Randeck Maar Research Articles

Gastropod palaeohabitats of Miocene Lake Randeck Maar and its hinterland defined by an actualistic genus‐level approach

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.

Fossil gastropods from Miocene Lake Randeck Maar and its hinterland (SW Germany)

Fossil gastropods from Miocene Lake Randeck Maar and its hinterland (SW Germany)

The salamandrid Chelotriton paradoxus from Enspel and Randeck Maars (Oligocene–Miocene, Germany)

The late Paleogene to early Neogene salamander Chelotriton paradoxus is redescribed on the basis of new and excellent material from two deposits, the late Oligocene Enspel locality and the Miocene Randeck Maar. C. paradoxus is characterised by the following features: (1) skull outline broad and parabolic, (2) snout abbreviated, with nasal only half the length of the frontal, (3) quadratojugal with a series of 3–5 spikes on the lateral margin, and (4) osteoderms larger than in other genera. Like extant Echinotriton, its trunk ribs bear extensive spikes (epipleural processes), with an elongated one on the 3rd rib. The Enspel sample of C. paradoxus shows greater variation in the size and number of quadratojugal spikes, whereas the best-preserved Randeck specimen bears exceptionally tall tubercles on all dermal bones and osteoderms and has a larger quadratojugal. Based on preliminary taphonomical data, we suggest that C. paradoxus probably led a predominantly aquatic life.

The Miocene Randeck Maar (SW Germany): Geological compilation and census of scientific excavations

The Randeck Maar belongs to the Urach-Kirchheim Volcanic Field in south-western Ger- many. It represents an ancient volcanic crater of phreatomagmatic origin that contains lake deposits of Early/Middle Miocene age (MN5). It is a Fossillagerstatte with remarkably well-preserved fossils, particularly plants, insects, and amphibians. In contrast to former studies, we suggest that the topo- graphic relief of the crater was up to 220 m. Since the exploration for fuel by O. Fraas in the middle of the 19 th century, eight excavations took place in the Randeck Maar which are summarised here for the first time.

The Randeck Maar: Palaeoenvironment and habitat differentiation of a Miocene lacustrine system

The Randeck Maar in S. Germany is a well-known fossil lagerstätte with exceptionally preserved fossils, particularly insects and plants, which thrived in and around the maar lake during the Mid-Miocene Climatic Optimum (late Early/early Middle Miocene, mammal zone MN5). We provide the first critical and detailed overview of the fauna and flora with lists of 363 previously published, partially revised, and newly identified taxa. Plant remains are the most diverse group (168 taxa), followed by insects (79). The flora points towards subhumid sclerophyllous forests and mixed mesophytic forests, the former being an indication for the occurrence of seasonal drought. Three main sections can be differentiated for the habitats of the Randeck Maar lake system: (1) Deep- and open-water lake habitats with local and short-termed mass occurrences of insect larvae, amphibians, and/or gastropods, while fish is particularly scarce. The interpretation of the water chemistry is problematic because contradictive palaeoenvironmental indicators for both brackish and freshwater conditions exist. (2) Shallow parts of the lake comprise a narrow reed-belt with insects and gastropods living on the exposed plant stems as well as turtles. (3) Crater slopes and surrounding plateaus were mainly covered by subhumid sclerophyllous to mixed mesophytic forests depending on sun exposition and soil conditions. Horses and other forest-dwellers preferably lived in forested habitats while proboscideans and rhinoceratids occupied more open habitats. Our study also brings up contradictive results that cannot be untangled with the current state of knowledge and thus directions for future studies are discussed.

Ein neues Sedimentprofil vom Randecker Maar (Unter-/Mittelmiozän, Schwäbische Alb)

Ein neues Sedimentprofil vom Randecker Maar (Unter-/Mittelmiozän, Schwäbische Alb)

A new salamandrid from the Miocene Randeck Maar, Germany

ABSTRACT A new species of salamandrid is named and described from the Miocene of Randeck Maar, a long-term volcanic lake deposit in southern Germany. Based on a fully articulated specimen, Ichthyosaura randeckensis is named and described as a 3–4 cm long newt with a robust posterolateral process of the frontal, a heavily ornamented skull roof, and a premaxilla with spike-like, parallel alary processes framing a slender fontanelle posteriorly. In a phylogenetic analysis of 14 salamandrid taxa and 38 morphological characters, I. randeckensis is found to nest with I. alpestris, with which it shares apomorphic character states in the morphology of premaxilla and nasal. The present analysis employed more morphological characters than hitherto considered, highlighting the need to conduct more osteological studies of extant salamanders. Its results are largely consistent with recent molecular phylogenetic studies: Tylototriton and Pleurodeles form a clade, with Notophthalmus and Euproctus falling within unresolved trichotomies, followed by Cynops and Ommatotriton as successive crownward clades, then Triturus sensu stricto (T. marmoratus and T. cristatus), and finally Lissotriton and Ichthyosaura as terminal sister taxa. SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP

Geometric morphometric analysis of a new Miocene bumble bee from the Randeck Maar of southwestern Germany (Hymenoptera: Apidae)

The first fossil bumble bee (Apinae: Bombini) from the Miocene Randeck Maar of southwestern Germany is described and illustrated. The specimen is subjected to a geometric morphometric analysis along with a diversity of other bumble bee species representing most major extant lineages, and particularly the subgenus Bombus s.s. The morphometric analysis supports the placement of the Randeck Maar species within Bombus s.s., as a species distinct from all others in the subgenus. It shows that extant subgenera of bumblebees were already derived in the early/middle Miocene. The Randeck Maar fossil is formally described as Bombus (Bombus) randeckensis Wappler & Engel sp. n..

Case 3544ApisarmbrusteriZeuner, 1931 (Insecta, Hymenoptera): proposed conservation by designation of a neotype

The purpose of this application, under Article 75.5 of the Code, is to conserve the name Apis armbrusteri Zeuner, 1931 for a species of fossil honey bee occurring in the Miocene fauna of southwestern Germany. The holotype is the hollow impression of a bee from the Early Miocene Böttingen Marmor and, aside from attributing the taxon to the tribe apini, no details regarding its specific identity can be gleaned from this specimen. Nonetheless, this name has been universally applied to the Early Miocene honey bees from Böttingen Marmor and the related contemporaneous site from the same crater series, Randeck Maar, since Zeuner & Manning (1976). Although A. armbrusteri is recognised as a nomen dubium, to resurrect the unused specific epithet Apis scheuthlei (Armbruster, 1938) for these bees would be counter to current usage and would destabilise a voluminous literature on honey bee evolution and ecology. It would also threaten the subgeneric name Cascapis Engel, 1999 as A. armbrusteri sensu Zeuner & Manning (1976), i.e. based on the Randeck Maar material, is its type species by original designation. Accordingly, it is proposed that the unidentifiable holotype be set aside and one of the more exquisitely preserved and easily diagnosable specimens from this same fauna be designated as neotype, thereby stabilising the honey bee taxonomy and bringing the application of the name A. armbrusteri in line with universal current usage.

Miocene honey bees from the Randeck Maar of southwestern Germany (Hymenoptera, Apidae)

The Miocene Randeck Maar (southwestern Germany) is one of the only sites with abundant material of fossil honey bees. The fauna has been the focus of much scrutiny by early authors who recognized multiple species or subspecies within the fauna. The history of work on the Randeck Maar is briefly reviewed and these fossils placed into context with other Tertiary and living species of the genus Apis Linnaeus (Apinae: Apini). Previously unrecorded specimens from Randeck Maar were compared with earlier series in an attempt to evaluate the observed variation. A morphometric analysis of forewing venation angles across representative Recent and Tertiary species of Apis as well as various non-Apini controls was undertaken to evaluate the distribution of variation in fossil honey bees. The resulting dendrogram shows considerable variation concerning the wing venation of Miocene Apini, but intergradation of other morphological characters reveals no clear pattern of separate species. This suggests that a single, highly variable species was present in Europe during the Miocene. The pattern also supports the notion that the multiple species and subspecies proposed by earlier authors for the Randeck Maar honey bee fauna are not valid, and all are accordingly recognized as Apis armbrusteri Zeuner.

Forewing venation angle measurements

The Miocene Randeck Maar (southwestern Germany) is one of the only sites with abundant material of fossil honey bees. The fauna has been the focus of much scrutiny by early authors who recognized multiple species or subspecies within the fauna. The history of work on the Randeck Maar is briefly reviewed and these fossils placed into context with other Tertiary and living species of the genus Apis Linnaeus (Apinae: Apini). Previously unrecorded specimens from Randeck Maar were compared with earlier series in an attempt to evaluate the observed variation. A morphometric analysis of forewing venation angles across representative Recent and Tertiary species of Apis as well as various non-Apini controls was undertaken to evaluate the distribution of variation in fossil honey bees. The resulting dendrogram shows considerable variation concerning the wing venation of Miocene Apini, but intergradation of other morphological characters reveals no clear pattern of separate species. This suggests that a single, highly variable species was present in Europe during the Miocene. The pattern also supports the notion that the multiple species and subspecies proposed by earlier authors for the Randeck Maar honey bee fauna are not valid, and all are accordingly recognized as Apis armbrusteri Zeuner.

A NEW FOSSIL HOVERFLY (INSECTA, DIPTERA: SYRPHIDAE) FROM THE RANDECK MAAR (EARLY MIOCENE, SOUTH-WEST GERMANY)

Abstract: Helophilus nothobombus sp. nov. (Diptera: Syrphidae) is described from Early Miocene lake sediments of the Randeck Maar (Swabian Alb, south-west Germany) and compared to other fossil species of the genus. Helophilus primarius Germar, 1837 and Helophilus villeneuvi Théobald, 1937 do not show diagnostic features that allow assignment to the genus Helophilus or even to the tribe Eristalini. Helophilus miocaenicus (Stackelberg, 1925) and H. nothobombus thus are the only plausible fossil species of the genus. The rat-tailed maggots of Helophilus most probably were part of the biocoenosis of the shores of the Randeck Maar lake. The frequency of larvae of Stratiomyidae shows that there were also suitable habitats for species of Helophilus and related genera.

Bemerkungen zur Sedimentation, Flora und dem Paläoklima des Randecker Maars (Unter-/Mittel-Miozän, Schwäbische Alb)

Bemerkungen zur Sedimentation, Flora und dem Paläoklima des Randecker Maars (Unter-/Mittel-Miozän, Schwäbische Alb)