Soft-bodied Fossils Research Articles

Statoliths from the Jurassic succession of south-west England, United Kingdom

The occurrence of statoliths within the Jurassic succession of south-west England and other parts of Europe is reviewed. Five ‘morphospecies’ have been identified, ranging in age from Hettangian to Kimmeridgian. With so little published information on statoliths, the presently known geological record is incomplete, although new occurrences are continually being discovered. The occurrence of statoliths, in the absence of soft-bodied fossils, may ultimately provide a more complete indication of the distribution of the soft-bodied host animals. At the present time, however, only one of the statolith ‘morphospecies’ can be, tentatively, linked to a known species of teuthid.

FACTORS CONTROLLING EXCEPTIONAL PRESERVATION IN CONCRETIONS

Concretions are an important source of soft-bodied fossils. In order to determine the controls on exceptional fossilization within concretions, we scored 88 concretion-bearing sites for 11 environmental and compositional variables together with presence/absence of soft-tissue preservation and analyzed their relationships using multiple correspondence analysis (MCA) and qualitative logistic regression. Sites yielding exceptional fossils were distributed randomly through the 88 examples considered, suggesting that exceptional preservation can occur in almost any environment where concretions form. The patterns of interaction of the variables in the MCA revealed that the most important factors controlling exceptional preservation in concretions are related to (1) the potential for fossil preservation in the broader depositional setting (i.e., how likely fossils are to be preserved without concretions but in the same depositional environment) and (2) the rate of concretion growth. In an analysis of the contribution of individual variables, logistic regression showed that two features correlate with the presence of soft-tissue preservation in concretions: (1) fine-grained host lithology, and (2) relatively constant δ13C values. The role of the first of these can be tested experimentally. Decay experiments on fish tissue in glass beads of three different sizes and therefore of different permeability showed that decay is inhibited, and mineral precipitation enhanced, in low-permeability sediments. Thus a process of positive feedback promotes exceptional preservation where early cementation results in a rapid decrease in permeability during concretion formation. The second feature, a relatively constant δ13C trend, suggests that certain patterns of concretion growth, pervasive growth or concentric growth with one growth layer, are more conducive to fossilization than others.

Stratigraphic controls of soft-bodied fossil occurrences in the Cambrian Chengjiang Biota Lagerstätte, Maotianshan Shale, Yunnan Province, China

The Early Cambrian Maotianshan Shale, exposed near Kunming, China, is one of the oldest and best-preserved Konservat Lagerstätten, containing the Chengjiang Biota. Although the fossils have been well-studied, the depositional processes and stratigraphic relationships amongst the fossil-bearing localities are poorly understood, largely due to limited continuous exposures and structural complexity in this area.In this study we use a detailed facies and stacking pattern analysis to delineate the depositional history and stratigraphic relationship of the Maotianshan. Sedimentologic observations from five prolific fossil localities of the Chengjiang Biota have yielded six distinct facies within the Maotianshan Shale. The three coarse-grained facies, composed of siltstones and very fine sandstones (F1–F3), contain sedimentary structures including hummocky cross stratification and combined flow ripples that are consistent with deposition within storm wave base. The fine grained facies, composed of interbedded silty mudstones and clay-rich mudstones (F4–F6), were deposited below the wave base and represent episodes of lower storm frequency and pelagic sedimentation.These six facies have specific stacking patterns, indicating the presence of five distinct depositional units. Each of those depositional units is bound on its upper and lower contact by a flooding surface. Fining-upward successions near the base of each stratigraphic unit are interpreted as short-lived marine transgressions; these are overlain by coarsening-upward stacked facies interpreted as a period of shoreline progradation.The fossils of the Chengjiang fauna are exclusively found in the coarsening-upward part of the depositional units. The oldest fossil-bearing intervals are associated with the most westerns sections in the study area. In contrast, the youngest fossil-bearing intervals are found in the most eastern sections. This time-transgressive relationship is interpreted to reflect a genetic relation between distinct sedimentary processes and environments, and the burial and preservation of the Chengjiang Biota.

EVIDENCE FOR BIOGENIC COPPER (HEMOCYANIN) IN THE MIDDLE CAMBRIAN ARTHROPOD MARRELLA FROM THE BURGESS SHALE

Beginning with the discovery of the middle Cambrian Burgess Shale, the rare examples of exceptional preservation of soft tissues in fine-grained strata have been celebrated as windows into the diversity and complexity of ancient marine animal life. Even so, with the loss of original organic compounds, the physiological attributes of the fossils can be inferred only on the basis of modern descendants or sister groups among extant representatives that can serve as analogs. To test whether soft-bodied fossils from the Burgess Shale and similar Cambrian Lagerstatten could preserve chemical evidence of their original biology, a number of specimens from different groups were analyzed with synchrotron-based X-ray fluorescence imaging to determine the spatial distribution of a range of elements, especially those in exceedingly trace amounts that cannot be detected by more conventional analytical methods. The relative distribution of common elements like Fe, K, Ti, and Ca is related to the composition of the host shale, abundance of pyrite, and presence or absence of preserved exoskeletal calcite. However, the black stain commonly preserved with the arthropod Marrella splendens is preferentially enriched in Cu due to localized residue in the carbon and minute crystals of chalcopyrite. This is interpreted as indicative of the original chemical composition of a primary biotic fluid, likely blood. Since modern-day arthropods generally utilize Cu-containing hemocyanin for oxygen transport, it is hypothesized that hemocyanin was the biogenic source of the observed Cu. This is the first chemical evidence for blood composition in the invertebrate fossil record. These observations reinforce the consensus molecular clock age for the hemocyanin gene family, which traces its origins back to the ‘Cambrian explosion’, thus providing evidence for the early origin of this oxygen carrier among some arthropod groups.

Fossil treasure house for exploring the Cambrian explosion

Since the 1980s, fossil assemblages of a similar composition and preservation state to the Burgess Shale fauna have been found in Cambrian shales in other parts of Laurentia, for example the Sirius Passet fauna in North Greenland, and in other Cambrian continents, for example the Chengjiang fauna in South China. Such fossil assemblages, termed as Burgess Shale-type fossil Lagerstatten, have long served as fossil treasure houses to explore the Cambrian explosion. In addition to the Chengjiang fauna, more than ten Burgess-Shale-type Lagerstatten are now known from the early to middle Cambrian shales of South China in a succession of stratigraphical horizons [3]. Comparison of such fossiliferous Lagerstatten in a chronological framework enables us to trace the evolutionary changes of biological communities in mud-dominated marine environments. Moreover, comparative studies between a single lineage from different horizons may reveal evolutionary trends in lineages through time. The Xiazhuang Assemblage discovered by Zeng et al. [4] is the latest addition of such wonderful fossil treasure houses. A brief survey shows that the Xiazhaung Assemblage generally resembles the Chengjiang fauna in faunal composition, yielding predominantly soft-bodied fossils, including arthropods, brachiopods, priapulids, lobopods and some problematic taxa, with arthropods being the most dominant group. Specimens illustrated by Zeng et al. [4] comprise a variety of species that are similar or identical to those from the Chengjiang fauna. However, some of the most common species, e.g. Kunmingella douvillei, have not been found in the Xiazhuang Assemblage. The current fossil collection of the Xiazhaung assemblages is rather limited in both number of specimens and species, largely due to constrained excavation. In contrast, 20 years of collecting the Chengjiang fauna at many sites across Eastern Yunnan has yielded more than 200 species and hundreds of thousands of specimens. It is therefore worthwhile to increase the intensity of fossil collection at different localities and sites.

A Chengjiang-type fossil assemblage from the Hongjingshao Formation (Cambrian Stage 3) at Chenggong, Kunming, Yunnan

A new Chengjiang-type fossil assemblage is reported herein from the lower part of the Hongjingshao Formation at Xiazhuang village of Chenggong, Kunming, Yunnan. The fossil assemblage, named as Xiazhuang fossil assemblage, yields predominantly soft-bodied fossils, including arthropods, brachiopods, priapulids, lobopods and some problematic taxa, with arthropods being the most dominant group. Preservation and composition of the fossil assemblage are very similar to the typical Chengjiang biota, which is preserved in the middle Yu’anshan Formation in the large area of eastern Yunnan. The associated trilobites demonstrate that the soft-bodied fossil assemblage belongs to the late Qiongzhusian in age (Stage 3, Cambrian), suggesting that the Hongjingshao Formation is probably a diachronous lithostratigraphic unit ranging from the upper Qiongzhusian to the lower Canglangpuan stages in eastern Yunnan. The fossil assemblage from the Xiazhuang area fills up the missing link between the typical older Chengjiang biota and the younger Malong and Guanshan biotas, making eastern Yunnan a unique area in the world to reveal the early evolutionary history of animals and palaeocommunity dynamics during the “Cambrian explosion”.

A new phyllopod bed-like assemblage from the Burgess Shale of the Canadian Rockies

Burgess Shale-type fossil assemblages provide the best evidence of the 'Cambrian explosion'. Here we report the discovery of an extraordinary new soft-bodied fauna from the Burgess Shale. Despite its proximity (ca. 40 km) to Walcott's original locality, the Marble Canyon fossil assemblage is distinct, and offers new insights into the initial diversification of metazoans, their early morphological disparity, and the geographic ranges and longevity of many Cambrian taxa. The arthropod-dominated assemblage is remarkable for its high density and diversity of soft-bodied fossils, as well as for its large proportion of new species (22% of total diversity) and for the preservation of hitherto unreported anatomical features, including in the chordate Metaspriggina and the arthropod Mollisonia. The presence of the stem arthropods Misszhouia and Primicaris, previously known only from the early Cambrian of China, suggests that the palaeogeographic ranges and longevity of Burgess Shale taxa may be underestimated.

Paleoredox and pyritization of soft-bodied fossils in the Ordovician Frankfort Shale of New York

Multiple beds in the Frankfort Shale (Upper Ordovician, New York State), including the original “Beecher9s Trilobite Bed,” yield fossils with pyritized soft-tissues. A bed-by-bed geochemical and sedimentological analysis was carried out to test previous models of soft-tissue pyritization by investigating environmental, depositional and diagenetic conditions in beds with and without soft-tissue preservation. Highly-reactive iron (FeHR), total iron (FeT), δ34S, organic carbon and redox-sensitive trace elements were measured. In particular, the partitioning of highly-reactive iron between iron-carbonates (Fe-carb), iron-oxides (Fe-ox), magnetite (Fe-mag), and pyrite (FeP) was examined. Overall, the multi-proxy sedimentary geochemical data suggest that the succession containing pyritized trilobite beds was deposited under a dysoxic water-column, in agreement with the paleontological data. The data do not exclude brief episodes of water-column anoxia characterized by a ferruginous rather than an euxinic state. However, the highest FeHR/FeT values and redox-sensitive trace element enrichments occur in siltstone portions of turbidite beds and in concretions, suggesting that subsequent diagenesis had a significant effect on the distribution of redox-sensitive elements in this succession. Moderately high FeHR/FeT and FeP/FeHR, low organic carbon, enriched δ34S, and the frequent presence of iron-rich carbonate concretions in beds with soft tissue preservation confirm that pyritization was favored where pore-waters were iron-dominated in sediments relatively poor in organic carbon.

Exceptional preservation of microbial lipids in Paleozoic to Mesoproterozoic sediments

Exceptional preservation of microbial lipids in Paleozoic to Mesoproterozoic sediments

Silurian horseshoe crab illuminates the evolution of arthropod limbs.

The basic arrangement of limbs in euarthropods consists of a uniramous head appendage followed by a series of biramous appendages. The body is divided into functional units or tagmata which are usually distinguished by further differentiation of the limbs. The living horseshoe crabs are remnants of a much larger diversity of aquatic chelicerates. The limbs of the anterior and posterior divisions of the body of living horseshoe crabs differ in the loss of the outer and inner ramus, respectively, of an ancestral biramous limb. Here we report a new fossil horseshoe crab from the mid-Silurian Lagerstätte in Herefordshire, United Kingdom (approximately 425 Myr B.P.), a site that has yielded a remarkably preserved assemblage of soft-bodied fossils. The limbs of the new form can be homologized with those of living Limulus, but retain an ancestral biramous morphology. Remarkably, however, the two limb branches originate separately, providing fossil evidence to suggest that repression or loss of gene expression might have given rise to the appendage morphology of Limulus. Both branches of the prosomal limbs of this new fossil are robust and segmented in contrast to their morphology in Cambrian arthropods, revealing that a true biramous limb was once present in chelicerates as well as in the mandibulates.

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.

Mechanism for Burgess Shale-type preservation

Exceptionally preserved fossil biotas of the Burgess Shale and a handful of other similar Cambrian deposits provide rare but critical insights into the early diversification of animals. The extraordinary preservation of labile tissues in these geographically widespread but temporally restricted soft-bodied fossil assemblages has remained enigmatic since Walcott's initial discovery in 1909. Here, we demonstrate the mechanism of Burgess Shale-type preservation using sedimentologic and geochemical data from the Chengjiang, Burgess Shale, and five other principal Burgess Shale-type deposits. Sulfur isotope evidence from sedimentary pyrites reveals that the exquisite fossilization of organic remains as carbonaceous compressions resulted from early inhibition of microbial activity in the sediments by means of oxidant deprivation. Low sulfate concentrations in the global ocean and low-oxygen bottom water conditions at the sites of deposition resulted in reduced oxidant availability. Subsequently, rapid entombment of fossils in fine-grained sediments and early sealing of sediments by pervasive carbonate cements at bed tops restricted oxidant flux into the sediments. A permeability barrier, provided by bed-capping cements that were emplaced at the seafloor, is a feature that is shared among Burgess Shale-type deposits, and resulted from the unusually high alkalinity of Cambrian oceans. Thus, Burgess Shale-type preservation of soft-bodied fossil assemblages worldwide was promoted by unique aspects of early Paleozoic seawater chemistry that strongly impacted sediment diagenesis, providing a fundamentally unique record of the immediate aftermath of the "Cambrian explosion."

Burgess shale−type biotas were not entirely burrowed away

Research Article| March 01, 2012 Burgess shale−type biotas were not entirely burrowed away Robert R. Gaines; Robert R. Gaines 1Geology Department, Pomona College, 185 E. Sixth Street, Claremont, California 91711, USA Search for other works by this author on: GSW Google Scholar Mary L. Droser; Mary L. Droser 2Department of Earth Sciences, University of California−Riverside, Riverside, California 92521, USA Search for other works by this author on: GSW Google Scholar Patrick J. Orr; Patrick J. Orr 3UCD School of Geological Sciences, University College Dublin, Dublin 4, Ireland Search for other works by this author on: GSW Google Scholar Daniel Garson; Daniel Garson 2Department of Earth Sciences, University of California−Riverside, Riverside, California 92521, USA Search for other works by this author on: GSW Google Scholar Emma Hammarlund; Emma Hammarlund 4Nordic Center for Earth Evolution, DK-5230 Odense M, Denmark5Department of Palaeozoology, Swedish Museum of Natural History, SE-104 05 Stockholm, Sweden Search for other works by this author on: GSW Google Scholar Changshi Qi; Changshi Qi 6Yunnan Key Laboratory for Palaeobiology, Yunnan University, Kunming 650091, China Search for other works by this author on: GSW Google Scholar Donald E. Canfield Donald E. Canfield 4Nordic Center for Earth Evolution, DK-5230 Odense M, Denmark Search for other works by this author on: GSW Google Scholar Author and Article Information Robert R. Gaines 1Geology Department, Pomona College, 185 E. Sixth Street, Claremont, California 91711, USA Mary L. Droser 2Department of Earth Sciences, University of California−Riverside, Riverside, California 92521, USA Patrick J. Orr 3UCD School of Geological Sciences, University College Dublin, Dublin 4, Ireland Daniel Garson 2Department of Earth Sciences, University of California−Riverside, Riverside, California 92521, USA Emma Hammarlund 4Nordic Center for Earth Evolution, DK-5230 Odense M, Denmark5Department of Palaeozoology, Swedish Museum of Natural History, SE-104 05 Stockholm, Sweden Changshi Qi 6Yunnan Key Laboratory for Palaeobiology, Yunnan University, Kunming 650091, China Donald E. Canfield 4Nordic Center for Earth Evolution, DK-5230 Odense M, Denmark Publisher: Geological Society of America Received: 14 Jun 2011 Revision Received: 24 Oct 2011 Accepted: 27 Oct 2011 First Online: 09 Mar 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 © 2012 Geological Society of America Geology (2012) 40 (3): 283–286. https://doi.org/10.1130/G32555.1 Article history Received: 14 Jun 2011 Revision Received: 24 Oct 2011 Accepted: 27 Oct 2011 First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Robert R. Gaines, Mary L. Droser, Patrick J. Orr, Daniel Garson, Emma Hammarlund, Changshi Qi, Donald E. Canfield; Burgess shale−type biotas were not entirely burrowed away. Geology 2012;; 40 (3): 283–286. doi: https://doi.org/10.1130/G32555.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Burgess Shale−type biotas occur globally in the Cambrian record and offer unparalleled insight into the Cambrian explosion, the initial Phanerozoic radiation of the Metazoa. Deposits bearing exceptionally preserved soft-bodied fossils are unusually common in Cambrian strata; more than 40 are now known. The well-documented decline of soft-bodied preservation following the Middle Cambrian represents the closure of a taphonomic window that was only intermittently open in marine environments thereafter. The prevailing hypothesis for this secular shift in taphonomic conditions of outer shelf environments is that soft-bodied biotas were literally burrowed away from the fossil record by increasing infaunal activity in muddy substrate environments; this would have affected geochemical gradients and increased the efficiency of organic matter recycling in sediments. New and recently published data, however, suggest a more complex scenario. Ichnologic and microstratigraphic data from Burgess Shale−type deposits indicate that (1) bioturbation exerts a limiting effect on soft-bodied preservation; (2) the observed increase in the depth and extent of bioturbation following the Middle Cambrian would have restricted preservation of Burgess Shale−type biotas in a number of settings; but (3) increasing depth and extent of bioturbation would not have affected preservation in many other settings, including the most richly fossiliferous portions of the Chengjiang (China) deposit and the Greater Phyllopod Bed of the Burgess Shale (Canada). Therefore, increasing bioturbation cannot account for the apparent loss of this pathway from the fossil record, and requires that other circumstances, including, but not limited to, widespread benthic anoxia, facilitated widespread exceptional preservation in the Cambrian. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

The demosponge Leptomitus cf. L. lineatus,first occurrence from the Middle Cambrian of Spain(Murero Formation, Western Iberian Chain)

The Middle Cambrian Murero Formation in the Iberian Chain (NE Spain) has yielded a small collection of softbodied fossils (palaeoscolecid worms, onychophorans, algae), a host of fossils from organisms with mineralized skeletons such as trilobites and brachiopods, and some trace fossils. This paper deals with the description of the only specimen of the demosponge Leptomitus known so far from Spain and its association with the brachiopod Micromitra, showing a probable case of commensalism by the latter over the former. The taphonomical study indicates that there was little or no disarticulation of the sponge spicules and suggests that a rather complex series of alteration processes has occurred since these organisms were buried.

Trace and rare earth element geochemistry of black shale and kerogen in the early Cambrian Niutitang Formation in Guizhou province, South China: Constraints for redox environments and origin of metal enrichments

Early Cambrian black shales of South China not only host important sponge, arthropod and other soft-bodied fossils that have helped to trace early metazoan diversification, but also show extreme enrichments of a number of trace metals in particular Ni, Mo and V. In this study, we use a new approach by analyzing rare earth elements in kerogen extracted from the black shales, together with a number of redox-sensitive trace element compositions and total organic carbon (TOC) concentrations in an early Cambrian black shale sequence in Zunyi, Guizhou province, South China, to place better constraints on the oceanic redox conditions and the origin of the extreme metal enrichment.Our data show significant negative Ce anomalies (Ce/Ce* as low as 0.4) occurring in kerogen, which indicate an oxygenated surface environment of primary productivity in consistent with the concept that the organic matter is mainly derived from organisms in the euphotic zone. Mass balance calculation suggests that the kerogen-associated REE can dominate the measured black shale REE budget, while similarity between our measured REE patterns and those of similarly aged phosphorites indicates that the REE content of ancient phosphorites may have also derived initially from organic matter.The redox-sensitive trace elements, such as U, V, Mo, and their ratios of U/Al, V/Al and Mo/Al in black shales show different correlation patterns with TOC contents. The upper black shales show a good metal/TOC correlation, but such a correlation is absent in the lower part. The lower black shales exhibit much higher metal enrichments compared to Black Sea sulphidic (euxinic) sediment. This is taken to indicate the presence of sulphidic bottom waters during the deposition of the lower black shales, including the Ni–Mo ore layer. In contrast, anoxic, non-sulphidic conditions occurred during the deposition of the upper black shales.Taking all these geochemical data together, we suggest that the early Cambrian South China seaway was strongly stratified and stagnant, and that euxinic bottom water conditions may have led to enrichment of the redox-sensitive metals such as U, V and Mo in the lower black shales, and in one case the occurrence of a polymetallic Ni–Mo sulphide ore bed bearing an extraordinarily extreme metal enrichment, which, according to the Mo/TOC and Ni/TOC ratios and much other geochemical evidence, may have been additionally influenced by hydrothermal input of metals within the rift basin as suggested by a number of previous studies.

Dynamic palaeoredox and exceptional preservation in the Cambrian Spence Shale of Utah

Garson, D.E., Gaines, R.R., Droser, M.L., Liddell, W.D. & Sappenfield, A. 2011: Dynamicpalaeoredox and exceptional preservation in the Cambrian Spence Shale of Utah. Le-thaia, DOI:10.1111⁄j.1502-3931.2011.00266.xBurgess Shale-type faunas provide a unique glimpse into the diversification of metazoanlife during the Cambrian. Although anoxia has long been thought to be a pre-requisitefor this particular type of soft-bodied preservation, the palaeoenvironmental conditionsthat regulated extraordinary preservation have not been fully constrained. In particular,the necessity of bottom water anoxia, long considered a pre-requisite, has been the sub-ject of recent debate. In this study, we apply a micro-stratigraphical, ichnologicalapproachtodeterminebottom wateroxygen conditionsunder,which BurgessShale-typebiotas were preserved in the Middle Cambrian Spence Shale of Utah. Mudstones of theSpence Shale are characterizedby fine scale (mm-cm)alternation between laminated andbioturbated intervals, suggesting high-frequency fluctuations in bottom water oxygena-tion. Whilst background oxygen levels were not high enough to support continuousinfaunal activity, brief intervals of improved bottom water oxygen conditions punctuatethe succession. A diverse skeletonized benthic fauna, including various polymerid trilo-bites, hyolithids, brachiopods and ctenocystoids suggests that complex dysoxic benthiccommunity was established during times when bottom water oxygen conditions werepermissive. Burgess Shale-type preservation within the Spence Shale is largely confinedto non-bioturbated horizons, suggesting that benthic anoxia prevailed in intervals, wherethese fossils were preserved. However, some soft-bodied fossils are found within weaklyto moderately bioturbated intervals (Ichnofabric Index 2 and 3). This suggests that Bur-gess Shale-type preservation is strongly favoured by bottom water anoxia, but may notrequire it in all cases. h Anoxia, Burgess Shale, Burgess Shale type-preservation, LangstonFormation, Spence Shale Member,Utah.Daniel E. Garson [daniel.garson@gmail.com], Department of Earth Sciences, University ofCalifornia, Riverside, CA 92521, USA; Robert R. Gaines [Robert.Gaines@pomona.edu],Geology Department, Pomona College, 185 E. Sixth St., Claremont, CA 91711, USA; MaryL. Droser [mary.droser@ucr.edu], Department of Earth Sciences, University of California,Riverside, CA 92521, USA; W. David Liddel [dave.liddell@usu.edu], Department ofGeology, Utah State University, Logan, UT 84322-4505, USA; Aaron Sappenfield[aaron.sappenfield@email.ucr.edu], Department of Earth Sciences, University of California,Riverside, CA 92521, USA; manuscript received on 14 September 2010; manuscript acceptedon 04 February 2011.

Glaciation and ~ 770 Ma Ediacara (?) Fossils from the Lesser Karatau Microcontinent, Kazakhstan

The Cambrian explosion, c. 530–515 Ma heralded the arrival of a diverse assembly of multicellular life including the first hard-shelled organisms. Fossils found in Cambrian strata represent the ancestors of most modern animal phyla. In contrast to the apparent explosiveness seen in the Cambrian fossil record, studies of molecular biology hint that the diversification observed in Cambrian strata was rooted in ancestry extending back into the Ediacaran (635–542 Ma). Fossil evidence for this mostly cryptic phase of evolution is derived from the soft-bodied fossils of the Ediacaran biota found throughout the world and bilaterian embryos found in the Doushantuo lagerstätte in South China. The first appearance of Ediacara fauna is thought to have followed the last of the ~ 750–635 Ma Neoproterozoic glacial episodes by 20–30 million years. In this paper, we present evidence for the oldest discovery of the ‘Ediacara’ discoidal fossils Nimbia occlusa and Aspidella terranovica (?) that predate the early Cryogenian glaciations by more than fifty million years. There is considerable disagreement over the significance of discoidal Ediacaran fossils, but our findings may support earlier suggestions that metazoan life has roots extending deeper into the Proterozoic Eon. We also confirm the presence of a Late Cryogenian (e.g. “Marinoan”) glaciation on the Lesser Karatau microcontinent including dropstones and striated clasts within the glacial strata.

Biodiversity and taphonomy of the Early Cambrian Guanshan biota, eastern Yunnan

The Guanshan biota from eastern Yunnan (Cambrian Series 2, early Stage 4) is a Burgess Shale-type fossil biota with abundant exceptionally preserved soft-bodied fossils after the discovery of the well-known Cambrian Chengjiang fauna and Kaili biota in South China. The geological settings, sedimentology, taphonomy, and the fossil assemblage of the Guanshan biota are briefly summarized here. The Guanshan biota consists of about 60 taxa belonging to more than 10 metazoan groups and algae, among which the lobopods, eldonids, hyolithids with helens, and green algae are reported for the first time. The common occurrence of soft-bodied preservation in many groups, notably the trilobites and brachiopods, makes the Guanshan biota a significant fossil lagerstatte for understanding the metazoan evolution during Cambrian explosion and taphonomy of the Burgess Shale-type fossils.

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.

Ediacaran body and trace fossils in Miette Group (Windermere Supergroup) near Salient Mountain, British Columbia, CanadaRevision of the paper was carried out by Dr. Guy Narbonne following the passing away of both Hans Hofmann (†deceased May 19, 2010) and Eric Mountjoy (†deceased June 18, 2010) after manuscript submission.

Siliciclastic beds in the upper part of the Miette Group in southeastern British Columbia have yielded an assemblage of late Ediacaran soft-bodied macrofossils and trace fossils. The macrofossils comprise Aspidella , Bradgatia ?, and Miettia salientensis gen. et sp. nov. The ichnofossils include Archaeonassa , Cochlichnus , Didymaulichnus ?, Gordia , Halopoa , Helminthoidichnites , Helminthopsis , Planolites , and a large, unnamed crawling trace. In addition, two types of unidentified problematica are recorded, representing either tubular Vendotaenia -like body fossils, or trace fossils. The Bradgatia? constitutes the youngest occurrence of this type of fossil, and is the first to be recorded from Laurentia, having previously been noted only in Avalonia. With Cloudina and Namacalathus in associated shallow-water platform carbonates, the Miette biota in the study area contains a combination of Namibian-type and Avalonian-type elements.