A botanical view of the ‘Baltic amber forest’: new evidence from seed plants, lichens and fungi

Baltic amber forms the largest amber deposit on earth and it is particularly well-known for the plethora of arthropod inclusions. The floristic composition, habitat types and climate of its Eocene source area, however, are still controversial. The differing suggestions range from early Eocene tropical to late Eocene temperate environments, and from lowland to montane forests. We screened a large number of inclusions from historic collections and from recently discovered amber pieces and found many inclusions of seed plants, lichens and microfungi that provide important insights into habitat structure and climate.Peer reviewe

Caspary’s fungi from Baltic amber : historic specimens and new evidence

Amber is a valuable source of Mesozoic and Cenozoic fossil fungi. The earliest amber-preserved fungi were described in the nineteenth and early twentieth centuries from Eocene Baltic amber. In 1907, Richard Klebs summarized the legacy of Robert Caspary based on his specimens, research notes and publications. This treatise contains descriptions and illustrations of 13 morphologies of fossil fungi which have not been investigated since. We managed to locate six of Caspary’s amber specimens and imaged and re-investigated the fossil fungi within. We provide amended descriptions of these six specimens, select new specimens from historic and recent collections which are probably conspecific with five fossils that appear to have been lost, and finally also describe and evaluate five newly found fossil fungi from Baltic amber. The fungi belong to the phylum Ascomycota (Subkingdom Dikarya). Only two of Caspary’s fungi can be confidently assigned to modern genera, Metacapnodium (Metacapnodiaceae) and Calicium (Caliciaceae). The new combination Calicium succini (Caspary) Rikkinen & A. R. Schmidt is made. The fossils originally placed in Acremonium, Cetraria, Gonatobotrys, Ramularia, Stilbum and Torula cannot be assigned to these genera, and should not be used as minimum age constrains for the respective lineages.Peer reviewe

Comment on the letter of the Society of Vertebrate Paleontology (SVP) dated April 21, 2020 regarding “Fossils from conflict zones and reproducibility of fossil‑based scientific data”: Myanmar amber

Non peer reviewe

The mid-Miocene Zhangpu biota reveals an outstandingly rich rainforest biome in East Asia

During the Mid-Miocene Climatic Optimum [MMCO, ~14 to 17 million years (Ma) ago], global temperatures were similar to predicted temperatures for the coming century. Limited megathermal paleoclimatic and fossil data are known from this period, despite its potential as an analog for future climate conditions. Here, we report a rich middle Miocene rainforest biome, the Zhangpu biota (~14.7 Ma ago), based on material preserved in amber and associated sedimentary rocks from southeastern China. The record shows that the mid-Miocene rainforest reached at least 24.2°N and was more widespread than previously estimated. Our results not only highlight the role of tropical rainforests acting as evolutionary museums for biodiversity at the generic level but also suggest that the MMCO probably strongly shaped the East Asian biota via the northern expansion of the megathermal rainforest biome. The Zhangpu biota provides an ideal snapshot for biodiversity redistribution during global warming

Gaia Early Data Release 3: Structure and properties of the Magellanic Clouds

We compare the Gaia DR2 and Gaia EDR3 performances in the study of the Magellanic Clouds and show the clear improvements in precision and accuracy in the new release. We also show that the systematics still present in the data make the determination of the 3D geometry of the LMC a difficult endeavour; this is at the very limit of the usefulness of the Gaia EDR3 astrometry, but it may become feasible with the use of additional external data. We derive radial and tangential velocity maps and global profiles for the LMC for the several subsamples we defined. To our knowledge, this is the first time that the two planar components of the ordered and random motions are derived for multiple stellar evolutionary phases in a galactic disc outside the Milky Way, showing the differences between younger and older phases. We also analyse the spatial structure and motions in the central region, the bar, and the disc, providing new insights into features and kinematics. Finally, we show that the Gaia EDR3 data allows clearly resolving the Magellanic Bridge, and we trace the density and velocity flow of the stars from the SMC towards the LMC not only globally, but also separately for young and evolved populations. This allows us to confirm an evolved population in the Bridge that is slightly shift from the younger population. Additionally, we were able to study the outskirts of both Magellanic Clouds, in which we detected some well-known features and indications of new ones

Staminate inflorescences with in situ pollen from Eocene Baltic amber reveal high diversity in Fagaceae (oak family)

Eocene Baltic amber forms the largest amber deposit worldwide; however, its source vegetation and climateare much debated. Representatives of the oak family (Fagaceae) were abundant in the Baltic amber source areabased on numerous inclusions of staminate inflorescences or individual florets, previously assigned to Castanea andQuercus. However, the actual generic and infrageneric diversity of Fagaceae from Baltic amber remained unknown.Using flower characteristics and section-diagnostic in situ pollen of staminate inflorescences and detached floret inclusions,we describe 18 fossil-species of Fagaceae making this family by far the most diverse plant family preservedin Baltic amber. We substantiate the occurrence of the Castaneoideae, Quercoideae (Quercus sect. Cyclobalanopsis/ Lobatae; Q. sect. Lobatae; Q. sect. Protobalanus), Trigonobalanoideae and the extinct genus Eotrigonobalanus.Among the 18 fossil-species, six are described as new: Q. aimeeana, Q. casparyi, Q. multipilosa, E. campanulata,E. conwentzii, E. longianthera; and one new combination is published: Q. brachyandra (≡ Castanea brachyandra).In addition, a lectotype is designated for the name Quercites meyerianus and neotypes are designated for the namesCastanea inclusa and Quercus longistaminea (≡ C. longistaminea). Members of the Fagaceae probably inhabitedazonal and zonal vegetation types of the amber source area, including bottomland flood-plains and stream banks(Q. sect. Lobatae), dry habitats (Q. sect. Lobatae, Q. sect. Protobalanus), peaty soils, riparian and swamp forests(Castanopsis, Eotrigonobalanus), as well as mixed mesophytic forests (castaneoids, Quercoideae, trigonobalanoids).Affinities to extant North American and E to SE Asian floras support the recent notion that late Eocene Baltic amber(38 – 34 Ma) was formed in a warm-temperate climate

Staminate inflorescences with in situ pollen from Eocene Baltic amber reveal high diversity in Fagaceae (oak family)

Eocene Baltic amber forms the largest amber deposit worldwide; however, its source vegetation and climateare much debated. Representatives of the oak family (Fagaceae) were abundant in the Baltic amber source areabased on numerous inclusions of staminate inflorescences or individual florets, previously assigned to Castanea andQuercus. However, the actual generic and infrageneric diversity of Fagaceae from Baltic amber remained unknown.Using flower characteristics and section-diagnostic in situ pollen of staminate inflorescences and detached floret inclusions,we describe 18 fossil-species of Fagaceae making this family by far the most diverse plant family preservedin Baltic amber. We substantiate the occurrence of the Castaneoideae, Quercoideae (Quercus sect. Cyclobalanopsis/ Lobatae; Q. sect. Lobatae; Q. sect. Protobalanus), Trigonobalanoideae and the extinct genus Eotrigonobalanus.Among the 18 fossil-species, six are described as new: Q. aimeeana, Q. casparyi, Q. multipilosa, E. campanulata,E. conwentzii, E. longianthera; and one new combination is published: Q. brachyandra (≡ Castanea brachyandra).In addition, a lectotype is designated for the name Quercites meyerianus and neotypes are designated for the namesCastanea inclusa and Quercus longistaminea (≡ C. longistaminea). Members of the Fagaceae probably inhabitedazonal and zonal vegetation types of the amber source area, including bottomland flood-plains and stream banks(Q. sect. Lobatae), dry habitats (Q. sect. Lobatae, Q. sect. Protobalanus), peaty soils, riparian and swamp forests(Castanopsis, Eotrigonobalanus), as well as mixed mesophytic forests (castaneoids, Quercoideae, trigonobalanoids).Affinities to extant North American and E to SE Asian floras support the recent notion that late Eocene Baltic amber(38 – 34 Ma) was formed in a warm-temperate climate

Species-level determination of closely related araucarian resins using FTIR spectroscopy and its implications for the provenance of New Zealand amber

Some higher plants, both angiosperms and gymnosperms, can produce resins and some of these resins can polymerize and fossilize to form ambers. Various physical and chemical techniques have been used to identify and profile different plant resins and have then been applied to fossilized resins (ambers), to try to detect their parent plant affinities and understand the process of polymerization, with varying levels of success. Here we focus on resins produced from today’s most resinous conifer family, the Araucariaceae, which are thought to be the parent plants of some of the Southern Hemisphere’s fossil resin deposits. Fourier transform infrared (FTIR) spectra of the resins of closely related Araucariaceae species were examined to test whether they could be distinguished at genus and species level and whether the results could then be used to infer the parent plant of a New Zealand amber. The resin FTIR spectra are distinguishable from each other, and the three Araucaria species sampled produced similar FTIR spectra, to which Wollemia resin is most similar. Interspecific variability of the FTIR spectra is greatest in the three Agathis species tested. The New Zealand amber sample is similar in key shared features with the resin samples, but it does differ from the extant resin samples in key distinguishing features, nonetheless it is most similar to the resin of Agathis australis in this dataset. However on comparison with previously published FTIR spectra of similar aged amber and older (Eocene) resinites both found in coals from New Zealand and fresh Agathis australis resin, our amber has some features that imply a relatively immature resin, which was not expected from an amber of the Miocene age

Breathing new life into plant amber inclusions using X-ray imaging

Plant inclusions in amber have been reported from Cretaceous to Miocene deposits worldwide. Botanical remains, such as vegetative and reproductive structures, can be remarkably preserved and permit comprehensive morphological studies. However, analyses with standard light microscopy are limited to external features, whereas internal structures remain inaccessible. Moreover, the small size of some inclusions, darkened or opaque amber, as well as syninclusions can limit assessing additional morphological feature of the plant fossil.In the past years, high-resolution X-ray tomography (also called microtomography or microCT) has been used to investigate internal structures of amber inclusions. This non-invasive method combines an X-ray source and a detector, with the specimen rotating in front of the X-ray source. X-rays enter the amber and generate projection images on the detector from various angles. A 3D volume can then be created by processing the stack of the 2D images with a proper software.We conducted lab-based and synchrotron radiation-based microtomography of plant inclusions from different amber localities, including Cretaceous Burmese amber (Myanmar), late Eocene Baltic amber (Kaliningrad, Russia) and Miocene Zhangpu amber (China), revealing an exceptional preservation of many specimens. These techniques allowed us to digitally dissect the plant inclusions and to visualize internal key features, which were essential for their taxonomic assignment.The quality of the scans varied, depending on the amber type, the age, as well as the preservation of the inclusion. In contrast to the lab-based micro-CT, synchrotron radiation-based micro-CT imaging achieved a higher spatial resolution. However, access to facilities with synchrotron radiation-based micro-CTs is limited and can be expensive. Moreover, the synchrotron radiation may cause a brownish discoloration of the amber, which is irreversible in some cases. This darkening does not occur when using a lab-based micro-CT and makes it overall particularly advantageous