Swedish Museum of Natural History
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The Indo-European flyway: Opportunities and constraints reflected by Common Rosefinches breeding across Europe.
No full textBrachiopods in early Mesozoic cryptic habitats: Continuous colonization, rapid adaptation, and wide geographic distribution
No full text Late Triassic and early Jurassic dikes and fissures in the Dachstein Limestone in the Northern Calcareous Alpsharbor mass occurrences of the rhynchonellide brachiopods Sulcirostra juvavica and Halorella amphitoma. To testrecent hypotheses about their paleoecology, we characterized these habitats using petrography, carbon stableisotopes, and trace element patterns, and found no evidence for hydrocarbon seepage or hydrothermal venting.Thus the brachiopods lived under normal-marine conditions, in darkness and absence of local photosyntheticprimary production, hence relying on the supply of limited and presumably small-sized food washed into thedikes and fissures. Because Halorella and Sulcirostra occur in dikes and fissures since the beginning of theirstratigraphic ranges, these rhynchonellides are not relics of formerly widely distributed taxa, but instead are twogenera that rapidly adapted to these habitats. Both Halorella and Sulcirostra occur also in late Triassic and earlyJurassic deep-water settings such as deep-marine sills and hydrocarbon seeps, indicating that close phylogeneticrelationships between submarine cave faunas and deep-sea faunas, as seen today, existed also in the earlyMesozoic, albeit among very different taxa. Another analogy to the modern cave fauna is the wide but disjunctgeographic distribution of Sulcirostra and Halorella, both found throughout the Tethys and Panthalassa oceans.Our findings support the view that submarine cave habitats were continuously colonized by new taxa throughoutEarth’s history.
Searching for a nearest living equivalent for Bennettitales: a promising extinct plant group for stomatal proxy reconstructions of Mesozoic pCO2
No full textTo understand Earth ́s climate variability and improve predictions of future climate change, studying past climates is an important avenue to explore. A previously published record of pCO2, across the Triassic– Jurassic boundary (TJB, ~201 Ma) of East Greenland, showed that Bennettitales (Anamozamites and Pterophyllum) responded in parallel to the empirically proven pCO2-responders Ginkgoales, reducing their stomatal densities by half across the TJB, indicating a transient doubling of pCO2. The abundance of fossil Bennettitales in Mesozoic strata and natural history museum collections worldwide offers enormous potential for further stomatal proxy pCO2 reconstructions, but a suitable nearest living equivalent (NLE) should ideally first be identified for this extinct plant group. Using specimens from herbarium collections, three species of cycads, historically considered the best NLE, were tested for pCO2 response, as well as two species of tree ferns, grown in experimental growth chambers. None responded to changes in pCO2, and were consequently rejected as NLEs. Finally, two species of ferns were selected from the literature, and produced very similar pCO2 compared to Ginkgoales. However, these understory ferns are not appropriate NLEs for Bennettitales due to differences in habitat and a distant evolutionary relationship. Future work should test additional plant groups, in particular seed plants such as basal angiosperms and Gnetales, for suitability as NLE for Bennettitales in pCO2 reconstructions, for example through biogeo- chemical fingerprinting using infrared microspectroscopy. Until an appropriate NLE is identified, Bennettitales pCO2 can be reconstructed based on cross-calibration of stomatal densities with those of co-occurring pCO2 responders, such as Ginkgoales
Qingjianglepas from the Qingjiang biota, an evolutionary dead-end of Cambrian helcionelloid mollusks?
No full textA minute limpet-shaped shell, Qingjianglepas elegans n. gen. n. sp., is reported from the 518 million-year-old Qingjiang biota in Hubei, China. The new shell exhibits a typical limpet morphology with a shell sculpture of strongly developed radial ribs, an anterior shell fold, and distinctive shell shape shift. Feature combinations such as in Qingjianglepas are unique among Cambrian mollusk assemblages, but strikingly resemble that of some modern fissurellids (keyhole and slit limpets; Vetigastropoda). The biological affinity of Qingjianglepas is discussed, but temporarily remains uncertain. Regardless, the heavily sculptured and limpet-shaped Qingjianglepas represents a previously unrecognized shell form, and hence significantly extends the morphological diversity of Cambrian mollusks. The abrupt ontogenetic change in shell morphology suggests that Qingjianglepas might change microhabitat throughout the growth of the animal. This study reveals that the phenomenon of limpetization occurred within early Cambrian total-group conchiferans. Furthermore, Qingjianglepas might represent an evolutionary dead-end in course of helcionelloid mollusk evolution, which marks the end of the Cambrian explosion of animals at the beginning of Cambrian Series 2
Genetic relationships between sympatric and allopatric Coregonus ciscoes in North and Central Europe
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Lethal microbial blooms delayed freshwater ecosystem recovery following the end-Permian extinction
No full textHarmful algal and bacterial blooms linked to deforestation, soil loss and global warming are increasingly frequent in lakes and rivers. We demonstrate that climate changes and deforestation can drive recurrent microbial blooms, inhibiting the recovery of freshwater ecosystems for hundreds of millennia. From the stratigraphic successions of the Sydney Basin, Australia, our fossil, sedimentary and geochemical data reveal bloom events following forest ecosystem collapse during the most severe mass extinction in Earth’s history, the end-Permian event (EPE; c. 252.2 Ma). Microbial communities proliferated in lowland fresh and brackish waterbodies, with algal concentrations typical of modern blooms. These initiated before any trace of post-extinction recovery vegetation but recurred episodically for >100 kyrs. During the following 3 Myrs, algae and bacteria thrived within short-lived, poorly-oxygenated, and likely toxic lakes and rivers. Comparisons to global deep-time records indicate that microbial blooms are persistent freshwater ecological stressors during warming driven extinction events.Also supported by National Science Foundation (grant EAR-1636625)</p
3D imaging of shark egg cases (Palaeoxyris) from Sweden with new insights into Early Jurassic shark ecology
No full textSeveral shark species produce egg cases as protective casings in which their embryos develop. These casings are composed of multiple layers of collagen and are extremely durable, making them prone to fossilisation. Here we document Palaeoxyris (Spirangium) ‒ fossil shark egg cases from Lower Jurassic successions of southern Sweden. We present high-resolution 3D images of Palaeoxyris based on microfocus X-ray computed tomography (μCT) of seven specimens, including fossils that were embedded within a sandstone matrix. Our examination of the internal structure of the egg cases revealed the possible remnants of a yolk and foetus in one specimen. The cases were most likely produced by hybodont sharks, as outlined in previous studies, and the occurrence of hybodont teeth from Lower Jurassic successions of Sweden support this. Palynological analysis of the matrix from one of the specimens hosting Palaeoxyris, indicates an early Hettangian age. The high percentage of spores (c. 60%) reveals that the egg cases were laid during the Transitional Spore Spike Interval following the end-Triassic mass extinction. The egg cases are found in conjunction with fossil horsetails; with the broader palynological and sedimentological evidence, this suggests an estuarine depositional setting, and potentially indicates that newborn sharks were living in habitats comparable to modern mangroves, as is often the case today.Also funded by Stockholms Universitet [SU FV-5.1.2-1035-15]</p
Using laser micropyrolysis to assess potential relationships between Cambrian tommotiids and organophosphatic brachiopods
No full textLaser micropyrolysis gas chromatography-mass spectrometry enables researchers to selectively obtain chemical information about the organic matter in specific parts of a variety of specimens, such as coals and fossils, in order to elucidate chemical composition. This paper briefly reviews the history of this type of pyrolysis and examines whether the technique can be used to isolate and recover biogeochemical signatures directly from the mineralised organophosphatic sclerites of Cambrian tommotiids—a group of enigmatic lophotrochozoans—and potentially related organophosphatic brachiopods. We analysed specimens of two tommotiids (Micrina etheridgei and Dailyatia sp.) and the paterinate brachiopod Askepasma toddense from the lower Cambrian of South Australia. Pyrolysate hydrocarbons from the sclerites of these species were detected and compared. Results indicate that A. toddense is more chemically complex than either of the two tommotiid taxa, but that M. etheridgei is compositionally more similar to A. toddense. Importantly, this study has demonstrated that laser micropyrolysis gas chromatography-mass spectrometry of Cambrian organophosphatic small shelly fossils yields detectable pyrolysates that have geochemical significance. It will be analytically possible and useful in the future to apply this technique to a larger sample set to elucidate deep time biogeochemical homologies, and to test intra-shell heterogeneity