Measurements of gastropods shell sizes from 23 fossil and extant long-lived lakes

Aim: To investigate shell size variation among gastropod faunas of fossil and recent long-lived European lakes and discuss potential underlying processes. Location: 23 long-lived lakes of the Miocene to Recent of Europe. Methods: Based on a dataset of 1412 species of both fossil and extant lacustrine gastropods, we assessed differences in shell size in terms of characteristics of the faunas (species richness, degree of endemism, differences in family composition) and the lakes (surface area, latitude and longitude of lake centroid, distance to closest neighbouring lake) using multiple and linear regression models. Because of a strong species-area relationship, we used resampling to determine whether any observed correlation is driven by that relationship. Results: The regression models indicated size range expansion rather than unidirectional increase or decrease as the dominant pattern of size evolution. The multiple regression models for size range and maximum and minimum size were statistically significant, while the model with mean size was not. Individual contributions and linear regressions indicated species richness and lake surface area as best predictors for size changes. Resampling analysis revealed no significant effects of species richness on the observed patterns. The correlations are comparable across families of different size classes, suggesting a general pattern. Main conclusions: Among the chosen variables, species richness and lake surface area are the most robust predictors of shell size in long-lived lake gastropods. Although the most outstanding and attractive examples for size evolution in lacustrine gastropods derive from lakes with extensive durations, shell size appears to be independent of the duration of the lake as well as longevity of a species. The analogue of long-lived lakes as 'evolutionary islands' does not hold for developments of shell size because different sets of parameters predict size changes.

Phenotypic evolution in a fossil gastropod species lineage: evidence for adaptive radiation?

Detecting speciation in the fossil record is a particularly challenging matter. Palaeontologists are usually confronted with poor preservation and limited knowledge on the palaeoenvironment. Even in the contrary case of adequate preservation and information, the linkage of pattern to process is often obscured by insufficient temporal resolution. Consequently, reliable documentations of speciation in fossils with discussions on underlying mechanisms are rare. Here we present a well-resolved pattern of morphological evolution in a fossil species lineage of the gastropod Melanopsis in the long-lived Lake Pannon. These developments are related to environmental changes, documented by isotope and stratigraphical data. After a long period of stasis, the ancestral species experiences a phenotypic change expressed as shift and expansion of the morphospace. The appearance of several new phenotypes along with changes in the environment is interpreted as adaptive radiation. Lake-level high stands affect distribution and availability of habitats and, as a result of varied functional demands on shell geometry, the distribution of phenotypes. The on-going divergence of the morphospace into two branches argues for increasing reproductive isolation, consistent with the model of ecological speciation. In the latest phase, however, progressively unstable conditions restrict availability of niches, allowing survival of one branch only.

Occurrence of mammalia relicts at site Nörre-Lyngby

Investigations at a Late Weichselian freshwater basin in northwestern Jutland, Denmark, yielded a fairly rich assemblage of vertebrate remains, mostly bones and teeth of small mammals. The remains are primarily allochthonous and the bones have been subjected to different taphonomic pathways and agents. AMS 14C-dates on terrestrial organic remains provided ages of Middle to Late Allerød time. Identifications revealed the first fossil record in Scandinavia of Rana arvalis, Sorex minutus, Ochotona cf. pusilla, Microtus gregalis, Microtus oeconomus, and Sicista cf. betulinu. Spermophilus cf. major and Desmana moschata, previously found only once and twice respectively, were retrieved, and Sorex araneus and Arvicola terrestris were recovered for the first time beyond the Atlantic chronozone. Ecologically, the Nørre Lyngby small mammal fauna can be characterized by its very high and almost equal proportions of boreal forest and steppe elements followed by a relatively high proportion of tundra elements. The fossil species share a modern area of sympatry north of the Caspian Sea from the river Volga in the west to the southern and western slopes of the Urals. If, however, the large Allerød mammals are added, the fauna is without modern analogues. The Nørre Lyngby fauna can be seen as a last expansion of the North European glacial fauna. Provided that an absolute chronology and a differentiated sea-level curve for the area can be established, the Nørre Lyngby fauna could become important for studies in mammalian dispersal and migration rates.

Late Miocene palaeoflora and palaeoclimate of Lincang (China)

The Miocene Lincang leaf assemblage is used in this paper as proxy data to reconstruct the palaeoclimate of southwestern Yunnan (SW China) and the evolution of monsoon intensity. Three quantitative methods were chosen for this reconstruction, i.e. Leaf Margin Analysis (LMA), Climate Leaf Analysis Multivariate Program (CLAMP), and the Coexistence Approach (CA). These methods, however, yield inconsistent results, particularly for the precipitation, as also shown in European and other East Asian Cenozoic floras. The wide range of the reconstructed climatic parameters includes the Mean Annual Temperature (MAT) of 18.5-24.7 °C and the Mean Annual Precipitation (MAP) of 1213-3711 mm. Compared with the modern Lincang climate (MAT, 17.3 °C; MAP, 1178.7 mm), the Miocene climate is slightly warmer, wetter and has a higher temperature seasonality. A detailed comparison on the palaeoclimatic variables with the coeval Late Miocene Xiaolongtan flora from the eastern part of Yunnan allows us to investigate the development and interactions of both South Asian and East Asian monsoons during the Late Miocene in southwest China, now under strong influence of these monsoon systems. Our results suggest that the monsoon climate has already been established in southwest Yunnan during the Late Miocene. Furthermore, our results support that both Southeast Asian and East Asian monsoons co-occurred in Yunnan during the Late Miocene.

Determination of ages and fossil Coleoptera fauna from eight sites in the London region

These data sets report the fossil beetle assemblages identified from the Mesolithic to Late Bronze Age at eight sites in the London region. All but one of the study sites are within 2 km of the modern course of the Thames. The sites produced 128 faunal assemblages that yielded 218 identified species in 41 families of Coleoptera (beetles).  Beetle faunas of Mesolithic age indicate extensive wetlands near the Thames, bordered by rich deciduous woodlands. The proportion of woodland species declined in the Neolithic, apparently because of the expansion of wetlands, rather than because of human activities. The Early Bronze Age faunas contained a greater proportion of coniferous woodland and aquatic (standing water) species. An increase in the dung beetle fauna indicates the presence of sheep, cattle and horses, and various beetles associated with crop lands demonstrate the local rise of agriculture, albeit several centuries after the beginnings of farming in other regions of Britain. Late Bronze Age faunas show the continued development of agriculture and animal husbandry along the lower Thames. About 33% of the total identified beetle fauna from the London area sites have limited modern distributions or are extinct in the U.K. Some of these species are associated with the dead wood found in primeval forests; others are wetland species whose habitat has been severely reduced in recent centuries. The third group is stream-dwelling beetles that require clean, clear waters and river bottoms.

Fossil record of foraminifera and ostracoda from the Elsterian-Saalian-Interglacial in Schleswig-Holstein, Germany

Die in den Ablagerungen des marinen Elster-Saale-Interglazials (= Holstein-See = Stör-Meer) gefundenen und als autochthon betrachteten Foraminiferen und Ostrakoden kommen alle noch rezent vor. In vielen Proben wurden daneben aus dem Tertiär und der Oberkreide aufgearbeitete Foraminiferen gefunden. In den Proben aus Muldsberg, Albersdorf und Esbjerg konnte eine gleichgerichtete Faunen-veränderung vom Liegenden zum Hangenden beobachtet werden. Die Formen der jeweils unteren Proben gehören subarktischen bis hochborealen Temperaturen, etwa vollmarinem Milieu und mindestens 30 m Wassertiefe an. Ins Hangende hinein wurde nach Foraminiferen und Ostrakoden das Meer flacher, wärmer und brackischer, bis es schließlich in den obersten Proben wattähnliche Verhältnisse mit wahrscheinlich etwas geringerer Temperatur als am heutigen südlichen Nordseerand erreichte. Diese Beobachtung stimmt überein mit den von GRAHLE (1936) an Mollusken gewonnenen Erkenntnissen und den Schlüssen, die andere Bearbeiter aus einzelnen Mikrofaunen zogen. Es wurde versucht, die Faunen der restlichen Aufschlüsse in das oben erwähnte Schema einzuordnen. Dies gelang nur in zwei Fällen nicht. In Oldenhütten ist das Versagen wahrscheinlich auf unentwirrte Lagerungsstörungen zurückzuführen, in der Austernbank Tarbek liegen abweichende fazielle Verhältnisse vor. Die restlichen Aufschlüsse zeigen, daß aus den vom Eis gestörten Sedimenten doch oft ein sinnvolles Bild rekonstruiert werden kann. Die im kälteren Teil der Holstein-See auftretende Foraminifere Elphidium subarcticum CUSHMAN scheint in den Absätzen des schleswig-holsteinischen Eem-Meeres zu fehlen.

Major, trace element and XRF data for sediments and fish tooth samples, from a shallow marine setting with varying redox conditions (Site U1356, Wilkes Land Margin, E.Antarctica)

Fossil fish teeth from pelagic open ocean settings are considered a robust archive for preserving the neodymium (Nd) isotopic composition of ancient seawater. However, using fossil fish teeth as an archive to reconstruct seawater Nd isotopic compositions in different sedimentary redox environments and in terrigenous-dominated, shallow marine settings is less proven. To address these uncertainties, fish tooth and sediment samples from a middle Eocene section deposited proximal to the East Antarctic margin at Integrated Ocean Drilling Program Site U1356 were analyzed for major and trace element geochemistry, and Nd isotopes. Major and trace element analyses of the sediments reveal changing redox conditions throughout deposition in a shallow marine environment. However, variations in the Nd isotopic composition and rare earth element (REE) patterns of the associated fish teeth do not correspond to redox changes in the sediments. REE patterns in fish teeth at Site U1356 carry a typical mid-REE-enriched signature. However, a consistently positive Ce anomaly marks a deviation from a pure authigenic origin of REEs to the fish tooth. Neodymium isotopic compositions of cleaned and uncleaned fish teeth fall between modern seawater and local sediments and hence could be authigenic in nature, but could also be influenced by sedimentary fluxes. We conclude that the fossil fish tooth Nd isotope proxy is not sensitive to moderate changes in pore water oxygenation. However, combined studies on sediments, pore waters, fish teeth and seawater are needed to fully understand processes driving the reconstructed signature from shallow marine sections in proximity to continental sources. This article is protected by copyright. All rights reserved.

(Table 1) Typical trace-fossil occurrences in DSDP Holes 56-436 and 56-435A

Trace fossils are in places abundant in cores from DSDP Leg 56 sites. They are particularly rich in the pelagic-clay sequence at Site 436. Some significant trace fossils, including Zoophycos, Teichichnus, Chondrites, rind and solid burrows, and pellet-armored rods, are described. The ichnofauna, except for pellet-armored rods in diatomaceous mudstone of the landward trench slope, is characterized by cosmopolitan bathyal to abyssal forms.

Calcium isotope fractionation in cultured, modern and fossil scleractinian coral skeleton

The present study investigates the influence of environmental (temperature, salinity) and biological (growth rate, inter-generic variations) parameters on calcium isotope fractionation (d44/40Ca) in scleractinian coral skeleton to better constrain this record. Previous studies focused on the d44/40Ca record in different marine organisms to reconstruct seawater composition or temperature, but only few studies investigated corals. This study presents measurements performed on modern corals from natural environments (from the Maldives for modern and from Tahiti for fossil corals) as well as from laboratory cultures (Centre Scientifique de Monaco). Measurements on Porites sp., Acropora sp., Montipora verrucosa and Stylophora pistillata allow constraining inter-generic variability. Our results show that the fractionation of d44/40Ca ranges from 0.6 to 0.1 per mil, independent of the genus or the environmental conditions. No significant relationship between the rate of calcification and d44/40Ca was found. The weak temperature dependence reported in earlier studies is most probably not the only parameter that is responsible for the fractionation. Indeed, sub-seasonal temperature variations reconstructed by d18O and Sr/Ca ratio using a multi-proxy approach, are not mirrored in the coral's d44/40Ca variations. The intergeneric variability and intrageneric variability among the studied samples are weak except for S. pistillata, which shows calcium isotopic values increasing with salinity. The variability between samples cultured at a salinity of 40 is higher than those cultured at a salinity of 36 for this species. The present study reveals a strong biological control of the skeletal calcium isotope composition by the polyp and a weak influence of environmental factors, specifically temperature and salinity (except for S. pistillata). Vital effects have to be investigated in situ to better constrain their influence on the calcium isotopic signal. If vital effects could be extracted from the isotopic signal, the calcium isotopic composition of coral skeletons could provide reliable information on the calcium composition and budget in ocean.

Nd and Sr isotope compositions, REE concentrations and Al/Ca ratios of different phases of surface sediments in the South Pacific

The radiogenic isotope composition of neodymium (Nd) and strontium (Sr) are useful tools to investigate present and past oceanic circulation or input of terrigenous material. We present Nd and Sr isotope compositions extracted from different sedimentary phases, including early diagenetic Fe-Mn coatings, "unclean" foraminiferal shells, fossil fish teeth, and detritus of marine surface sediments (core-tops) covering the entire midlatitude South Pacific. Comparison of detrital Nd isotope compositions to deep water values from the same locations suggests that "boundary exchange" has little influence on the Nd isotope composition of western South Pacific seawater. Concentrations of Rare Earth Elements (REE) and Al/Ca ratios of "unclean" planktonic foraminifera suggest that this phase is a reliable recorder of seawater Nd isotope composition. The signatures obtained from fish teeth and "nondecarbonated" leachates of bulk sediment Fe-Mn oxyhydroxide coatings also agree with "unclean" foraminifera. Direct comparison of Nd isotope compositions extracted using these methods with seawater Nd isotope compositions is complicated by the low accumulation rates yielding radiocarbon ages of up to 24 kyr, thus mixing the signal of different ocean circulation modes. This suggests that different past seawater Nd isotope compositions have been integrated in authigenic sediments from regions with low sedimentation rates. Combined detrital Nd and Sr isotope signatures indicate a dominant role of the Westerly winds transporting lithogenic material from South New Zealand and Southeastern Australia to the open South Pacific. The proportion of this material decreases toward the east, where supply from the Andes increases and contributions from Antarctica cannot be ruled out.

Strontium and neodymium isotope data for barite separates and pore waters, and isotope and concentration data for foraminifera and fish teeth from DSDP Leg 85 sediments

Strontium and neodymium isotopic data are reported for barite samples chemically separated from Late Miocene to Pliocene sediments from the eastern equatorial Pacific. At a site within a region of very high productivity close to the equator, 87Sr/86Sr ratios in the barite separates are indistinguishable from those of foraminifera and fish teeth from the same samples. However, at two sites north of the productivity maximum barite separates have slightly, but consistently lower (averaging 0.000062) ratios than the coexisting phases, although values still fall within the total range of published values for the contemporaneous seawater strontium isotope curve. We examine possible causes for this offset including recrystallization of the foraminifera, fish teeth or barite, the presence of non-barite contaminants, or incorporation of older, reworked deep-sea barite; the inclusion of a small amount of hydrothermal barite in the sediments seems most consistent with our data, although there are difficulties associated with adequate production and transportation of this phase. Barite is unlikely to replace calcite as a preferred tracer of seawater strontium isotopes in carbonate-rich sediments, but may prove a useful substitute in cases where calcite is rare or strongly affected by diagenesis. In contrast to the case for strontium, neodymium isotopic ratios in the barite separates are far from expected values for contemporary seawater, and appear to be dominated by an (unobserved) eolian component with high neodymium concentration and low 143Nd/144Nd. These results suggest that the true potential of barite as an indicator of paleocean neodymium isotopic ratios and REE patterns will be realized only when a more selective separation procedure is developed.