Lagerstatten

Exceptional preservation of non-biomineralized arthropods, sponges and vermiform taxa occurs in the Darriwilian (Middle Ordovician) Llanfallteg Formation of South Wales, UK. The assemblage contains elements typical of Ordovician communities juxtaposed with those more commonly associated with Cambrian Konservat-Lagerstätten. This assemblage is
preserved in rocks of a deep-marine succession dominated by fine-grained siliciclastic and volcaniclastic density-current
deposits. Non-biomineralized taxa of Cambrian aspect are preserved as pyritized carbonaceous compressions on the spectrum of Burgess Shale-type preservation. Trilobites with phosphatized digestive structures have also been recovered. The assemblage of the Llanfallteg Formation Konservat-Lagerstätte demonstrates that some Burgess Shale-type faunal elements survived into the Middle Ordovician within cool, deep-water refugia in the Welsh Basin, offshore from communities dominated by typical Ordovician taxa.

Plusieurs Lagerstätten à échinodermes ont été découverts au cours des dix dernières années dans l'Ordovicien supérieur de l'Anti-Atlas oriental (Tafilalt occidental, Maroc). Ces niveaux ont livré des assemblages particulièrement riches et diversifiés d'échinodermes. La préservation exceptionnelle de ces organismes témoigne d'un enfouissement rapide et in situ de communautés benthiques particulièrement denses constituées quasi-exclusivement d'échinodermes. Trois assemblages sont décrits : Bou Nemrou (Sandbien basal), piste de Jorf (Sandbien supérieur) et enfin, Tizi n'Mouri (Katien supérieur). L'intérêt scientifique majeur de ces faunes (implications paléoécologiques et paléogéographiques) est brièvement présenté. Enfin, la préservation de ces gisements, qui constituent un élément majeur du patrimoine paléontologique du Sud marocain, est abordée. Late Ordovician echinoderm Lagerstätten from the eastern Anti-Atlas (Morocco): an example of exceptional scientific heritage worthy of protection. Abstract. In the last ten years, several Late Ordovician echinoderm Lagerstätten have been discovered in the eastern Anti-Atlas (western Tafilalt) of Morocco. These levels have yielded extremely rich and diverse echinoderm assemblages. The exquisite preservation of most organisms suggests rapid and in-situ burial of large, particularly dense benthic communities largely dominated by echinoderms. Three « starfish beds » are briefly described: Bou Nemrou (earliest Sandbian), piste de Jorf (late Sandbian), and Tizi n'Mouri (late Katian). The major scientific relevance of these faunas is outlined herein (for example their palaeoecological and palaeogeographical implications). Finally, the conservation of these levels, which represent a major piece of the palaeontological heritage of southern Morocco, is discussed.

Documentation of non-or weakly biomineralizing animals that lived during the Furongian is essential for a comprehensive understanding of the diversification dynamics of metazoans during the early Palaeozoic. However, the fossil record of 'soft'-bodied metazoans is particularly scarce for this critical time interval, consisting of rare fossils found at a dozen or so localities worldwide. Here we report new occurrences of exceptional preservation in Furongian (Jiangshanian) strata of the McKay Group near Cranbrook, British Columbia, Canada. This locality had already yielded trilobites with phosphatised guts, with all specimens representing the same species and occurring within a 10-m-thick interval. Two stratigraphically higher horizons with soft-tissue preservation are reported herein; one has yielded a ctenophore and an aglaspidid arthropod, the other a trilobite with a phosphatised gut belonging to a different species than the previously described specimens. The ctenophore represents the first Furongian record of the phylum and the first reported occurrence of Burgess Shale-type preservation in the upper Cambrian of Laurentia. The aglaspidid belongs to a new species of Glypharthrus, and is atypical in having twelve trunk tergites and an anteriorly narrow 'tailspine'. These features suggest that the tailspine of aglaspidids evolved from the fusion of a twelfth trunk segment with the telson. They also confirm the vicissicaudatan affinities of these extinct arthropods. Compositional analyses suggest that aglaspidid cuticle was essentially organic with a thin biomineralised (apatitic) outer layer. The trilobite reveals previously unknown gut features, such as medial fusion of digestive glands, possibly related to enhanced capabilities for digestion , storage, or the assimilation of food. The new fossils demonstrate that conditions conducive to soft-tissue preservation repeatedly developed in the outer shelf environment represented by the Furongian strata near Cranbrook. Future exploration of the c. 600-m-thick, mudstone-dominated upper part of the section may result in more abundant discoveries of exceptional fossils.

Exceptional fossil deposits exhibiting soft-part preservation, or Konservat-Lagerstätten, are prevalent in Cambrian rocks and provide detailed information on fossil assemblages not available from conventional deposits. It has long been recognised that many of these assemblages exhibit certain taxonomic similarities, with many elements seemingly having cosmopolitan distributions. These types of assemblages, particularly those of Cambrian age, have become known as Burgess Shale-type (BST) biotas, named for the famous deposit in the Canadian Rocky Mountains where fossils preserved in this way were first discovered. This study provides the first broad-scale analysis of the assemblage relationships between all major BST biotas. We compiled a database of the presences and absences of over 600 genera within 12 Lagerstätten from Laurentia, Siberia, South China and East Gondwana, ranging in age from Cambrian Series 2 through Series 3 (late-early to middle Cambrian; c. 518-502 Ma), and analysed this using a variety of quantitative methods in order to investigate the relationships between these sites. Non-metric multidimensional scaling (NMDS) ordination, cluster analysis and Parsimony Analysis of Ende-micity (PAE) were used to group localities and examine relationships. We also used Bayesian inference and illustrate the benefits of this approach to biogeographic studies. Results suggest that both space and time have important effects on the taxonomic constitution of BST biotas, and that the similarity of these assemblages appears to increase from Series 2 through Series 3, largely driven by increases in cosmopolitanism of biomineralised taxa such as trilobites and brachiopods. There is also evidence of higher-level taxonomic turnover across this period. Endemic taxa help amplify these patterns, despite their frequent exclusion from biogeographic analyses.

The Lower Ordovician Fezouata Lagerstätte from Morocco (central Anti-Atlas, Zagora area) has yielded abundant and diverse soft-bodied fossils. Most described taxa were epibenthic or pelagic, so that little is known about the enbobenthic components of the fauna. Here we report the discovery of a locally abundant element of the biota, a palaeoscolecid worm, which may have played an important ecological role in the community. Palaeoscolecids had a long, annulated body with an eversible tooth-bearing pharynx. They probably represent stem priapulids, but unlike them, they were protected by biomineralized (phosphatic) microscopic plates covering most of the body. These sclerites are commonly found isolated within SSF assemblages, thus considerably extending the fossil record 24 of the group that ranges from the Cambrian Series 2 (Stage 3) to the upper Silurian. Like priapulids, palaeoscolecids might have been important bioturbators, contributing to the substrate colonization in the lower Palaeozoic. The discovery of abundant material (38 specimens) in the Fezouata Shale (Lower Ordovician, Morocco) allows us to reconsider their possible lifestyle, habitat and feeding habits. All the specimens belong to Palaeoscolex? tenensis, a species previously only known from a fragment of cuticle from the Floian of Bohemia (Czech Republic). Some exhibit remains of the gut and tail spines, all features that are highly informative with regard to the ecology of these extinct organisms, but rarely preserved. The phosphatic nature of the plates is demonstrated by compositional analyses and interpreted with regard to the diagenetic context of the Fezouata Shale as primary. We also hypothesize that (at least) some palaeoscolecids were makers of Tomaculum-type ichnofossils, which are elongate clusters of faecal pellets, and show that they ingested a notable amount of sediment during the normal course of feeding. The presence of Palaeoscolex? tenensis in the Lower Ordovician of Morocco further documents the great faunal similarities between Perunica and northern Gondwana at that time.

Four distinct echinoderm Lagerstätten have recently been discovered in the Upper Ordovician of the eastern Anti-Atlas, Morocco. They have yielded hundreds of exquisitely preserved specimens. Their taphonomy and associated lithology both suggest rapid, in situ burial. Here we discuss the diverse range of assemblages represented and their significance to the diversity of echinoderms in the Lower Palaeozoic. The oldest assemblage (Izegguirene Formation, lowermost Caradoc) is dominated by eocrinoids, large ophi-uroids, and mitrate stylophorans associated with rare crinoids. It shows strong similarities with slightly older faunas described from the underlying Ouine-Inirne Formation (Llandeilian) in the Central Anti-Atlas. The second assemblage (lower part of the Lower Ktaoua Formation, lower-middle Caradoc) is composed of eocrinoids (Cardiocystites) and small ophiuroids (encrinasterid indet.). The third assemblage was collected in the upper part of the Lower Ktaoua Formation (lowermost Ashgill). This 'starfish' bed is dominated by ophiuroids and large solutes, associated with common diploporites and rhombiferans, and rare crinoids and mitrates. Finally, the youngest assemblage (lower part of Upper Tiouririne Formation, lower Ashgill) has yielded abundant remains of edrioasteroids and rhombiferans.

In the central Anti-Atlas (Morocco; Zagora region), the Fezouata Shale has yielded an extraordinary fossil Lagerstätte documenting the initial stages of the Great Ordovician Biodiversification Event. This Lagerstätte contains abundant and exceptionally well-preserved fossils (EPF) exhibiting soft-bodied preservation as well as " hard " , mineralized parts of extinct organisms. While soft-bodied preservation in the Fezouata Shale is confined to a few stratigraphic intervals, other fossiliferous intervals contain only shelly fossils in sandstone lenses (SL). Placed in the context of a previously established depositional model, EPF are interpreted as autochthonous assemblages buried by storm deposits, close to storm wave-base. There, the current component of storms is reduced compared to proximal settings and weak oscillation is dominant resulting in the record of oscillation ripples. In contrast, bioclastic accumulations were generated upslope in shallower, more proximal lower shoreface environments. There, the current component of storms was significant, as suggested by the disarticu-lation of skeletal remains. Bioclastic materials are localized in SL, which are lenses a few tens of centimeters in thickness and a few meters in width and length. These lenses commonly display erosive bases and convex tops, resulting in a lobate or a channel-lobe morphology. A large amount of sediment was thus rapidly deposited, resulting in the rapid burial of allochthonous material across a strongly localized surface of the sea floor. Integrating both sedimentological and paleontological evidence, intervals yielding EPF are considered as Konservat-Lagerstätten (KsL), in contrast with bioclastic accumulations defined as Konzentrat-Lagerstätten (KzL). Thus, KsL assemblages are interpreted to approximate biocenoses, in which organisms experienced rapid burial by distal tempestites, while KzL assemblages more likely correspond to thanatocenoses, locally deposited by storm back-currents. Here, a genetic link between KsL and KzL is suggested within the Fezouata Shale. Both types of Lagerstätten were related to storm activity, but at different depths.

The Astaneh-Sarband area is located in the northern part of the NW-SE aligned Sanandaj-Sirjan metamorphic belt and consists mainly of Mesozoic schists, Middle Jurassic to Middle Tertiary intrusive rocks and related contact metamorphic aureoles, and pegmatites. Regional metamorphism in the area has reached a peak of greenschist facies, but further metamorphism has occurred locally, associated with granitoid emplacement. Mineralization at Deh Hosein prospect occurs in the form of quartz, quartz-sulfide and quartz-gossan veins and veinlets (partly sheeted in structure) and is mainly hosted by Jurassic meta-sedimentary rocks. Gold occurs in “invisible” form in the arsenopyrite and bismuth-bearing minerals of Deh Hosein and reaches 13.3 ppm. Other notable concentrations are copper (up to 10%), tin (up to 6.7%), tungsten, and bismuth. At Astaneh, gold mineralization is confined to the NW-SE trending Astaneh intrusion and the Shirmazd granodioritic stock. Gold mineralization occurs (in both visible and invisible forms and reaches up to 9.5 ppm) mainly as NE-trending quartz- and quartz-sulfide veins and veinlets, as well as disseminations in the Shirmazd stock and the intersecting microgranodiorite dykes, and in some nearby, smaller, altered granitic stocks. The Nezam Abad mineralization is hosted by a Lower-Mid Eocene quartz diorite unit cut by several aplitic and quartz or quartz-tourmaline veins. Gold occurs as “invisible” form predominantly in arsenopyrite with bismuth inclusions at Nezam Abad and reaches 36.2 ppm. In all three occurrences, gold shows positive correlations with arsenic, bismuth, selenium, silver, tellurium, and antimony. According to arsenopyrite geothermometry, the mineralization formed at temperatures of 380° to 565°C. Oxygen and sulfur isotope data suggest a mixed magmatic-metamorphic source for the ore. Pb isotope ratios from the sulfide and host rock samples of the prospects indicate a good agreement between the lead ratios of the ore of Deh Hosein and the hosting meta-sandstone, the ore of Astaneh and the Shirmazd Stock, and the ore of Nezam Abad and the hosting quartz diorite. The Pb isotope signatures of the ore from the three occurrences show also rather close ratios. According to the plumbotectonics model, the lead in the ores has a lower crustal Pb component. The studied occurrences share some similarities in terms of their mineralogy, geochemistry, formation temperatures, isotope ratios, alteration, and occurrence of gold. They also indicate many similar features with the “intrusion-related gold systems” that have been described from Alaska, the Yukon and other parts of the world.

The Upper Ordovician (lower Katian) Bobcaygeon and Verulam formations from the Lake Simcoe region of Ontario contain a highly diverse echinoderm assemblage that is herein recognized as a Konservat-Lagerstätte. Although fossil crinoids have long been recognized from these formations, the fauna has not received a comprehensive taxonomic evaluation since Springer's classic 1911 monograph. Recent extensive collection and preparation of new material from the Bobcaygeon and Verulam formations near Brechin, Ontario recovered numerous exceptionally preserved crinoid specimens with arms, stems, and attachment structures intact. The Brechin Lagerstätte is the most taxonomically diverse Katian crinoid fauna, with more than 20 crinoid genera represented in this collection. Here, all dicyclic crinoids belonging to subclass Camerata from the Brechin Lagerstätte are evaluated. The following four genera and seven species are described from the fauna, including one new genus and four new species: Reteocrinus stellaris, Reteocrinus alveolatus, Archaeocrinus sundayae n. sp., Archaeocrinus maraensis n. sp., Priscillacrinus elegans n. gen. n. sp., Cleiocrinus regius, and Cleiocrinus lepidotus n. sp. The exceptional preservation of this collection provides an opportunity to describe more fully the morphologic and ontogenetic details of known Ordovician crinoid taxa, to conduct a taxonomic re-evaluation of many species, to describe new taxa, and to provide a framework for subsequent studies of crinoid community paleoecology.

Mass extinctions have altered the trajectory of evolution a number of times over the Phanerozoic. During these periods of biotic upheaval a different selective regime appears to operate, although it is still unclear whether consistent survivorship rules apply across different extinction events. We compare variations in diversity and disparity across the evolutionary history of a major Paleozoic arthropod group, the Eurypterida. Using these data, we explore the group's transition from a successful, dynamic clade to a stagnant persistent lineage, pinpointing the Devonian as the period during which this evolutionary regime shift occurred. The late Devonian biotic crisis is potentially unique among the " Big Five " mass extinctions in exhibiting a drop in speciation rates rather than an increase in extinction. Our study reveals eurypterids show depressed speciation rates throughout the Devonian but no abnormal peaks in extinction. Loss of morphospace occupation is random across all Paleozoic extinction events; however, differential origination during the Devonian results in a migration and subsequent stagnation of occupied morphospace. This shift appears linked to an ecological transition from euryhaline taxa to freshwater species with low morphological diversity alongside a decrease in endemism. These results demonstrate the importance of the Devonian biotic crisis in reshaping Paleozoic ecosystems.

Exceptionally preserved fossils yield crucial information about the evolution of Life on Earth. The Fezouata Biota from the Lower Ordovician of Morocco is a Konservat-Lagerstätte of major importance, and it is today considered as an 'Ordovician Burgess Shale.' This biota was discovered only some 15 years ago, but geological studies of the area date back to the beginning of the 20th century. Pioneering geological investigations lead to the discovery of Ordovician strata in the Anti-Atlas (1929) and ultimately resulted in their formal subdivision into four main strat-igraphic units (1942). In the Agdz area, the presence of fossiliferous Tremadocian (Lower Ordovician) strata was suspected as early as 1939, but only definitively confirmed in 1955. In the 1960s–1990s, Jacques Destombes provided the first detailed biostratigraphic framework for the Lower Ordovician of the Anti-Atlas, and collected thousands of fossils that were subsequently described in a series of monographs. In the early 2000s, exceptionally preserved fossils were discovered in the Fezouata Shale (Tremadocian–late Floian) in the central Anti-Atlas by Mohamed 'Ou Saïd' Ben Moula. This biota, now known as the Fezouata Biota, is of utmost importance, for it demonstrates the extent in the fossil record of non-biomineralising animals typical of the 'Cambrian Explosion' into the Ordovician, during the 'Great Ordovician Biodiversification.' Although most components are still in need of formal descriptions, a fairly good picture of the composition and organisation of this biota, and how it contributes to our understanding of the early evolution of metazoan communities, can now be depicted. Moreover, recent studies have substantially clarified the biostratigraphical and palaeoenvironmental context of the Fezouata Shale, and are now being followed up by detailed investigations of the taphonomy, geochemistry and micropalaeontology of this unique Konservat-Lagerstätte. These efforts will soon greatly benefit from the recovery of fresh, unweathered samples from drill cores.