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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). [ABSTRACT FROM AUTHOR]

The Messel Pit is a Konservat-Lagerstätte in Germany, representing the deposits of a latest early to earliest middle Eocene maar lake, and one of the first palaeontological sites to be included on the list of UNESCO World Heritage Sites. One aspect of Messel that makes it so extraordinary is that its sediments are rich in different fossilised organisms – microfossils, plants, fungi, invertebrate animals and vertebrates – that are rarely preserved together. We present an updated list of all taxa, named or not, that have been documented at Messel, comprising 1409 taxa, which represent a smaller but inexactly known number of biological species. The taxonomic list of Labandeira and Dunne (2014) contains serious deficiencies and should not be used uncritically. Furthermore, we compiled specimen lists of all Messel amphibians, reptiles and mammals known to us. In all, our analyses incorporate data from 32 public collections and some 20 private collections. We apply modern biodiversity-theoretic techniques to ascertain how species richness tracks sampling, to estimate what is the minimum asymptotic species richness, and to project how long it will take to sample a given proportion of that minimum richness. Plant and insect diversity is currently less well investigated than vertebrate diversity. Completeness of sampling in aquatic and semiaquatic, followed by volant, vertebrates is higher than in terrestrial vertebrates. Current excavation rates are one-half to two-thirds lower than in the recent past, leading to much higher estimates of the future excavation effort required to sample species richness more completely, should these rates be maintained. Species richness at Messel, which represents a lake within a paratropical forest near the end of the Early Eocene Climate Optimum, was generally higher than in comparable parts of Central Europe today but lower than in present-day Neotropical biotopes. There is no evidence that the Eocene Messel ecosystem was a "tropical rainforest." [ABSTRACT FROM AUTHOR]

The Messel Pit is an ancient maar lake that preserves an ecosystem from the last greenhouse phase of Earth's climate with exceptional fidelity. There are two main competing hypotheses to explain the occurrence of animal fossils at Messel: asphyxiation in layers of heavy, toxic gases like carbon dioxide, and death following ingestion of surface water contaminated by cyanobacterial toxins. Both hypotheses imply mortality much higher than the null hypothesis of accidental death, for instance by drowning. We tested these hypotheses amongst bats by recourse to a unique survey on bats that drowned in modern swimming pools. We further conducted experiments on the fate of fresh bat carcasses that simulate drowning. Finally, we estimated the annual rate of bat fossil production at Messel. Overall, there are few good surveyed predictors of whether bats drown in swimming pools: most physical parameters like pool size or the height and distance of obstructions were not associated with mortality, although pool liner type would be a good candidate parameter for future study. In our experiments, carcasses with water-filled lungs tend to sink more quickly than those with air-filled lungs; all carcasses that initially sink "bloat and float" at shallow depths, but all floaters eventually disarticulate and sink within days to weeks. Our estimates of annual bat mortality at Palaeolake Messel are of the same order of magnitude as mortality in swimming pools. Mass mortality horizons for vertebrates are very rare at Messel. In sum, our quantitative analyses provide no evidence that bat mortality at Messel rises above background levels. [ABSTRACT FROM AUTHOR]

Palynological studies of lacustrine sediments in Eocene maar craters on the Sprendlinger Horst (Hesse, SW Germany) are complemented by 26 core samples from Groß-Zimmern. In addition, diatoms have been studied to assess palaeolimnological conditions. The palynomorph assemblage proves a middle Eocene age more or less coeval to the upper part of the nearby lacustrine succession at Messel. The core includes 33 m of massive to finely laminated bituminous shale abruptly following the underlying breccia of the diatreme filling. The lacustrine deposits are characterised by frequent mass movements and redeposition probably due to tectonic activity in combination with syn- and postsedimentary subsidence in the lake basin. Together with a diatom assemblage characteristic for shallow to moderately deep water, this indicates that the core was drilled in the area of a marginal syncline rather than in the centre of the basin. Freshwater conditions with low nutrient levels were inferred for Lake Groß-Zimmern from diatoms and coccal green algae. Despite the strong disturbance of the sedimentary record, results of cluster analysis and non-metric multidimensional scaling (NMDS) of the palynomorph assemblages can be compared to the undisturbed succession from Messel. This includes successional stages of the azonal vegetation in the crater area during an initial and early recolonisation phase as well as in the zonal vegetation, which are related to the reoccupation of the crater area by a thermophilic forest. Furthermore, slight changes of the climate can be inferred. [ABSTRACT FROM AUTHOR]

To reconstruct the palaeoenvironment and changes within the vegetation, 68 core samples were analysed palynologically from the lacustrine filling of the Eocene maar lake of Offenthal (Hesse, SW Germany). The lacustrine succession includes 16 m of clastic sediments overlain by 13 m of finely laminated bituminous shale. Based on a revised 40Ar/39Ar age of ~ 47.8 ± 0.3 Ma, the lacustrine filling at Offenthal can be dated as uppermost lower Eocene to lowermost middle Eocene which is almost coeval to part of the nearby lacustrine succession at Messel. Cluster and non-metric multidimensional scaling (NMDS) analyses of well-preserved palynomorph assemblages reveal successional stages during the recolonisation of the maar lake and its surroundings which are related to lithological changes. Furthermore, the palynomorph assemblages from Offenthal are compared with assemblages from Messel by NMDS analysis to find similarities and differences during the recolonisation of volcanically disturbed habitats in Central Europe during Paleogene greenhouse conditions. Based on the similar succession in the vegetation at both lakes, four different phases can be distinguished during recolonisation and reestablishment of the vegetation at these sites: (1) an initial phase, (2) a recolonisation phase, (3) a recovery phase, (4) a climax phase. [ABSTRACT FROM AUTHOR]

Several teiid specimens (frontal, vertebra, maxillae) are described from the late Eocene of Europe (MP17, Phosphorites du Quercy). The results of phylogenetic analyses confirm that these European Eocene fossils belong to teiid lizards and more specifically to the subfamily Tupinambinae. So far, the Paleogene record of teiids is limited to South America and no occurrence of crown teiids is known in Europe. This disjunct distribution of teiids during the Eocene suggests transatlantic dispersal and this possibility is discussed. The presence of teiids in the European fossil record is brief (limited to standard level MP17). The circumstances that prevented the persistence of an invading clade in Europe are examined. Ecological (e.g. biotic interactions) and/or demographic (Allee effect) processes may have been involved. [ABSTRACT FROM AUTHOR]

We analysed the sediment and small fish coprolites from the 140-m thick lacustrine sediments of the middle Eocene maar lake Messel using material from different outcrops and from the Research Drilling Project 2001 (RDP 2001). The microfauna and microflora of Lake Messel underwent detectable changes during the lake's existence. However, only few of these changes can be satisfyingly interpreted to date. We suggest a three-level ecozonation for the history of Lake Messel on the basis of our microfossil analyses. Our results are not in full concordance with the current geological interpretation of the sediments and thus may spark further investigation and discussion. [ABSTRACT FROM AUTHOR]

There have been only a few studies on squamates from the late Oligocene of Europe, resulting in significant gaps in our knowledge of the reptile faunas from the latest Paleogene. Here, we report on new late Oligocene fossil material from two German localities, Herrlingen 11 (MP 28) and Herrlingen 9 (MP 29). The material can be assigned to the following major clades: Iguanidae, Gekkota, Lacertidae, Amphisbaenia, and Anguimorpha. The iguanid material shows that this clade was much more widely distributed in the Oligocene of Europe than previously thought, and also represents the youngest known record of this clade for Eurasia and Africa, with the exception of Madagascar. Although very fragmentary, the gekkotan material appears to be more similar to early Miocene forms such as Euleptes or Gerandogekko, rather than to early Oligocene taxa like Cadurcogekko, as indicated by the small size and morphology. The resemblance of the gekkotan fossils to Miocene forms suggests potential faunal turnover prior to the Paleogene-Neogene transition. The amphisbaenian material is represented by several types; the first can be allocated to Blanidae based on tooth count and the presence of a small 4th and an enlarged 3rd tooth, which is a derived feature. The second type is attributed to Palaeoblanus. Other cranial material is assigned to Amphisbaenia indet. The lacertid material consists of several amblyodont forms such as Dracaenosaurus, Pseudeumeces and Mediolacerta, as typically seen in other Oligocene deposits from Europe, but also includes non-ambylodont taxa such as Plesiolacerta and an undetermined lacertid. Especially common among the material are anguimorphs, which are here represented by Ophisaurus and a form that appears identical to the French Oligocene taxon described as Dopasia coderetensis. Reinvestigation of the European Oligocene " Dopasia" (= Ophisaurus) shows that the taxa described as D. frayssensis and D. coderetensis are markedly different from the members of the clade Ophisaurus in the morphology of the posterior dentary region and that those taxa cannot be allocated to this genus. For this reason, we erected a new generic name: Ophisauromimus gen. nov. The composition of the Herrlingen fauna shows an interesting mix of ancient Paleogene and more modern Neogene faunal elements, while overall bearing many similarities to contemporaneous faunas from France. [ABSTRACT FROM AUTHOR]

The lower Eocene lacustrine sediments of the Messel fossil site in Germany yielded a very rich and diversified avifauna. Most of the well-preserved skeletons stem from small-sized birds, whereas complete specimens of larger avian species are rare. There exist, however, a number of isolated feet of larger birds, eight of which are described in the present study. Except for one, all of these specimens exhibit broken leg bones with missing ends, which suggests that they represent feeding remains of predators or scavengers. Crocodilians, which are very abundant and diversified in the fossil record of Messel, are the most likely candidates, and the preservation of the Messel feet corresponds well with that of unambiguous crocodilian feeding remains from the late Oligocene of Europe. The eight feet described in the present study belong to just as many different species, most of which are otherwise unknown in the fossil record of Messel. Except for one, all specimens probably are from terrestrial taxa. These fossils attest to a hidden diversity of medium-sized to large terrestrial birds in the Messel palaeoenvironment and a bias in the taphonomic composition of the bird community towards the remains of small to medium-sized avian species. [ABSTRACT FROM AUTHOR]

In this paper, part of the amphisbaenian fossil record from the european Eocene is revised. There is no evidence for the existence of amphisbaenian lizards in Europe or on other continents during the Late Cretaceous. Crown amphisbaenians were present in Europe in the early Paleocene and throughout the Paleogene, with the notable exception of the middle Eocene. In particular, they were not found at Messel. European fossil taxa previously assigned to the amphisbaenians are briefly reviewed, and a description of some representative specimens from the Eocene fossil record is presented: dentary and vertebrae from Mutigny (early Eocene, France) are referred to the North American genus Anniealexandria; fossils from the late Eocene of the Phosphorites du Quercy (France) are attributed to Blanidae, and they are the earliest secure occurrence of Blanidae in the fossil record; and dentaries and maxillae from Grisolles (middle-late Eocene, Paris Basin, France) are referred to a new species, Louisamphisbaena ferox. Global distribution of fossil amphisbaenians in the Eocene reveals at least one episode of dispersal between North America and Europe during the early Eocene. Finally, some explanations are suggested for the absence of crown amphisbaenians at Messel and in the European middle Eocene. [ABSTRACT FROM AUTHOR]