description. Shell globular, large, largest specimen ca. 90 mm high, 80 mm wide; apical angle 90°-100°; last whorl higher than spire; spire gradate; whorls convex with slightly inclined to almost horizontal ramp in late whorls; ramp more inclined in early whorls; last whorl somewhat deflected downward; whorls ornamented with rows of spirally arranged nodes and spiral cords between them; spiral cords may also cross nodes; most prominent nodes situated at edge of ramp with nodes pointing in adapical abaxial direction; up to 11 nodes on last whorl; row of weaker, spirally elongated nodes in suprasutral position in spire whorls, 2 undulating spiral cords between adapical rows of nodes; base convex, evenly rounded, not demarcated from whorl face; base ornamented with rows of spirally elongated nodes of similar strength as nodes of second row; base with spiral cords between rows of nodes.

Remarks.
A species that is known as Purpuroidea subcoronata (Hörnes, 1856) (Roemer, 1841), he introduced the name Turbo subcoronatus which therefore is a replacement name. Meanwhile, Pleurotomaria coronata has been transferred to the Pleurotomariida genus Worthenia and recently to the genus Nodocingulum Karapunar and Nützel, 2021. Worthenia coronata is certainly not conspecific with the species described and illustrated by Hörnes (1856). The material identified as Turbo subcoronatus by Hörnes (1856) represents an undescribed species. Purpuroidea moosleitneri sp. nov. has a more acute, elevated spire than that species, its ramp is more inclined; it has more spiral cords on the whorl face; the second row of nodes is covered by succeeding whorls; its whorl face is straight, not convex. Purpuroidea ferenczii Kutassy, 1927 from the Late Triassic (Norian) Dachsteinkalk of Hungary closely resembles Purpuroidea moosleitneri sp. nov. However, Purpuroidea ferenczii has a narrower spiral angle, the adapical nodes are less pronounced, and it has more spiral cords that are closer to each other (see Kutassy 1927Kutassy , 1932Kutassy , 1934Kutassy , 1937 (Fig. 19). Purpuroidea ferenczii was listed by Zapfe (1962, p. 348) as being present in the Gosaukamm reefs and it is likely that his specimens represent Purpuroidea moosleitneri.
Purpuroidea dilophosignata Fallahi et al., 1983 has only two rows of nodes and lacks ornament on the base. Purpuroidea taramellii (Stoppani) as figured by Tommasi (1903, pl. 3, figs. 25, 26) has smaller nodes and a narrower apical angle. Purpuroidea baconica Kittl, 1900 has only a single row of nodes and a narrower apical angle. Purpuroidea carpathica Jekelius, 1935 is much more high-spired and differs in ornamentation.
Apart from these recent references, Angularia Koken was also included in the widely used handbooks of Cossmann (1906) and Wenz (1938Wenz ( -1944 including descriptions and illustrations.
Based on this evidence, under Art. 23.9.2, we here declare Angularia Busk, 1881 to be a nomen oblitum, and Angularia Koken, 1892 a nomen protectum.
Etymology. According to its occurrence in coral-rich limestones.
Material. Three specimens from Gaissau; holotype SNSB-BSPG 2021 XVI 19b;paratype SNSB-BSPG 2009 IV 43a and2009 IV 41b. Description. Shell fusiform, moderately high-spired; spire gradate with angulation at mid-whorl of last whorl, somewhat above suture in spire whorls; high, steep ramp, with straightto-slightly convex outline, concave above angulation; whorl face straight below angulation; axially elongated nodes on angulation, ca. 15 nodes per whorls; whorls ornamented with strengthened growth lines, prosocline on ramp, orthocline prosocyrt below ramp and on base; growth lines forming sinus at angulation; whorls adpressed in narrow zone at suture with growth lines strongly curving in adapertural direction; base strongly convex with evenly rounded transition to whorl face.
Remarks. Several similar Late Triassic species were placed in the genus Angularia for instance A. multinodosa Kutassy, 1937 andA. plicata Kutassy, 1937. None of these species have the angulation as low as Angularia corallina sp. nov. on the spire whorls. A similar species was illustrated as Pleurotomaria obliqua Terquem from the Hettangian of Luxembourg by Meier and Meiers (1988, fig. 13a, b). This specimen differs from Angularia corallina in lacking nodes on the angulation. It certainly does not represent Pleurotomaria obliqua which is much broader nor does it represent the genus Pleurotomaria. Instead, this Hettangian specimen can be placed in Angularia.
Remarks. Pictavia unites many Mesozoic littoriniform to bulbous, smooth-shelled species that are difficult to differentiate from each other. Some of them are close to Coelostylindiae. Gründel and Kaim (2006) reported Late Jurassic (Oxfordian) Pictavia species having smooth larval shells that are close to the Late Triassic type species of Coelostylina, C. conica, from the Late Triassic St. Cassian Formation, as recently reported by Hausmann et al. (2021).
Description. Shell turbiniform, bulbous, with acute spire; relatively large, 85 mm high, 72 wide; whorls evenly convex, rapidly expanding, smooth; whorls embrace at rounded periphery; body whorl much higher than spire; transition from whorl face to base evenly rounded; base rounded convex; aperture and umbilical region not observed.
Remarks. Eight Triassic nominate species have been assigned to Pictavia. Pictavia sp. resembles P. alsatica (Koken, 1898) from the Anisian Muschelkalk. Pictavia comes (Ammon, 1878), and P. limnaeoides (Ammon, 1878) from the Norian Hauptdolomit of the Alps are similar but much smaller. Pictavia silicea (Quenstedt, 1858) from the Late Jurassic of Germany is similar but much smaller (Gründel et al. 2019, pl. 2, figs. 17, 18). The Late Jurassic species Globularia hebertana (d'Orbigny, 1851) from France is similar and also rather large (Fischer and Weber 1997, pl. 16, fig. 10). However, the Eocene type species of Globularia Swainson, 1840 has a lower spire and is more globular. Without more information about growth-line pattern, aperture and early ontogenetic shell, an identification is hardly possible. Given the exceptional large size of the present specimen, we assume that it represents a yet undescribed species.
Remarks. High-spired caenogastropods with umbilicus or an umbilical chink are diverse and abundant in the Triassic, and are commonly assigned to the genera Coelostylina or Omphaloptychia which could represent synonyms. Coelostylina has a well-documented type species including a well-preserved type specimen from the St. Cassian Formation (Hausmann et al. 2021). By contrast Omphaloptychia nota, the type species of Omphaloptychia is not documented as well and its type material is not as well preserved.
Description. Shell of about eight whorls, apex missing, 65 mm high, 26 mm wide; shell high-spired, conical; apical angle ca. 35°; whorl face distinctly convex; periphery low on whorls where whorls embrace; whorls smooth; sutures distinct; transition from whorl face to base rounded; base distinctly convex.
Remarks. This specimen resembles Coelostylina? sp. 2, but has a more convex, extended base. Coelostylina? sp. 3 has a less convex whorl face.
Description. Shell of about six whorls, apex missing, 41 mm high, 21 mm wide; shell high-spired, conical; apical angle ca. 30°; whorl face convex; periphery low on whorls where whorls embrace; whorls smooth; sutures distinct; transition from whorl face to base rounded; base flatly convex.
Remarks. This specimen resembles Coelostylina? sp. 1, but has a somewhat more convex whorl face, more distinct sutures, and a flatter base. Coelostylina? sp. 3 has a flatter whorl face and indistinct sutures.
Range. Capitanian )-Pliensbachian (Cossmann 1913;Gründel 2007a). Wenz (1938) noted that Protorcula ranges to the Bajocian, but we do not know the reference for this occurrence. Protorcula? quadricostata Gründel, 2007b from the Sinemurian differs very much from the type species of Protorcula in teleoconch ornament and is likely not a member of the genus. Nützel and Senowbari-Daryan (1999) and  reported Protorcula from the Norian/Rhaetian Nayband Formation, Iran.
Remarks. This high-spired shell with concave whorl face resembles some Jurassic/Cretaceous Nerineidae. However, knowledge of the aperture and internal folds would be needed to place it in that group. To date, Nerineidae have no certain fossil record in the Triassic.
Description. Shell high-spired, slender, acutely conical; apical angle 30°; ca. 8 whorls preserved, 46 mm high, 17 wide; earlier preserved whorls with ca. ten orthocline axial ribs, separated by wide interspaces, and two spiral cords; adapical spiral cord situated above mid-whorl; abapical spiral cord above suture; intersections of axial ribs and spiral cords nodular; last whorl with two additional spiral cords intercalated between primary spiral cords; last preserved whorl with distinctly more axial ribs as earlier whorls (ca. 15 ribs); sutures shallow but distinct; base convex, with at least three nodular spiral cords.
Infraclass Autolamellibranchiata Grobben, 1894Subclass Pteriomorphia Beurlen, 1944 Order Arcoida Stoliczka, 1871 Superfamily Arcoidea Lamarck, 1809 Family Parallelodontidae Dall, 1898 Subfamily Grammatodontinae Branson, 1942 Genus Grammatodon Meek and Hayden, 1860 Subgenus Cosmetodon Branson, 1942 Type species. Arca keyserlingii d´Orbigny, 1850 (original designation). (Richardson, 1843 Remarks. Knight and Morris (2020) indicated a close similarity between Arca buckmanni Richardson, 1843 and Cucullaea hettangiensis Terquem, 1855, but they kept both species separately, based on a supposedly greater elongation of the former. Because the type material of Cucullaea hettangiensis seems to be lost and the description and figures in Terquem (1855) do not show a difference to Arca buckmanni in the elongation or in any other feature, we regard both taxa tentatively as synonyms. The presence of this Jurassic species (as "Parallelodon hettangiensis") in the Upper Rhaetian reef limestone was already recognized by Zapfe (1963). We include the two specimens of Cosmetodon from the Rhaetian of east-central Iran described in open nomenclature by Hautmann (2001) in G. (C.) buckmanni. In the Rhaetian, Grammatodon (Cosmetodon) buckmanni was thus a trans-Tethyan species, which survived the end-Triassic mass extinction.
Rhaetavicula contorta (Portlock, 1843)  Description. The studied specimens show the characteristic twisted appearance of the left valve, which is ornamented by up to 20 radial ribs intercalated in two ranks.
Remarks. This species was widespread in the Rhaetian of Europe, North America and the Tethys realm (Hautmann 2001).

Description.
Internal mold of a left valve, showing the characteristic strongly convex and obliquely curved main body of the shell, the markedly convex anterior auricle, and the short but well-developed posterior auricle.
Remarks. Because the ornamentation of the shell exterior is not preserved, a species assignment is not possible.
Description. Shell medium-sized, obliquely oval in outline. Dorsal margin straight, without differentiated auricles or wings. Beak not terminal, umbo slightly protruding above hinge margin. Ornamentation of broad concentric folds. Ligament not observed.
Remarks. This taxon is represented by two incomplete internal molds of right valves. Neither its ligament area nor the anterior part of the shell is preserved, which makes a full determination impossible. Shape and ornamentation of the shell resemble Retroceramus Koshelkina, 1957, a genus that is most common in the Jurassic of high palaeo-latitudes (Damborenea 1990;Zakharov et al. 2020), but has also been questionable reported from the Late Triassic (Cox et al. 1969 Description. Shell pteriiform, bialate, inequivalve. Left valve strongly convex, with small anterior auricle and elongated posterior wing. Ornamentation with 10-11 first-order radial ribs. Second-order ribs intercalated at about 30-50% of shell height, most prominent on posterior part of the valves, faint or absent anteriorly. Third-order ribs occasionally present but faint. Posterior wing smooth except for weak radial ridges parallel to hinge margin, which are invisible in internal molds. Right valve slightly convex, with small anterior auricle forming a deep embayment toward disc. Posterior wing large and elongated. Disc of right valve retrocrescent, covered with faint radial ribs intercalated in two ranks. Remarks. This species is very variable in terms of its ornamentation, which is reflected by considerable taxonomic splitting, as reviewed by Waagen (1901). The impression from our limited material is that there is much variation with regard to the ornamentation within populations.
Oxytoma inaequivalve (Sowerby, 1821) is among the species of the Oberrhät Limestone that survived into the Jurassic.

Material.
One left valve from Rötelwand NHMW 2021/0122/0024; one external mold of a right valve from Gosaukamm NHMW 2021/0121/0037; two right valves from Rötelwand (Gaissau) NHMW 2021/0122/0023, 2021/0122/0025. Description. Disc of right valve up to 4 cm high, covered with 20-24 radial plicae arranged in pairs. Apical angle of disc c. 80°. Posterior disc margin with numerous transverse ridges. Anterior auricle of right valve well developed, with deep byssal notch; posterior auricle of right valve large, with three radial ridges. Disc of left valve with ribs intercalated in two ranks: second-order ribs notably weaker than first-order ribs.
Remarks. This species was introduced by Goetel (1917) as a subspecies of Pecten favrii Stoppani, 1863. Hautmann (2001 noted that Goetel's (1917) taxon can be separated consistently from Stoppani's species based on the much lower number of plicae and the smaller apical angle. The material from the Oberrhät Limestone confirms this conclusion.

Discussion
The demise of the widespread reefs and mountain-building carbonate platforms in the western Tethys is one of the hallmarks of the end-Triassic mass extinction event. At the Rötelwand, the guild of reef-building corals is only present with three genera and species (admittedly more species exist Table 3 Bivalve taxa reported from the "Oberrhät-Riffkalk" by Zapfe (1963). Because most taxa were not figured in Zapfe (1963), genus assignments could not be verified in most cases. However, genus names for well-known species were adapted according to the recent literature. 21 of the present genera survived the T-J extinction event, whereas ten became extinct. Zapfe's (1963) report of two unidentified species of the families Megalodontidae and Burmesiidae suggest the presence of two addition genera; thus, the reported overall genuslevel diversity of bivalves from the "Oberrhät-Riffkalk" is 33 genera Zapfe (1963)  in Retiophyllia; see above) in the studied samples, only one of which Pinacophyllum survived the extinction with certainty. Cycliphyllia and possibly also Retiopyhllia did not survive the perturbation at the end of the Rhaetian. Globally, corals were hit severely, with recent estimations of generic loss between 51 and 53% (Kiessling et al. 2009), based on an updated compilation of stratigraphic ranges by Lathuilière and Marchal (2009) as well as data from the PBDB. However, the present study is not focused on the reefs themselves but on their associated fauna. Our documentation confirms that the diversity of such "accessory" faunas may be much larger than that of the reef builders that provide their ecological context.  and  suggested that reef-associated taxa and taxa that preferred carbonate substrata have had a significantly higher extinction risk than level-bottom dwellers during the end-Triassic mass extinction, which seems plausible: if reefs disappear, reef dwellers lose their habitats and might also become extinct. Our new data on reef dwellers or reef-associated invertebrates and the facies of the fossiliferous rocks from Gaissau (Rötelwand Reef, Salzburg area) and Gosaukamm (Dachstein Mountains) provide an opportunity to test this hypothesis.
Among the 11 foraminiferid genera found in the studied thin sections, eight have had their last appearance in the Rhaetian. Thus, Foraminifera at the Rötelwand locality suffered 73% extinction at the genus level, which is well above the average marine genus extinction (46.8%; Bambach et al. 2004) during this event. This high extinction of Foraminifera is contrasted by a surprisingly low extinction proportion of reef-associated mollusc taxa (bivalves and gastropods), which are present with 47 identified genera from the studied latest Triassic reefal carbonates (bivalve data also include Zapfe's 1963 study). Among these, only 12 genera became extinct (25.5%) at the end of the Triassic. However, most of the species are known only from the Late Triassic, except for two bivalve species (Grammatodon (C.) buckmanni and Oxytoma inaequivalve) from our material (Table 2) and one bivalve species described by Zapfe ("Ostrea anomala" = Liostrea hisingeri; Zapfe 1963), which are also known from the Jurassic.
Gastropods are present with 17 genera and 19 species. Six of these species are described as new, including two relatively large and conspicuous ones (Microschiza rhaetica and Purpuroidea moosleitneri) that are also abundant. It is remarkable that such species have not been described earlier from this well-researched area. This is probably due to their rather spotty or not easily accessible occurrence. None of the present gastropod species is known to cross the Triassic-Jurassic boundary, but this is common in gastropods, because Triassic species are usually restricted to a single stage, and many are known from a single or few occurrences (Nützel 2005b). Among the 17 gastropod genera, three do not cross the boundary and became extinct during the end-Triassic crisis. However, most genera (82%) survived and are also known from Jurassic and Cretaceous deposits. Most of the present genera originated in the Triassic (eight in the Late Triassic) and only two in the Permian. Taken together, the gastropod fauna has a Triassic character, although most genera survived into the Jurassic. Nützel (2005b, fig. 1) showed that the Rhaetian gastropod standing diversity is very low (ca. 200 species including those in open nomenclature), and the drop from the Norian is pronounced. However, the Rhaetian is much shorter than the Norian (Rhaetian: 4 Ma, Norian: 13 Ma; Gradstein et al. 2004), and according to , the number of Rhaetian fossil occurrences is generally very low, so that sample standardization would be needed to correct for these differences. The gastropod species diversity peaks in the Carnian (Nützel 2005b), which is largely due to the extremely diverse fauna of the St. Cassian Formation. This Liberation Lagerstätte (Roden et al. 2020) is characterized by low lithification, so that small, fragile gastropods can be easily extracted. By contrast, the Upper Rhaetian Reef Limestone and the Gosaukamm carbonates are strongly lithified. Most of the studied gastropod species are medium-sized or large, and must be extracted from the rock by laborious preparation, whereas tiny gastropod species are lacking. The study of the thin sections revealed that small gastropods were present, but they cannot be extracted. This taphonomic bias must be taken into account when the St. Cassian fauna is compared with the present one. Pieroni et al. (2021) emphasized that the study of gastropods from latest Triassic carbonate platforms is necessary to understand the evolution of their diversity dynamics during that critical time interval despite their commonly poor preservation.
It is remarkable that the present gastropod fauna resembles the Hettangian gastropod fauna from Luxembourg (Brouch), as reported by Terquem (1855), Meier and Meiers (1988), Monari et al. (2011), andGründel (2011). Both faunas are dominated by similar species representing the genus Microschiza. Moreover, similar species representing the genera Pleurotomaria, Trochotoma, Angulomphalus, and Angularia, among others, are present at both sites. It seems that this Hettangian fauna consists largely of descendants or close relatives of the latest Triassic Tethyan gastropod faunas. This similarity is also remarkable, because Brouch represents a non-reefal, siliciclastic (sandstone)-dominated environment (Faber and Weiss 2005). Differences between both faunas may be explained with this facies difference, notably the absence of Purpuroidea at Brouch.
The here described bivalve fauna is essentially a subset of the 41 bivalve taxa described by Zapfe (1963 ; Table 3). Although Zapfe (1963) did not figure the majority of his material, an assignment of the new material to his identifications is possible in most cases, although taxonomic names were partly revised herein.
All bivalve species identified in this study were epifaunal, either byssally attached or reclining (Table 2), which is expected for a reefal environment that is dominated by hard substratum. The vast majority of species described by Zapfe (1963) was also epifaunal, but the presence of few burrowing heterodonts and anomalodesmats in his collection indicates the occasional presence of soft substratum, such as pockets filled with mud within or between the reefs. Palaeogeographically, all identified bivalve species occurred Tethys-wide in the Triassic, although some are known in the eastern Tethys only from isolated occurrences ( Table 2).
The bivalve fauna represents an assemblage that is typical of latest Triassic reef and carbonate platform environments. As noted above, the end-Triassic mass extinction affected these settings heavily, probably because of an ocean acidification event (Hautmann 2004;Hautmann et al. 2008a). This event was followed by a short-term interruption of carbonate deposition (Hautmann 2004;Hautmann et al. 2008a;Greene et al. 2012;McRoberts et al. 2012) and a long-lasting reef eclipse (Kiessling et al. 2009;Lathuilière and Marchal 2009). Consequently, it could be expected that reef and carbonate platform associated taxa also suffered above average, but surprisingly, this seems not to be the case. Among the herein recorded bivalve genera, three (Rhaetavicula, Cassianella, Schafhaeutlia) out of seven (42.8%) went extinct, which is comparable to the average extinction of marine bivalve genera at the end of the Triassic (40.5%; Hautmann et al. 2008a). The small size of this dataset limits the significance of this comparison, but the result is also in accordance with Zapfe's (1963) larger dataset. Accepting his determinations at the genus level with slight modifications (Table 3), only 9 out of 30 reported genera (30%) went extinct. It should be noted that some determinations in Zapfe (1963) require revision, but the general pattern (no elevated extinction in reef-associated taxa) is likely robust. It is also notable that a bivalve-dominated level-bottom fauna in a siliciclastic setting of the latest Triassic of South Tibet (Hautmann et al. 2008b) suffered much higher extinction at the genus level (53.8%) than the reef-related bivalves reported in this study (30%). We note that the genus level might be inappropriate for the study of extinction patterns, because differences in the ecology among species of the same genus cannot be ruled out. However, the above-cited analyses of  and  were also calculated at the genus level; thus, the difference between the results is not an artifact of the taxonomic level. Moreover, the genus is still a low taxonomic category that reflects close phylogenetic relationships of the included species, which usually share similar niches (niche conservatism; e.g., Pyron et al. 2015). Therefore, it is unlikely that a genus comprises species that belong to entirely different guilds.
In summary, the expectation that the end-Triassic reef extinction should have been matched by an elevated extinction of reef-associated taxa is confirmed for foraminifers, but not for gastropods and bivalves. Given the low number of Rhaetian marine invertebrate occurrences , this unexpected observation is relevant for the interpretation of the end-Triassic mass extinction and requires an explanation. The present case study on dwellers of one of the most important latest Triassic reef complexes adds significantly to this discussion, regardless of whether it is a local exception or not. We suggest that the studied Rhaetian gastropod and bivalve genera were not obligate reef dwellers, but had a broader ecological capacity or that they shifted their habitats following the extinction of reefs. This is indicated by the presence of many of the studied gastropod genera in siliciclastic level-bottom settings in the Hettangian of Luxembourg (see above), and likewise, most of the surviving bivalve genera are known from level-bottom settings in the Early Jurassic (e.g., Aberhan 1992). We conclude that most of the Late Triassic reef-dwelling molluscs of the latest Triassic reefs of Austria had sufficient ecological plasticity to survive the global downfall of reef ecosystems in other habitats. Batten's (1973) proposal that a major gastropod faunal turnover occurred after the Rhaetian needs to be tested. private collections. Susana Ester Damborena and Stefano Monari provided helpful reviews. Simon Schneider and Mike Reich for helpful remarks and editorial corrections. We thank Philippe Bouchet for helping with the reversal of precedence for Angularia. Manuela Schellenberger assisted with photography. Elisabeth Lange prepared some of the studied specimens. Stefan Sónyi provided thin sections for facies and reef builder analysis. Alexander Lukeneder and Thomas Nichterl gave access to the collections at the NHMW. Walter Krispler gave us access to his private collection. Baran Karapunar provided valuable advice on the taxonomy of the pleurotomariidan species. János Szabó provided a photograph of the type specimen of Purpuroidea ferenczii. Vittorio Pieroni helped to clarify the identity of Trochotoma praecursor. The Deutsche Forschungsgemeinschaft (DFG) is acknowledged for the financial support (projects NU 96/13-1, NU 96/14-1). This research received support from the SYNTHESYS Project (http:// www. synth esys. info/), which is financed by a European Community Research Infrastructure Action under the FP7 "Capacities" Program (AT TAF-1797) and provided a grant to AN for a collection visit to NHMW.
Funding Open Access funding enabled and organized by Projekt DEAL.
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