Olaf Höltke

Deep-time (=pre-Quaternary) maar lakes and certain other, hydrologically deep volcanogenic lakes, are often excellent Konservat-Lagerstätten representing unique windows into past biota and ecosystems. Many deposits from such lakes contain animal and plant remains in extraordinary preservation, often with soft tissues or fine morphological and anatomical details preserved. Such Lagerstätten have the potential to provide in-depth information on a variety of organisms, which is important for understanding their biology and ecology, their evolution and palaeobiogeography, but also for elucidating entire ecosystems with their numerous biotic and abiotic interactions. The formation of such Lagerstätten is intimately linked to volcanic processes, amongst which phreatomagmatic explosions that formed maar-diatreme volcanoes are probably the most important, but also other volcanic processes can lead to the formation of deep volcanogenic lakes (e.g. in certain calderas). Maar lakes and other volcanogenic Konservat-Lagerstätten occur in a large number of volcanically active regions worldwide, although older deposits are often difficult to access as they are more likely to be eroded or covered by younger deposits. The accessibility of many of the better-known localities is often connected to the mining of natural resources, ranging from diamonds, to volcanic rocks such as basalts to the lacustrine sediments that may have filled volcanic craters, including diatomites and ‘oil-shales’. Most or even all of the maar and other volcanogenic lakes presented here in greater detail, can be considered as important geoheritage sites. Although currently some of these deposits have at least some kind of legal protection as monuments of natural heritage, others remain in danger of being exploited commercially for natural resources and hence, ultimately destroyed. Moreover, many scientific questions related to these ancient lakes and their biota covered here in more detail, as well as those related to lakes only briefly mentioned in passing, have not been posed, let alone answered. This makes maar lakes and other volcanogenic lakes important resources for present-day and future research. The present contribution should be seen as a global call to scientists to find further localities that represent similar volcanogenic lacustrine settings, as they may be the source of vital and surprising new information about the plants, animals, and environments of the past. Examples of pre-Quaternary maar and other volcanogenic lakes that are presented here in greater detail include the following localities: Paleocene: Menat (France); Eocene: Messel, Eckfeld (Germany), Mahenge (Tanzania); Oligocene: Enspel, Rott, Hammerunterwiesenthal, Baruth, Kleinsaubernitz (Germany); Miocene: Foulden Maar, Hindon Maar Complex (New Zealand), Randeck Maar, Hirnkopf-Maar, Höwenegg, Öhningen (Germany); Pliocene: Ruppach-Goldhausen (Germany), Camp dels Ninots (Spain).

In recent years, new findings and new methods (stable isotopes of oxygen, zinc, and nitrogen; 2D and 3D modeling; and geometric morphometric analyses of the teeth) have enhanced our knowledge of the Neogene shark fauna and its paleobiology. Several papers deal with the large Otodus (Megaselachus) species, including the construction of a 3D model, as well as insights into its lifestyle and diet. In addition, the skeletal remains of Carcharias gustrowensis, Carcharodon hastalis, and Keasius parvus and a natural tooth set of Carcharodon hubbelli have been described in the last 13 years, and the dentition of the Neogene species Carcharoides catticus, Megachasma applegatei, and Parotodus benedenii has been reconstructed. Stable isotope analyses of the teeth from the Neogene species of Araloselachus, Carcharias, Carcharodon, Galeocerdo, Hemipristris, and Mitsukurina have given insights into the trophic positions of these genera during the Neogene, and shark teeth preserved near the skeletal remains of prey animals (mammals) and shark bite traces on these remains provide direct evidence of trophic interactions. The tooth shape, fossil locality, and paleoenvironment have been used to better understand the taxa Carcharhinus dicelmai, Megalolamna paradoxodon, Pachyscyllium dachiardii, and P. distans. Among extant species, Galeorhinus galeus can be traced back to the Eocene. Alopias superciliosus, Rhincodon typus, and possibly A. vulpinus can be traced back to the Oligocene. Species present by the Miocene include Alopias vulpinus, Carcharhinus amblyrhynchoides, C. amblyrhynchos, C. albimarginatus, C. amboinensis, C. brachyurus, C. brevipinna, C. falciformis, C. glaucus, C. leucas, C. limbatus, C. longimanus, C. macloti, C. obscurus, C. perezi, C. sealei, Centrophorus granulosus, Cetorhinus maximus, Dalatias licha, Deania calcea, Galeocerdo cuvier, Glyphis glyphis, Heptranchias perlo, Isurus paucus, Lamna nasus, Negaprion brevirostris, Odontaspis ferox, Pseudocarcharias kamoharai, Sphyrna media, S. mokarran, and possibly Carcharodon carcharias. First appearing in the Pliocene are Scymnodon ringens, Somniosus rostratus, and Zameus squamulosus. For some extant species (Carcharias taurus, Hexanchus griseus, Isurus oxyrinchus, Notorynchus cepedianus, and Sphyrna zygaena), it is not clear whether the assigned Neogene teeth represent the same species. The application of new methods to more fossil shark taxa, a detailed search for shark fossils, and better knowledge of the dentition of extant species (especially those with minute-sized teeth) will further enhance our knowledge of the evolution and paleobiology of sharks.

In the last years, new findings and new methods (stable isotopes of oxygen, zinc and nitrogen, 2D and 3D modelling, geometric morphometric analyses of the teeth) have enhanced our knowledge of the Neogene shark fauna and its palaeobiology. Several papers deal with the large Otodus (Megselachus) species, including the construction of a 3D model as well as insights into lifestyle and diet. In addition, skeletal remains of Carcharias gustrowensis, Carcharodon hastalis, Keasius parvus and a natural tooth set of Carcharodon hubbelli have been described in the last 13 years, and the dentition of the Neogene species Carcharoides catticus, Megachasma applegatei and Parotodus benedenii have been reconstructed. Stable isotope analyses of the teeth from the Neogene species of Araloselachus, Carcharias, Carcharodon, Galeocerdo, Hemipristris, and Mitsukurina have given insights into the trophic position of these genera during the Neogene, and shark teeth preserved near skeletal remains of prey animals (mammals) and shark bite traces on these remains provide direct evidence of trophic interactions. Tooth shape, fossil locality and palaeoenvironment have been used to better understand the taxa Carcharhinus dicelmai, Megalolamna paradoxodon, Pachyscyllium dachiardii and P. distans. Among extant species, Galeorhinus galeus can be traced back to the Eocene. The following taxa can be traced back to the Oligocene: ?Alopias superciliosus, and Rhincodon typus. Species already present in the Miocene include: Alopias vulpinus, Carcharhinus amblyrhynchoides, C. amblyrhynchos, C. albimarginatus, C. amboinensis, C. brachyurus, C. brevipinna, C. falciformis, C. glaucus, C. leucas, C. limbatus, C. longimanus, C. macloti, C. obscurus, C. perezi, C. sealei, ?Carcharodon carcharias, Centrophorus granulosus, Cetorhinus maximus, Dalatias licha, Deania calcea, Galeocerdo cuvier, , Glyphis glyphis, Heptranchias perlo, Isurus paucus, Lamna nasus, Negaprion brevirostris, Odontaspis ferox, Pseudocarcharias kamoharai, Sphyrna media, S. mokarran. First appearing in the Pliocene are: Scymnodon ringens, Somniosus rostratus, Zameus squamulosus. For some extant species (Carcharias taurus, Hexanchus griseus, Isurus oxyrinchus, Notorynchus cepedianus, Sphyrna zygaena) it is not clear if the assigned Neogene teeth represent the same species. Applying these new methods to more fossil shark taxa, a detailed search for shark fossils, as well as better knowledge of the dentition of extant species (especially those with minute-sized teeth) will further enhance knowledge of the evolution and palaeobiology of sharks.

The silvana-beds are the main component of the Upper Freshwater Molasse (“Obere Süßwassermolasse” or OSM) in southern Germany, Austria and Switzerland, named after the land snail Palaeotachea silvana (Klein, 1853). After initial disputes in the literature, in the 1920’s, malacologist Wilhelm Wenz better defined the silvana-beds lithology and its three informal subunits based on terrestrial gastropods. The silvana-beds mainly consist of limestone, marl and clay, eventually with sandy components. Despite remaining an informal stratigraphical unit, the silvana-beds is a practical tool for stratigraphic determination in the field and for paleomalacology studies. Information about the land snail communities of the silvana-beds are scattered in the literature and museum collections. Therefore, here we compile all this information and conduct a detailed biogeographic comparison of these localities’ snail faunas, based on similarity indices. For that purpose, all communities (containing at least six terrestrial gastropod species, from a total of 28 localities) within the silvana-beds and the adjoining coeval Bad Urach volcanic region were analyzed, based on four similarity indices and follow-up cluster analyses. The land snail communities of the silvana-beds formed six clusters (defined by ca. 50% similarity) according to the Sørensen-Dice index, five clusters by the Kulczynski and Ochiai indices, and four ones by the Simpson index. Despite some differences in the resulting dendrograms, enough similarity in the clustering was found for a meaningful comparison. The resulting clusters can be largely explained by geographic position, as is the case of the two main groupings recovered, representing the German Bavarian and Baden-Württemberg states. Some inconsistencies in the composition of the clusters might be explained by different stratigraphic positions within the silvana-beds, distinct paleoenvironmental conditions influencing the faunal composition, or the absence of key species.

In an abandoned sand pit near Ballendorf (Alb-Donau District, Baden-Württemberg, sediments of the Upper Marine Molasse (Lower Miocene) are present. In these sediments, 30 shark and ray genera were identified (Aetobatus, Alopias, Araloselachus, Carcharhinus, Carcharias, Centrophorus, Chaenogaleus, Dasyatis, Galeocerdo, Hemipristis, Iago, Isistius, Isogomphodon, Keasius, Notorynchus, Pachyscyllium, Paragaleus, Physogaleus, Pristiophorus, Raja, Rhinobatos, Rhinoptera, Rhizoprionodon, Rhynchobatus, Scyliorhinus, Sphyrna, Squalus, Squatina, Taeniurops, Triakis). However, in this paper we only illustrate and describe the 23 taxa not already discussed in previous publications on the Upper Marine Molasse deposits of Äpfingen, Rengetsweiler and Ursendorf, apart from two exceptions: teeth from jaw positions not previously illustrated, and specimens that are better preserved than those in the previous publications. Specimens only determined as “sp.” were illustrated because it cannot be ruled out that they represent different species to the ones published earlier. Nearly all of the taxa found have recent relatives, only Araloselachus, Keasius and Physogaleusare extinct. Most of the recovered taxa lived on or near the bottom in the shelf region. Alopias and possibly also Keasius lived higher in the water column. With Isistius, a taxon living in the oceanic realm was present, and the Recent representatives of Centrophorus live in deeper waters. Nearly all taxa fed on invertebrates and/or fishes; Isistius also fed as an ectoparasite. Additionally, two generalist feeders (Galeocerdo, Notorynchus) and one filter feeder (Keasius) were identified. The species Carcharias crassidens, which is not common in the Upper Marine Molasse, was also verified. Other fossils which were found in this deposit are remnants of odontocete cetaceans, molluscs, balanid barnacles, algae, and teeth of terrestrial mammals. The palaeoenvironment was a warm, shallow water habitat. Based on greater proximity to the palaeo-coastline, the water depth was probably less than in other Upper Marine Molasse deposits.

Herein, we revise an extensive set of mollusc fossils from the Upper Freshwater Molasse deposits of Öhningen palaeolake (SW Germany; Middle Miocene, MN7). Based on material housed in paleontological collections in Europe and North America, we present the first thorough systematic account of the phylum from this historic locality. A total of ten species were identified from Öhningen: three freshwater gastropods (Lymnaea dilatata Noulet, 1854, Gyraulus cf. applanatus (Thomä), Planorbarius mantelli (Dunker)), two terrestrial gastropods (Granaria cf. schuebleri (Klein), Palaeotachea sylvestrina (Schlotheim)), and five bivalves (Anodonta splendens Goldfuss, A. lavateri (Münster), Pseudunio flabellatus (Goldfuss), “Dreissena” sp., Pisidium escheri (Mayer-Eymar, 1865)). Three freshwater and five terrestrial gastropod genera mentioned in older literature could not be found in the available material. Ours is the first report of a Dreissenidae from Öhningen.

The Randeck Maar lake sediments from SW Germany were deposited during a climatic phase known as the Mid‐Miocene Climatic Optimum, providing a unique window into this last favourable period for a more thermophilous fauna in Central Europe. Previous palaeoecological reconstructions of Randeck Maar's environment focused on the flora and vertebrate fauna. Here, we present a palaeoecological analysis using gastropods as proxies by means of an actualistic genus‐level approach. This approach is grounded in comparisons of habitat preferences between extant and fossil congeners and thus obviously requires a sound taxonomic framework. Despite being commonly applied in the literature, this approach has hardly been defined so far. Therefore, we thoroughly delineate it, exploring its applicability, potential and shortcomings. The molluscan fauna of Randeck Maar counts with 32 species of continental snails, mostly terrestrial pulmonates, related to the following palaeohabitats: littoral, supralittoral, rocky walls, shrubland, forests and open habitats. The gastropods indicate a warm‐temperate climate with a dry season, in line with previous works on Randeck Maar's flora and vertebrates.

Here is given an account, based on museum collections, of the fossil land and freshwater gastropods from Dischingen (Baden-Württemberg state, SW Germany). The fossiliferous outcrops belong to the Silvana Beds unit of the Upper Freshwater Molasse group, of late Early to early Middle Miocene age (Neogene European Land Mammal Zone MN 5). In total, 35 gastropod species were found (seven freshwater and 28 terrestrial), mainly belonging to Pulmonata, but also with representatives of Neritimorpha and Caenogastropoda. Seven species are reported here for the first time from Dischingen: Palaina diezi, Radix socialis, Granaria sp., Serrulina? sp., Discus pleuradrus, Punctum pumilio, and Oxyloma minima.

Herein we present an account of the fossil terrestrial and freshwater gastropods from the locality of Hohenmemmingen (Baden-Württemberg state, SW Germany) based on museum collections. The fossil outcrops belong to the Silvana Beds of the Upper Freshwater Molasse, being of Early/Middle Miocene age. In total, 23 gastropod species, all pulmonates, are documented in the material (whereas 33 species had been previously reported in the literature): five freshwater species and 18 terrestrial. From an actualistic palaeoecological approach, this palaeoevironment featured a humid and warm forest cover, with a well-vegetated and likely shallow water body.