Lasanius,an exceptionally preserved Silurian jawless fish from Scotland

The fossil record of non-biomineralizing, soft-bodied taxa is our only direct evidence of the early history of vertebrates. A robust reconstruction of the affinities of these taxa is critical to unlocking vertebrate origins and understanding the evolution of skeletal tissues, but these taxa invariably have unstable and poorly supported phylogenetic positions. At the cusp between mineralized bony vertebrates and entirely soft-bodied vertebrates is the enigmatic Lasanius, a purported anaspid from the Silurian of Scotland. Interpretations of its affinity and significance are conflicted, principally because of its poorly understood anatomy due to taphonomic distortion and loss of soft-tissues. Here we use an array of modern techniques to reassess the anatomy of Lasanius via a comprehensive study of 229 complete and partial specimens. A new reconstruction clarifies the identity and position of preserved features, including paired sensory organs, a notochord, and digestive tract, supporting the vertebrate affinities of this genus. SEM-EDS trace element mapping suggests a bone-like composition of mineralized parts, but finds no evidence for mineralized dermal armour. Phylogenetic analysis recovers Lasanius as an early stem-cyclostome, and subsequent analysis supports the rejection of alternative placements (such as stem-gnathostome). We highlight that while distinguishing between the early cyclostome and gnathostome condition is problematic, increasing confidence in the anatomy of key taxa, such as Lasanius, is vital for increased stability throughout the early vertebrate tree.     

The phylogenetic distribution of tubulin:Tyrosine ligase

Summary The post-translational addition of tyrosine toa-tubulin, catalyzed by tubulin:tyrosine ligase, has been previously reported in mammals and birds. The present study demonstrated that significant ligase activity was present in representative organisms from several other major vertebrate classes (chondrichthyes through reptiles) and that both substrate and enzyme from all vertebrates investigated were compatible with mammalian ligase and tubulin in the tyrosination reaction. None of the invertebrate tissues examined showed incorporation of tyrosine, phenylalanine or dihydroxyphenylalanine intoa tubulin under conditions allowing significant incorporation of these compounds in vertebrate supernatant samples. The failure of invertebrate tubulin to incorporate tyrosine in vitro did not appear to be due to saturation of the carboxyl terminal position with tyrosine or the presence of a soluble inhibitor of ligase activity.Although tubulin amino acid composition has been highly conserved throughout evolution, a major evolutionary divergence is described based upon biochemical differences whereby invertebrate tubulin cannot be tyrosinated or posttranslationally modified with phenylalanine or dihydroxyphenylalanine under conditions suitable for the incorporation of these compounds by vertebratea tubulin.     

Comparative anatomy and histology of xenarthran osteoderms

Reconstruction of soft tissues in fossil vertebrates is an enduring challenge for paleontologists. Because inferences must be based on evidence from hard tissues (typically bones or teeth), even the most complete fossils provide only limited information about certain organ systems. Osteoderms ("dermal armor") are integumentary bones with high fossilization potential that hold information about the anatomy of the skin in many extant and fossil amniotes. Their importance for functional morphology and phylogenetic research has recently been recognized, but studies have focused largely upon reptiles, in which osteoderms are most common. Among mammals, osteoderms occur only in members of the clade Xenarthra, which includes armadillos and their extinct relatives: glyptodonts, pampatheres, and, more distantly, ground sloths. Here, I present new information on the comparative morphology and histology of osteoderms and their associated soft tissues in 11 extant and fossil xenarthrans. Extinct mylodontid sloths possessed simple, isolated ossicles, the presence of which is likely plesiomorphic for Xenarthra. More highly derived osteoderms of glyptodonts, pampatheres, and armadillos feature complex articulations and surface ornamentation. Osteoderms of modern armadillos are physically associated with a variety of soft tissues, including nerve, muscle, gland, and connective tissue. In some cases, similar osteological features may be caused by two or more different tissue types, rendering soft-tissue inferences for fossil osteoderms equivocal. Certain osteological structures, however, are consistently associated with specific soft-tissue complexes and therefore represent a relatively robust foundation upon which to base soft-tissue reconstructions of extinct xenarthrans.     

Synchrotron x‐ray fluorescence analysis reveals diagenetic alteration of fossil melanosome trace metal chemistry

A key feature of the pigment melanin is its high binding affinity for trace metal ions. In modern vertebrates trace metals associated with melanosomes, melanin‐rich organelles, can show tissue‐specific and taxon‐specific distribution patterns. Such signals preserve in fossil melanosomes, informing on the anatomy and phylogenetic affinities of fossil vertebrates. Fossil and modern melanosomes, however, often differ in trace metal chemistry; in particular, melanosomes from fossil vertebrate eyes are depleted in Zn and enriched in Cu relative to their extant counterparts. Whether these chemical differences are biological or taphonomic in origin is unknown, limiting our ability to use melanosome trace metal chemistry to test palaeobiological hypotheses. Here, we use maturation experiments on eye melanosomes from extant vertebrates and synchrotron rapid scan‐x‐ray fluorescence analysis to show that thermal maturation can dramatically alter melanosome trace element chemistry. In particular, maturation of melanosomes in Cu‐rich solutions results in significant depletion of Zn, probably due to low pH and competition effects with Cu. These results confirm fossil melanosome chemistry is susceptible to alteration due to variations in local chemical conditions during diagenesis. Maturation experiments can provide essential data on melanosome chemical taphonomy required for accurate interpretations of preserved chemical signatures in fossils.     

A silicified bird from Quaternary hot spring deposits

The first avian fossil recovered from high-temperature hot spring deposits is a three-dimensional external body mould of an American coot (Fulica americana) from Holocene sinters of Yellowstone National Park, Wyoming, USA. Silica encrustation of the carcass, feathers and colonizing microbial communities occurred within days of death and before substantial soft tissue degradation, allowing preservation of gross body morphology, which is usually lost under other fossilization regimes. We hypothesize that the increased rate and extent of opal-A deposition, facilitated by either passive or active microbial mediation following carcass colonization, is required for exceptional preservation of relatively large, fleshy carcasses or soft-bodied organisms by mineral precipitate mould formation. We suggest physico-chemical parameters conducive to similar preservation in other vertebrate specimens, plus distinctive sinter macrofabric markers of hot spring subenvironments where these parameters are met.     

Buoyancy mechanisms limit preservation of coleoid cephalopod soft tissues in Mesozoic Lagerstätten

Coleoid cephalopods are characterized by internalization of their shell, and are divided into the ten‐armed Decabrachia (squids and cuttlefish) and the eight‐armed Vampyropoda (octopuses and vampire squid). They have a rich fossil record predominantly of the limited biomineralized skeletal elements they possess: arm hooks, statoliths, mouthparts (the buccal mass) and internal shell (gladius or pen), although exquisitely preserved soft tissue coleoids are known from several Lagerstätten worldwide. Recent studies have shown that although morphological similarities between extant decabrachian gladii and fossil examples exist, no known examples of fossil decabrachians are currently known. However, molecular clock data and phylogenetic bracketing suggest that they should be present in Lagerstätten that are rich in vampyropod soft tissue fossils (i.e. Hâkel and Hâdjoula Lagerstätten, Cretaceous, Lebanon). We propose that a hitherto unknown taphonomic bias pertaining to the differing methods of buoyancy control within coleoid groups limits preservation potential. Both negatively and neutrally buoyant decabrachians use chemical buoyancy control (ammonia) whereas vampyropods do not. In the event of rapid burial in an environment conducive to exceptional preservation, ammonia dramatically decreases the ability of the decabrachian carcass to generate the required pH for authigenic calcium phosphate replacement, limiting its preservation potential. Moreover, the greater surface area and comparatively fragile dermis further decrease the potential for fossilization. This taphonomic bias may have contributed to the lack of preserved labile soft‐tissues in other cephalopods groups such as the ammonoids.     

Influence of microbial biofilms on the preservation of primary soft tissue in fossil and extant archosaurs

Background

Mineralized and permineralized bone is the most common form of fossilization in the vertebrate record. Preservation of gross soft tissues is extremely rare, but recent studies have suggested that primary soft tissues and biomolecules are more commonly preserved within preserved bones than had been presumed. Some of these claims have been challenged, with presentation of evidence suggesting that some of the structures are microbial artifacts, not primary soft tissues. The identification of biomolecules in fossil vertebrate extracts from a specimen of Brachylophosaurus canadensis has shown the interpretation of preserved organic remains as microbial biofilm to be highly unlikely. These discussions also propose a variety of potential mechanisms that would permit the preservation of soft-tissues in vertebrate fossils over geologic time.

Methodology/Principal Findings

This study experimentally examines the role of microbial biofilms in soft-tissue preservation in vertebrate fossils by quantitatively establishing the growth and morphology of biofilms on extant archosaur bone. These results are microscopically and morphologically compared with soft-tissue extracts from vertebrate fossils from the Hell Creek Formation of southeastern Montana (Latest Maastrichtian) in order to investigate the potential role of microbial biofilms on the preservation of fossil bone and bound organic matter in a variety of taphonomic settings. Based on these analyses, we highlight a mechanism whereby this bound organic matter may be preserved.

Conclusions/Significance

Results of the study indicate that the crystallization of microbial biofilms on decomposing organic matter within vertebrate bone in early taphonomic stages may contribute to the preservation of primary soft tissues deeper in the bone structure.     

Early vertebrate evolution

Debate over the origin and evolution of vertebrates has occupied biologists and palaeontologists alike for centuries. This debate has been refined by molecular phylogenetics, which has resolved the place of vertebrates among their invertebrate chordate relatives, and that of chordates among their deuterostome relatives. The origin of vertebrates is characterized by wide‐ranging genomic, embryologic and phenotypic evolutionary change. Analyses based on living lineages suggest dramatic shifts in the tempo of evolutionary change at the origin of vertebrates and gnathostomes, coincident with whole‐genome duplication events. However, the enriched perspective provided by the fossil record demonstrates that these apparent bursts of anatomical evolution and taxic richness are an artefact of the extinction of phylogenetic intermediates whose fossil remains evidence the gradual assembly of crown gnathostome characters in particular. A more refined understanding of the timing, tempo and mode of early vertebrate evolution rests with: (1) better genome assemblies for living cyclostomes; (2) a better understanding of the anatomical characteristics of key fossil groups, especially the anaspids, thelodonts, galeaspids and pituriaspids; (3) tests of the monophyly of traditional groups; and (4) the application of divergence time methods that integrate not just molecular data from living species, but also morphological data and extinct species. The resulting framework will provide for rigorous tests of rates of character evolution and diversification, and of hypotheses of long‐term trends in ecological evolution that themselves suffer for lack of quantitative functional tests. The fossil record has been silent on the nature of the transition from jawless vertebrates to the jawed vertebrates that have dominated communities since the middle Palaeozoic. Elucidation of this most formative of episodes likely rests with the overhaul of early vertebrate systematics that we propose, but perhaps more fundamentally with fossil grades that await discovery.     

Evidence for targeted elasmobranch predation on thalassinidean shrimp in the Miocene Taliao Formation,NE Taiwan

Terrestrial and marine invertebrate organisms both leave records of their activities in the sediment in the form of trace fossils, at least during certain stages of their ontogeny. In contrast, trace fossils produced by vertebrate organisms are scarce, although terrestrial trace fossils provide exclusive insights into the social behaviour of their producers. In the marine realm, vertebrate trace fossils are relatively rare, difficult to identify and problematic to interpret. However, in certain settings, observations on serendipitously preserved and exposed trace fossils can shed light on the predatory behaviour of marine vertebrates. In Miocene outer shelf to nearshore sandstones of the Taliao Formation in NE Taiwan, large numbers of bowl‐shaped trace fossils can be observed. Morphology and size range (diameter typically 10–30 cm, average depth around 10 cm) of these trace fossils agree well with feeding traces of modern stingrays, and the trace fossil Piscichnus waitemata, which has been attributed to bottom feeding rays. Stingrays direct a jet of water from their mouths to excavate a bowl‐shaped pit to expose their prey. In the material filling the excavated bowl, broken pieces of two other common trace fossils, Ophiomorpha and Schaubcylindrichnus, are often found, and in a number of cases, vertical shafts of Ophiomorpha surrounded by dispersed pieces of wall material have been observed. In contrast, surrounding sediment rarely contains this kind of broken pieces of wall material. These observations clearly indicate that stingrays specifically targeted the producers of the trace fossils: thalassinoid crustaceans and worms, respectively. The targeted predation of these relatively deep burrowers furthermore suggests that the rays used their electroreceptive organs to locate the prey; as such, direct targeting of buried prey only based on olfactory senses has been shown to be ineffective in experiments with extant myliobatiform rays.     

Three-dimensional soft tissue preservation revealed in the skin of a non-avian dinosaur

The most commonly preserved soft tissues associated with ornithischian dinosaurs are skin remains. The apparent resistance of hadrosaur skin to decay, and its abundance in the fossil record relative to that of other tetrapods, has been attributed to factors such as thickness and composition. Here we report additional intrinsic factors within hadrosaur skin: 3D-preserved eumelanin-bearing bodies, dermal cells and blood vessel fragments in an organic matrix composed of protein fossilization products. The skin is much thinner than that of living mammals of similar size. It is likely that the preservation of hadrosaur skin is related to the arrangement of the layers composing it.     

The Evolutionary Emergence of Vertebrates From Among Their Spineless Relatives

The evolutionary origin of vertebrates has been debated ad nauseam by anatomists, paleontologists, embryologists, and physiologists, but it is only now that molecular phylogenetics is providing a more rigorous framework for the placement of vertebrates among their invertebrate relatives that we can begin to arrive at concrete conclusions concerning the nature of ancient ancestors and the sequence in which characteristic anatomical features were acquired. Vertebrates tunicates and cephalochordates together comprise the chordate phylum, which along with echinoderms and hemichordates constitute the deuterostomes. The origin of vertebrates and of jawed vertebrates is characterized by a doubling of the vertebrate genome, leading to hypotheses that this genomic event drove organismal macroevolution. However, this perspective of evolutionary history, based on living organisms alone, is an artifact. Phylogenetic trees that integrate fossil vertebrates among their living relatives demonstrate the gradual and piecemeal assembly of the gnathostome body plan. Unfortunately, it has not been possible to demonstrate gradual assembly of the vertebrate body plan. This is not because vertebrates are irreducibly complex but because many of the characters that distinguish vertebrates from invertebrates are embryological and cellular and, therefore, inherently unfossilizable.

The nerve hemoglobin of the bivalve mollusc Spisula solidissima: molecular cloning, ligand binding studies, and phylogenetic analysis

Members of the hemoglobin (Hb) superfamily are present in nerve tissue of several vertebrate and invertebrate species. In vertebrates they display hexacoordinate heme iron atoms and are typically expressed at low levels (microM). Their function is still a matter of debate. In invertebrates they have a hexa- or pentacoordinate heme iron, are mostly expressed at high levels (mM), and have been suggested to have a myoglobin-like function. The native Hb of the surf clam, Spisula solidissima, composed of 162 amino acids, does not show specific deviations from the globin templates. UV-visible and resonance Raman spectroscopy demonstrate a hexacoordinate heme iron. Based on the sequence analogy, the histidine E7 is proposed as a sixth ligand. Kinetic and equilibrium measurements show a moderate oxygen affinity (P(50) approximately 0.6 torr) and no cooperativity. The histidine binding affinity is 100-fold lower than in neuroglobin. Phylogenetic analysis demonstrates a clustering of the S. solidissima nerve Hb with mollusc Hbs and myoglobins, but not with the vertebrate neuroglobins. We conclude that invertebrate nerve Hbs expressed at high levels are, despite the hexacoordinate nature of their heme iron, not essentially different from other intracellular Hbs. They most likely fulfill a myoglobin-like function and enhance oxygen supply to the neurons.     

The nature and significance of invertebrate cartilages revisited: distribution and histology of cartilage and cartilage-like tissues within the Metazoa

Tissues similar to vertebrate cartilage have been described throughout the Metazoa. Often the designation of tissues as cartilage within non-vertebrate lineages is based upon sparse supporting data. To be considered cartilage, a tissue should meet a number of histological criteria that include composition and organization of the extracellular matrix. To re-evaluate the distribution and structural properties of these tissues, we have re-investigated the histological properties of many of these tissues from fresh material, and review the existing literature on invertebrate cartilages. Chondroid connective tissue is common amongst invertebrates, and differs from invertebrate cartilage in the structure and organization of the cells that comprise it. Groups having extensive chondroid connective tissue include brachiopods, polychaetes, and urochordates. Cartilage is found within cephalopod mollusks, chelicerate arthropods and sabellid polychaetes. Skeletal tissues found within enteropneust hemichordates are unique in that the extracellular matrix shares many properties with vertebrate cartilage, yet these tissues are completely acellular. The possibility that this tissue may represent a new category of cartilage, acellular cartilage, is discussed. Immunoreactivity of some invertebrate cartilages with antibodies that recognize molecules specific to vertebrate bone suggests an intermediate phenotype between vertebrate cartilage and bone. Although cartilage is found within a number of invertebrate lineages, we find that not all tissues previously reported to be cartilage have the appropriate properties to merit their distinction as cartilage.     

Identification and tissue-specific expression of a promethin-like homolog in amphioxus <Emphasis Type="Italic">Branchiostoma belcheri</Emphasis>

Promethins have been shown to be present in the vertebrates examined so far, yet little is known to date about them in invertebrates. Here we isolated a cDNA encoding a promethin-like homolog from the gut cDNA library of the amphioxus Branchiostoma belcheri, a cephalochordate occupying a nodal position transient from invertebrates to vertebrates. It contained a 504 bp open reading frame corresponding to a protein of 167 amino acids. Primary structural examination showed that the deduced promethin-like homolog was a transmembrane protein with three potential transmembrane helices, resembling the vertebrate promethins. Phylogenetic analysis showed that B. belcheri promethin-like homolog was located at the base of the vertebrate counterparts, suggesting that it represents the archetype of vertebrate promethins. Both Northern blotting and in situ hybridization histochemistry revealed a tissue-specific expression pattern of promethin-like gene, like that of mammalian promethins. This is the first report on invertebrate promethin-like homolog, paving the way for further insights into the evolution and function of promethins.     

The Feeding Strategies of the Leech Erpobdella octoculata (L.): A Laboratory Study

The feeding behaviour of the freshwater leech Erpobdella octoculata was analysed by exposing potential invertebrate and vertebrate prey organisms (alive, wounded or dead) to leech attack in dishes, in the laboratory. The fact that E. octoculata is a macrophagous feeder that swallows living prey organisms whole (preferentially Chironomus larvae) is documented. However, it was repeatedly observed that adult leeches sucked the body fluids from wounded larvae. Likewise, cut pieces of earthworms, dead crustaceans and crushed water snails were attacked and the soft parts sucked in with the aid of the unarmed pharynx. Adult leeches sucked the body fluids from dead, decaying bodies of vertebrates (fish, newt larvae). Newly hatched young are blood suckers that rapidly attacked the wounded regions of Chironomus larvae and other invertebrates such as crushed water snails. It is concluded that the common leech E. octoculata is not only a predator, but also a fluid sucker and a scavenger. The ecological implications of this finding are discussed.     

Decay of vertebrate characters in hagfish and lamprey (Cyclostomata) and the implications for the vertebrate fossil record

The timing and sequence of events underlying the origin and early evolution of vertebrates remains poorly understood. The palaeontological evidence should shed light on these issues, but difficulties in interpretation of the non-biomineralized fossil record make this problematic. Here we present an experimental analysis of decay of vertebrate characters based on the extant jawless vertebrates (Lampetra and Myxine). This provides a framework for the interpretation of the anatomy of soft-bodied fossil vertebrates and putative cyclostomes, and a context for reading the fossil record of non-biomineralized vertebrate characters. Decay results in transformation and non-random loss of characters. In both lamprey and hagfish, different types of cartilage decay at different rates, resulting in taphonomic bias towards loss of 'soft' cartilages containing vertebrate-specific Col2α1 extracellular matrix proteins; phylogenetically informative soft-tissue characters decay before more plesiomorphic characters. As such, synapomorphic decay bias, previously recognized in early chordates, is more pervasive, and needs to be taken into account when interpreting the anatomy of any non-biomineralized fossil vertebrate, such as Haikouichthys, Mayomyzon and Hardistiella.     

The ‘Tully Monster’ is not a vertebrate: characters,convergence and taphonomy in Palaeozoic problematic animals

The affinity of Tullimonstrum gregarium, a pincer‐mouthed, soft bodied bilaterian, has been subject to debate since its recovery from Carboniferous coal deposits at Mazon Creek, Illinois. After decades of impasse focused on mollusc, arthropod and annelid attributes, two recent, yet conflicting, high‐profile studies concluded that the ‘Tully Monster’ is a vertebrate, a relative of lampreys or jawed fishes. Here, we find that structures described as supporting vertebrate, and particularly crown vertebrate, affinity face significant challenges from biological, functional and taphonomic perspectives. Problems with comparator choice, interpretation of taphonomic processes at Mazon Creek and estimation of convergence within the bilaterian tree may have misled these recent studies, leading to conclusions which do not accommodate current understanding of the vertebrate record. For example, the absence of taphonomically‐expected synapomorphies in Tullimonstrum (e.g. otic capsules, body pigment) calls into question vertebrate identity and implies that convergence or deeper origins are responsible for vertebrate‐like traits. Further, phylogenetic placement within vertebrates is only made possible by the constraints of a chordate‐only dataset with limited outgroups and use of selective characters. Long‐discussed alternative placements among molluscs (e.g. heteropod gastropods), arthropods (e.g. anomalocarids) or elsewhere within non‐vertebrate deuterostomes are more congruent. Indeed, many of these lineages independently evolved vertebrate‐like traits, including complex eyes and ‘teeth’. Thus, given the totality of evidence, Tullimonstrum should be excluded from the vertebrate crown. Potential assignments for aberrant bilaterians, common throughout the Palaeozoic fossil record, need to be considered in light of the number and likelihood of required exceptions to established schemes.     

Cranial cartilages: Players in the evolution of the cranium during evolution of the chordates in general and of the vertebrates in particular

The present contribution is chiefly a review, augmented by some new results on amphioxus and lamprey anatomy, that draws on paleontological and developmental data to suggest a scenario for cranial cartilage evolution in the phylum chordata. Consideration is given to the cartilage-related tissues of invertebrate chordates (amphioxus and some fossil groups like vetulicolians) as well as in the two major divisions of the subphylum Vertebrata (namely, agnathans, and gnathostomes). In the invertebrate chordates, which can be considered plausible proxy ancestors of the vertebrates, only a viscerocranium is present, whereas a neurocranium is absent. For this situation, we examine how cartilage-related tissues of this head region prefigure the cellular cartilage types in the vertebrates. We then focus on the vertebrate neurocranium, where cyclostomes evidently lack neural-crest derived trabecular cartilage (although this point needs to be established more firmly). In the more complex gnathostome, several neural-crest derived cartilage types are present: namely, the trabecular cartilages of the prechordal region and the parachordal cartilage the chordal region. In sum, we present an evolutionary framework for cranial cartilage evolution in chordates and suggest aspects of the subject that should profit from additional study.     

Fossil-Lagerstätten,palaeoecology and preservation of invertebrates and vertebrates from the Devonian in the eastern Anti-Atlas,Morocco

In some Devonian strata in the eastern Anti-Atlas, fossil invertebrates are abundant, display a high taxonomic diversity and indicate many shifts in palaeoecology. This is reflected in changes in faunal composition of invertebrates and vertebrates. Fossils of jawed vertebrates of late Lochkovian and younger age have been recorded and are relatively common with their abundance and diversity increasing towards the Late Devonian. Environmental changes in the Devonian also left their mark in the preservation of vertebrates and invertebrates from the Anti-Atlas, which varies strongly through time and regionally. This variation partially reflects environmental changes linked with the evolution of small marine basins during the disintegration of the continental shelf of Gondwana in this region, fluctuations of the regional sea level and other environmental changes. To improve our understanding of these ecological changes, of shifts in preservation through the succession and of the formation of Fossil-Lagerstätten, we analysed the mineral composition of some invertebrate and vertebrate samples of Devonian and Early Carboniferous age by Raman spectroscopy and X-ray diffraction. Additionally, we characterized some of these Fossil-Lagerstätten using palaeontological and sedimentological parameters. We examined eight Devonian Konzentrat-Lagerstätten and two Konservat-Lagerstätten with soft-tissue preservation (the Famennian Thylacocephalan Layer and the Hangenberg Black Shale of the southern Maïder). The last two are the first Konservat-Lagerstätten described from the Devonian of North Africa. The taphonomic and oceanic settings suggest that these Konservat-Lagerstätten are formed because of stagnation (related to vertical restriction of water exchange and water depth rather than limited spatial water exchange and a lateral restriction) in the relatively small Maïder Basin with limited water exchange with the neighbouring Tafilalt Basin. The temporally low oxygen levels in the Maïder Basin are a possible reason for the reduced chondrichthyan diversity (missing demersal and shallow water species) compared to the Tafilalt Platform.     

Chemical preservation of tail feathers from Anchiornis huxleyi,a theropod dinosaur from the Tiaojishan Formation (Upper Jurassic,China)

A panel of geochemical techniques is used here to investigate the taphonomy of fossil feathers preserved in association with the skeleton of the Jurassic theropod Anchiornis huxleyi. Extant feathers were analysed in parallel to test whether the soft tissues morphologically preserved in the fossil also exhibit a high degree of chemical preservation. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) indicate that clays and iron oxide pseudomorphs occur in the surrounding sediment and also reveal the preservation of melanosome-like microbodies in the fossil. Carbon gradient along a depth profile and co-occurrence of carbon and sulphur are shown in the fossil by elastic backscattering (EBS) and particle-induced x-ray emission (PIXE), which are promising techniques for the elemental analysis of fossil soft tissues. The molecular composition of modern and fossil soft tissues was assessed from micro-attenuated total reflectance fourier transform infrared spectroscopy (micro-ATR FTIR), solid-state ¹³C nuclear magnetic resonance (CP-MAS ¹³C NMR) and pyrolysis gas chromatography mass spectrometry in the presence of TMAH (TMAH-Py-GC-MS). Results indicate that the proteinaceous material that comprises the modern feathers is not present in the fossil feathers. The fossil feathers and the embedding sediment exhibit a highly aliphatic character. However, substantial differences exist between these samples, revealing that the organic matter of the fossil feathers is, at least partially, derived from original constituents of the feathers. Our results suggest that, despite the morphological preservation of Anchiornis feathers, original proteins, that is keratin, were probably not preserved in the 160-myr-old feathers.