Molecular preservation of the pigment melanin in fossil melanosomes

Fossilized anuran soft tissues reveal a new taphonomic model for the Eocene Geiseltal Konservat-Lagerstätte, Germany

The Eocene Geiseltal Konservat-Lagerstätte (Germany) is famous for reports of three dimensionally preserved soft tissues with sub-cellular detail. The proposed mode of preservation, direct replication in silica, is not known in other fossils and has not been verified using modern approaches. Here, we investigated the taphonomy of the Geiseltal anurans using diverse microbeam imaging and chemical analytical techniques. Our analyses confirm the preservation of soft tissues in all body regions but fail to yield evidence for silicified soft tissues. Instead, the anuran soft tissues are preserved as two layers that differ in microstructure and composition. Layer 1 comprises sulfur-rich carbonaceous microbodies interpreted as melanosomes. Layer 2 comprises the mid-dermal Eberth-Katschenko layer, preserved in calcium phosphate. In addition, patches of original aragonite crystals define the former position of the endolymphatic sac. The primary modes of soft tissue preservation are therefore sulfurization of melanosomes and phosphatization of more labile soft tissues, i.e., skin. This is consistent with the taphonomy of vertebrates in many other Konservat-Lagerstätten. These findings emphasize an emerging model for pervasive preservation of vertebrate soft tissues via melanosome films, particularly in stagnation-type deposits, with phosphatization of more labile tissues where tissue biochemistry is favorable.

Characterization of Sulfur-Rich Microbial Organic Matter in Jurassic Carbonates Using Laser-Assisted Mass Spectrometry

Laser desorption-ionization mass spectrometry (MS) shows great potential for in situ molecular analysis of planetary surfaces and microanalysis of space-returned samples or (micro)fossils. Coupled with pyrolysis gas chromatography-mass spectrometry (Py-GC-MS) in ESA's ExoMars project, this technique could help assess further the origin of sulfur-bearing organic matter (OM) recently detected on Mars. To unravel this potential, we analyzed sulfurized microbial OM from ca. 150 million year-old carbonates with laser desorption-ionization mass spectrometry (single- and two-step: LDI-MS and L2MS), in comparison with time-of-flight secondary-ion mass spectrometry (ToF-SIMS), gas chromatography-mass spectrometry (GC-MS), and Py-GC-MS. We show that LDI-MS and L2MS readily detect sulfur-bearing moieties such as (alkyl)thiophenes and (alkyl)benzothiophenes. The mineral matrix, however, made the identification of sulfur-bearing molecules challenging in our L2MS experiment. The dominance of small aromatic hydrocarbons (≤14 carbons) in the LDI-MS and L2MS of the extracted soluble and insoluble OM and of the bulk rock is consistent with the low thermal maturity of the sediment and contrasts with the predominance of larger polycyclic aromatic structures commonly observed in meteorites with these techniques. We detected inorganic ions, in particular VO+, in demineralized OM that likely originate from geoporphyrins, which derive from chlorophylls during sediment diagenesis. Finally, insoluble OM yielded distinct compositions compared with extracted soluble OM, with a greater abundance of ions of mass-to-charge ratio (m/z) over 175 and additional N-moieties. This highlights the potential of laser-assisted MS to decipher the composition of macromolecular OM, in particular to investigate the preservation of biomacromolecules in microfossils. Studies comparing diverse biogenic and abiogenic OM are needed to further assess the use of this technique to search for biosignatures.

Taphonomic experiments reveal authentic molecular signals for fossil melanins and verify preservation of phaeomelanin in fossils

Melanin pigments play a critical role in physiological processes and shaping animal behaviour. Fossil melanin is a unique resource for understanding the functional evolution of melanin but the impact of fossilisation on molecular signatures for eumelanin and, especially, phaeomelanin is not fully understood. Here we present a model for the chemical taphonomy of fossil eumelanin and phaeomelanin based on thermal maturation experiments using feathers from extant birds. Our results reveal which molecular signatures are authentic signals for thermally matured eumelanin and phaeomelanin, which signatures are artefacts derived from the maturation of non-melanin molecules, and how these chemical data are impacted by sample preparation. Our model correctly predicts the molecular composition of eumelanins in diverse vertebrate fossils from the Miocene and Cretaceous and, critically, identifies direct molecular evidence for phaeomelanin in these fossils. This taphonomic framework adds to the geochemical toolbox that underpins reconstructions of melanin evolution and of melanin-based coloration in fossil vertebrates.

Recent Advances in Characterization of Melanin Pigments in Biological Samples

The melanin pigments eumelanin (EM) and pheomelanin (PM), which are dark brown to black and yellow to reddish-brown, respectively, are widely found among vertebrates. They are produced in melanocytes in the epidermis, hair follicles, the choroid, the iris, the inner ear, and other tissues. The diversity of colors in animals is mainly caused by the quantity and quality of their melanin, such as by the ratios of EM versus PM. We have developed micro-analytical methods to simultaneously measure EM and PM and used these to study the biochemical and genetic fundamentals of pigmentation. The photoreactivity of melanin has become a major focus of research because of the postulated relevance of EM and PM for the risk of UVA-induced melanoma. Our biochemical methods have found application in many clinical studies on genetic conditions associated with alterations in pigmentation. Recently, besides chemical degradative methods, other methods have been developed for the characterization of melanin, and these are also discussed here.

An ancestral hard-shelled sea turtle with a mosaic of soft skin and scutes

The transition from terrestrial to marine environments by secondarily aquatic tetrapods necessitates a suite of adaptive changes associated with life in the sea, e.g., the scaleless skin in adult individuals of the extant leatherback turtle. A partial, yet exceptionally preserved hard-shelled (Pan-Cheloniidae) sea turtle with extensive soft-tissue remains, including epidermal scutes and a virtually complete flipper outline, was recently recovered from the Eocene Fur Formation of Denmark. Examination of the fossilized limb tissue revealed an originally soft, wrinkly skin devoid of scales, together with organic residues that contain remnant eumelanin pigment and inferred epidermal transformation products. Notably, this stem cheloniid-unlike its scaly living descendants-combined scaleless limbs with a bony carapace covered in scutes. Our findings show that the adaptive transition to neritic waters by the ancestral pan-chelonioids was more complex than hitherto appreciated, and included at least one evolutionary lineage with a mosaic of integumental features not seen in any living turtle.

Biomolecular histology as a novel proxy for ancient DNA and protein sequence preservation

Researchers' ability to accurately screen fossil and subfossil specimens for preservation of DNA and protein sequences remains limited. Thermal exposure and geologic age are usable proxies for sequence preservation on a broad scale but are of nominal use for specimens of similar depositional environments. Cell and tissue biomolecular histology is thus proposed as a novel proxy for determining sequence preservation potential of ancient specimens with improved accuracy. Biomolecular histology as a proxy is hypothesized to elucidate why fossils/subfossils of some depositional environments preserve sequences while others do not and to facilitate selection of ancient specimens for use in molecular studies.

Biosourced quinones for high-performance environmentally benign electrochemical capacitors via interface engineering

Biosourced and biodegradable organic electrode materials respond to the need for sustainable storage of renewable energy. Here, we report on electrochemical capacitors based on electrodes made up of quinones, such as Sepia melanin and catechin/tannic acid (Ctn/TA), solution-deposited on carbon paper engineered to create high-performance interfaces. Sepia melanin and Ctn/TA on TCP electrodes exhibit a capacitance as high as 1355 mF cm-2 (452 F g-1) and 898 mF cm-2 (300 F g-1), respectively. Sepia melanin and Ctn/TA symmetric electrochemical capacitors operating in aqueous electrolytes exhibit up to 100% capacitance retention and 100% coulombic efficiency over 50,000 and 10,000 cycles at 150 mA cm-2 (10 A g-1), respectively. Maximum power densities as high as 1274 mW cm-2 (46 kW kg-1) and 727 mW cm-2 (26 kW kg-1) with maximum energy densities of 0.56 mWh cm-2 (20 Wh kg-1) and 0.65 mWh cm-2 (23 Wh kg-1) are obtained for Sepia melanin and Ctn/TA.

Spatiotemporal Control of Melanin Synthesis in Liquid Droplets

Melanins are natural biopolymers that have remarkable properties including UV-protection, coloration, and antioxidant activity. Their biosynthesis is regulated both spatially and temporally and involves supramolecular templating and compartmentalization of enzymes and reactants within specialized organelles called melanosomes. In contrast, the laboratory-based bulk synthesis of melanin by tyrosine or dopamine oxidation is a poorly controlled process, resulting in materials with undefined properties. Inspired by the pigment's biosynthesis, we developed a methodology to spatiotemporally regulate melanin formation in liquid droplets. The spatial control is achieved by sequestration of the reaction in dextran-rich droplets of a polyethylene glycol/dextran aqueous two-phase system, where the use of a photocleavable protected tyrosine provides a temporal control over its enzymatic oxidation-polymerization. We show that the liquid droplets allow for confined local reactivity as they serve as reaction centers for melanin synthesis and compartmentalize the melanin product. This methodology opens tremendous opportunities for applications in skincare and biomedicine.

Comparative soft-tissue preservation in Holocene-age capelin concretions

Determining how soft tissues are preserved and persist through geologic time are continuing challenge because decay begins immediately after senescence while diagenetic transformations generally progress over days to millions of years. However, in recent years, carbonate concretions containing partially-to-fully decayed macroorganisms have proven to be remarkable windows into the diagenetic continuum revealing insights into the fossilization process. This is because most concretions are the result of biologically induced mineral precipitation caused by the localized decay of organic matter, which oftentimes preserves a greater biological signal relative to their host sediment. Here we present a comparative lipid biomarker study investigating processes associated with soft-tissue preservation within Holocene-age carbonate concretions that have encapsulated modern capelin (Mallotus villosus). We focus on samples collected from two depositional settings that have produced highly contrasting preservation end-members: (1) Kangerlussuaq, Greenland: a marine environment, which, due to isostatic rebound, has exposed strata containing concretions exhibiting exceptional soft-tissue preservation (6-7 kya), and (2) Greens Creek, Ottawa, Canada: a paleo brackish-to-freshwater marine excursion containing concretions exhibiting skeletal remains (~11 kya). Lipid biomarker analysis reveals endogenous capelin tissues and productive waters at Kangerlussuaq that are in sharp contrast to Greens Creek concretions, which lack appreciable capelin and environmental signals. Comparable distributions of bacterial fatty acids and statistical analyses suggest soft-tissue preservation within concretions is agnostic to specific heterotrophic decay communities. We, therefore, interpret preservation within carbonate concretions may represent a race between microbially induced authigenic precipitation and decay. Namely, factors resulting in exceptional preservation within concretions likely include: (1) organic matter input, (2) rate of decay, (3) carbonate saturation, (4) porewater velocity, and (5) rate of authigenic (carbonate) precipitation resulting in arrested decay/bacterial respiration due to cementing pore spaces limiting the diffusion of electron acceptors into the decay foci.

Chemistry and Analysis of Organic Compounds in Dinosaurs

This review provides an overview of organic compounds detected in non-avian dinosaur fossils to date. This was enabled by the development of sensitive analytical techniques. Non-destructive methods and procedures restricted to the sample surface, e.g., light and electron microscopy, infrared (IR) and Raman spectroscopy, as well as more invasive approaches including liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS), time-of-flight secondary ion mass spectrometry, and immunological methods were employed. Organic compounds detected in samples of dinosaur fossils include pigments (heme, biliverdin, protoporphyrin IX, melanin), and proteins, such as collagens and keratins. The origin and nature of the observed protein signals is, however, in some cases, controversially discussed. Molecular taphonomy approaches can support the development of suitable analytical methods to confirm reported findings and to identify further organic compounds in dinosaur and other fossils in the future. The chemical properties of the various organic compounds detected in dinosaurs, and the techniques utilized for the identification and analysis of each of the compounds will be discussed.

Preservation and Taphonomy of Fossil Insects from the Earliest Eocene of Denmark

Simple Summary

Insect fossils dating 55 million-years-old from the Stolleklint Clay and Fur Formation of Denmark are known to preserve both fine morphological details and color patterns. To enhance our understanding on how such fragile animals are retained in the fossil record, we examined a pair of beetle elytra, a wasp and a damselfly using sensitive analytical techniques. In our paper, we demonstrate that all three insect fossils are composed of cuticular remains (that is, traces of the exoskeleton) that, in turn, are dominated by the natural pigment eumelanin. In addition, the beetle elytra show evidence of a delicate lamellar structure comparable to multilayered reflectors that produce metallic hues in modern insects. Our results contribute to improved knowledge on the process of fossilization of insect body fossils in marine environments.

Abstract

Marine sediments of the lowermost Eocene Stolleklint Clay and Fur Formation of north-western Denmark have yielded abundant well-preserved insects. However, despite a long history of research, in-depth information pertaining to preservational modes and taphonomic pathways of these exceptional animal fossils remains scarce. In this paper, we use a combination of scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDX), transmission electron microscopy (TEM) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) to assess the ultrastructural and molecular composition of three insect fossils: a wasp (Hymenoptera), a damselfly (Odonata) and a pair of beetle elytra (Coleoptera). Our analyses show that all specimens are preserved as organic remnants that originate from the exoskeleton, with the elytra displaying a greater level of morphological fidelity than the other fossils. TEM analysis of the elytra revealed minute features, including a multilayered epicuticle comparable to those nanostructures that generate metallic colors in modern insects. Additionally, ToF-SIMS analyses provided spectral evidence for chemical residues of the pigment eumelanin as part of the cuticular remains. To the best of our knowledge, this is the first occasion where both structural colors and chemical traces of an endogenous pigment have been documented in a single fossil specimen. Overall, our results provide novel insights into the nature of insect body fossils and additionally shed light on exceptionally preserved terrestrial insect faunas found in marine paleoenvironments.

Biodegradation of bio-sourced and synthetic organic electronic materials towards green organic electronics

Ubiquitous use of electronic devices has led to an unprecedented increase in related waste as well as the worldwide depletion of reserves of key chemical elements required in their manufacturing. The use of biodegradable and abundant organic (carbon-based) electronic materials can contribute to alleviate the environmental impact of the electronic industry. The pigment eumelanin is a bio-sourced candidate for environmentally benign (green) organic electronics. The biodegradation of eumelanin extracted from cuttlefish ink is studied both at 25 °C (mesophilic conditions) and 58 °C (thermophilic conditions) following ASTM D5338 and comparatively evaluated with the biodegradation of two synthetic organic electronic materials, namely copper (II) phthalocyanine (Cu-Pc) and polyphenylene sulfide (PPS). Eumelanin biodegradation reaches 4.1% (25 °C) in 97 days and 37% (58 °C) in 98 days, and residual material is found to be without phytotoxic effects. The two synthetic materials, Cu-Pc and PPS, do not biodegrade; Cu-Pc brings about the inhibition of microbial respiration in the compost. PPS appears to be potentially phytotoxic. Finally, some considerations regarding the biodegradation test as well as the disambiguation of "biodegradability" and "bioresorbability" are highlighted.

Melanins as Sustainable Resources for Advanced Biotechnological Applications

Melanins are a class of biopolymers that are widespread in nature and have diverse origins, chemical compositions, and functions. Their chemical, electrical, optical, and paramagnetic properties offer opportunities for applications in materials science, particularly for medical and technical uses. This review focuses on the application of analytical techniques to study melanins in multidisciplinary contexts with a view to their use as sustainable resources for advanced biotechnological applications, and how these may facilitate the achievement of the United Nations Sustainable Development Goals.

Taphonomic patterns mimic biologic structures: diagenetic Liesegang rings in Mesozoic coleoids and coprolites

Because of physiology of coleoids, their fossils preserve soft-tissue-remains more often than other cephalopods. Sometimes, the phosphatized soft-tissues, particularly parts of the muscular mantle, display dark circular patterns. Here, we showcase that these patterns, here documented for fossil coleoids from the Jurassic of Germany and the Cretaceous of Lebanon, superficially resemble chromatophores (which enable living coleoids to alter their coloration). We examined and chemically analyzed the circular structures in these specimens, describe them, and discuss their genesis. Based on their structure and color, we visually differentiate between three types of circles. By comparison with similar structures, we suggest that these structures are not biogenic but Liesegang rings, which formed due to reaction-diffusion processes very soon after death.

Recent advances in heteromorph ammonoid palaeobiology

Heteromorphs are ammonoids forming a conch with detached whorls (open coiling) or non-planispiral coiling. Such aberrant forms appeared convergently four times within this extinct group of cephalopods. Since Wiedmann's seminal paper in this journal, the palaeobiology of heteromorphs has advanced substantially. Combining direct evidence from their fossil record, indirect insights from phylogenetic bracketing, and physical as well as virtual models, we reach an improved understanding of heteromorph ammonoid palaeobiology. Their anatomy, buoyancy, locomotion, predators, diet, palaeoecology, and extinction are discussed. Based on phylogenetic bracketing with nautiloids and coleoids, heteromorphs like other ammonoids had 10 arms, a well-developed brain, lens eyes, a buccal mass with a radula and a smaller upper as well as a larger lower jaw, and ammonia in their soft tissue. Heteromorphs likely lacked arm suckers, hooks, tentacles, a hood, and an ink sac. All Cretaceous heteromorphs share an aptychus-type lower jaw with a lamellar calcitic covering. Differences in radular tooth morphology and size in heteromorphs suggest a microphagous diet. Stomach contents of heteromorphs comprise planktic crustaceans, gastropods, and crinoids, suggesting a zooplanktic diet. Forms with a U-shaped body chamber (ancylocone) are regarded as suspension feeders, whereas orthoconic forms additionally might have consumed benthic prey. Heteromorphs could achieve near-neutral buoyancy regardless of conch shape or ontogeny. Orthoconic heteromorphs likely had a vertical orientation, whereas ancylocone heteromorphs had a near-horizontal aperture pointing upwards. Heteromorphs with a U-shaped body chamber are more stable hydrodynamically than modern Nautilus and were unable substantially to modify their orientation by active locomotion, i.e. they had no or limited access to benthic prey at adulthood. Pathologies reported for heteromorphs were likely inflicted by crustaceans, fish, marine reptiles, and other cephalopods. Pathologies on Ptychoceras corroborates an external shell and rejects the endocochleate hypothesis. Devonian, Triassic, and Jurassic heteromorphs had a preference for deep-subtidal to offshore facies but are rare in shallow-subtidal, slope, and bathyal facies. Early Cretaceous heteromorphs preferred deep-subtidal to bathyal facies. Late Cretaceous heteromorphs are common in shallow-subtidal to offshore facies. Oxygen isotope data suggest rapid growth and a demersal habitat for adult Discoscaphites and Baculites. A benthic embryonic stage, planktic hatchlings, and a habitat change after one whorl is proposed for Hoploscaphites. Carbon isotope data indicate that some Baculites lived throughout their lives at cold seeps. Adaptation to a planktic life habit potentially drove selection towards smaller hatchlings, implying high fecundity and an ecological role of the hatchlings as micro- and mesoplankton. The Chicxulub impact at the Cretaceous/Paleogene (K/Pg) boundary 66 million years ago is the likely trigger for the extinction of ammonoids. Ammonoids likely persisted after this event for 40-500 thousand years and are exclusively represented by heteromorphs. The ammonoid extinction is linked to their small hatchling sizes, planktotrophic diets, and higher metabolic rates than in nautilids, which survived the K/Pg mass extinction event.

Chemical Imaging of Retinal Pigment Epithelium in Frozen Sections of Zebrafish Larvae Using ToF-SIMS

Variants of the SLC24A5 gene, which encodes a putative potassium-dependent sodium-calcium exchanger (NCKX5) that most likely resides in the melanosome or its precursor, affect pigmentation in both humans and zebrafish (Danio rerio). This finding suggests that genetic variations influencing human skin pigmentation alter melanosome biogenesis via ionic changes. Gaining an understanding of how changes in the ionic environment of organelles impact melanosome morphogenesis and pigmentation will require a spatially resolved way to characterize the chemical environment of melanosomes in pigmented tissue such as retinal pigment epithelium (RPE). The imaging mass spectrometry technique most suited for this type of cell and tissue analysis is time-of-flight secondary ion mass spectrometry (ToF-SIMS) because it is able to detect many biochemical species with high sensitivity and with submicron spatial resolution. Here, we describe chemical imaging of the RPE in frozen-hydrated sections of larval zebrafish using cryo-ToF-SIMS. To facilitate the data interpretation, positive and negative polarity ToF-SIMS image data were transformed into a single hyperspectral data set and analyzed using principal component analysis. The combination of a novel protocol and the use of multivariate data analysis allowed us to discover new marker ions that are attributable to leucodopachrome, a metabolite specific to the biosynthesis of eumelanin. The described methodology may be adapted for the investigation of other classes of molecules in frozen tissues from zebrafish and other organisms.

Chemical Evaluation of Eumelanin Maturation by ToF-SIMS and Alkaline Peroxide Oxidation HPLC Analysis

Residual melanins have been detected in multimillion-year-old animal body fossils; however, confident identification and characterization of these natural pigments remain challenging due to loss of chemical signatures during diagenesis. Here, we simulate this post-burial process through artificial maturation experiments using three synthetic and one natural eumelanin exposed to mild (100 °C/100 bar) and harsh (250 °C/200 bar) environmental conditions, followed by chemical analysis employing alkaline hydrogen peroxide oxidation (AHPO) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). Our results show that AHPO is sensitive to changes in the melanin molecular structure already during mild heat and pressure treatment (resulting, e.g., in increased C-C cross-linking), whereas harsh maturation leads to extensive loss of eumelanin-specific chemical markers. In contrast, negative-ion ToF-SIMS spectra are considerably less affected by mild maturation conditions, and eumelanin-specific features remain even after harsh treatment. Detailed analysis of ToF-SIMS spectra acquired prior to experimental treatment revealed significant differences between the investigated eumelanins. However, systematic spectral changes upon maturation reduced these dissimilarities, indicating that intense heat and pressure treatment leads to the formation of a common, partially degraded, eumelanin molecular structure. Our findings elucidate the complementary nature of AHPO and ToF-SIMS during chemical characterization of eumelanin traces in fossilized organismal remains.

Electronic Transport in the Biopigment Sepia Melanin

Eumelanin is the most common form of the pigment melanin in the human body, with diverse functions including photoprotection, antioxidant behavior, metal chelation, and free radical scavenging. Melanin also plays a role in melanoma skin cancer and Parkinson's disease. Sepia melanin is a natural eumelanin extracted from the ink sac of cuttlefish. Eumelanin is an ideal candidate to eco-design technologies based on abundant, biosourced, and biodegradable organic electronic materials to alleviate the environmental footprint of the electronics sector. Herein, the focus is on the reversible electrical resistive switching in dry and wet Sepia eumelanin pellets, pointing to the possibility of predominant electronic transport satisfying conditio sine qua non to develop melanin-based electronic devices. These findings shed light on the possibility to describe the transport physics of dry eumelanin using the amorphous semiconductor model. Results are of tremendous importance for the development of sustainable organic electronics.

Insights into a 429-million-year-old compound eye

In all arthropods the plesiomorphic (ancestral character state) kind of visual system commonly is considered to be the compound eye. Here we are able to show the excellently preserved internal structures of the compound eye of a 429 Mya old Silurian trilobite, Aulacopleura koninckii (Barrande, 1846). It shows the characteristic elements of a modern apposition eye, consisting of 8 (visible) receptor cells, a rhabdom, a thick lens, screening pigment (cells), and in contrast to a modern type, putatively just a very thin crystalline cone. Functionally the latter underlines the idea of a primarily calcitic character of the lens because of its high refractive properties. Perhaps the trilobite was translucent. We show that this Palaeozoic trilobite in principle was equipped with a fully modern type of visual system, a compound eye comparable to that of living bees, dragonflies and many diurnal crustaceans. It is an example of excellent preservation, and we hope that this manuscript will be a starting point for more research work on fossil evidence, and to develop a deeper understanding of the evolution of vision.

Exceptionally preserved 'skin' in an Early Cretaceous fish from Colombia

Studies of soft tissue, cells and original biomolecular constituents preserved in fossil vertebrates have increased greatly in recent years. Here we report preservation of 'skin' with chemical and molecular characterization from a three-dimensionally preserved caudal portion of an aspidorhynchid Cretaceous fish from the equatorial Barremian of Colombia, increasing the number of localities for which exceptional preservation is known. We applied several analytical techniques including SEM-EDS, FTIR and ToF-SIMS to characterize the micromorphology and molecular and elemental composition of this fossil. Here, we show that the fossilized 'skin' exhibits similarities with those from extant fish, including the wrinkles after suffering compression stress and flexibility, as well as architectural and tissue aspects of the two main layers (epidermis and dermis). This similarity extends also to the molecular level, with the demonstrated preservation of potential residues of original proteins not consistent with a bacterial source. Our results show a potential preservation mechanism where scales may have acted as an external barrier and together with an internal phosphate layer resulting from the degradation of the dermis itself creating an encapsulated environment for the integument.

New preparation techniques for molecular and in-situ analysis of ancient organic micro- and nanostructures

Organic microfossils preserved in three dimensions in transparent mineral matrices such as cherts/quartzites, phosphates, or carbonates are best studied in petrographic thin sections. Moreover, microscale mass spectrometry techniques commonly require flat, polished surfaces to minimize analytical bias. However, contamination by epoxy resin in traditional petrographic sections is problematic for the geochemical study of the kerogen in these microfossils and more generally for the in situ analysis of fossil organic matter. Here, we show that epoxy contamination has a molecular signature that is difficult to distinguish from kerogen with time-of-flight secondary ion mass spectrometry (ToF-SIMS). This contamination appears pervasive in organic microstructures embedded in micro- to nano-crystalline carbonate. To solve this problem, a new semi-thin section preparation protocol without resin medium was developed for micro- to nanoscale in situ investigation of insoluble organic matter. We show that these sections are suited for microscopic observation of Proterozoic microfossils in cherts. ToF-SIMS reveals that these sections are free of pollution after final removal of a <10 nm layer of contamination using low-dose ion sputtering. ToF-SIMS maps of fragments from aliphatic and aromatic molecules and organic sulfur are correlated with the spatial distribution of organic microlaminae in a Jurassic stromatolite. Hydrocarbon-derived ions also appeared correlated with kerogenous microstructures in Archean cherts. These developments in analytical procedures should help future investigations of organic matter and in particular, microfossils, by allowing the spatial correlation of microscopy, spectroscopy, precise isotopic microanalyses, and novel molecular microanalyses such as ToF-SIMS.

Hierarchical biota-level and taxonomic controls on the chemistry of fossil melanosomes revealed using synchrotron X-ray fluorescence

Fossil melanosomes, micron-sized granules rich in melanin in vivo, provide key information for investigations of the original coloration, taxonomy and internal anatomy of fossil vertebrates. Such studies rely, in part, on analysis of the inorganic chemistry of preserved melanosomes and an understanding of melanosome chemical taphonomy. The extent to which the preserved chemistry of fossil melanosomes is biased by biotic and abiotic factors is, however, unknown. Here we report the discovery of hierarchical controls on the inorganic chemistry of melanosomes from fossil vertebrates from nine biotas. The chemical data are dominated by a strong biota-level signal, indicating that the primary taphonomic control is the diagenetic history of the host sediment. This extrinsic control is superimposed by a biological, tissue-level control; tissue-specific chemical variation is most likely to survive in fossils where the inorganic chemistry of preserved melanosomes is distinct from that of the host sediment. Comparative analysis of our data for fossil and modern amphibians reveals that most fossil specimens show tissue-specific melanosome chemistries that differ from those of extant analogues, strongly suggesting alteration of original melanosome chemistry. Collectively, these findings form a predictive tool for the identification of fossil deposits with well-preserved melanosomes amenable to studies of fossil colour and anatomy.

Recent advances in amniote palaeocolour reconstruction and a framework for future research

Preserved melanin pigments have been discovered in fossilised integumentary appendages of several amniote lineages (fishes, frogs, snakes, marine reptiles, non-avialan dinosaurs, birds, and mammals) excavated from lagerstätten across the globe. Melanisation is a leading factor in organic integument preservation in these fossils. Melanin in extant vertebrates is typically stored in rod- to sphere-shaped, lysosome-derived, membrane-bound vesicles called melanosomes. Black, dark brown, and grey colours are produced by eumelanin, and reddish-brown colours are produced by phaeomelanin. Specific morphotypes and nanostructural arrangements of melanosomes and their relation to the keratin matrix in integumentary appendages create the so-called 'structural colours'. Reconstruction of colour patterns in ancient animals has opened an exciting new avenue for studying their life, behaviour and ecology. Modern relationships between the shape, arrangement, and size of avian melanosomes, melanin chemistry, and feather colour have been applied to reconstruct the hues and colour patterns of isolated feathers and plumages of the dinosaurs Anchiornis, Sinosauropteryx, and Microraptor in seminal papers that initiated the field of palaeocolour reconstruction. Since then, further research has identified countershading camouflage patterns, and informed subsequent predictions on the ecology and behaviour of these extinct animals. However, palaeocolour reconstruction remains a nascent field, and current approaches have considerable potential for further refinement, standardisation, and expansion. This includes detailed study of non-melanic pigments that might be preserved in fossilised integuments. A common issue among existing palaeocolour studies is the lack of contextualisation of different lines of evidence and the wide variety of techniques currently employed. To that end, this review focused on fossil amniotes: (i) produces an overarching framework that appropriately reconstructs palaeocolour by accounting for the chemical signatures of various pigments, morphology and local arrangement of pigment-bearing vesicles, pigment concentration, macroscopic colour patterns, and taphonomy; (ii) provides background context for the evolution of colour-producing mechanisms; and (iii) encourages future efforts in palaeocolour reconstructions particularly of less-studied groups such as non-dinosaur archosaurs and non-archosaur amniotes.

Taphonomic experiments resolve controls on the preservation of melanosomes and keratinous tissues in feathers

Fossils are a key source of data on the evolution of feather structure and function through deep time, but their ability to resolve macroevolutionary questions is compromised by an incomplete understanding of their taphonomy. Critically, the relative preservation potential of two key feather components, melanosomes and keratinous tissue, is not fully resolved. Recent studies suggesting that melanosomes are preferentially preserved conflict with observations that melanosomes preserve in fossil feathers as external moulds in an organic matrix. To date, there is no model to explain the latter mode of melanosome preservation. We addressed these issues by degrading feathers in systematic taphonomic experiments incorporating decay, maturation and oxidation in isolation and combination. Our results reveal that the production of mouldic melanosomes requires interactions with an oxidant and is most likely to occur prior to substantial maturation. This constrains the taphonomic conditions under which melanosomes are likely to be fossilized. Critically, our experiments also confirm that keratinous feather structures have a higher preservation potential than melanosomes under a range of diagenetic conditions, supporting hitherto controversial hypotheses that fossil feathers can retain degraded keratinous structures.

Chemical characterization of pterosaur melanin challenges color inferences in extinct animals

Melanosomes (melanin-bearing organelles) are common in the fossil record occurring as dense packs of globular microbodies. The organic component comprising the melanosome, melanin, is often preserved in fossils, allowing identification of the chemical nature of the constituent pigment. In present-day vertebrates, melanosome morphology correlates with their pigment content in selected melanin-containing structures, and this interdependency is employed in the color reconstruction of extinct animals. The lack of analyses integrating the morphology of fossil melanosomes with the chemical identification of pigments, however, makes these inferences tentative. Here, we chemically characterize the melanin content of the soft tissue headcrest of the pterosaur Tupandactylus imperator by alkaline hydrogen peroxide oxidation followed by high-performance liquid chromatography. Our results demonstrate the unequivocal presence of eumelanin in T. imperator headcrest. Scanning electron microscopy followed by statistical analyses, however, reveal that preserved melanosomes containing eumelanin are undistinguishable to pheomelanin-bearing organelles of extant vertebrates. Based on these new findings, straightforward color inferences based on melanosome morphology may not be valid for all fossil vertebrates, and color reconstructions based on ultrastructure alone should be regarded with caution.

Applications of chemical imaging techniques in paleontology

Chemical imaging techniques, based on a combination of microscopy and spectroscopy, are designed to analyse the composition and spatial distribution of heterogeneous chemical complexes within a sample. Over the last few decades, it has become an increasingly popular tool for characterizing trace elements, isotopic information and organic biomarkers (molecular biosignatures) found in fossils. Here, we introduce the analytical principle of each technique and the interpretation of the chemical signals, followed by a review of the main applications of these techniques in paleontology. We also demonstrate that each technique is associated with pros and cons, and the current limitations and obstacles associated with the use of each specific technique should be taken into account before being applied to fossil samples. Finally, we propose that, due to the rapid advances in the available technology and overall trends towards more multi-disciplinary studies in paleontology, chemical imaging techniques can be expected to have broader applications in paleontology in the near future.

Mechanistic understanding of monovalent cation transport in eumelanin pigments

Recent research advances in charge-conducting materials have enabled the transformation of the naturally-occurring materials into crucial components in many technologies, including renewable energy storage devices or bioelectronics. Among various candidates, eumelanins are promising charge storage materials, exhibiting hybrid electronic ionic conductivity in a hydrated environment. The chemical and electrochemical properties of eumelanins are relatively well studied; however, the structure-property relationship is still elusive up to date. Herein, we reported the mesoscale structure of eumelanins and its impact on the charge transport. X-ray scattering suggests that eumelanin pigments exhibit the semi-crystalline structure with ordered d-spacings. These unique mesoscale structures further influence the charge transport mechanism with the cations of various sizes. Understanding the structures with consequent electrochemical properties suggest that eumelanins can further be tuned to serve as high-performance naturally-occurring charge storage materials.

Tissue-specific geometry and chemistry of modern and fossilized melanosomes reveal internal anatomy of extinct vertebrates

Recent reports of nonintegumentary melanosomes in fossils hint at functions for melanin beyond color production, but the biology and evolution of internal melanins are poorly understood. Our results show that internal melanosomes are widespread in diverse fossil and modern vertebrates and have tissue-specific geometries and metal chemistries. Tissue-specific chemical signatures can persist in fossils despite some diagenetic overprint, allowing the reconstruction of internal soft-tissue anatomy in fossil vertebrates, and suggest that links between melanin and metal regulation have deep evolutionary origins in vertebrates.

Recent discoveries of nonintegumentary melanosomes in extant and fossil amphibians offer potential insights into the physiological functions of melanin not directly related to color production, but the phylogenetic distribution and evolutionary history of these internal melanosomes has not been characterized systematically. Here, we present a holistic method to discriminate among melanized tissues by analyzing the anatomical distribution, morphology, and chemistry of melanosomes in various tissues in a phylogenetically broad sample of extant and fossil vertebrates. Our results show that internal melanosomes in all extant vertebrates analyzed have tissue-specific geometries and elemental signatures. Similar distinct populations of preserved melanosomes in phylogenetically diverse vertebrate fossils often map onto specific anatomical features. This approach also reveals the presence of various melanosome-rich internal tissues in fossils, providing a mechanism for the interpretation of the internal anatomy of ancient vertebrates. Collectively, these data indicate that vertebrate melanins share fundamental physiological roles in homeostasis via the scavenging and sequestering of metals and suggest that intimate links between melanin and metal metabolism in vertebrates have deep evolutionary origins.

Fossil insect eyes shed light on trilobite optics and the arthropod pigment screen

Fossilized eyes permit inferences of the visual capacity of extinct arthropods^1-3. However, structural and/or chemical modifications as a result of taphonomic and diagenetic processes can alter the original features, thereby necessitating comparisons with modern species. Here we report the detailed molecular composition and microanatomy of the eyes of 54-million-year-old crane-flies, which together provide a proxy for the interpretation of optical systems in some other ancient arthropods. These well-preserved visual organs comprise calcified corneal lenses that are separated by intervening spaces containing eumelanin pigment. We also show that eumelanin is present in the facet walls of living crane-flies, in which it forms the outermost ommatidial pigment shield in compound eyes incorporating a chitinous cornea. To our knowledge, this is the first record of melanic screening pigments in arthropods, and reveals a fossilization mode in insect eyes that involves a decay-resistant biochrome coupled with early diagenetic mineralization of the ommatidial lenses. The demonstrable secondary calcification of lens cuticle that was initially chitinous has implications for the proposed calcitic corneas of trilobites, which we posit are artefacts of preservation rather than a product of in vivo biomineralization^4-7. Although trilobite eyes might have been partly mineralized for mechanical strength, a (more likely) organic composition would have enhanced function via gradient-index optics and increased control of lens shape.

Paleoproteomics of Mesozoic Dinosaurs and Other Mesozoic Fossils

Molecular studies have contributed greatly to our understanding of evolutionary processes that act upon virtually every aspect of living organisms. However, these studies are limited with regard to extinct organisms, particularly those from the Mesozoic because fossils pose unique challenges to molecular workflows, and because prevailing wisdom suggests no endogenous molecular components can persist into deep time. Here, the power and potential of a molecular approach to Mesozoic fossils is discussed. Molecular methods that have been applied to Mesozoic fossils-including iconic, non-avian dinosaurs- and the challenges inherent in such analyses, are compared and evaluated. Taphonomic processes resulting in the transition of living organisms from the biosphere into the fossil record are reviewed, and the possible effects of taphonomic alteration on downstream analyses that can be problematic for very old material (e.g., molecular modifications, limitations of on comparative databases) are addressed. Molecular studies applied to ancient remains are placed in historical context, and past and current studies are evaluated with respect to producing phylogenetically and/or evolutionarily significant data. Finally, some criteria for assessing the presence of endogenous biomolecules in very ancient fossil remains are suggested as a starting framework for such studies.

The Early Origin of Feathers

Feathers have long been regarded as the innovation that drove the success of birds. However, feathers have been reported from close dinosaurian relatives of birds, and now from ornithischian dinosaurs and pterosaurs, the cousins of dinosaurs. Incomplete preservation makes these reports controversial. If true, these findings shift the origin of feathers back 80 million years before the origin of birds. Gene regulatory networks show the deep homology of scales, feathers, and hairs. Hair and feathers likely evolved in the Early Triassic ancestors of mammals and birds, at a time when synapsids and archosaurs show independent evidence of higher metabolic rates (erect gait and endothermy), as part of a major resetting of terrestrial ecosystems following the devastating end-Permian mass extinction.

Fossilised Biomolecules and Biomarkers in Carbonate Concretions from Konservat-Lagerstätten

In the vast majority of fossils, the organic matter is degraded with only an impression or cast of the organism remaining. In rare cases, ideal burial conditions result in a rapid fossilisation with an exceptional preservation of soft tissues and occasionally organic matter. Such deposits are known as Lagerstätten and have been found throughout the geological record. Exceptional preservation is often associated with finely crystalline quartz (e.g., cherts), fine sediments (e.g., muds) or volcanic ashes. Other mechanisms include burial in anoxic/euxinic sediments and in the absence of turbidity or scavenging. Exceptional preservation can also occur when an organism is encapsulated in carbonate cement, forming a concretion. This mechanism involves complex microbial processes, resulting in a supersaturation in carbonate, with microbial sulfate reduction and methane cycling the most commonly suggested processes. In addition, conditions of photic zone euxinia are often found to occur during concretion formation in marine environments. Concretions are ideal for the study of ancient and long-extinct organisms, through both imaging techniques and biomolecular approaches. These studies have provided valuable insights into the evolution of organisms and their environments through the Phanerozoic and have contributed to increasing interest in fields including chemotaxonomy, palaeobiology, palaeoecology and palaeophysiology.

Melanosomes: Biogenesis, Properties, and Evolution of an Ancient Organelle

Melanosomes are organelles that produce and store melanin, a widespread biological pigment with a unique suite of properties including high refractive index, semiconducting capabilities, material stiffness, and high fossilization potential. They are involved in numerous critical biological functions in organisms across the tree of life. Individual components such as melanin chemistry and melanosome development have recently been addressed, but a broad synthesis is needed. Here, we review the hierarchical structure, development, functions, and evolution of melanosomes. We highlight variation in melanin chemistry and melanosome morphology and how these may relate to function. For example, we review what is known of the chemical differences between different melanin types (eumelanin, pheomelanin, allomelanin) and whether/how melanosome morphology relates to chemistry and color. We integrate the distribution of melanin across living organisms with what is known from the fossil record and produce hypotheses on its evolution. We suggest that melanin was present in life forms early in evolutionary history and that melanosomes evolved at the origin of organelles. Throughout, we discuss the (sometimes gaping) holes in our knowledge and suggest areas that need particular attention as we move forward in our understanding of these still-mysterious organelles and the materials that they contain.

Preservation potential of keratin in deep time

Multiple fossil discoveries and taphonomic experiments have established the durability of keratin. The utility and specificity of antibodies to identify keratin peptides has also been established, both in extant feathers under varying treatment conditions, and in feathers from extinct organisms. Here, we show localization of feather-keratin antibodies to control and heat-treated feathers, testifying to the repeatability of initial data supporting the preservation potential of keratin. We then show new data at higher resolution that demonstrates the specific response of these antibodies to the feather matrix, we support the presence of protein in heat-treated feathers using ToF-SIMS, and we apply these methods to a fossil feather preserved in the unusual environment of sinter hot springs. We stress the importance of employing realistic conditions such as sediment burial when designing experiments intended as proxies for taphonomic processes occurring in the fossil record. Our data support the hypothesis that keratin, particularly the β-keratin that comprises feathers, has potential to preserve in fossil remains.

Characterization of natural photonic crystals in iridescent wings of damselfly Chalcopteryx rutilans by FIB/SEM, TEM, and TOF-SIMS

The iridescent wings of the Chalcopterix rutilans damselfly (Rambur) (Odonata, Polythoridae) are investigated with focused ion beam/scanning electron microscopy, transmission electron microscopy, and time-of-flight secondary ion mass spectrometry. The electron microscopy images reveal a natural photonic crystal as the source of the varying colors. The photonic crystal has a consistent number and thickness (∼195 nm) of the repeat units on the ventral side of the wing, which is consistent with the red color visible from the bottom side of the wing in all regions. The dorsal side of the wing shows strong color variations ranging from red to blue depending on the region. In the electron microscopy images, the dorsal side of the wing exhibits varied number and thicknesses of the repeat units. The repeat unit spacings for the red, yellow/green, and blue regions are approximately 195, 180, and 145 nm, respectively. Three-dimensional analysis of the natural photonic crystals by time-of-flight secondary ion mass spectrometry reveals that changes in the relative levels of Na, K, and eumelanin are responsible for the varying dielectric constant needed to generate the photonic crystal. The photonic crystal also appears to be assembled with a chemical tricomponent layer structure due to the enhancement of the CH₆N₃⁺ species at every other interface between the high/low dielectric constant layers.

A Comparison of Common Mass Spectrometry Approaches for Paleoproteomics

The last two decades have seen a broad diversity of methods used to identify and/or characterize proteins in the archeological and paleontological record. Of these, mass spectrometry has opened an unprecedented window into the proteomes of the past, providing protein sequence data from long extinct animals as well as historical and prehistorical artifacts. Thus, application of mass spectrometry to fossil remains has become an attractive source for ancient molecular sequences with which to conduct evolutionary studies, particularly in specimens older than the proposed limit of amplifiable DNA detection. However, "mass spectrometry" covers a range of mass-based proteomic approaches, each of which utilize different technology and physical principles to generate unique types of data, with their own strengths and challenges. Here, we discuss a variety of mass spectrometry techniques that have or may be used to detect and characterize archeological and paleontological proteins, with a particular focus on MALDI-MS, LC-MS/MS, TOF-SIMS, and MSi. The main differences in their functionality, the types of data they produce, and the potential effects of diagenesis on their results are considered.

Pigmented anatomy in Carboniferous cyclostomes and the evolution of the vertebrate eye

The success of vertebrates is linked to the evolution of a camera-style eye and sophisticated visual system. In the absence of useful data from fossils, scenarios for evolutionary assembly of the vertebrate eye have been based necessarily on evidence from development, molecular genetics and comparative anatomy in living vertebrates. Unfortunately, steps in the transition from a light-sensitive ‘eye spot’ in invertebrate chordates to an image-forming camera-style eye in jawed vertebrates are constrained only by hagfish and lampreys (cyclostomes), which are interpreted to reflect either an intermediate or degenerate condition. Here, we report—based on evidence of size, shape, preservation mode and localized occurrence—the presence of melanosomes (pigment-bearing organelles) in fossil cyclostome eyes. Time of flight secondary ion mass spectrometry analyses reveal secondary ions with a relative intensity characteristic of melanin as revealed through principal components analyses. Our data support the hypotheses that extant hagfish eyes are degenerate, not rudimentary, that cyclostomes are monophyletic, and that the ancestral vertebrate had a functional visual system. We also demonstrate integument pigmentation in fossil lampreys, opening up the exciting possibility of investigating colour patterning in Palaeozoic vertebrates. The examples we report add to the record of melanosome preservation in Carboniferous fossils and attest to surprising durability of melanosomes and biomolecular melanin.

Biochemistry and adaptive colouration of an exceptionally preserved juvenile fossil sea turtle

The holotype (MHM-K2) of the Eocene cheloniine Tasbacka danica is arguably one of the best preserved juvenile fossil sea turtles on record. Notwithstanding compactional flattening, the specimen is virtually intact, comprising a fully articulated skeleton exposed in dorsal view. MHM-K2 also preserves, with great fidelity, soft tissue traces visible as a sharply delineated carbon film around the bones and marginal scutes along the edge of the carapace. Here we show that the extraordinary preservation of the type of T. danica goes beyond gross morphology to include ultrastructural details and labile molecular components of the once-living animal. Haemoglobin-derived compounds, eumelanic pigments and proteinaceous materials retaining the immunological characteristics of sauropsid-specific β-keratin and tropomyosin were detected in tissues containing remnant melanosomes and decayed keratin plates. The preserved organics represent condensed remains of the cornified epidermis and, likely also, deeper anatomical features, and provide direct chemical evidence that adaptive melanism – a biological means used by extant sea turtle hatchlings to elevate metabolic and growth rates – had evolved 54 million years ago.

Cellular preservation of musculoskeletal specializations in the Cretaceous bird Confuciusornis

The hindlimb of theropod dinosaurs changed appreciably in the lineage leading to extant birds, becoming more ‘crouched' in association with changes to body shape and gait dynamics. This postural evolution included anatomical changes of the foot and ankle, altering the moment arms and control of the muscles that manipulated the tarsometatarsus and digits, but the timing of these changes is unknown. Here, we report cellular-level preservation of tendon- and cartilage-like tissues from the lower hindlimb of Early Cretaceous Confuciusornis. The digital flexor tendons passed through cartilages, cartilaginous cristae and ridges on the plantar side of the distal tibiotarsus and proximal tarsometatarsus, as in extant birds. In particular, fibrocartilaginous and cartilaginous structures on the plantar surface of the ankle joint of Confuciusornis may indicate a more crouched hindlimb posture. Recognition of these specialized soft tissues in Confuciusornis is enabled by our combination of imaging and chemical analyses applied to an exceptionally preserved fossil.

Birds have a more crouched posture compared to their theropod dinosaur ancestors. Here, Jiang and colleagues describe a lower hindlimb of the Early Cretaceous bird Confuciusornis with soft tissues apparently preserved even as molecules, indicating a somewhat more modern posture in ancient birds.

Pre-plaque conformational changes in Alzheimer's disease-linked Aβ and APP

Reducing levels of the aggregation-prone Aβ peptide that accumulates in the brain with Alzheimer's disease (AD) has been a major target of experimental therapies. An alternative approach may be to stabilize the physiological conformation of Aβ. To date, the physiological state of Aβ in brain remains unclear, since the available methods used to process brain tissue for determination of Aβ aggregate conformation can in themselves alter the structure and/or composition of the aggregates. Here, using synchrotron-based Fourier transform infrared micro-spectroscopy, non-denaturing gel electrophoresis and conformational specific antibodies we show that the physiological conformations of Aβ and amyloid precursor protein (APP) in brain of transgenic mouse models of AD are altered before formation of amyloid plaques. Furthermore, focal Aβ aggregates in brain that precede amyloid plaque formation localize to synaptic terminals. These changes in the states of Aβ and APP that occur prior to plaque formation may provide novel targets for AD therapy.

Functions of fungal melanin beyond virulence

Melanins are ancient biological pigments found in all kingdoms of life. In fungi, their role in microbial pathogenesis is well established; however, these complex biomolecules also confer upon fungal microorganisms the faculty to tolerate extreme environments such as the Earth's poles, the International Space Station and places contaminated by toxic metals and ionizing radiation. A remarkable property of melanin is its capacity to interact with a wide range of electromagnetic radiation frequencies, functioning as a protecting and energy harvesting pigment. Other roles of fungal melanin include scavenging of free radical, thermo-tolerance, metal ion sequestration, cell development, and mechanical-chemical cellular strength. In this review, we explore the various functions ascribed to this biological pigment in fungi and its remarkable physicochemical properties.

The evolutionary convergence of mid-Mesozoic lacewings and Cenozoic butterflies

Mid-Mesozoic kalligrammatid lacewings (Neuroptera) entered the fossil record 165 million years ago (Ma) and disappeared 45 Ma later. Extant papilionoid butterflies (Lepidoptera) probably originated 80–70 Ma, long after kalligrammatids became extinct. Although poor preservation of kalligrammatid fossils previously prevented their detailed morphological and ecological characterization, we examine new, well-preserved, kalligrammatid fossils from Middle Jurassic and Early Cretaceous sites in northeastern China to unravel a surprising array of similar morphological and ecological features in these two, unrelated clades. We used polarized light and epifluorescence photography, SEM imaging, energy dispersive spectrometry and time-of-flight secondary ion mass spectrometry to examine kalligrammatid fossils and their environment. We mapped the evolution of specific traits onto a kalligrammatid phylogeny and discovered that these extinct lacewings convergently evolved wing eyespots that possibly contained melanin, and wing scales, elongate tubular proboscides, similar feeding styles, and seed–plant associations, similar to butterflies. Long-proboscid kalligrammatid lacewings lived in ecosystems with gymnosperm–insect relationships and likely accessed bennettitalean pollination drops and pollen. This system later was replaced by mid-Cretaceous angiosperms and their insect pollinators.

Molecular evidence of keratin and melanosomes in feathers of the Early Cretaceous bird Eoconfuciusornis

Microbodies associated with feathers of both nonavian dinosaurs and early birds were first identified as bacteria but have been reinterpreted as melanosomes. Whereas melanosomes in modern feathers are always surrounded by and embedded in keratin, melanosomes embedded in keratin in fossils has not been demonstrated. Here we provide multiple independent molecular analyses of both microbodies and the associated matrix recovered from feathers of a new specimen of the basal bird Eoconfuciusornis from the Early Cretaceous Jehol Biota of China. Our work represents the oldest ultrastructural and immunological recognition of avian beta-keratin from an Early Cretaceous (∼130-Ma) bird. We apply immunogold to identify protein epitopes at high resolution, by localizing antibody-antigen complexes to specific fossil ultrastructures. Retention of original keratinous proteins in the matrix surrounding electron-opaque microbodies supports their assignment as melanosomes and adds to the criteria employable to distinguish melanosomes from microbial bodies. Our work sheds new light on molecular preservation within normally labile tissues preserved in fossils.

New occurrences of fossilized feathers: systematics and taphonomy of the Santana Formation of the Araripe Basin (Cretaceous), NE, Brazil

Here we describe three fossil feathers from the Early Cretaceous Santana Formation of the Araripe Basin, Brazil. Feathers are the most complex multiform vertebrate integuments; they perform different functions, occurring in both avian and non-avian dinosaurs. Despite their rarity, fossil feathers have been found across the world. Most of the Brazilian feather fossil record comes from the Santana Formation. This formation is composed of two members: Crato (lake) and Romualdo (lagoon); both of which are predominantly reduced deposits, precluding bottom dwelling organisms, resulting in exceptional preservation of the fossils. Despite arid and hot conditions during the Cretaceous, life teemed in the adjacency of this paleolake. Feathered non-avian dinosaurs have not yet been described from the Crato Member, even though there are suggestions of their presence in nearby basins. Our description of the three feathers from the Crato laminated limestone reveals that, despite the small sample size, they can be referred to coelurosaurian theropods. Moreover, based on comparisons with extant feather morphotypes they can be identified as one contour feather and two downy feathers. Despite their rareness and low taxonomic potential, fossilized feathers can offer insights about the paleobiology of its owners and the paleoecology of the Araripe Basin.