Exceptional Fossil Preservation Research Articles

The origin and early evolution of roots.

Geological sites of exceptional fossil preservation are becoming a focus of research on root evolution because they retain edaphic and ecological context, and the remains of plant soft tissues are preserved in some. New information is emerging on the origins of rooting systems, their interactions with fungi, and their nature and diversity in the earliest forest ecosystems. Remarkably well-preserved fossils prove that mycorrhizal symbionts were diverse in simple rhizoid-based systems. Roots evolved in a piecemeal fashion and independently in several major clades through the Devonian Period (416 to 360 million years ago), rapidly extending functionality and complexity. Evidence from extinct arborescent clades indicates that polar auxin transport was recruited independently in several to regulate wood and root development. The broader impact of root evolution on the geochemical carbon cycle is a developing area and one in which the interests of the plant physiologist intersect with those of the geochemist.

Deciphering Exceptional Preservation of Fossils Using Trace Elemental Imaging

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Les nodules du Carbonifère supérieur du Lagerstätte de Montceau-les-Mines, France : historique de la Collection Sotty 2

The Muséum national d’Histoire naturelle, Paris (France), housed in its palaeontological collections numerous fossil specimens from a French locality of exceptional fossil preservation: the Montceau-les-Mines Lagerstätte (Late Carboniferous). The collection on the Montceau-les-Mines Lagerstätte was given to the Museum of Paris in 1997. Under the MNHN direction, it is managed in the regional museum of Autun. It contains more than 100,000 nodules bearing animal and fossil plants, three-dimensionally preserved in sideritic concretions. These collections are computerized and regularly consulted and studied by scientists from the whole world.

Phosphorus sources for phosphatic Cambrian carbonates

The fossilization of organic remains and shell material by calcium phosphate minerals provides an illuminating, but time-bounded, window into Ediacaran–Cambrian animal evolution. For reasons that remain unknown, phosphatic fossil preservation declined significantly through Cambrian Series 2. Here, we investigate the phosphorus (P) sources for phosphatic Cambrian carbonates, presenting sedimentological, petrographic, and geochemical data from the Cambrian Series 2–3 Thorntonia Limestone, Australia, some of the youngest Cambrian strata to display exceptional phosphatic preservation of small shelly fossils. We find that within Thorntonia sediments, phosphate was remobilized by organic decay and bacterial iron reduction, with subsequent reprecipitation largely as apatite within the interiors of small shelly fossils. We discuss the merits of bioclastic-derived, organic matter–bound, or iron-bound P as potential sources to these strata. Petrographic observations suggest that the dissolution of phosphatic skeletal material did not provide the P for fossil preservation. In contrast, high organic carbon contents imply significant organic fluxes of P to Thorntonia sediments. Sedimentology and iron-speciation data indicate that phosphorus enrichment occurred during times of expanded anoxic, ferruginous conditions in subsurface water masses, suggesting that phosphorus adsorption to iron minerals precipitating from the water column provided a second significant P source to Thorntonia sediments. Simple stoichiometric models suggest that, by themselves, neither organic carbon burial nor an iron shuttle can account for the observed phosphorus enrichment. Thus, we infer that both processes were necessary for the observed phosphorus enrichment and subsequent fossil preservation in the Thorntonia Limestone.

Exceptional fossil preservation demonstrates a new mode of axial skeleton elongation in early ray-finned fishes

Elongate body plans have evolved independently multiple times in vertebrates, and involve either an increase in the number or in the length of the vertebrae. Here, we describe a new mechanism of body elongation in saurichthyids, an extinct group of elongate early ray-finned fishes. The rare preservation of soft tissue in a specimen of Saurichthys curionii from the Middle Triassic (Ladinian) of Switzerland provides significant new information on the relationship between the musculature and the skeleton. This new fossil material shows that elongation in these fishes results from doubling the number of neural arch-like elements per myomeric segment. This unique way of generating an elongate body plan demonstrates the evolutionary lability of the vertebral column in non-teleostean fishes. The shape and arrangement of preserved myosepta suggest that S. curionii was not a highly flexible fish, in spite of the increase in the number of neural arch-like elements.

INVOLVEMENT OF MICROBIAL MATS IN DELAYED DECAY: AN EXPERIMENTAL ESSAY ON FISH PRESERVATION

Microbial mats have been implicated in exceptional fossil preservation. Few analyses have addressed how these complex-multilayered biofilms promote fossil preservation. The sequence of changes during decay of neon tetra fish were tracked up to 27 months, and their decomposition in mats was compared against nonmat sediments (control fish). Statistically significant differences in quantitative variables (length, width, and thickness) are provided (ANOVA test, in all cases, P, 0.001). Changes in the qualitative features (body-head, fins, scale connection, and eye and body coloration) were phenetically analyzed resulting in two clusters and highlighting that notable differences in decay began at day 15. Mat fish how a delayed decomposition maintaining the external and internal body integrity, in which soft organs were preserved after 27 months as shown by Magnetic Resonance Imaging. We discuss how the organization, structure, and activity of this community are interrelated, favoring exceptional preservation. Microbial mats entomb the fish from the earliest stages, forming a Ca-rich coat over the carcass while embedding it in an anoxic condition. This quick entombment provides important protection against abiotic and/or biotic agents.

Biomarkers reveal the role of photic zone euxinia in exceptional fossil preservation: An organic geochemical perspective

Photic zone euxinia (PZE) has proven important for elucidating biogeochemical changes that occur during oceanic anoxic events, including mass extinction and conditions associated with unique fossil preservation. Organic geochemical analyses of a 380 Ma invertebrate fossil, which included well-preserved soft tissues, from the Gogo Formation (Canning Basin, Western Australia) showed biomarkers and stable isotopic values characteristic of PZE and a consortium of sulfate-reducing bacteria, which lead to exceptional fossil and biomarker preservation. The carbonate concretion contained phytoplankton, green sulfur bacteria (Chlorobi), and sulfate-reducing bacteria biomarkers with an increasing concentration toward the nucleus where the fossil is preserved. The spatial distribution of cholestane unequivocally associated with the fossilized tissue and its high relative abundance to the total steranes suggest that the fossil is a crustacean. The presence of an active sulfur cycle in this Devonian system, including sulfate reduction and the resulting PZE, played a pivotal role in the preservation of soft tissue from the fossil and its associated low-maturity biomarker ratios.

Spatial variation in the diversity and composition of the Lower Cambrian (Series 2, Stage 3) Chengjiang Biota, Southwest China

Strata hosting the Lower Cambrian (Series 2, Stage 3) Chengjiang Biota (Maotianshan Shale Member, Yu'anshan Formation) occur throughout the eastern part of Yunnan Province, Southwest China. In this study, literature-based faunal inventories from 10 areas (representing 34 localities), together with 22,038 new specimens collected at three localities from three of the 10 areas, were analyzed quantitatively to assess large-scale spatial variation in taxonomic diversity and composition. Our analyses show substantial co-variation between local paleoenvironmental settings and species diversity, and suggest the presence of three general taphofacies in the Maotianshan Shale Member, from west to east: low diversity (26 species) characterizes the Wuding area, where fossiliferous strata have undergone extensive bioturbation; high diversity (215 species) characterizes the Chengjiang–Haikou–Anning areas, where fossiliferous strata consist of stacked couplets of thin event and background mudstone layers; moderate diversity (55 species) characterizes the Malong area, where fossiliferous strata consist of indistinctly bedded shale showing fewer single-event layers but abundant background layers. In spite of variations in sampling effort between sites, spatial patterns in species diversity and community composition were controlled primarily by variation in depositional environments along a proximal offshore to lower shoreface gradient, which influenced both ecological and taphonomic factors. The offshore settings (Haikou–Chengjiang–Anning areas) show relatively high species diversity and exceptional preservation of soft-bodied fossils, reflecting rapid burial in distal tempestites. Relatively high degrees of bioturbation, time-averaging and hydrodynamic disturbance caused a substantial decrease in the quality of preservation and number of soft-bodied species in the Wuding and Malong areas. Arthropods are the most diverse group in most localities, followed by priapulids, poriferans, brachiopods, lobopods and hyoliths.This study shows that the Chengjiang Biota lends itself very well to high resolution characterization of spatial variation in taxonomic diversity, faunal composition and fossil preservation. Furthermore, the Chengjiang Biota may provide a unique opportunity to assess the roles of environmental factors, taphonomy and ecological controls on species diversity at local to regional spatial scales.

Exceptional preservation of Mn-oxidizing microbes in cave stromatolites (El Soplao, Spain)

Many ferromanganese stromatolites of El Soplao Cave (N Spain) are characterized for the exceptional preservation and high diversity of microbial fossils, probably representing the best example of microbial preservation described in ferromanganese deposits so far.The El Soplao stromatolites are mainly formed by polymetallic Mn-rich oxides with subordinate and variable amounts of detrital material, and consist of both dendritic and laminar microfacies. In both microfacies, microbial forms are abundant in the relatively pure Mn-oxide rich material, whereas they are scarce in areas with significant detrital material. Microbial forms are observed either in cross section, completely embedded in the Mn-oxide-rich matrix, or in three dimensions lining the walls of pores. Based on their morphology, we have separated the most abundant microbial forms into six main morphotypes and six additional submorphotypes, most of which can be assigned to bacteria. Most morphotypes consist of coccoid, coccobacilus, or filamentous forms. Therefore they are not diagnostic of any particular bacterial group. However, the ovoid cells of morphotype B show cylindrical polar protuberances typical of prosthecate alpha-Proteobacteria. On the basis of characteristic morphological features, three submorphotypes of morphotype B can be assigned to three alpha-Proteobacteria genera: Hyphomicrobium, Pedomicrobium, and Caulobacter. This ascription is supported by the well known Mn-oxidizing behavior of both Pedomicrobium and Caulobacter, and by the common presence of Hyphomicrobium in ferromanganese deposits elsewhere.The excellent microbial preservation is partly related to the origin of the ferromanganese oxides, i.e. extracellular precipitation induced by microbial metabolism. Other factors contributing to the good microbial preservation are the relatively low degree of diagenetic alteration, and the relatively high accretion rates of stromatolites compared to other ferromanganese deposits. The generally low degree of diagenesis is likely because the stromatolites have remained relatively stable and at a rather low temperature since they were formed at least 1Ma ago. Still, some stromatolites have suffered diagenetic alteration (partial dissolution and replacement by calcium carbonates and Fe-rich oxides), obscuring or even obliterating their bioforms. The El Soplao case represents an example of how easily biogenic Mn oxides can be altered, and their bioforms blurred, in a relatively short geological time span in spite of being in a relatively stable, alkaline, and low-temperature setting. A geological implication is that the absence of bioforms in other ferromanganese deposits, including rock varnish and Precambrian iron formations, does not disprove their possible biogenic origin, since the high chemical reactivity of biogenic manganese oxides makes them highly vulnerable to diagenesis.

Coelacanths from the Middle Triassic Luoping Biota, Yunnan, South China, with the earliest evidence of ovoviviparity

The fossil record of coelacanths is patchy, with very few taxa known from the Triassic of Asia. We report here two new genera and species of coelacanths from the Luoping Biota, a recently found site of exceptional fossil preservation from Yunnan, South China. The first new taxon, Luopingcoelacanthus eurylacrimalis, is based on four specimens, which together show most aspects of the anatomy. One specimen shows two small coelacanths inside the ventral portion of the abdominal cavity, and these are interpreted as intrauterine embryos, close to birth size, based on comparisons with previously reported embryos of the fossil coelacanths Rhabdoderma and Undina, and the extant genus Latimeria. Our new find extends the evidence for ovoviviparity in coelacanths back from the Late Jurassic to the Middle Triassic. The second new taxon, Yunnancoelacanthus acrotuberculatus, is based on one specimen, and differs from Luopingcoelacanthus in the dentary, lachrymojugal, number of rays of the first dorsal fin, and especiall...

Exceptional fossil preservation during CO 2 greenhouse crises?

Exceptional fossil preservation may require not only exceptional places, but exceptional times, as demonstrated here by two distinct types of analysis. First, irregular stratigraphic spacing of horizons yielding articulated Triassic fishes and Cambrian trilobites is highly correlated in sequences in different parts of the world, as if there were short temporal intervals of exceptional preservation globally. Second, compilations of ages of well-dated fossil localities show spikes of abundance which coincide with stage boundaries, mass extinctions, oceanic anoxic events, carbon isotope anomalies, spikes of high atmospheric carbon dioxide, and transient warm-wet paleoclimates. Exceptional fossil preservation may have been promoted during unusual times, comparable with the present: CO 2 greenhouse crises of expanding marine dead zones, oceanic acidification, coral bleaching, wetland eutrophication, sea level rise, ice-cap melting, and biotic invasions.

Petrographic and SIMS pyrite sulfur isotope analyses of Ediacaran chert nodules: Implications for microbial processes in pyrite rim formation, silicification, and exceptional fossil preservation

The lower Ediacaran Doushantuo Formation in the Yangtze Gorges area contains exceptionally preserved microfossils, including the earliest known animal resting eggs and embryos. These fossils are preserved in cm-sized chert nodules, which typically have a microbial mat fragment in the center, a silica cortex, a pyrite rim, and an outer rim of blocky calcite. Petrographic analysis indicates that the formation of the blocky calcite rim postdates that of the pyrite rim and silica cortex. The pyrite rim grew centripetally during early diagenesis, representing a reaction front that was determined by the dynamics between ambient Fe 2+ and H 2S, the latter of which was derived from bacterial sulfate reduction (BSR) of mat fragment in nodule center. The silica cortex was formed pervasively through replacement of carbonate sediments prior to compaction. Secondary ion mass spectroscopy (SIMS) sulfur isotopes of individual pyrite crystals (δ 34S py − SIMS) in pyrite rims and matrices show highly positive values (15.2–39.8‰). The pyrite rims do not show an isotopic gradient between small crystals formed in outer rim during early diagenesis and large crystals formed in inner rim during subsequent overgrowth. Although rim pyrite in the same chert nodule has consistent δ 34S py − SIMS values, there are significant spatial and stratigraphic variations in δ 34S py − SIMS values of both matrix and rim pyrite. Overall, isotopic fractionation between pyrite and carbonate associated sulfate (CAS) is small (< 22‰). The isotopic and petrographic data can be interpreted as evidence for rapid BSR of highly metabolizable organic matter in a diagenetic environment with limited sulfate availability, local anoxia, high Fe 2+ concentration, and low sedimentation rate. The embryonic nodules nucleated on microbial mat fragments and stayed in the BSR zone during early diagenesis, when rapid BSR in the nodule center generated outward-diffusing H 2S that was confined by readily available Fe 2+ to precipitate the pyrite rim. The precipitation of the silica cortex was facilitated by localized pH change related to BSR and pyrite precipitation, with silica sourced from silica-rich Precambrian seawater and from microbially mediated clay diagenesis. Like the pyrite rim, the silica cortex was also formed rapidly during early diagenesis, leading to the exceptional preservation of microfossils within these nodules.

Census of the Indian Springs Lagerstätte, Poleta Formation (Cambrian), western Nevada, USA

Intervals of exceptional fossil preservation collectively termed the Indian Springs Lagerstätte occur in the middle member of the Poleta Formation (Cambrian, Series 2, Stage 3) in Esmeralda County, Nevada, USA. The preserved macrofauna and taphonomic modes are similar to those of the Spence Shale Lagerstätte of Utah (Cambrian Series 3). The Indian Springs macrofauna mostly consists of biomineralizing organisms such as trilobites, helicoplacoids, hyolithids and inarticulate brachiopods. Multi-element taxa such as helicoplacoids and chancelloriids are commonly articulated. Examples of preserved nonbiomineralized anatomy include mantle setae of brachiopods, demosponge skeletons, hyolithid gut tracts, trilobite appendages, algae, cyanobacteria, and body parts of nonbiomineralizing arthropods. The Indian Springs Lagerstätte is dominated by fine siliciclastics, and was deposited in an offshore shelf setting subjected to storm-initiated sediment pulses. Exceptional preservation was facilitated by obrution-type deposition, presumably in dysoxic or anoxic muds, and in environments where organismic remains were removed from durophagous carnivores and scavengers, including bioturbators.

From clergymen to computers—the advent of virtual palaeontology

Palaeontology was established as a science in the Victorian era, yet has roots that stretch deeper into the recesses of history. More than 2000 years ago, the Greek philosopher Aristotle deduced that fossil sea shells were once living organisms, and around 500 ad Xenophanes used fossils to argue that many areas of land must have previously been submarine. In 1027, the Persian scholar Avicenna suggested that organisms were fossilized by petrifying fluids; this theory was accepted by most natural philosophers up until the eighteenth century Enlightenment, and even beyond. The late 1700s were notable for the work of Georges Cuvier who established the reality of extinction. This, coupled with advances in the recognition of faunal successions made by the canal engineer William Smith, laid the framework for the discipline that would become known as palaeontology. As the nineteenth century progressed, the scientific community became increasingly well organized. Most fossil workers were gentleman scientists and members of the clergy, who self‐funded their studies in a new and exciting field. Many of the techniques used to study fossils today were developed during this ‘classical’ period. Perhaps the most fundamental of these is to expose a fossil by splitting the rock housing it, and then conduct investigations based upon the exposed surface (Fig. 1). This approach has served the science well in the last two centuries, having been pivotal to innumerable advances in our understanding of the history of life. Nevertheless, there are many cases where splitting a rock in this way results in incomplete data recovery; those where the fossils are not flattened, but are preserved in three‐dimensions. Even the ephemeral soft‐tissues of organisms are occasionally preserved in a three‐dimensional state, for example in the Herefordshire, La Voulte Sûr Rhone and Orsten ‘Fossil Lagerstätten’ (sites of exceptional fossil preservation). These rare and precious deposits provide a wealth of information about the history of life on Earth, and are perhaps our most important resource in the quest to understand the palaeobiology of extinct organisms. With the aid of twenty‐first century technology, we can now make the most of these opportunities through the field of ‘virtual palaeontology’—computer‐aided visualization of fossils.A split nodule showing the fossil within, in this case a cockroachoid insect. Fossil 4 cm long (From Garwood &amp; Sutton, in press).image

Lateritization and Bauxitization Events

Laterites and bauxites are produced in tropical soils by weathering, which enriches iron (of laterites) and alu- mina (of bauxites)—as well as trace elements such as nickel, gold, phosphorus, and niobium—to ore grade. La- terites and bauxites can be redeposited into sedimentary sequences, and remain as ores if not transported far and diluted with other materials. The age of redeposited laterites and bauxites, and of bauxitic and lateritic pa- leosols, can be established from the geologic age of overlying rocks, an approach especially effective in pale- osols within sequences of isotopically datable volcanic rocks. Lateritic profiles can also be dated by paleomag- netic inclination in special cases in which land masses such as in Australia and India drifted long distances northward during Cenozoic time. In addition, cryptomelane and other K-Mn oxides can be dated by K-Ar and 40Ar-39Ar techniques to obtain multiple ages from different crystals in a single relict paleosol. Compilation of new and more accurate laterite and bauxite ages reveals unusually widespread and intense laterite and bauxite formation during events of less than 100 k.y. duration at 2, 12, 16, 35, 48, 55, 65 and 100 Ma. Such events can also be inferred at times older than 100 Ma from paleolatitudinal distribution of laterites and bauxites, but these are poorly sampled. Laterite and bauxite peaks were coeval with times of global high warmth and pre- cipitation, elevated atmospheric carbon dioxide, oceanic anoxia, exceptional fossil preservation, and mass ex- tinction. These CO2 greenhouse events and attendant titration of carbonic acid with soils are interpreted as transient fluctuations in the atmosphere produced by meteorite impact, flood basalt volcanism, and methane outbursts. Concentration of bauxite and laterite resources, in particular stratigraphic horizons formed during greenhouse crises, suggests the usefulness of an event stratigraphic approach to exploration and exploitation of these and related ores.

New specimens of the avian taxa Eurotrochilus (Trochilidae) and Palaeotodus (Todidae) from the early Oligocene of Germany

We describe new specimens of stem group representatives of Trochilidae (hummingbirds) and Todidae (todies) from the Rupelian of Frauenweiler in southern Germany. The hummingbird fossil constitutes the fourth record of Eurotrochilus inexpectatus. It consists only of wing and pectoral girdle elements, but shows the previously unknown crista deltopectoralis of the humerus, whose shape differs from modern hummingbirds. The carpometacarpus bears a well-developed processus intermetacarpalis, which is a further synapomorphy of Eurotrochilus and crown group Trochilidae. The disarticulated partial skeleton of the tody allows a definitive taxonomic assignment of the Frauenweiler species to Palaeotodus itardiensis Mourer-Chauvire, and likewise exhibits so far unknown osteological details, including the morphologies of the quadrate and scapula. We further comment on the exceptional taphonomy and preservation of avian fossils from the Frauenweiler clay pit, where terrestrial birds are represented only by small to very small species, whose skeletons are always strongly disarticulated.

High-precision 40Ar/ 39Ar age for the Jehol Biota

Abundant fossils of the terrestrial Jehol Biota, including plants, insects, dinosaurs, birds, mammals and freshwater invertebrates, were discovered from the Yixian Formation and the overlying Jiufotang Formation in Inner Mongolia, Hebei Province and Liaoning Province, northeastern China. Because of the exceptional preservation of fossils, the Jehol Biota is one of the most important Mesozoic lagerstätten and is referred to as a “Mesozoic Pompeii”. The Jehol Biota has provided a rare opportunity to address questions about the origin of birds, the evolution of feathers and flight, the early diversification of angiosperms and the timing of placental mammal radiation. Six tuff samples and two basalt samples collected from the Tuchengzi, the Yixian and the Jiufotang formations near the classic outcrops in western Liaoning, NE China yielded high-precision 40Ar/ 39Ar ages. We obtain an age of 129.7 ± 0.5 Ma for a basaltic lava from the bottom of the Yixian Formation and an age of 122.1 ± 0.3 Ma for a tuff from the lowermost part of the overlying Jiufotang Formation. Our age results provide an age calibration of the whole Yixian Formation and show that the whole formation was deposited entirely within Early Cretaceous time over an interval of ~ 7 Ma.

Geophysical and geological signatures of relative sea level change in the upper Wheeler Formation, Drum Mountains, West-Central Utah: A perspective into exceptional preservation of fossils

The Middle Cambrian Wheeler Formation in Utah is renowned for its exceptionally preserved fossils. Herein, geophysical techniques (gamma ray spectrometry and magnetic susceptibility), carbonate analyses, lithofacies, and fossils are used to characterize limestones and calcareous mudrocks of the upper portion of the middle Wheeler Formation and the upper Wheeler Formation in the Drum Mountains, West-Central Utah. This succession was deposited on a mixed carbonate-siliciclastic ramp within the House Range Embayment, an eastward incursion of deeper water, created and bounded on the southeast by a normal fault. Geophysical data clearly reveal variations in carbonate versus clay content. Observed patterns among outcrop geophysical data, lithofacies, and fossils are interpreted within the contexts of relative sea level changes and a sequence stratigraphic model. Above a basal interval of rhythmically-bedded limestones interpreted to have been deposited on the middle part of the ramp during a period of relatively low sea level, lithofacies, rising gamma ray and rising magnetic susceptibility track a transgression, which culminates in a maximum flooding surface (MFS). This MFS is near the base of a “hot zone”: an ~ 6-m-thick interval of exceptional preservation ( Konservat-Lagerstätte), highest magnetic susceptibility, highest gamma ray values, highest clay content, and with a bulk carbonate content of ~ 4–20%. The basal layer of this zone contains abundant, fully articulated specimens of agnostids and tiny polymerid trilobites. Exceptionally preserved fossils, such as non-trilobite arthropods, priapulid and annelid worms, hyolithids, phyllocarid arthropods with soft parts, algae, and fragile sponges, are much more abundant within this hot zone than in other strata of the succession. These specimens are preserved in very thin-bedded to laminated mudrock, only rarely interrupted by macroscopic signs of bioturbation. Stratigraphically above the hot zone is a thick unit of mudrock in which both gamma ray and magnetic susceptibility decrease, gradually at first and then precipitously to very low levels; in concert, few soft-bodied specimens have been recovered from this upper interval. The gradual decrease in geophysical responses is interpreted to be the result of gradual shallowing during highstand, caused mainly by progradation of the carbonate factory; it was followed by an abrupt regression. Mudrocks are capped by burrow-mottled grainstone and stromatolitic boundstone, representing a lowstand or the earliest transgressive phase of the next cycle. These observations lead to the following conclusions: (1) the upper Wheeler Formation represents most of a third or fourth-order cycle of relative sea level change on a mixed carbonate-siliciclastic ramp, rather than a period of shallow-water lagoonal sedimentation as previously proposed; (2) superimposed on this overall cycle are several (perhaps many) higher-order fluctuations in relative sea level; (3) when the present results are coupled with results of earlier workers, who interpreted the lower and middle Wheeler Formation as a major transgression and regression, the Wheeler Formation of the Drum Mountains involves two major sea level cycles, rather than one; (4) the Konservat-Lagerstätte was preserved in the deepest-water, early-highstand portion of the upper Wheeler sequence; and (5) these results support earlier hypotheses that Konservat-Lagerstätten in mixed carbonate-siliciclastic successions are most likely to occur during late transgression to early highstand, given that low energy, anoxic conditions prevailed.

Palaeometry: Non-destructive analysis of fossil materials

Palaeometry involves the combined use of different non-destructive analytical techniques on the study of fossil and subfossil materials. This work reports the results of the first Palaeometric analysis using Visible Fluorescence Induced by the UV-Light and PIXE (Particle Induced X-ray Emission spectrometry) applied on fossil samples from Tlayua quarry, Mexico (Tlayua Formation, Early Cretaceous, Albian). This paper provides a short discussion on the results implications for the understanding of the fossilization process occurred on Tlayua. Also, results suggest the presence of characteristic fossil fingerprints for the exceptional preservation of fossils for this Konservat-Lagerstatte, determined by the contents of elements such as Calcium, Phosphorus, Manganese, Iron and Arsenic.

Biomats, biofilms, and bioglue as preservational agents for arthropod trackways

Due to divergent taphonomic selection, corresponding body and trace fossils are rarely found in the same rocks. In addition to this general rule, arthropod trackways are preferentially preserved in particular settings: (1) lithographic limestones, where toxic bottom waters account for the exceptional preservation of body fossils at the end of their “mortichnial” trackways; (2) estuarine and lacustrine biolaminites that yield blurred surface tracks as well as the sharper undertracks; and (3) Cambrian intertidal sands before the Precambrian/Cambrian substrate revolution had reached this environment. In all these ichnotopes, the original presence of protective microbial films can be inferred from sedimentary structures. By analogy, it is hypothesised that microbes (“bioglue”) may have been involved in the preservation of trackways in eolian dune sands. The absence of arthropod tracks in Ediacaran sands and silts means either that arthropods had not yet evolved or that they were as yet too tiny to pierce the tougher biomats of the time.