Federica Grandi

The Early Pliocene maar deposits of Camp dels Ninots (Catalonia, NE Iberia) have produced an exceptionally well-preserved fossil assemblage. Among the large mammals, a large bovid stands out, represented by 14 individuals, including 8 nearly complete and partially articulated skeletons. Here we provide a comprehensive description and systematic evaluation of this material, previously referred to Alephis tigneresi , including an in-depth comparison with specimens assigned to Parabos , Alephis , and other large Late Miocene and Early Pliocene Eurasian and African bovids. We revise the genera Alephis and Parabos , recognizing five valid species across both groups, and refer the Camp dels Ninots bovid to Parabos tigneresi . We further explore the possible relationships of Parabos and Alephis within Bovinae, finding that they could either be the earliest European representatives of stem Bovini or among the last surviving members of the Miocene Tragoportacini radiation. Additionally, the exceptionally preserved skeletons of P. tigneresi provide paleoecological evidence of adaptation to humid, vegetated environments, confirming reconstruction of the paleoenvironment of the Camp dels Ninots maar lake, while also showing traits associated with mixed to open habitats, suggesting potentially broad habitat preferences for P. tigneresi .

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).

The taphonomic study of two complete and anatomically connected individuals of Tapirus arvernensis from the Pliocene site of Camp dels Ninots (Caldes de Malavella, Spain) strengthens the attribution to a konservat-Lagerstätte deposit. The macroscopic analysis showed the absence of weathering, predation marks, and scarce superficial modification. Different surface colourations have been observed, highlighting white alteration. A selection of samples was analysed through ESEM-EDX, XRD and FTIR. Results suggest preservation of histological features and absence of microtunneling associated with biotic digestion of bioapatite. Specific white alteration of bone surfaces are attributed to a slightly different phase of the bone apatite, with higher crystallinity index and heavier loss in biogenic carbonates. Together with the presence of silicon-rich crusts and infillings that cover bone surfaces, it is now suspected that some interference of the volcanic activity that occurred in the past could have been responsible for an optimal preservation of the osteological material. A slow remineralisation could have been caused by hydrothermal activity still active in the area that caused the absence of bacterial activity in a lacustrine context and left the specimens undisturbed. These results could proportionate new data to understand fossil diagenetic mechanisms that could potentially allow exceptional preservation in maar contexts.