Meride Limestone Research Articles

The history of palaeontological research and excavations at Monte San Giorgio

There is a long history of palaeontological excavations at Monte San Giorgio (Switzerland) and the adjoining Monte Pravello—Monte Orsa (Italy), aimed at finding well-preserved skeletons of Middle Triassic vertebrates. The first fossils were discovered in the mid-Nineteenth Century during mining of black shales (scisti bituminosi) near Besano, Italy, with further finds in the early Twentieth Century through industrial-scale mining. Studies of the material generated international interest and prompted formal palaeontological excavations on both sides of the border. The earliest excavations took place in 1863 and 1878, with the most extensive between 1924 and 1968. Systematic excavations have continued up to the present day, focusing on six distinct fossiliferous horizons: the Besano Formation and the overlying Meride Limestone with the Cava inferiore, Cava superiore, Cassina, Sceltrich and Kalkschieferzone beds. All these have provided material for study and display, with Monte San Giorgio itself recently designated a UNESCO World Heritage Site. The workers and organisations involved, locations excavated and material recovered are described herein.

Revision of the Middle Triassic coelacanth Ticinepomis Rieppel 1980 (Actinistia, Latimeriidae) with paleobiological and paleoecological considerations

Coelacanths form today an impoverished clade of sarcopterygian fishes, which were somewhat more diverse during their evolutionary history, especially in the Triassic. Since the first description of the coelacanth Ticinepomis peyeri from the Besano Formation of the UNESCO World Heritage Site of Monte San Giorgio (Canton Ticino, Switzerland), the diversity of coelacanths in the Middle Triassic of this area of the western Paleo-Tethys has been enriched with discoveries of other fossil materials. At Monte San Giorgio, two specimens of Heptanema paradoxum and several specimens of the unusual coelacanth Rieppeliaheinzfurreri, have been reported from the Meride Limestone and the Besano Formation, respectively. Another unusual coelacanth, Foreyia maxkuhni, and two specimens referred to Ticinepomis cf. T. peyeri have been described from the isochronous and paleogeographical close Prosanto Formation at the Ducanfurgga and Strel sites (near Davos, Canton Graubünden). In the framework of the revision of the coelacanth material from the Besano Formation kept in the collection of the Paläontologisches Institut und Museum der Universität Zürich (Switzerland), we reviewed the genus Ticinepomis on the basis of the holotype and four new referred specimens. Several morphological traits that were little and/or not understood in T. peyeri are here clarified. We re-evaluate the taxonomic attribution of the material of Ticinepomis cf. T. peyeri from the Prosanto Formation. Morphological characters are different enough from the type species, T. peyeri, to erect a new species, Ticinepomis ducanensis sp. nov., which is shown to be also present in the Besano Formation of Monte San Giorgio, where it is represented by fragmentary bone elements. The recognition of a new coelacanth species indicates that the diversity of this slow-evolving lineage was particularly high in this part of the Western Tethys during the Middle Triassic, especially between 242 and 240 million years ago.

A NEW COELACANTH SPECIMEN WITH ELONGATE RIBS FROM THE MIDDLE TRIASSIC (LADINIAN) KALKSCHIEFERZONE OF MONTE SAN GIORGIO (CANTON TICINO, SWITZERLAND)

A new finding of a coelacanth from the upper Ladinian upper Kalkschieferzone of the Meride Limestone Formation of Monte San Giorgio (UNESCO World Heritage area) is described. It represents the first known coelacanth from the Middle Triassic that undoubtedly bears elongate thin ribs. The incompleteness of the specimen prevents a reliable taxonomic assignment or the erection of a new species, however some characters, mainly scale morphology, are very similar to those of the holotype of Heptanema paradoxum Bellotti, 1857 from the roughly coeval Perledo Formation of Northern Italy. Elongate ribs are not reported in original descriptions of H. paradoxum, however small portion of ribs are visible among the scales of the holotype. Accordingly, the new specimen is tentatively ascribed to Heptanema as Heptanema cf H. paradoxum.

A NEW SPECIES OF SAURICHTHYS (ACTINOPTERYGII: SAURICHTYDAE) FROM THE MIDDLE TRIASSIC OF MONTE SAN GIORGIO

A new species of the actinopterygian fish genus Saurichthys is described on the basis of several specimens from the Sceltrich beds (Meride Limestone Formation) of the UNESCO World Heritage area of Monte San Giorgio. The new species shows among other characters, unsegmented lepidotrichia in all fins and elongated and wide paired fins, suggesting a different adaptation for swimming and catching preys with respect to other Saurichthys species of Monte San Giorgio. Phylogenetic analysis suggests that the new species is closely related to the Saurorhynchus species group. The new finding adds further knowledge to the plasticity and functional adaptations of the genus Saurichthys, which was one of the most successful actinopterygians of the Triassic.

Gastropods from the Sceltrich beds of Monte San Giorgio (Meride Limestone, Ladinian, Canton Ticino, Switzerland)

Gastropods from the Sceltrich beds of Monte San Giorgio (Meride Limestone, Ladinian, Canton Ticino, Switzerland)

A new Ladinian (Middle Triassic) mysidacean shrimp (Crustacea, Lophogastrida) from northern Italy and southern Switzerland

AbstractSince the end of the nineteenth century, many paleontological studies have been developed on the Middle Triassic localities of the Monte San Giorgio area (Canton Ticino, Switzerland, and Lombardy, Italy). These localities were inscribed in 2003 and 2010 in the UNESCO World Heritage List due to their paleontological relevance. New crustaceans are here described from the Kalkschieferzone member of the upper Ladinian Meride Limestone, outcropping near Besnasca-Cà del Frate (Viggiù, Italy) and Meride (Mendrisio, Switzerland). Several hundred specimens of a new genus and new species of Lophogastrida, named here Vicluvia lombardoae, improve information on Triassic mysidaceans (sensu lato), a group of shrimp-like crustaceans presently including hundreds of species worldwide distributed in marine and freshwater environments. The paper discusses the relations between Vicluvia n. gen. and the other fossil genera belonging to the same family. Vicluvia lombardoae n. gen. n. sp. exhibits two dorsally vanishing transverse grooves with their branches regularly bending toward the posterior margin of the shield and a telson with a rounded and setose apex. It was probably a euryhaline species living in a transitional environment affected by frequent and ephemeral salinity variations. Middle Triassic taphonomic windows have preserved specimens of lophogastrids in shallow basins along the Tethys, from the present Alps to China as well as in the German Basin.UUID: http://zoobank.org/1623e8f9-2ceb-4cd6-bcbe-4f05a873e1ff

Taphonomic variation within a Middle Triassic fossil lagerstätte (Cassina beds, Meride Limestone) at Monte San Giorgio

Middle Triassic sediments at Monte San Giorgio, a UNESCO heritage site on the Switzerland-Italy border, have famously sourced well-preserved vertebrate fossils. Taphonomic studies of reptiles in the Besano Formation and in the Cava inferiore, Cava superiore and Cassina beds of the Meride Limestone, and fish in the Besano Formation have already elucidated changes in palaeoenvironment through time in sediments that predominantly comprise black shale and carbonate lithologies. Saurichthys skeletons from the Ladinian Cassina beds were scored for articulation and completeness, with the resulting data sorted to test for variation among layers and lithologies in the 2.7-m thick section. The greatest abundance of skeletons was found in finely laminated sediments, a reduced number in event bed sediments and an absence in volcanic ash deposits. No particular bed showed better or worse preservation. The final state of a skeleton entering the fossil record was the result of the mode of deposition and rate of sedimentation with the additional influence of features at the sediment surface, notably microbial mat growth and its ability to stick carcasses to substrate.

Re‐evaluation of the ontogeny and reproductive biology of the Triassic fish Saurichthys (Actinopterygii, Saurichthyidae)

AbstractViviparity has evolved independently at least 12 times in ray‐finned fishes. However, the fossil record of actinopterygian viviparity is poor, with only two documented occurrences. Both of these are from the non‐teleost actinopterygian Saurichthys, and include S. curionii and S. macrocephalus from the Middle Triassic Meride Limestone (Monte San Giorgio, Switzerland). Here, we present new data on the reproductive biology of these species, giving unprecedented insights into their life‐history. Based on positional and preservational criteria, six specimens were identified as unambiguously gravid. Embryos were positioned dorsal to the gastrointestinal tract, parallel to the axial skeleton and to each other, in the posterior two‐thirds of the abdominal region. A minimum of 16 embryos are preserved in the most fecund females and, based on the largest preserved embryos and smallest preserved neonates, birth must have occurred at 7–12% of maternal fork length. Embryonic crania and teeth are relatively well‐ossified, however ossification of the parietal region is delayed. In the postcranium, the median scale rows and lepidotrichia are ossified, but not the lateral scale rows. Ossified squamation and gradual allometric growth suggests that neonates did not undergo metamorphosis and were relatively precocial. When considered in a phylogenetic context, neither live birth nor internal fertilization appears to represent the primitive state for saurichthyid fishes.

Osteology of a New Specimen of Macrocnemus aff. M. fuyuanensis (Archosauromorpha, Protorosauria) from the Middle Triassic of Europe: Potential Implications for Species Recognition and Paleogeography of Tanystropheid Protorosaurs

Over the past two decades, a wealth of marine and terrestrial reptiles, including protorosaurian archosauromorphs, has been described from Triassic shales and limestone layers in southern China. Recovered from the eastern margin of the Tethys Ocean, these forms often show remarkable similarities to taxa that were previously known and described from Europe, i.e., the western Tethyan margin. One protorosaurian that is known from the western and the eastern Tethyan province is the genus Macrocnemus, with currently three recognized species: 1) M. bassanii from the Middle Triassic Besano Formation and Meride Limestone (late Anisian – early Ladinian), UNESCO World Heritage Site Monte San Giorgio, Ticino, Switzerland; 2) M. obristi from the Prosanto Formation (early Ladinian) of the Ducan area, Grisons, Switzerland; and 3) M. fuyuanensis from the Falang Formation (Ladinian), Yunnan Province, southern China. Recently a new specimen, PIMUZ T 1559, from the upper Besano Formation at Meride, Ticino, Switzerland, was prepared, revealing a disarticulated skeleton which includes most of the cranium and lower jaw, pre-caudal vertebral column and ribs, the forelimbs, and girdle elements. Unambiguously assignable to the genus Macrocnemus, it evinces particularly gracile elongated cervical ribs, as well as a humerus/radius ratio that is comparable only to that of M. fuyuanensis from southern China. Based on this feature we tentatively recognize the new specimen as M. aff. fuyuanensis from Europe. The position and exquisite preservation of the clavicle and interclavicle in this specimen allows a revision of the shoulder girdle of Macrocnemus when articulated, which also has implications for closely related protorosaurian taxa, such as the long-necked Tanystropheus. Furthermore, differences in the shape and morphology of the interclavicle including pointed wing-like lateral processes and a short, fusiform caudal process represent rare discrete characters that allow separation of the specimens of M. bassanii from the new specimen of M. aff. fuyuanensis.

New holostean fishes (Actinopterygii: Neopterygii) from the Middle Triassic of the Monte San Giorgio (Canton Ticino, Switzerland).

The new neopterygian genus Ticinolepis, including two new species T. longaeva and T. crassidens is described from Middle Triassic carbonate platform deposits of the Monte San Giorgio. The anatomy of this fish shows a mosaic of halecomorph and ginglymodian characters and, thus, the new taxon probably represents a basal holostean. During the latest Anisian to earliest Ladinian the two new species coexisted in the intraplatform basin represented by the uppermost Besano Formation, but only T. longaeva sp. nov. inhabited the more restricted basin represented by the Ladinian Meride Limestone (except for the Kalkschieferzone). The more widely distributed type species shows interesting patterns of intraspecific variation including ontogenetic changes and morphological variation over time. The second species presents anatomical features that strongly indicate a strictly durophagous diet. The different distribution of the species is interpreted as a result of habitat partitioning and different adaptability to palaeoenvironmental changes.

A NEW GENUS AND SPECIES OF THE FAMILY TRACHYPACHIDAE (COLEOPTERAN, ADEPHAGA) FROM THE UPPER LADINIAN (MIDDLE TRIASSIC) OF MONTE SAN GIORGIO

A new genus and species of fossil Trachypachidae Praedodromeus sangiorgiensis gen. n sp. n. (Coleoptera, Trachypachidae, Eodromeinae), with well developed asymmetrical mandibles, shorter than the head, subrectangular pronotum and slender tibiae, longer than femora, is described from the Kalkschieferzone (uppermost member of the Meride Limestone) of the Swiss side of Monte San Giorgio. Trachypachidae are terrestrial Coleoptera well represented in the Mesozoic fossil record by the extinct family Eodromeinae. Up to now, more than 33 fossil species belonging to 13 genera of Eodromeinae have been described. The new species is part of a collection of fossil insects that includes members of at least six different orders. Based on the ecology of corresponding extant taxa, this insect assemblage provides new insights on the paleoenvironment of Monte San Giorgio area during the Late Ladinian. The assemblage includes terrestrial taxa that support the presence of emerged land and taxa with long-lasting aquatic larval stage (as Plecoptera and Ephemeroptera) that confirm the presence of stable fresh water basins.

A new basal actinopterygian fish from the Late Ladinian of Monte San Giorgio (Canton Ticino, Switzerland)

A new taxon of Late Ladinian basal actinopterygian is described on the basis of a single specimen from the Meride Limestone (Kalkschieferzone) of Meride (Canton Ticino, Switzerland). The species is characterized by a single plate-like branchiostegal, a suboperculum larger than the operculum, a maxillary fixed and posteriorly expanded, a large and rectangular dermopterotic and a large triangular dermosphenotic; the scales are rectangular to rhomboidal, the lepidotrichia of median fins are segmented from their base and the caudal fin shows epaxial rays. These features resemble the condition of the Redfieldiiformes, a freshwater fish group, whose presence in Europe is still controversial, owing to poor preservation of specimens found so far.

Palaeoenvironmental significance of organic facies and stable isotope signatures: the Ladinian San Giorgio Dolomite and Meride Limestone of Monte San Giorgio (Switzerland, WHL UNESCO)

AbstractThe over 600 m thick Ladinian carbonate section of Monte San Giorgio (World Heritage List, United Nations Educational, Scientific and Cultural Organization, Switzerland), including the San Giorgio Dolomite and the Meride Limestone, was analysed with respect to its sedimentology, organic‐matter content (Rock‐Eval and palynofacies) and stable carbon and oxygen‐isotope composition. Application of geochemical proxies and optical data (transmitted light microscopy, epifluorescence, cathodoluminescence and scanning electron microscopy) allowed the assessment of the relative sea‐level trend and the characterization of the organic‐matter content. Three main organic‐matter assemblages were defined according to their composition and stratigraphic position. Overall, results suggest immature organic matter, predominantly of marine bacterial origin with an upsection‐increasing land plant‐derived contribution. Forcing factors controlling organic‐matter accumulation include changes in sea‐level, productivity and runoff which, in turn, were probably promoted by periods of rainfall following explosive volcanic activity. Enhanced productivity during sea‐level highstands is considered to have played a key role in black‐shale formation under anoxic–sulphidic conditions (mainly in the Besano Formation). In contrast, sea‐level lowstands, coupled with intensified runoff, resulted in increased basin restriction and in deposition of laminated limestone, mainly under lower dysoxic to anoxic conditions (chiefly in the Lower Meride Limestone). Under the latter conditions, benthic microbial activity produced most of the hydrogen‐rich organic matter, contributed to carbonate precipitation and also played a major role in taphonomic control on vertebrate fossil preservation. In more general terms, the Monte San Giorgio section proved to be an excellent testing ground, making it possible to compare diverse approaches with each other and, more specifically, to relate optical evidence to geochemical signatures.

Integrated Ladinian bio-chronostratigraphy and geochrononology of Monte San Giorgio (Southern Alps, Switzerland)

New biostratigraphic data significantly improve the age assignment of the Ladinian succession of Monte San Giorgio (UNESCO World Heritage List site, Southern Alps, Switzerland), whose world-famous fossil marine vertebrate faunas are now dated to the substage and zone levels. High-resolution single-zircon U–Pb dating was performed using ID-TIMS and chemical abrasion (CA) pre-treatment technique on volcanic ash layers intercalated in the biostratigraphically-defined intervals of the Meride Limestone. It yielded ages of 241.07 ± 0.13 Ma (Cava superiore beds, P. gredleri Zone), 240.63 ± 0.13 Ma (Cassina beds, P gredleri/P. archelaus transition Zone) and 239.51 ± 0.15 Ma (Lower Kalkschieferzone, P. archelaus Zone). Our results suggest that the time interval including the vertebrate-bearing Middle Triassic section spans around 4 Myr and is thus significantly shorter than so far assumed. The San Giorgio Dolomite and the Meride Limestone correlate with intervals of the Buchenstein Formation and the Wengen Formation in the reference section at Bagolino, where the Global boundary Stratotype Section and Point (GSSP) for the base of the Ladinian was defined. The new radio-isotopic ages of the Meride Limestone are up to 2 Myr older than those published for the biostratigraphically-equivalent intervals at Bagolino but they are consistent with the recent re-dating of the underlying Besano Formation, also performed using the CA technique. Average sedimentation rates at Monte San Giorgio are by more than an order of magnitude higher compared to those assumed for the Buchenstein Formation, which formed under sediment-starved pelagic conditions, and reflect prevailing high subsidence and high carbonate mud supply from the adjoining Salvatore/Esino platforms. Finally, the high-resolution U–Pb ages allow a correlation of the vertebrate faunas of the Cava superiore/Cava inferiore beds with the marine vertebrate record of the Prosanto Formation (Upper Austroalpine), so far precluded by the poor biostratigraphic control of the latter.

Co-occurrence of Neusticosaurus edwardsii and N. peyeri (Reptilia) in the Lower Meride Limestone (Middle Triassic, Monte San Giorgio)

A newly opened excavation in the Cassina beds of the Lower Meride Limestone (Monte San Giorgio UNESCO World Heritage List, Canton Ticino, Switzerland), has yielded a pachypleurosaurid (Reptilia: Sauropterygia) specimen which is identified as Neusticosaurus peyeri. The resulting co-occurrence of N. peyeri and N. edwardsii, the latter so far regarded as the sole species of the genus present in this horizon, challenges the hypothesis of a single anagenetic lineage in Neusticosaurus species from Monte San Giorgio. In addition, it leads to a reconsideration of the phylogenetic inferences about Neusticosaurus evolution in the Monte San Giorgio area. The stratigraphic distribution of the Neusticosaurus species in the Monte San Giorgio basin is updated on the basis of recent finds.

Facies, depositional environment, and palaeoecology of the Middle Triassic Cassina beds (Meride Limestone, Monte San Giorgio, Switzerland)

The Ladinian Cassina beds belong to the fossiliferous levels of the world-famous Middle Triassic Monte San Giorgio Lagerstätte (UNESCO World Heritage List, Canton Ticino, Southern Alps). Although they are a rich archive for the depositional environment of an important thanatocoenosis, previous excavations focused on vertebrates and particularly on marine reptiles. In 2006, the Museo Cantonale di Storia Naturale (Lugano) started a new research project focusing for the first time on microfacies, micropalaeontological, palaeoecological and taphonomic analyses. So far, the upper third of the sequence has been excavated on a surface of around 40 m2, and these new data complete those derived from new vertebrate finds (mainly fishes belonging to Saurichthys, Archaeosemionotus, Eosemionotus and Peltopleurus), allowing a better characterization of the basin. Background sedimentation on an anoxic to episodically suboxic seafloor resulted in a finely laminated succession of black shales and limestones, bearing a quasi-anaerobic biofacies, which is characterized by a monotypic benthic foraminiferal meiofauna and has been documented for the first time from the whole Monte San Giorgio sequence. Event deposition, testified by turbidites and volcaniclastic layers, is related to sediment input from basin margins and to distant volcanic eruptions, respectively. Fossil nekton points to an environment with only limited connection to the open sea. Terrestrial macroflora remains document the presence of emerged areas covered with vegetation and probably located relatively far away. Proliferation of benthic microbial mats is inferred on the basis of microfabrics, ecological considerations and taphonomic (both biostratinomic and diagenetic) features of the new vertebrate finds, whose excellent preservation is ascribed to sealing by biofilms. The occurrence of allochthonous elements allows an insight into the shallow-waters of the adjoining time-equivalent Salvatore platform. Finally, the available biostratigraphic data are critically reviewed.

Exceptional preservation of embryos in the actinopterygian Saurichthys from the Middle Triassic of Monte San Giorgio, Switzerland

New excavations in the famous Monte San Giorgio area, close to the historical sites where the Cassina beds crop out (Lower Meride Limestone, Early Ladinian), revealed an interesting vertebrate fauna, including several specimens of the actinopterygian fish Saurichthys. Among the prepared specimens, three specimens of Saurichthys contain embryos, and in one example the embryos are preserved with traces of the soft parts, most probably phosphatized musculature. This discovery is of particular relevance because fossil embryos with preserved soft parts are extremely rare. In addition, although viviparity had previously been described for Saurichthys, the new specimens are rather better evidence and add further support to this reproductive mode.

A NEW EARLY SEMIONOTIDAE (SEMIONOTIFORMES, ACTINOPTERYGII) FROM THE UPPER LADINIAN OF MONTE SAN GIORGIO AREA SOUTHERN SWITZERLAND AND NORTHERN ITALY)

The early history of the Semionotiformes is still scarcely known as, apart from the Permian Acentrophorus , most of the Early and Middle Triassic taxa traditionally ascribed to this order are often poorly known and/or they actually belong to other groups. Sangiorgioichthys aldae gen. n. sp. n. is described from the Upper Ladinian Kalkschieferzone (Upper Meride Limestone) of the Monte San Giorgio area on specimens coming from both Italy and Switzerland. The new genus is ascribed to the family Semionotidae as it shows several of the characters usually considered as diagnostic of the family itself, even if no real synapomorphies have been so far proposed for it. As a Semionotidae, Sangiorgioichthys gen. n. has an almost complete circumorbital series, large ascending process of the premaxilla, rostral and nasals almost tube-like, short maxilla, several suborbital bones posterior and ventral to the infraorbitals, long antero-dorsal process of the suboperculum, sensory canal system very rich in pores, mid dorsal ridge scales with an incipient spine. Peculiar characters of the new genus are dermal skull bones completely covered by ganoine, a very large ventral infraorbital almost attaining the anterior edge of the preoperculum, two ‘ventral’ suborbitals, very elongate anterior supraorbital bone, dentition made of a number of tiny pencil-like teeth, anterior and posterior lateral line scales differentiated.

CAELATICHTHYS GEN. N.: A NEW PALAEONISCIFORM FROM THE MIDDLE TRIASSIC OF NORTHERN ITALY AND CANTON TICINO (SWITZERLAND)

A new genus of palaeonisciformes, Caelatichthys gen. n., is described on the basis of a well preserved material from the Kalkschieferzone (Meride Limestone) of Ca' del Frate (Viggiu, Varese) and Meride (Canton Ticino, Switzerland). This small sized fish, with elongate-fusiform body, is characterized by a dermosphenotic in contact with the ventral margin of the dermopterotic, the absence of contact of dermopterotic+dermosphenotic and the nasal bone, the lack of supraorbital bones, the presence of 4-5 infraorbital elements and small premaxilla meeting at the mid-line. Two species were recognized within this genus: C. nitens gen. n., sp. n. and C. meridensis gen. n. sp. n., each exclusive of a single locality. The two species differ in the development of dermal bone ornamentation, in specimens of the same size, and mainly in the pattern of the fulcra of the anal fin. This character cannot be ascribed to sexual dimorphism, as the two fishes showing the two kinds of anal fin were never found together in the same assemblage. The existence of two species of this new genus confirms the great variability of the faunal composition of the different fossiliferous levels of the Kalkschieferzone, with eight species described formally and other whose study is in progress. The good state of preservation of several specimens from Ca' del Frate also made it possible to reconstruct the growth stages of C. nitens n. gen. n. sp.

CTENOGNATHICHTHYS BELLOTTII (DE ALESSANDRI, 1910): NOMENCLATURAL PROBLEMS AND STRATIGRAPHICAL IMPORTANCE OF THIS MIDDLE TRIASSIC ACTINOPTERYGIAN FISH

The existence of one of the original specimens of Ctenognathichthys bellottii (De Alessandri 1910), figured and labelled as ‘type specimen’ by De Alessandri himself, raises a nomenclatural question as there is also a neotype designated by Burgin (1992). The International Commission of Zoological Nomenclature has been asked to rule on the validity of the neotype. As some of the requirements for the designation of a neotype were not met, the holotype should be treated as the name-bearing type. The discovery of this species in both the Besano Formation (Grenzbitumenzone Auct .) and the Perledo-Varenna Formation is very important from a stratigraphic point of view, confirming that the so called Perledo fish-fauna is composed of different assemblages. In fact, the Perledo fauna has most species in common with the Ca’ del Frate (Viggiu, Varese, Italy) fauna from the Kalkschieferzone (uppermost Meride Limestone), which is latest Ladinian in age, while a few of the Perledo species have been found also in the Grenzbitumenzone and/or in the lower Meride Limestone of Lower Ladinian age.