The Different Paleoenvironments of the Vellberg's Middle Triassic Lagerstätten

A Middle Triassic palaeontological gold mine: The vertebrate deposits of Vellberg (Germany)

Authors:

Schoch et al

Abstract:

The lacustrine deposits of Vellberg, southern Germany, rank among the richest vertebrate fossil-lagerstätten of the Triassic worldwide. Continued excavation over one decade produced two chondrichthyans, 14 taxa of bony fishes, seven temnospondyls, one chroniosuchian, the stem-turtle Pappochelys, two procolophonians, four lepidosauromorphs, a choristodere, four archosauriforms, three pseudosuchian archosaurs, and around ten further reptile taxa only known by teeth. Sedimentary facies, fossil assemblage composition, and taphonomy suggest this deposit comprises a succession of rather different water bodies, situated on a floodplain dominated by dolomitic muds: (1) a coal swamp with occasional reptiles and temnospondyls, (2) a large but shallow, brackish lagoon inhabited by Bakevellia, Acrodus, Nothosaurus, and the temnospondyl Plagiosternum, (3) a small and shallow, well-protected, oligohaline freshwater lake dominated by various temnospondyls, and (4) a larger (6 km) and deeper freshwater lake, again with a rich fauna of fishes, temnospondyls, and small aquatic reptiles that was eventually filled by dolomitic coastal muds. Reworking and desiccation cracks indicate repeated phases of regression and drought, during which bonebeds formed and skeletons of terrestrial tetrapods were deposited.

A Homerian Silurian Arthropod had a Unique Brood Caring Mode

Tiny individuals attached to a new Silurian arthropod suggest a unique mode of brood care

Authors:

Briggs et al

Abstract:

The ∼430-My-old Herefordshire, United Kingdom, Lagerstätte has yielded a diversity of remarkably preserved invertebrates, many of which provide fundamental insights into the evolutionary history and ecology of particular taxa. Here we report a new arthropod with 10 tiny arthropods tethered to its tergites by long individual threads. The head of the host, which is covered by a shield that projects anteriorly, bears a long stout uniramous antenna and a chelate limb followed by two biramous appendages. The trunk comprises 11 segments, all bearing limbs and covered by tergites with long slender lateral spines. A short telson bears long parallel cerci. Our phylogenetic analysis resolves the new arthropod as a stem-group mandibulate. The evidence suggests that the tethered individuals are juveniles and the association represents a complex brooding behavior. Alternative possibilities—that the tethered individuals represent a different epizoic or parasitic arthropod—appear less likely.

A new Burgess Shale-type Lagertatte From the Ediacaran NeoProterozoic Mongolia

A new Burgess Shale-type deposit from the Ediacaran of western Mongolia

Authors:

Dornbos et al

Abstract:

Preservation of soft-bodied organisms is exceedingly rare in the fossil record. One way that such fossils are preserved is as carbonaceous compressions in fined-grained marine sedimentary rocks. These deposits of exceptional preservation are known as Burgess Shale-type (BST) deposits. During the Cambrian Period, BST deposits are more common and provide a crucial view of early animal evolution. The earliest definitive fossil evidence for macroscopic animal-grade organisms is found in the preceding Ediacaran Period. BST deposits from the Ediacaran are rarer and lack conclusive evidence for animals. Here we report the discovery of a new Ediacaran BST deposit with exceptional preservation of non-mineralizing macro-organisms in thinly bedded black shale from Zavkhan Province, western Mongolia. This fossil assemblage, here named the Zuun-Arts biota, currently consists of two new species of probable macroscopic multicellular benthic algae. One species, Chinggiskhaania bifurcata n. gen., n. sp., dominates the biota. The other species, Zuunartsphyton delicatum n. gen., n. sp., is known from three specimens. SEM-EDS analysis shows that the fossils are composed of aluminosilicate clay minerals and some carbon, a composition comparable to fossils from the Cambrian Burgess Shale biota. This discovery opens a new window through which to view late Precambrian life.

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An Amazing Lagerstatte From Upper Jurassic Patagonia

FIRST GLIMPSE OF THE SILICIFIED HOT SPRING BIOTA FROM A NEW JURASSIC CHERT DEPOSIT IN THE DESEADO MASSIF, PATAGONIA, ARGENTINA

Authors:

Massini et al

Abstract:

Jurassic hot-spring chert deposits in the Deseado Massif, Patagonia, Argentina, have been known for over two decades, but the associated biota has only begun to be documented recently, and thus far only from a small number of localities. Here we report the discovery of a large complex of well-exposed Upper Jurassic epithermal siliceous deposits represented by organic-rich cherts preserved within the geothermal system from La Bajada, Santa Cruz, Argentina. The chert samples analyzed so far contain exceptionally well-preserved, in-situ and transported, tri-dimensionally silicified plants, animals and microorganisms. Plants include equisetaleans (Equisetum thermale), ferns and gymnosperms. Among them, well-preserved in-situ osmundaceous rhizomes in different developmental stages are the dominant component of the taphoflora. Conifers are represented by wood, seeds, leaves and pollen tentatively assigned to the families Araucariaceae and Cheirolepidiaceae. The assemblage also contains vegetative and reproductive structures of fungi, oomycetes, cyanobacteria, algae, testate amoebas, ciliates and numerous remains of unresolved taxonomic affinity. Microorganisms are preserved isolated in the chert matrix or directly associated with plants and other organic remains in mutualistic, parasitic and saprotrophic engagements. Also present are numerous coprolites and arthropod remains that, along with the named microorganisms, are indicative of trophic relationships in the ecosystem. Altogether, this fossil assemblage suggests that distal paleoenvironments within the geothermal system are preserved at La Bajada. The diversity, abundance, and exceptional preservation of fossils in the La Bajada ecosystem provides a unique window into the geological past that offers a substantial contribution to the reconstruction of middle Mesozoic terrestrial ecosystems.

The Earliest Known Pelagic Jellyfish Found in Stage 3 Cambrian China

The earliest pelagic jellyfish with rhopalia from Cambrian chengjiang Lagerstätte

Authors:

Han et al

Abstract:

Modern cnidarian medusae generally show a triphasic life cycle with a succession of a larva, a sessile polyp and a pelagic medusa stage. The debate around the metagenesis of sessile polyps into pelagic medusae has lasted for more than 100 years. When pelagic forms originated is not clear. Hitherto the earliest crown-group medusae have been found at Cambrian Stage 5 (traditional Middle Cambrian, 509 Ma) in Utah, while diverse stem-group medusozoans were found in the basal Cambrian Fortunian Stage. No reliable medusae have been found from Cambrian Series 2 Stage 3 (ca. 521 Ma), although the marine benthic community teemed with many phyla of bilaterians, sponges, and ctenophores. Here we reinterpret Yunnanoascus haikouensis Hu et al., 2007, originally described as a ctenophore, as a pelagic, predatory, crown-group medusozoan, based on the presence of rhopalia, possible radial canals, and marginal tentacles. The medusae were a predatory member of the pelagic food web at the middle level of the ocean at Cambrian Stage 3.

The Dinosaur Graveyards at Las Águilas, Mexico Were a Campanian Cretaceous River Delta Environment

Age and depositional environment of the “dinosaur graveyard” at Las Águilas, southern Coahuila, NE Mexico

Authors:

Vogt et al

Abstract:

Here we provide a detailed description of the upper Campanian sediment succession at Las Águilas, southern Coahuila, northeastern Mexico, including the first absolute age dating for this interval, paleoenvironmental reconstructions and taphonomic observations on the abundant dinosaur remains at the locality. Stratigraphic investigations of the dinosaur-bearing succession at the Las Águilas vertebrate fossil area near Porvenir de Jalpa reveal a diverse vertebrate assemblage, including dinosaurs, crocodilians and turtles. New findings in adjacent sites include eusuchian crocodylomorphs, four different kinds of turtles, dromaeosaurids, lambeosaurines, pterosaurs and elasmosaurid plesiosaurs. Strontium isotope measurements on fossil oyster shells provide an absolute age of 73 ± 1 Ma for the lower part of the Las Águilas section. The locality is thus of late Campanian age. The vertebrate, invertebrate and plant materials as well as the sediment structures observed in a 50 m thick predominantly siliciclastic succession of the Cerro del Pueblo Formation suggest deposition in an extensive delta plain environment. The facies succession indicates a short-termed cyclicity of limnic, brackish and shallow marine environments during the late Campanian–early Maastrichtian Cerro del Pueblo Formation with numerous layers containing dinosaur fossil remains.

The Emu Bay Shale Cambrian Konservat-Lagerstätte

The Emu Bay Shale Konservat-Lagerstätte: a view of Cambrian life from East Gondwana

Authors:

Paterson et al

Abstract:

Recent fossil discoveries from the lower Cambrian Emu Bay Shale (EBS) on Kangaroo Island, South Australia, have provided critical insights into the tempo of the Cambrian explosion of animals, such as the origin and seemingly rapid evolution of arthropod compound eyes, as well as extending the geographical ranges of several groups to the East Gondwa-nan margin, supporting close faunal affinities with South China. The EBS also holds great potential for broadening knowl-edge on taphonomic pathways involved in the exceptional preservation of fossils in Cambrian Konservat-Lagerstätten. EBS fossils display a range of taphonomic modes for a variety of soft tissues, especially phosphatization and pyritization, in some cases recording a level of anatomical detail that is absent from most Cambrian Konservat-Lagerstätten.

A new Ediacaran NeoProterozoic Lagerstatte Sheds Light on Rangeomorphs

The Beothukis/Culmofrons problem and its bearing on Ediacaran macrofossil taxonomy: evidence from an exceptional new fossil locality

Authors:

Liu et al

Abstract:

The late Ediacaran siliciclastic successions of eastern Newfoundland, Canada, are renowned for their fossils of soft-bodied macro-organisms, which may include some of the earliest animals. Despite the potential importance of such fossils for evolutionary understanding, the taxonomic framework within which Ediacaran macrofossils are described is not clearly defined. Rangeomorphs from a newly discovered fossil surface on the Bonavista Peninsula, Newfoundland, require us to reconsider contemporary use of morphological characters to distinguish between genera and species within Ediacaran taxa. The new surface exhibits remarkable preservational fidelity, resolving features smaller than 0.1 mm in dimension in both frondose and non-frondose taxa. Such preservation permits the recognition of rarely observed fourth- and fifth-order rangeomorph branching, offering unparalleled opportunities to investigate the fine-scale construction of rangeomorph taxa including Culmofrons plumosa Laflamme et al., 2012. Our observations enable resolution of taxonomic issues relating to rangeomorphs, specifically overlap between the diagnoses of the frondose genera Beothukis Brasier and Antcliffe, 2009 and Culmofrons. We propose a taxonomic framework for all Ediacaran macrofossils whereby gross architecture, the presence/absence of discrete morphological characters and consideration of growth programme are used to distinguish genera, whereas morphometric or continuous characters define taxa at the species level. On the basis of its morphological characters, Culmofrons plumosa is herein synonymized to a species (Beothukis plumosa comb. nov.) within the genus Beothukis. This discussion emphasizes the need to standardize the taxonomic approach used to describe Ediacaran macrofossil taxa at both the genus and species levels, and raises important considerations for future formulation of higher-level taxonomic groups.

Eocene Paleogene Eohippus Found With Fossil Fetus

Description of a Well Preserved Fetus of the European Eocene Equoid Eurohippus messelensis

Authors:

Lorenz Franzen et al

Abstract:

The early Middle Eocene locality of Grube Messel, near Darmstadt (Germany), is famous for its complete vertebrate skeletons. The degree of preservation of soft tissues, such as body silhouettes, internal organs and gut contents, is frequently remarkable. The present specimen was analyzed for remnants of the reproductive system. Classic anatomy and osteology and high-resolution micro-x-ray were applied to describe the fetus of the European Eocene equoid Eurohippus messelensis. Scanning electronic microscopy (SEM) was used for determination of soft tissue remnants. The fetus is the earliest and best-preserved fossil specimen of its kind. The postcranial fetal skeleton is almost complete and largely articulated, allowing the conclusion that the pregnant mare was in late gestation. The apparent intrauterine position of the fetus is normal for the phase of pregnancy. Death of mare and fetus were probably not related to problems associated with parturition. Soft tissue interpreted as the uteroplacenta and a broad uterine ligament are preserved due to bacterial activity and allow considerations on the evolutionary development of the structures.

New Fossil From Darriwilian Ordovician Winneshiek Lagerstätte in Iowa Sheds Light on Sea Scorpion, Horseshoe Crab Relationship

A new Ordovician arthropod from the Winneshiek Lagerstätte of Iowa (USA) reveals the ground plan of eurypterids and chasmataspidids

Authors:

Lamsdell et al

Abstract:

Euchelicerates were a major component of Palaeozoic faunas, but their basal relationships are uncertain: it has been suggested that Xiphosura—xiphosurids (horseshoe crabs) and similar Palaeozoic forms, the synziphosurines—may not represent a natural group. Basal euchelicerates are rare in the fossil record, however, particularly during the initial Ordovician radiation of the group. Here, we describe Winneshiekia youngae gen. et sp. nov., a euchelicerate from the Middle Ordovician (Darriwilian) Winneshiek Lagerstätte of Iowa, USA. Winneshiekia shares features with both xiphosurans (a large, semicircular carapace and ophthalmic ridges) and dekatriatan euchelicerates such as chasmataspidids and eurypterids (an opisthosoma of 13 tergites). Phylogenetic analysis resolves Winneshiekia at the base of Dekatriata, as sister taxon to a clade comprising chasmataspidids, eurypterids, arachnids, and Houia. Winneshiekia provides further support for the polyphyly of synziphosurines, traditionally considered the stem lineage to xiphosurid horseshoe crabs, and by extension the paraphyly of Xiphosura. The new taxon reveals the ground pattern of Dekatriata and provides evidence of character polarity in chasmataspidids and eurypterids. The Winneshiek Lagerstätte thus represents an important palaeontological window into early chelicerate evolution.

New Cambrian Lagerstätte Suggests Original Burgess Shale Diversity an Anomaly

Soft-bodied biota from the middle Cambrian (Drumian) Rockslide Formation, Mackenzie Mountains, northwestern Canada

Authors:

Kimmig et al

Abstract:

A new Burgess Shale-type Lagerstätte is described from the middle Cambrian (Series 3, Drumian) Rockslide Formation of the Mackenzie Mountains, Northwest Territories, Canada. The Rockslide Formation is a unit of deeper water ramp to slope, mixed carbonate, and siliciclastic facies deposited on the northwestern margin of Laurentia. At the fossil-bearing locality, the unit onlaps a fault scarp cutting lower Cambrian sandstones. There it consists of a succession of shale and thick-laminated to thin-bedded lime mudstone, calcareous sandstone, and greenish-colored calcareous mudstone, overlain by shallower water dolostones of the Avalanche Formation, which is indicative of an overall progradational sequence. The Rockslide Formation is of similar age to the Wheeler and Marjum formations of Utah, belonging to the Bolaspidella Biozone. Only two 1 m thick units of greenish mudstone exhibit soft-bodied preservation, with most specimens coming from the lower interval. However, the biota is common but not as diverse as that of other Lagerstätten such as the Burgess Shale in its type area. The shelly fauna is dominated by the hyolith Haplophrentis carinatus Matthew, 1899 along with sparse linguliformean brachiopods, agnostoid arthropods, and ptychoparioid trilobites. The nonmineralized biota includes the macrophytic alga Margaretia dorus Walcott, 1911, priapulid worms, and the carapaces of a number of arthropods. The arthropods belong to Isoxys mackenziensis n. sp., Tuzoia cf. T. guntheri Robison and Richards, 1981; Branchiocaris? sp., Perspicaris? dilatus Robison and Richards, 1981; and bradoriids, along with fragments of arthropods of indeterminate affinities. The style of preservation indicates that most soft parts underwent complete biodegradation, leaving just the more resistant materials such as chitinous arthropod cuticles. The range of preservation and similarity to the coeval biotas preserved in Utah suggests that the composition of this Lagerstätte is probably representative of the community living on the relatively deep-water ramp or slope during middle Cambrian time in Laurentia. This would argue that the extraordinary diversity of the Burgess Shale at Mount Field is anomalous.

A 50 Year MegaDrought Wrought Nasty Lake Killing Dodos, Others in Mauritius

Nine hundred kilometers off the east coast of Madagascar lies the tiny island paradise of Mauritius. The waters are pristine, the beaches bright white, and the average temperature hovers between 22°C and 28°C (72°F to 82°F) year-round. But conditions there may not have always been so idyllic. A new study suggests that about 4000 years ago, a prolonged drought on the island left many of the native species, such as dodo birds and giant tortoises, dead in a soup of poisonous algae and their own feces.

The die-off happened in an area known as Mare aux Songes, which once held a shallow lake that was an important source of fresh water for nonmigratory animals. Today, it’s just a grassy swamp, but beneath the surface, fossils are so common and so well preserved that the area qualifies as what scientists call a Lagerstätte, which in German means “storage space.” "What I wanted to know was, how did this drought cause this graveyard?” says Erik de Boer, a paleoecologist at the University of Amsterdam. “How did so many animals die?”

To find out, de Boer and colleagues analyzed sediment cores taken from the area. The layers in a core contain markers that can help scientists reconstruct an ecosystem’s history, such as preserved pollens and microbes. About 4200 years ago, monsoon activity declined dramatically, causing a 50-year megadrought on the island. The cores revealed that during the same time period, the ancient lake became a muddy, salty swamp. “Annually, the lake would get some fresh water in, however this drinking water turned foul during the dry season,” de Boer says.

Things got bad fairly quickly for local animals once the lake began to dry up, the team reports in the current issue of The Holocene. Sanitation appears to have become a major issue with so many animals crowding around the shrinking source of fresh water. “The animals lived around the edges, and the excrements probably got mixed up in the wetlands," de Boer says. "It’s like a big toilet.” Even worse, the researchers’ analysis shows that the feces-flooded waters encouraged the growth of single-celled algae and bacteria—diatoms and cyanobacteria—which can cause poisonous algal blooms. The circumstances combined to create what the scientists refer to as a “deadly cocktail” that they think killed many of the animals preserved as fossils at Mare aux Songes today.

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An Upper Jurassic Lagerstätte Found in Mongolia

Upper Jurassic Lagerstätte Shar Teg, southwestern Mongolia

Authors:

Ponomarenko et al

Abstract:

One of the most interesting Mesozoic Lagerstätten, Shar Teg in southwestern Mongolia, is reviewed. The geological structure and oryctocoenoses of Shar Teg are described. Shar Teg is one of the most diverse Jurassic Lagerstätten in terms of fossils represented. Fossils from Shar Teg include aquatic and terrestrial plants, mollusks, crustaceans, insects, fishes, amphibians, reptiles, and mammals. Insects are the most diverse group. To date, a total of 297 species of 161 families and 22 orders have been described or recorded in Shar Teg, making it possible to reconstruct comprehensively the Jurassic biota of the locality. The oryctocoenosis composition is peculiar; it includes only six species described from other localities. The oryctocoenosis appears to link the faunas of eastern Asia, Central Asia, and Europe. A total of 31 new species are described.

New Discoveries at From the Jehol Biota Lagerstatte

The Jehol Biota, an Early Cretaceous terrestrial Lagerstätte: new discoveries and implications

Author:

Zhou

Abstract:

The study of the Early Cretaceous terrestrial Jehol Biota, which provides a rare window for reconstruction of a Lower Cretaceous terrestrial ecosystem, is reviewed with a focus on some of the latest progress. A newly proposed definition of the biota based on paleoecology and taphonomy is accepted. Although the Jehol fossils are mainly preserved in two types of sedimentary rocks, there are various types of preservation with a complex mechanism that remains to be understood. New discoveries of significant taxa from the Jehol Biota, with an updated introduction of its diversity, confirm that the Jehol Biota represents one of the most diversified biotas of the Mesozoic. The evolutionary significance of major biological groups (e.g. dinosaurs, birds, mammals, pterosaurs, insects, and plants) is discussed mainly in the light of recent discoveries, and some of the most remarkable aspects of the biota are highlighted. The global and local geological, paleogeographic, and paleoenvironmental background of the Jehol Biota have contributed to the unique composition, evolution, and preservation of the biota, demonstrating widespread faunal exchanges between Asia and other continents caused by the presence of the Eurasia–North American continental mass and its link to South America, and confirming northeastern China as the origin and diversification center for a variety of Cretaceous biological groups. Although some progress has been made on the reconstruction of the paleotemperature at the time of the Jehol Biota, much more work is needed to confirm a possible link between the remarkable diversity of the biota and the cold intervals during the Early Cretaceous. Finally, future directions for the study of the Jehol Biota are proposed that highlight the great potential of more comprehensive and multidisciplinary studies to further our understanding of the biological and geological implications of the Jehol Lagerstätte.

The Paleoenvironment of Oligocene Paleogene Patagonia

Reconstruction of a fossil forest reveals details of the palaeoecology, palaeoenvironments and climatic conditions in the late Oligocene of South America

Authors:

Brea et al

Abstract:

This research focuses on the three-dimensional reconstruction of an in situ forest based on fossil wood assemblages recovered in the Rancahué Formation (Upper Oligocene), Neuquén, Argentina. Atherospermataceae, Lauraceae, Nothofagaceae, Eucryphiaceae, Cunoniaceae and Myrtaceae specimens are described. The mapping of a forest floor section and in situ tree diameters enabled the estimation of the following palaeoecological quantitative data: tree density, dominance, basal area, biomass, diametric classes, canopy height, and age classes. Palaeoclimatical data was determined on the basis of physiognomic anatomical features using multivariate anatomical analyses. These results were compared with other proxies including Carlquist's index, Coexistence Approach (CA), Nearest Living Relatives (NLRs), and growth-rings analyses. The structural data from the Aluminé forest inferred from these analyses includes: tree density of 463–701 trees/ha, mean height of 15.22 m, dominance of the genus Nothofagoxylon (89.66 m2/ha), total basal area of 158.20 m2/ha, biomass between 43 and 712 tn/ha and mean age of 223 years (specimens between 31 and 700 years old). These results are comparable to those of mature low-to-middle altitude extant forests dominated by Nothofagus and developed under humid-temperate conditions. Based on the NLRs method, the Aluminé forest has a floristic composition similar to the present-day Valdivian forest. The persistence of Nothofagus as the dominant element in temperate rainforests correlates with regimes where large-scale disturbances, such as volcanism and earthquakes are prevalent. The fossil taxa are closely related to the extant Laurelia, Persea, Eucryphia, Nothofagus, Weinmannia, Myrceugenia and Luma. The forest shows intermixed deciduous and evergreen elements, and taxa with shade-intolerance and intermediate shade tolerance. Also, the majority of these taxa need soils with available water. The integrated analysis of multiple sets of proxy data suggests that the late Oligocene forest grew under temperate and humid climate, while the eco-anatomical features and sedimentary data provide information about the environmental stress conditions of its development and the violent causes of burial.

A Eurypterid Lagerstätte From Pridoli Silurian Pennsylvania

A NEW EURYPTERID LAGERSTÄTTE FROM THE UPPER SILURIAN OF PENNSYLVANIA

Authors:

Vrazo et al

Abstract:

Eurypterids are generally rare in the fossil record, but occasionally occur in abundance. The genus Eurypterus, in particular, is well known from certain upper Silurian Lagerstätten of the northern Appalachian basin (New York and Ontario), but occurs far less frequently in the central and southern Appalachian basin (Pennsylvania, Maryland, and West Virginia, respectively). The recent discovery of an exceptionally preserved mass assemblage of Eurypterus in the upper Tonoloway Formation (upper Ludlow–Přídolí) of Pennsylvania provides new information on the behavior and life habitat of the genus in this region. Eurypterids at this locality are found in thinly laminated, calcareous shale deposited within the lower intertidal to shallow subtidal zone of a coastal mudflat or sabkha. Rare associated fauna of limited diversity, and evaporitic and desiccation features in associated beds, suggest a stressed environment with variable salinity and possible hypoxic conditions. Most eurypterids are disarticulated and fragmentary, but several fully articulated, exceptionally preserved specimens are present. Exoskeletal features and taphonomic indices values indicate a molt rather than death assemblage, and the presence of arthropod trackways suggests that Eurypterus sp. may have molted en masse in the vicinity of the burial site. Sequence stratigraphic interpretation of the site suggests that preservation of eurypterid remains is the result of occupation of ephemeral environmental (salinity/oxygen) conditions during a transgression. The occurrence of this new Lagerstätte within the upper Silurian succession of the central Appalachians, an interval which had heretofore yielded only rare, fragmentary remains, indicates that eurypterids were more prevalent in this region than previously thought.

How the Early Cretaceous Jehol Lagerstatte Fossilized

A MODEL FOR ORGANIC FOSSILIZATION OF THE EARLY CRETACEOUS JEHOL LAGERSTÄTTE BASED ON THE TAPHONOMY OF “EPHEMEROPSIS TRISETALIS”

Authors:

Pan et al

Abstract:

The taphonomic pathways of “Ephemeropsis trisetalis” nymphs (mayfly larvae) were systematically investigated based on fossils of different preservational types, collected during three high–stratigraphic-resolution (mm to cm) excavations in the Lower Cretaceous Yixian Formation in the Sihetun area of western Liaoning, China. All fossils studied are fully articulated either in three or two dimensions, which indicates that decay was terminated at a stage before the exoskeleton became disarticulated. We conclude that the Jehol organic skeletons represent at least two general types of preservation produced by pyritization and collapse/compression, respectively. The two-dimensional compressions show no evidence for authigenic minerals, but the three-dimensionally preserved fossils are wholly or partially pyritized. Our study also indicates that aluminosilicate clay and pyrite mineralization are closely associated with fossil “Ephemeropsis trisetalis” nymphs, suggesting that both clay and pyrite played important roles in lacustrine fossil preservations, as in some marine fossil Lagerstätten. We propose a general model for organic tissue fossilization in the Jehol Lagerstätte based on study of taphonomy of “Ephemeropsis trisetalis” nymphs.

"Prosauropod" Bonebeds Were Laid Down During a Humid, Heavily Vegetated Environment

Taphonomy, deposition and pedogenesis in the Upper Triassic dinosaur beds of Trossingen

Authors:

Schoch et al

Abstract:

The Upper Norian (Late Triassic) red-beds of the Knollenmergel (Trossingen-Formation) are famous for their richness in prosauropod dinosaurs. Among the most productive localities, the Obere Mühle (Rutschete) at Trossingen (SW Germany) stands out for the large number of skeletons found in the early 20th century and the wide stratigraphic range of finds within a 12-m sequence of monotonous floodplain mudstones. New excavations at the original site have been carried out since 2007, aimed at securing taphonomic, sedimentological and palaeopedological data on the formation of the deposit. Based on the findings of the present and earlier excavations, the following conclusions can be drawn. (1) The Obere Mühle yields at least two different types of vertebrate lagerstaetten: (1) miring deposits, preserving numerous articulated skeletons in “life-like” postures and all stages of subsequent decomposition and (2) more regular sheet flood deposits, producing only a few skeletons (e.g. turtles), which were disarticulated into body parts and single elements, or in bonebeds. (2) The deposits were laid down in numerous successive cycles of sedimentation, interrupted by pedogenic phases. A broad range of pedologic features is recognised, leading to the interpretation of the deposits as paleo-vertisols and aridisols. This indicates a long depositional history for the whole section, interrupted by arid phases in which few vertebrates were preserved and life was probably less rich. (3) The occurrence of vertebrate skeletons correlates with more humid periods and traces of intense vegetation. (4) Weathering played a significant role in some beds of the Trossingen section. The absence of smaller tetrapods could be caused by intense weathering.

What Were the Cambrian Yunnanozoans?

New data on the palaeobiology of the enigmatic yunnanozoans from the Chengjiang Biota, Lower Cambrian, China

Authors:

Cong et al

Abstract:

Interpretation of the enigmatic soft-bodied yunnanozoans from the Lower Cambrian (Stage 3, Series 2) Chengjiang Biota has remained controversial for decades because of their strange body plan and their variable taphonomic alteration. Proposed affinities have ranged from stem bilaterian to stem vertebrate. A study of over seven hundred slabs, many newly collected, from five sections at two localities demonstrates that yunnanozoans have sclerotized dorsal and axial segments, a body cavity, a unique feeding region and a coiled alimentary canal. Although two genera have been previously discriminated, all specimens have the same number of filamentous arches (seven pairs) and of ventral circular structures (four pairs); this indicates that Haikouella Chen, Huang and Li, 1999 is a junior synonym of Yunnanozoon Hou, Ramsköld and Bergström, 1991. Our analysis reveals new details of the putative pharyngeal pores of Yunnanozoon lividum, and although there are similarities with the gill slits of deuterostomes, the question of their homology remains moot. The filamentous arches and their supporting rods were probably sclerotized and represent a specialized feeding structure. Yunnanozoans exhibit characters that are open to a number of alternative interpretations of putative homology, encompassing comparisons with deuterostomes and protostomes (including members of the Platyzoa). Given their unique features, and the current lack of secure homologies, the affinities of yunnanozoans should continue to be considered in a wider bilaterian context.

A New Helmetiid Arthropod From The Early Cambrian China

A New Helmetiid Arthropod From The Early Cambrian Chengjiang Lagerstätte, Southwest China

Authors:

Zhao et al

Abstract:

A new arthropod, Haifengella corona new genus new species is described from the early Cambrian Chengjiang Lagerstätte (Series 2, Stage 3), Yunnan Province, southwest China. It is readily assignable to helmetiida based on gross morphology of the tergum. The new helmetiid is unique in having the marginal spines extending over one-third of the total body width. The weakly sclerotized tergum consists of six thoracic tergites with edge-to-edge tergite articulations. The sub-trapezoidal cephalic shield has a pair of long spines projecting from each posterolateral corner. A prehypostomal sclerite (anterior sclerite) recesses in the anterior margin of the cephalic shield, and a pair of bulges that are close to the prehypostomal sclerite in the cephalic shield are presumed to be the position of ventral eyes. Each of the thoracic tergites exhibits a pair of long spines projecting from the posterolateral corners. The semicircular pygidium carries one terminal spine and two pairs of lateral spines.