Fossilization Process Research Articles

The Fossilised Birth-Death Model is Identifiable.

Time-dependent birth-death sampling models have been used in numerous studies for inferring past evolutionary dynamics in different biological contexts, e.g. speciation and extinction rates in macroevolutionary studies, or effective reproductive number in epidemiological studies. These models are branching processes where lineages can bifurcate, die, or be sampled with time-dependent birth, death, and sampling rates, generating phylogenetic trees. It has been shown that in some subclasses of such models, different sets of rates can result in the same distributions of reconstructed phylogenetic trees, and therefore the rates become unidentifiable from the trees regardless of their size. Here we show that widely used time-dependent fossilised birth-death (FBD) models are identifiable. This subclass of models makes more realistic assumptions about the fossilisation process and certain infectious disease transmission processes than the unidentifiable birth-death sampling models. Namely, FBD models assume that sampled lineages stay in the process rather than being immediately removed upon sampling. Identifiability of the time-dependent FBD model justifies using statistical methods that implement this model to infer the underlying temporal diversification or epidemiological dynamics from phylogenetic trees or directly from molecular or other comparative data. We further show that the time-dependent fossilised-birth-death model with an extra parameter, the removal after sampling probability, is unidentifiable. This implies that in scenarios where we do not know how sampling affects lineages we are unable to infer this extra parameter together with birth, death, and sampling rates solely from trees.

Non-destructive Analytical Study of Raman Spectra Variations and Mechanisms of Calcite and Aragonite in Modern and Fossilized Oysters.

Oyster fossils are some of the most common bivalve mollusk fossils found all over the world, they are different from other fossils because the oyster is still alive in the present day, and the body structure of modern oyster is almost the same as that of ancient one. Therefore, we designed a control experiment comparing the Raman spectra of minerals from both modern oysters and fossil oysters to explore the mechanism of oyster's fossilization process, which is considered to be helpful for investigating biological evolution or paleoenvironment. The oyster fossil sample was found in Nagi-Cho, Okayama Prefecture, Japan. We focused on the variations of band position and full width half-maximum of ν1 Raman band (symmetric stretching mode) of calcite (CaCO3) from modern and fossil oysters and the mineral conversion between calcite and aragonite (CaCO3) around the adductor muscle inside the oyster. Compared to modern oysters, the ν1 band at around 1086 cm-1 of calcite from oyster fossils shifted to a high wavenumber region, and the possible reason for this phenomenon is considered an elemental substitution between Ca2+ and Mg2+. As for aragonite around adductor muscle in fossil oysters, it has been found by Raman spectra that most of the aragonite has been converted into calcite because calcite has a relatively more stable structure.

Report of bioerosions and cells in Cainotheriidae (Mammalia, Artiodactyla) from the phosphorites of Quercy (SW France)

The phosphorites of the Quercy from SouthWest France are well known for fossils preserved in 3D with phosphatized soft-tissues. Given that phosphatization is known to favor fine cellular preservation, the present study delves into the histological analysis of white and brown bones of Cainotheriidae (Artiodactyla) recently excavated from the DAM1 site near Caylus. Microscopy revealed that the white bones were completely filled with bacterial erosions, while the brown bones showed a pristine histology and intralacunar content resembling fossilized osteocytes in some areas. After decalcification, a brown bone revealed an abundance of blood vessel-like structures, innumerable osteocyte-like structures with canaliculi and a few chondrocyte-like structures, while a white bone revealed only blood vessel-like structures that looked eaten away. All the data combined suggest the brown bones were shielded from bacterial attacks and were filled with fossilized organic matter and original biological structures. The data taken all together do not support that these structures are casts, but indeed original and endogenous cells. This study encourages further histochemical and mineralogical analyses on Quercy fossils and the unique taphonomy of DAM1 to better understand fossilization processes and their impact on the color of bones, the chemistry of skeletal tissues, soft tissues, and cells.

Biomolecules in Pleistocene fossils from tropical cave indicate fossil biofilm

Finding biomolecules in fossils is a challenging task due to their degradation over time from physical, chemical, and biological factors. The primary hypothesis for explaining the presence of biomolecules in fossilized bones tissues suggests their survival in the fossilization process. In contrast, some of these biomolecules could either derive from bacteria biofilm, thus without a direct relationship with the fossil record or could be an artifact from measurement procedures. Raman spectroscopy studies across various fossil ages and environments have detected multiple bands ranging from 1200 to 1800 cm−1 associative of organic compounds. However, the significance of these bands remains elusive. Our research aims to address this issue through a deep Raman spectroscopy investigation on Pleistocene teeth from Tayassu and Smilodon populator. These fossils were obtained from a well-preserved stratigraphic succession in Toca de Cima do Pilão cave, near the National Park of Serra da Capivara in semiarid Brazil. We propose two hypotheses to explain the presence of organic compounds related to 1200 to 1800 cm−1 Raman spectral range in fossil tissues: (i) these bands are biological signatures of preserved fossil biomolecules, or (ii) they are exogenous biological signatures associated with the bacterial biofilm formation during post-depositional processes. Our results align with the latter hypothesis, followed by biofilm degradation. However, the specific mechanisms involved in the natural biofilm degradation in fossil records remain unexplored in this study. In our case, the formation of biofilm on fossil bones is attributed to the oligotrophic conditions of the cave sediment matrix. We present a comprehensive model to elucidate the existence of biofilm on fossilized tissues, emphasizing the pivotal role of post-depositional processes, especially water action, in the cave environment. As the fossils were discovered in a cave setting, post-depositional processes significantly contribute to the formation of the biofilm matrix. Although our study provides insights into biofilm formation, further research is needed to delve into the specific mechanisms driving natural biofilm degradation in fossils.

A new non-destructive method to decipher the origin of organic matter in fossils using Raman spectroscopy.

Ancient biomolecules provide a unique perspective on the past but are underutilized in paleontology because of challenges in interpreting the chemistry of fossils. Most organically preserved soft tissues in fossils have been altered by thermal maturation during the fossilization process, obscuring original chemistry. Here, we use a comprehensive program of thermal maturation experiments on soft tissues from diverse extant organisms to systematically test whether thermally altered biosignatures can be discriminated using Raman spectroscopy. All experimentally matured samples show chemical signatures that are superficially similar. Comparative analysis of Raman spectra following peak deconvolution, however, reveals strong tissue-specific signals. Application of this approach to fossils from the Bolca (49 Ma) and Libros (10 Ma) Konservat-Lagerstätten successfully discriminates fossil vertebrate soft tissue from that of fossil plants. Critically, our data confirm that a robust interrogation of Raman spectra coupled with multivariate analysis is a powerful tool to shed light on the taxonomic origins of thermally matured fossil soft tissues.

Taphonomy and paleohistology of a dinosaur rib from Marília Formation, Bauru Group, in the state of Minas Gerais, Brazil

The Bauru Group (Campanian–Maastrichtian) has one of the richest fossil records of Cretaceous in South America. All dinosaur fossils from this unit were assigned to Saurischia, most of them poorly preserved. We present the histological and taphonomic analysis of a dinosaur dorsal rib fragment from the Marília Formation in the western state of Minas Gerais. Thin sections were prepared to describe the microstructures of the bone tissue and the fossilization processes involved in preserving the specimen. An elemental analysis was also performed to verify the chemical composition of the fossil and rock matrix. Haversian bone was identified in the rib cortex, and no growth marks or an external fundamental system were found. The rib probably belonged to a saurischian dinosaur because of its plank shape and elliptical cross-section. Hypotheses regarding taphonomic processes were inferred. An extended period of subaerial exposure, followed by high-energy transport, was interpreted due to extensive fractures and signs of abrasion on the outer surface of the bone. Pyrite pseudomorphs (framboids) indicate that the bone was deposited in a reductive environment. After burial, the rapid precipitation of calcite and alkaline stability allowed the preservation of apatite during the recrystallization phase. The manganese hydroxides were deposited on apatite crystals during early diagenesis. We concluded that the fossil rib presented a common taphonomic bias identified among vertebrate fossils of the Bauru Group, which is associated with the exposure of the bones to arid and semiarid climates, their transport into the depositional environments and pedogenetic influence during fossil diagenesis.

Extinct and extant termites reveal the fidelity of behavior fossilization in amber

Fossils encompassing multiple individuals provide rare direct evidence of behavioral interactions among extinct organisms. However, the fossilization process can alter the spatial relationship between individuals and hinder behavioral reconstruction. Here, we report a Baltic amber inclusion preserving a female-male pair of the extinct termite species Electrotermes affinis. The head-to-abdomen contact in the fossilized pair resembles the tandem courtship behavior of extant termites, although their parallel body alignment differs from the linear alignment typical of tandem runs. To solve this inconsistency, we simulated the first stage of amber formation, the immobilization of captured organisms, by exposing living termite tandems to sticky surfaces. We found that the posture of the fossilized pair matches trapped tandems and differs from untrapped tandems. Thus, the fossilized pair likely is a tandem running pair, representing the direct evidence of the mating behavior of extinct termites. Furthermore, by comparing the postures of partners on a sticky surface and in the amber inclusion, we estimated that the male likely performed the leader role in the fossilized tandem. Our results demonstrate that past behavioral interactions can be reconstructed despite the spatial distortion of body poses during fossilization. Our taphonomic approach demonstrates how certain behaviors can be inferred from fossil occurrences.

Exploring Nuances in Second Language Acquisition: An Error Analysis Perspective

This study employs error analysis as a pivotal lens to scrutinize the intricacies of second language learning, emphasizing the unique accents manifested through learners’ mistakes. Departing from the confines of contrastive analysis, the research aims to illuminate the processes of acquiring a second language. Key facets of language acquisition, including transfer, interference, and the fossilization process, are investigated to provide insights into the development of learners’ interlanguage. The study conducts a comparative analysis of early and late language learning, emphasizing the impact of cognitive, psychological, and social factors on the learning trajectory. Motivational influences, encompassing instrumental and integrative motives, are explored in connection to their effects on learning outcomes. This research not only contributes to a deeper understanding of error patterns in second language acquisition but also advocates for methodologies that surpass the constraints of contrastive analysis, offering potential avenues for more effective language learning strategies.

Two-photon excitation fluorescence microspectroscopy protocols for examining fluorophores in fossil plants

Fluorescence emission is common in plants. While fluorescence microscopy has been widely used to study living plants, its application in quantifying the fluorescence of fossil plants has been limited. Fossil plant fluorescence, from original fluorophores or formed during fossilization, can offer valuable insights into fluorescence in ancient plants and fossilization processes. In this work, we utilize two-photon fluorescence microspectroscopy to spatially and spectrally resolve the fluorescence emitted by amber-embedded plants, leaf compressions, and silicified wood. The advanced micro-spectroscope utilized, with its pixel-level spectral resolution and line-scan excitation capabilities, allows us to collect comprehensive excitation and emission spectra with high sensitivity and minimal laser damage to the specimens. By applying linear spectral unmixing to the spectrally resolved fluorescence images, we can differentiate between (a) the matrix and (b) the materials that comprise the fossil. Our analysis suggests that the latter correspond to durable tissues such as lignin and cellulose. Additionally, we observe potential signals from chlorophyll derivatives/tannins, although minerals may have contributed to this. This research opens doors to exploring ancient ecosystems and understanding the ecological roles of fluorescence in plants throughout time. Furthermore, the protocols developed herein can also be applied to analyze non-plant fossils and biological specimens.

The Fossilization: What Initial Representations of Future Instructors?

Previous research has shown the influence of teachers' initial representations on their assimilation and transmission of scientific concepts to students. In this regard, the aim of the present study is to identify the difficulties faced by future Life and Earth Sciences (LES) teachers in assimilating the concept of fossilization, particularly those related to the mobilization of time and space. Using a mixed-methods approach, we designed a questionnaire that was administered to 30 trainee teachers at the RCJET in Fez, selected by simple random sampling. The data was processed using statistical data processing software (answers to closed questions) and the content analysis method (answers to open and semi-open questions). Various types of obstacles to the mobilization of time and space were detected. The inability to apply the principle of actualism. The conception of the evolution of fossilization processes outside the space-time framework. The inability to conceive fossilization as a contingent and exceptional phenomenon, requiring a long time, difficult to observe with the naked eye, difficult to experiment due to their taking place in different palaeogeographic sites. They also raised the need for special training in geology. As a result, we are proposing an increase in the number of hours spent on practical work, the scheduling of geological field trips, the development of new methods and approaches, and the integration of Information and Communication Technologies (ICT). In order to generalise and validate its results, although they were significant, our research will be extended to a larger sample, and in other countries.

Osteohistological analysis and preservation stage of Coendou magnus Lund, 1839 (Rodentia, Erethizontidae) fossils recovered at Toca da Barriguda Cave, Northeastern Brazil

Studies on taxonomy, taphonomy, and paleoecology have been conducted on fossils from carbonate caves, however, surveys detailing the fossilization processes and bone microstructure of specimens from caves are still scarce. Our paper provides an osteohistological analysis and X-ray diffraction of a fossil rib from the extinct South American porcupine Coendou magnus Lund. Our results allowed us to interpret that there was microstructural preservation and low replacement of the organic part of the bone by minerals present in the surrounding sediments, such as apatite and abundant non-silicate minerals in sedimentary rocks, characterizing preservation in an environment with poor weathering. Keywords: cave, X-ray diffraction, late Pleistocene, histology, porcupine.

Still potentially deadly after all these years: how to safely handle and display radioactive dinosaurs and other fossils

Most curators and collection managers responsible for a geological collection will be aware of the risk posed by rocks and minerals which emit ionising radiation and will have put measures in place to reduce this risk to collection users. However, fewer people are aware that fossils, ranging from fish to dinosaurs, and even coprolites can be radioactive too. A fossil may be radioactive if it has been exposed to uranium-bearing fluids during diagenesis and fossilisation processes. Any uranium-enriched groundwater moving through nearby porous deposit can contaminate the rocks and fossils with radioactive elements. Over time the skeletons or other remains being fossilised incorporate these elements into their min- eral structure, such that the concentration of radioactive elements in fossils may be greater than that in the host rock. The greater the volume of fossil material, e.g. a large dinosaur bone, the greater the potential for higher levels of radioactivity, and a greater risk to hu- mans (although some small specimens can be highly radioactive). Whilst most radioactive fossils may not present a danger to health through direct absorption of radiation, unless there is prolonged exposure at close quarters (e.g. hundreds of hours), a risk is posed by the ingestion or inhalation of small radioactive particles derived from the specimen. Here, we describe what measures can be taken to reduce these risks and also provide a list of locations around the world known to yield radioactive fossils, which we hope can be augmented by others. The general principles discussed here are widely applicable, but it is recommended that specialist advice is sought to comply with national regulations in each instance. In ad- dition to the health risks posed by these specimens, there are also legal penalties for failing to comply with regulations.

Structural control and Ostwald ripening as essential mechanisms during the fossilization process of sea urchin (Balanocidaris? Lambert) spines from Lower Cretaceous of Southern Spain

ABSTRACT A comparative study has been made between some cidaroid fossil spines from Lower Cretaceous of southern Spain and other contemporary ones. The modern spines are a composite material formed by calcite nanocrystals oriented with their optical axes parallel to the elongated direction, which behave as a single crystal. Transmission Petrographic Microscopy (TPM) observations of the fossil spines prove that it is a calcite single crystal, whose optical axis coincides with the direction of elongation (as in the current spines). This paper presents a crystallographic approach to propose a secondary crystallisation mechanism, specifically the Ostwald ripening process, through a structural analysis that compares the spines and the conditions observed during the fossilisation process.

K-Means Clustering to Enhance the Petrified Wood Composition Data Analyses and Its Interpretation

Geologically, the fossilization of wood materials into fossils requires appropriate conditions, some of which have been preserved for millions of years. In nature, the organic mass of wood must be quickly replaced by inorganic elements before it decomposes under harsh geological conditions. Anorganic oxides such as silica-oxide, are known to be the main components of most wood specimens (up to 80%). The presence of alkaline oxides such as sodium and potassium oxide seems to play a major role in the presence of dissolved silica during petrification. However, their significance in the petrification phenomenon that occurs in fossilized plant wood is not yet known. Therefore, in this study, cluster analysis was conducted to determine the relationship between the presence of silica and alkaline compounds in petrified wood fossils. The approach used was -means clustering supported by the Elbow Method, which aims to review and order a complex set of data into subsets, thus allowing interpretation. The results showed that the clustering of the fossil wood composition data was optimal at = 3. There is a fair correlation between the presence of silica and alkali oxide compounds (-0.504 to -0.387), as well as with another inorganic compounds (+0.957). The presence of sodium and potassium is strongly correlated during silicification (+0.905). Additionally, the results of data clustering made the wood fossilization process susceptible to describe, especially through data regression. The data visualization provides more facts and proper explanations of the role of alkaline oxides in wood silicification. This study furthers our understanding of wood fossilization, especially the diagenesis of wood chemical composition in geological history.

Mammal taphonomy from a singular Late Pleistocene debris‐flow tank deposit in northeastern Brazil

ABSTRACTAn integrated taphonomic analysis was applied to a tank deposit from the Zabelê Palaeontological Site (ZPS) in northeast Brazil. The unique sedimentological evidence documents the origin of the mammal assemblage via debris flow. Optically stimulated luminescence (OSL) dates put the ZPS in the later Marine Isotope Stage (MIS) 3, which was a time when it was colder and there were fewer trees. The study revealed that the Zabelê's periphery accumulation was the result of the short transport of specimens and their entrainment by debris flow. This hydraulic transport caused the preferential orientation of the bioclasts (north–southwest). Comparisons were made with other Pleistocene tank deposits, suggesting the occurrence of common megamammal taxa. Temporal mixing was evidenced by the long time interval recorded by OSL ages and the co‐occurrence of distinct degrees of fragmentation, weathering, and fossil diagenesis. Permineralization and staining of Fe3+ and Mn colour patterns were identified as fossilization processes with preservation of the original bone hydroxyapatite without substitution. The comparison with other tank deposits revealed common signatures (disarticulated and fragmented with moderate abrasion) and signs of reworking. Finally, the savanna‐adapted herbivore megamammals from ZPS, such as Eremotherium, Notiomastodon, Toxodon, and Glyptotherium, are congruent with the forest decline from MIS 3 to the Last Glacial Maximum.

Mayfly larvae preservation from the Early Cretaceous of Brazilian Gondwana: Analogies with modern mats and other Lagerstätten

The Crato Formation paleoentomofauna is noticeable for its high abundance, diversity and morphological fidelity, so the preservational approach of the Ephemeroptera larvae fossils becomes relevant, since they are aquatic insects living in a lacustrine environment of one of the major terrestrial ecosystems of the Early Cretaceous in the Gondwana supercontinent. The mayfly larvae fossils were analyzed under a stereomicroscope and a scanning electron microscope with coupled x-ray spectroscopy (SEM/EDX) for morphological, textural and geochemical purposes. The microfabric analysis confirms the most recent hypothesis that the main factor responsible for the preservation of the Crato Formation fossils was the influence of the microbial mats on the fossilization process. The microscopic signatures left by the mats occur in the insect’s cuticle and internal parts, represented by micro cracks and wrinkles, micro spheres, filaments and mineralized EPS. These features have been compared in light with deposits containing Quaternary microbial mats in the Vermelha Lagoon and its associated salt pans, in Brazil. Also, we discussed our results with taphonomic data of other mayfly larvae fossils from the Lagerstätten La Huérguina (Spain) and Yixian (China) Formations, specifically in relation to the taphonomic settings regarding these Early Cretaceous ephemeropterans. This study corroborates to the idea of the fundamental role of the microbial mats in the exquisite preservation of the Crato Formation invertebrate fossils, with an approach that permits some fundamental paleoenvironmental and paleoclimatic inferences for the Aptian of the Araripe Basin, in Brazil.

Chemical and elementary characterization of Spongiophyton nanum: Understanding the phylogeny, paleoenvironment, and fossilization processes of an enigmatic flora

The record of thalloid macrofossils in the North-Northwest region of the Paraná Basin is less studied compared to that of invertebrate paleofauna in the same area. Consequently, the lack of important information regarding the niches occupied by thalloid embryophytes during early land colonization in this coastal paleoenvironment is evident. This study presents the first chemical and elemental data on Spongiophyton for this region of the basin, offering insights into its paleoenvironment and fossilization processes and providing considerations about the phylogeny of this enigmatic assemblage Spongiophyton nanum Kräusel emend. Chaloner et al. (1974) collected fragments from an outcropping rock in Jaciara, Mato Grosso, Brazil, and studied them using scanning electron microscope/energy X-ray dispersive spectrometer (EDS) and Fourier transform infrared (FTIR) spectroscopy techniques. The EDS analysis showed the highest elemental concentration of carbon, oxygen, and calcium as the main elements of the cuticle composition. Silicon and aluminum were better represented inside the pores than in other areas of the cuticle. The high carbon concentration in the cuticle suggested an anoxic condition prevalent during the deposition of the fine-grained sediments, which prevented its oxidation before and during diagenesis. The carbon present in the EDS spectra was restricted to the cuticle area, and the FTIR spectra indicated the presence of some functional groups, both related to the original organic matter, possibly cutin. Based on elemental characterization, the fossilization of S. nanum may involve more than one process, such as carbonification and mineralization, and S. nanum has more affinities with lichen groups.

Preservational modes of some ichthyosaur soft tissues (Reptilia, Ichthyopterygia) from the Jurassic Posidonia Shale of Germany

AbstractKonservat‐Lagerstätten, such as the Toarcian (Early Jurassic) Posidonia Shale of southwestern Germany, are renowned for their spectacular fossils. Ichthyosaur skeletons recovered from this formation are frequently associated with soft tissues; however, the preserved material ranges from three‐dimensional, predominantly phosphatized structures to dark films of mainly organic matter. We examined soft‐tissue residues obtained from two ichthyosaur specimens using an integrated ultrastructural and geochemical approach. Our analyses revealed that the superficially‐looking ‘films’ in fact comprise sections of densely aggregated melanosome (pigment) organelles sandwiched between phosphatized layers containing fibrous microstructures. We interpret this distinct layering as representing condensed and incompletely degraded integument from both sides of the animal. When compared against previously documented ichthyosaur fossils, it becomes readily apparent that a range of preservational modes exists between presumed ‘phosphatic’ and ‘carbonized’ soft‐tissue remains. Some specimens show high structural fidelity (e.g. distinct integumentary layering), while others, including the fossils examined in this study, retain few original anatomical details. This diversity of soft‐tissue preservational modes among Posidonia Shale ichthyosaurs offers a unique opportunity to examine different biostratinomic, taphonomic and diagenetic variables that potentially could affect the process of fossilization. It is likely that soft‐tissue preservation in the Posidonia Shale was regulated by a multitude of factors, including decay efficiency and speed of phosphatic mineral nucleation; these in turn were governed by a seafloor with sustained microbial mat activity fuelled by high organic matter input and seasonally fluctuating oxygen levels.

Biostratinomy of the enigmatic tubular organism Aulozoon soliorum, the Rawnsley Quartzite, South Australia

The Ediacaran fauna (574–539 Ma) are the first macroscopic community forming organisms on Earth, thus providing unique insight into the origins and evolution of complex life. However, the assignment of most Ediacaran organisms to specific phyla and kingdoms remains difficult due to their commonly non-analogous body plans and soft-bodied nature, which often results in the loss of diagnostic features through the processes of death and fossilization. Notably, this taphonomic overprint is not imparted equally to all Ediacaran organisms and is particularly exaggerated for the morphotypic grouping of tubular organisms. This morphogroup is comprised of macroscopic organisms with elongate, hollow, and simple body plans and is the most abundant Ediacaran morphogroup. However, the simple and hollow morphology of tubular organisms results in a broadly low preservation potential. In turn, this commonly limits the reconstruction of in vivo morphology, muddles taxonomic assignment, obfuscates phylogenetic affinities, and inhibits understanding of their broader significance. Fortunately, previous studies of abundant tubular taxa have demonstrated that taxon-level biostratinomic investigations can, in part, account for this low preservation potential. Such studies inform a more complete understanding of the morphogroup, providing novel insight into the paleobiology, paleoecology, and biomaterials of tubular taxa. To contribute to this biostratinomically-geared assessment of Ediacaran tubular organisms, this study analyzes the preservation of Aulozoon soliorum, an abundant tubular organism from the Rawnsley Quartzite of South Australia. This investigation demonstrates that Aulozoon is preserved via five preservational modes, which inform a novel in vivo reconstruction of Aulozoon as a sessile, fluid-filled, cylindrical organism with a holdfast and a thin, organic, and featureless body wall. The preservational modes identified here additionally inform a taphonomic framework under which Aulozoon fossils can be interpreted, thus furthering holistic understanding of the morphogroup-specific preservational variability of Ediacaran tubular organisms.

Low- and high-molecular weight fractions of geological ambers detected by evolved gas analysis-mass spectrometry

We used evolved gas analysis-mass spectrometry (EGA-MS) to characterize a pool of ambers belonging to different geological varieties, with the aim of obtaining information on both their non-polymeric and polymeric components. Small molecular components can be trapped in amber during the fossilization process. Their characterization can provide insights into the maturation process of amber and help in determining its age and botanical origin. Most of the analyzed ambers showed two gas evolution regions, corresponding to the desorption of low-molecular weight compounds at low temperature, and to the pyrolysis of the macromolecular matrix at high temperature. We established characteristic m/z signals of the non-polymeric and polymeric fractions, and we were able to classify most of the samples in agreement with the available literature. We also performed principal component analysis of diterpenoid ambers using their average mass spectra. This allowed us to differentiate between succinite and rumanite ambers, which showed very similar spectra. The results demonstrate that EGA-MS constitutes a reliable technique to obtain information on the molecular composition of ambers, and on their relative content of low- and high-molecular weight fractions.