Madelaine Böhme

The Miocene Climatic Optimum: evidence from ectothermic vertebrates of Central Europe

Abstract Data sets of Central European temporal distributions of thermophilic ectothermic vertebrates (Channidae, Varanidae, Chamaeleonidae, Cordylidae, Tomistomidae, Alligatoridae, giant turtles) and of North Alpine Foreland Basin (NAFB) distributions of ectothermic vertebrates adapted to dryer habitats (Albanerpeton inexpectatum, Salamandra sansaniensis, Bufo cf. viridis, Chamaeleo caroliquarti, Gekkonidae, Varanus hofmanni, Bransateryx sp.) are analysed. Two main migration events of thermophilic ectotherms at 20 Ma and 18 Ma in the Lower Miocene are discerned. They indicate the beginning of the Miocene Climatic Optimum in Central Europe (42–45°N palaeolatitude) with a lower limit of the mean annual temperature (MAT) of 17.4°C derived from the minimal MAT of their extant relatives. Furthermore, additional palaeobotanical data and records of bauxite point to a MAT of 22°C. This warm and humid optimum peaked at 18–16.5 Ma (Ottnangian, Karpatian), and is confirmed by the coexistence of all investigated thermophilic taxa. The following period (Early Badenian) is characterised by probably unchanged temperatures but a seasonality in precipitation with dry periods up to six months. Two major seasonal phases between 16.3 and ∼15.7 Ma (earliest Early Badenian) and between 14.7 and ∼14.5 Ma (Early/Middle Badenian transition) are indicated by an immigration of dry adapted taxa from the surrounding karst plateau to the NAFB. It is presumed that the tectonical reorganisation of the Central Paratethys realm had considerable influence on this regional humidity pattern. The warm period ended abruptly between 14.0 and 13.5 Ma (Middle/Late Badenian transition) with major regional extinction events of most of the thermophilic groups in Central Europe and a drop of the MAT of probably more than 7°C to temperatures around 14.8–15.7°C. This drop can be attributed predominantly to a decrease of more than 11°C of the minimum cold months temperature. This temperature decrease marked the beginning of a climatic zonation of the European continent and is also evidenced by a progressively southward disappearance of the crocodile Diplocynodon from 38–45°N palaeolatitude to 30–37°N during the Middle and earliest Late Miocene. The results correlate well with palaeobotanical data from the mid-latitudes of Europe and North America, and the deep-sea temperature curve generated from oxygen isotope ratios.

Insectivores and bat (Mammalia) from the late Middle Miocene of Gratkorn (Austria): biostratigraphic and ecologic implications

The discovery of a late Sarmatian (latest Middle Miocene) small mammal fauna at the base of the clay pit St. Stefan near Gratkorn is of primary importance for the biostratigraphic and ecologic comprehension of the faunal evolution during the late Middle Miocene of Central Europe. In this paper five species of insectivores and one bat are described. The gymnure Schizogalerix voesendorfensis is the most abundant species of the small mammal fauna. The Gratkorn sample represents the earliest occurrence of the species in the fossil record. A single molar of a second, large-sized Galericinae cannot be attributed to any known species. The new talpid Desmanodon fluegeli n. sp. shares similarities with the Anatolian lineage D. minor / D. major. An exceptionally well preserved mandible of the large shrew Dinosorex cannot be determinate at the species level. In addition, some rare remains of the bat cf. Myotis sp. are also reported. From biogeographical point of view the insectivore fauna can be related to eastern Central European / Anatolian assemblages. Although taphonomic biases are suspected, the environmental conditions proposed on the basis of sedimentary analyzes (open forest with moist soil) can contribute to the low alpha diversity of insectivores in this locality.

The Antiquity of the Rhine River: Stratigraphic Coverage of the Dinotheriensande (Eppelsheim Formation) of the Mainz Basin (Germany)

Background Mammalian fossils from the Eppelsheim Formation (Dinotheriensande) have been a benchmark for Neogene vertebrate palaeontology since 200 years. Worldwide famous sites like Eppelsheim serve as key localities for biochronologic, palaeobiologic, environmental, and mammal community studies. So far the formation is considered to be of early Late Miocene age (∼9.5 Ma, Vallesian), representing the oldest sediments of the Rhine River. The stratigraphic unity of the formation and of its fossil content was disputed at times, but persists unresolved. Principal Findings Here we investigate a new fossil sample from Sprendlingen, composed by over 300 mammalian specimens and silicified wood. The mammals comprise entirely Middle Miocene species, like cervids Dicrocerus elegans, Paradicrocerus elegantulus, and deinotheres Deinotherium bavaricum and D. levius. A stratigraphic evaluation of Miocene Central European deer and deinothere species proof the stratigraphic inhomogenity of the sample, and suggest late Middle Miocene (∼12.5 Ma) reworking of early Middle Miocene (∼15 Ma) sediments. This results agree with taxonomic and palaeoclimatic analysis of plant fossils from above and within the mammalian assemblage. Based on the new fossil sample and published data three biochronologic levels within the Dinotheriensand fauna can be differentiated, corresponding to early Middle Miocene (late Orleanian to early Astaracian), late Middle Miocene (late Astaracian), and early Late Miocene (Vallesian) ages. Conclusions/Significance This study documents complex faunal mixing of classical Dinotheriensand fauna, covering at least six million years, during a time of low subsidence in the Mainz Basin and shifts back the origination of the Rhine River by some five million years. Our results have severe implications for biostratigraphy and palaeobiology of the Middle to Late Miocene. They suggest that turnover events may be obliterated and challenge the proposed ‘supersaturated’ biodiversity, caused by Middle Miocene superstites, of Vallesian ecosystems in Central Europe.

The pika Prolagus (Ochotonidae, Lagomorpha, Mammalia) in the late Middle Miocene fauna from Gratkorn (Styrian Basin, Austria)

Although the importance of pikas (Ochotonidae, Lagomorpha, Mammalia) in biostratigraphic and palaeoecologic purposes comes more and more to light, this family continues to be understudied in Austria and Central Europe in general. Two mandibles of the widespread and longliving genus Prolagus have been recently excavated from the new fossil locality Gratkorn. They are ascribed to Prolagus oeningensis, and represent the youngest occurrence of the genus in the Styrian Basin at around 12-12.2 Ma (Late Sarmatian s. str., late Middle Miocene). This discovery completes our knowledge on ochotonid evolution in the peri-Paratethyan area leading to hypothesize differences in the evolutionary history of P. oeningensis in central-eastern and Western Europe.

Snakes from Griesbeckerzell (Langhian, Early Badenian), North Alpine Foreland Basin (Germany), with comments on the evolution of snake faunas in Central Europe during the Miocene Climatic Optimum

ABSTRACT Two fossil-bearing levels at Griesbeckerzell (the central part of the North Alpine Foreland Basin; Early Badenian, Mittlere Serie of the Upper Freshwater Molasse) have produced a rich reptile fauna that includes a large number of snakes, i.e. Grisbeckerzell lb (OSM E, 15.0–14.9 Ma): Boidae: Python sp.; Colubridae: “Coluber” cf. caspioides; Vipendae: Vipera sp. (“oriental vipers” group) or Daboia sp.; Griesbeckerzell la (beginning of unit OSM F, 14.77 Ma): Boidae: Bavarioboa aff. hermi, cf. Bavarioboa sp., Python sp.; Colubridae: “Coluber” cf. caspioides, Coluber hungaricus, “Coluber” sp., Texasophis cf. meint, Natrix sp.; Elapidae: Micrurus cf. gallicus; Viperidae: Vipera sp. (“Oriental vipers” group), Vipera sp. (“European vipers” group; “Vipera aspis complex”). The Miocene Climatic Optimum (MCO) is documented in central Europe by the presence of highly thermophilous reptile taxa, including Python sp., which is the most thermophilous reptile known from the European Neogene. The presence of Python sp. in Griesbeckerzell 1 a pushes up the last appearance date (LAD) of this large Booidea in central Europe into the early Middle Miocene. The dramatic decrease in temperatures after 14.0 Ma (i.e. below 16°C in mean annual air temperature) was most probably responsible for the extinction of the European non-Erycinae Booidea, regardless of food competition. The genus Bavarioboa (Bavarioboa aff. hermi) and possibly “Coluber” caspioides (“Coluber” cf. caspioides) both have their LADs in Griesbeckerzell la; Coluber hungaricus probably represents the earliest appearance (FAD) of this colubrid snake. Palaeoclimatic analyses of the herpetofauna indicate for both Griesbeckerzell levels humid conditions of between 750 and 1 025 mm mean annual precipitation. Temperature estimates combined with palaeobotanical data indicate a warm, subtropical climate with mean annual temperatures of 18.6 to 20.8°C, cold month temperatures with 12.6 to 13.3°C, and warm month temperatures with 25.1 to 28.1°C.

Middle Miocene remains of Alytes (Anura, Alytidae) as an example of the unrecognized value of fossil fragments for evolutionary morphology studies

ABSTRACT. Fragmentary anuran remains (an ilium and radioulna) from the middle Miocene of Moratilla 2 (Teruel Province, Spain) are identified, using qualitative characters and geometric morphometrics, as belonging to a new unnamed species of midwife toad, of the extant anuran genus Alytes (Alytidae). The Moratilla 2 fossils of Alytes are dated to ca. 16–17 Ma, prior to the early splits that resulted in the current Alytes diversification. Our biometric study of the fossil radioulnar fragment, an element usually considered uninformative, has revealed convergent adaptive trends in forearm locomotor performance within the genus. This finding would have remained hidden otherwise, because neither molecular approaches nor the comparative osteology of living forms would have detected it. A model for the evolutionary history of midwife toads is proposed, as a case example of how molecular phylogeographic results can be combined with morphological and paleontological studies at the genus level. Historical models of morphological adaptation at low taxonomic and anatomical levels now seem feasible using quantitative reconstructions of fossil fragments. In the future, these models can be compared with independently derived data based on environmental history.

A new giant salamander (Urodela, Pancryptobrancha) from the Miocene of Eastern Europe (Grytsiv, Ukraine)

ABSTRACT We present new and well-preserved giant salamander material from the Miocene of the Grytsiv locality, Ukraine. Disarticulated skull and postcranial bones from two individuals are described as a new taxon, Ukrainurus hypsognathus, gen. et sp. nov. U. hypsognathus is characterized by poorly ossified bone tissues, relatively inflexible mandibles, a high dentary, a crista on the lingual surface of the dentary, a pars dentalis of the dentary that is composed of a dental lamina and a subdental surface, presence of an eminentia dorsalis on the squamosal, a broad pericondylar facet on the occipital, extremely elongated prezygapophyses, and hemal processes with an elongate, oval base. Moreover, U. hypsognathus shows evidence of strong mandibular levator muscles that indicate great biting force. A phylogenetic analysis of all well-understood Tertiary and Recent giant salamanders recovers a monophyletic group of Asian and North American cryptobranchids, but places U. hypsognathus outside crown group Cryptobranchidae. This result suggests that Cryptobranchidae originated in Asia and dispersed to North America. The oldest representative of crown Cryptobranchidae is Aviturus exsecratus from the terminal Paleocene of the Nemegt Basin, Mongolia.

Bio-magnetostratigraphy and environment of the oldest Eurasian hominoid from the Early Miocene of Engelswies (Germany).

The paleobiogeography of hominoids exhibits a puzzling pattern of migrations between and within Africa and Eurasia. A precise dating of hominoid-bearing localities is therefore essential to reveal the timing, direction and possible causes of dispersals. Here, we present a bio-magnetostratigraphic analysis of the section of Engelswies (Southern Germany, Upper Freshwater Molasse, North Alpine Foreland Basin) where the oldest Eurasian hominoid was found. Our paleomagnetic results reveal a very short normal and a reverse magnetic polarity for the entire section. The polarity record is correlated to the Astronomical Tuned Neogene Time Scale using an integrated stratigraphic approach. This approach follows the chronostratigraphic framework for the Upper Freshwater Molasse, which combines magnetostratigraphy with biostratigraphic, lithostratigraphic and (40)Ar/(39)Ar dating results. According to this outcome, the reverse polarity of the Engelswies section most likely correlates to magnetochron C5Cr. The origin of the short normal polarity remains enigmatic. The magnetostratigraphic calibration and the evolutionary level of the Engelswies small mammal fauna suggest an age of 17.1-17.0Ma (Early Karpatian, Early Miocene) for the oldest Eurasian hominoid, and roughly confirm the estimates of Heizmann and Begun (2001). The estimated age suggests that the first hominoids in Eurasia are contemporaneous with Afro-Arabian afropithecins, and dispersal may have been facilitated by intra-Burdigalian (∼18-17Ma) sea-level low stands and the beginning of the Miocene Climate Optimum. The paleoclimatic and environmental reconstruction of the Engelswies locality indicates a lakeshore environment near dense subtropical rain forest vegetation, where paratropical temperatures (mean annual temperature around 20°C) and humid conditions (mean annual precipitation>1.100mm) prevailed.

The late Middle Miocene (Sarmatian s.str.) fossil site Gratkorn - the first decade of research, geology, stratigraphy and vertebrate fauna

This article summarises the history of research, the geological background and the stratigraphy of the Gratkorn locality (SE Austria). Since its discovery in 2005, 65 vertebrate taxa, comprising fishes, amphibians, reptiles, birds, and small and large mammals have been documented, as well as a variety of plant and invertebrate fossils. Due to its origin from a rapidly accumulated floodplain paleosol, time-averaging is low and the taphocoenose reflects well the original vertebrate community. The Gratkorn site is dated by integrated stratigraphy, but independent from vertebrate biochronology, to about 12.2–12.0 Ma (late Middle Miocene). Thus, it probably yields the most diverse, systematically excavated vertebrate fauna of that age in Europe and is an extremely important benchmark for a vertebrate-based, continental biostratigraphy of the Central Paratethyan realm and beyond.

Pronounced Peramorphosis in Lissamphibians-Aviturus exsecratus (Urodela, Cryptobranchidae) from the Paleocene-Eocene Thermal Maximum of Mongolia

Background The oldest and largest member of giant salamanders (Cryptobranchidae) Aviturus exsecratus appears in the latest Paleocene (near the Paleocene–Eocene Thermal Maximum) of Mongolia. Based on femoral and vertebral morphology and metrics, a terrestrial adaptation has been supposed for this species. Methodology/Principal Findings A detailed morphological reinvestigation of published as well as unpublished material reveals that this salamander shows a vomerine dentition that is posteriorly shifted and arranged in a zigzag pattern, a strongly developed olfactory region within the cranial cavity, and the highest bone ossification and relatively longest femur among all fossil and recent cryptobranchids. Conclusions/Significance The presence of these characteristics indicates a peramorphic developmental pattern for Aviturus exsecratus. Our results from Av. exsecratus indicate for the first time pronounced peramorphosis within a crown-group lissamphibian. Av. exsecratus represents a new developmental trajectory within both fossil and recent lissamphibian clades characterized by extended ontogeny and large body size, resembling the pattern known from late Paleozoic eryopines. Moreover, Av. exsecratus is not only a cryptobranchid with distinctive peramorphic characters, but also the first giant salamander with partially terrestrial (amphibious) lifestyle. The morphology of the vomers and dentaries suggests the ability of both underwater and terrestrial feeding.