Lucy Muir

The Late Ordovician (Hirnantian, approximately 445 million years ago) extinction event was among the largest known, with 85% species loss [ 1 ]. Post-extinction survival faunas are invariably low diversity, especially benthic communities [ 2 ], but ecological structure was restored relatively rapidly [ 1 ]. This pattern, however, reflects organisms with robust skeletons, as only one exceptionally preserved Hirnantian fossil biota was previously known [ 3, 4 ]; in particular, almost no Hirnantian sponges have been recorded. Our study reveals an extraordinarily diverse, sponge-dominated community thriving immediately after the Hirnantian extinction in Zhejiang, South China. Several contemporaneous sites preserve a total diversity of over 75 sponge species, many with preserved soft tissues, in pronounced contrast to normal survival and early recovery faunas. This diversity is unprecedented for any Hirnantian fossil group, and the fauna provides a unique window into a post-extinction ecosystem. The sponges are often large and structurally complex and represent numerous different lineages that survived the extinction. Layers with abundant sponge remains were deposited after other mass extinctions [ 5, 6 ], suggesting a general pattern of sponge abundance during collapse of Phanerozoic marine ecosystems. It is possible that the conditions of ecological collapse increase the particulate food sources for sponges, while they themselves are relatively unaffected by the crises. Furthermore, the abundance of sponges in the Hirnantian sequence of South China may have aided post-extinction ecosystem recovery by stabilizing the sediment surface, allowing sessile suspension feeders such as brachiopods, corals, and bryozoans to recover rapidly.

The fossil record of conulariids (Cnidaria, Scyphozoa) extends downward into the topmost part of the Ediacaran System, but the first appearance of diverse, widespread conulariids is in siliciclastic rock units of Early Ordovician age, which collectively host at least six conulariid genera. Some of these same units also contain Sphenothallus, a probable medusozoan that frequently co-occurs with conulariids in Ordovician and younger deposits. Lower Ordovician conulariid localities are distributed among five (originally) Southern Hemisphere terranes, namely Core Gondwana (Archaeoconularia, Eoconularia and Teresconularia), Armorica (Conularia azaisi), Avalonia (Archaeoconularia, Eoconularia and Exoconularia), Perunica (Archaeoconularia, Conularia and Conulariella) and South China (Conulariella). C. azaisi, currently known from the Southern Montagne Noire (France), probably represents a new genus. Sphenothallus occurs in South China, North China (Korea), Armorica (Southern Montagne Noire) and Core Gondwana (Morocco). In southeastern Morocco, Burgess Shale-type Konservat-Lagerstätten in the Fezouata Shale (Tremadocian–Floian) yield Archaeoconularia sp., Eoconularia sp. and at least one species of Sphenothallus. This low-diversity conulariid assemblage is most similar to the Tremadocian assemblage of Wales (Avalonia), which likewise consists of a single species each of Archaeoconularia and Eoconularia. In the Fezouata Shale, Archaeoconularia sp. and Eoconularia sp. frequently occur in monospecific mass associations. Such associations probably represent an original clumped distribution on the seafloor. Additionally, some Eoconularia sp. occur in V-like pairs or radial clusters, and also some specimens were attached at the apical end to a phosphatic brachiopod or to a corner sulcus of a larger specimen of Eoconularia sp. Similar conulariid/brachiopod associations, consisting of Conularia trentonensis and Onniella sp., occur in the Upper Ordovician (Katian) Collingwood Shale of southern Ontario, Canada.

xceptional 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.

My Fezouata data observation have been cited in this publication via communications to the authors. The Protomonaxonida consist of a heterogeneous group of early fossil sponges traditionally assigned to the demosponges. However, an affinity to the hexactinellid-like Reticulosa has also been suggested, and their relationships are potentially critical to understanding the origins of the extant sponge classes. In this paper, the relationships of the protomonaxonid sponges to each other and to other sponge groups have been reassessed, using previously described specimens as well as new material from the Burgess Shale of Canada and the Hetang Biota of South China. The sponges fall into two coherent groups, one consisting of taxa with long, mostly sub-longitudinal spicules, and the other with complex arrays composed of tracts of minute (millimetre-scale) monaxons, which grade into aspiculate taxa such as the Vauxiidae. Previous ideas relating the Protomonaxonida to extant demosponge linea...

Abstract: The Cambrian, Ordovician and Silurian distributions of non-stromatoporoid sponges are reviewed. The earliest Cambrian faunas contain mostly hexactinellids, with protomonaxonids dominating middle Cambrian assemblages. There are no obvious palaeobiogeographical patterns, with many genera being found widely. Vauxiids, lithistids and heteractinids are apparently confined to low latitudes, but this may be due to a poor fossil record. Most known Ordovician faunas are from low latitudes, although some high-latitude faunas are known, which contain reticulosan hexactinellids and protomonaxonids. There is some division of faunas within Laurentia, into eastern and western provinces, with the western assemblage extending across low northern latitudes during the Late Ordovician. During the Silurian Period, sponge diversity was very low during the Llandovery Epoch, probably partly owing to lack of habitat for taxa restricted to carbonate facies, and also because of sampling bias. There ...

The Builth Inlier contains a sequence of siliciclastic and volcanic rocks of Middle to Late Ordovician age, representing a range of water depths in a volcanic island setting. Sponges are preserved at sites representing all preserved palaeoenvironments; they are a major part of the fauna at many localities and are dominant in abundance and in diversity at a minimum of five sites. The currently known sponge diversity of the inlier is 128 species. Based on long-term collecting, the distributions of sponge groups are observed to be largely correlated with palaeobathymetry. The faunas representing the shallowest-water (sandy facies) are dominated by large, robust, monaxon-bearing sponges, thick-walled hexactine-bearing forms, and agglutinating sponges. In slightly deeper water (fine sand facies), only robust hexactine-bearing sponges have been found. Below normal wave base (primarily siltstone facies), protomonaxonids and reticulosans occur; protomonaxonids were dominant above storm wave base and reticulosans in the deepest settings. The diversity of sponges both within and between localities is unexpectedly high, with sponges usually being the most diverse group at sites with a degree of exceptional preservation. Only a few genera or species have been found at more than one locality, indicating either random sampling of extremely diverse communities, or highly restricted and patchy distributions with much higher total diversity. If the Builth Inlier is typical of Ordovician siliciclastic environments in general, then Ordovician community diversity has been significantly underestimated.

The Cambrian Burgess Shale-type biotas form a globally consistent ecosystem, usually dominated by arthropods. Elements of these communities continued into the Early Ordovician at high latitude, but our understanding of ecological changes during the Great Ordovician Biodiversification Event (GOBE) is currently limited by the paucity of Ordovician exceptionally preserved open-marine faunas. Here we clarify the early stages of the GOBE by describing a new open-marine Konservat-Lagerstätte from the Early Ordovician of Wales. The Afon Gam Biota includes many lineages typical of the Cambrian Burgess Shale-type biotas, but the most abundant groups were sponges, algae and worms, with non-trilobite arthropods being unexpectedly rare. Labile tissues occur abundantly in the sponges and are also present in other groups, including brachiopods and hyoliths. Taphonomic biases are considered and rejected as explanations for arthropod rarity; the preserved biota is considered to be an approximation to the original community composition. We note that other exceptionally preserved communities in the Welsh Ordovician are also sponge-dominated, suggesting a regional change in benthic ecology during the early stages of the GOBE.

Please contact me if you would like a copy of this paper. Pelmatozoans diversified primarily during the Middle and Late Ordovician Period, with Early Ordovician records being much more limited, resulting in many gaps in our knowledge of the early stages of their diversification. Dissociated pelmatozoan ossicles have been found abundantly in one section in the Tonggao Formation (Tetragraptus approximatus Biozone, Floian, Early Ordovician). Most of the ossicles are thecal plates and stem ossicles from hemicosmitoid and glyptocystitoid cystoids. Thecal plates of ‘Cheirocrinus’ sp., Polycosmites sp., and other plates of uncertain affinity are described. A different ossicle type, Pentagonopentagonalis (col.), may represent crinoid remains; this would be one of the earliest occurrences of the class. The thecal ossicles and columnals are all considered, as both sets of data are desirable to determine the most complete estimate of generic diversity. The echinoderm ossicles may have been transported in from shallower water palaeoenvironments and clusters of ossicles may represent coprolites or regurgitates. Estimates of Early Ordovician palaeogeography that place this site at 30°S or near the palaeoequator are supported by the physiological requirements of the primitive echinoderms described herein.

Please contact me if you would like a copy of this paper.
The Cambrian, Ordovician and Silurian distributions of non-stromatoporoid sponges are reviewed. The earliest Cambrian faunas contain mostly hexactinellids, with protomonaxonids dominating middle Cambrian assemblages. There are no obvious palaeobiogeographical patterns, with many genera being found widely. Vauxiids, lithistids and heteractinids are apparently confined to low latitudes, but this may be due to a poor fossil record. Most known Ordovician faunas are from low latitudes, although some high-latitude faunas are known, which contain reticulosan hexactinellids and protomonaxonids. There is some division of faunas within Laurentia, into eastern and western provinces, with the western assemblage extending across low northern latitudes during the Late Ordovician. During the Silurian Period, sponge diversity was very low during the Llandovery Epoch, probably partly owing to lack of habitat for taxa restricted to carbonate facies, and also because of sampling bias. There was a dramatic increase in diversity through the Silurian Period, mostly owing to an apparent diversification in the demosponges; however, there are many ghost lineages, indicating that their fossil record is poorly known. Non-lithistid sponges are very poorly known, with few recorded outside Euramerica. The currently available data for Early Palaeozoic sponges are too incomplete to allow any reliable palaeobiogeographical inferences.

A new locality exposing Tremadocian (Early Ordovician) graptolitic shales in Hunan Province, South China, has yielded an exceptionally well-preserved annulated worm. This palaeoscolecidan is described as Waflascolex changdensis gen. et sp. nov. and reveals extremely fine detail of the cuticle organization and plating array. The new taxon is characterized by three critical characters: incomplete plate rows that occur only on the posterior end of the worm (except in the posterior-most area) and do not extend over the entire circumference or along the entire trunk; a regular rhomboidal array of platelets around intercalations; and reduced cuticular organization at the posterior termination. The unique cuticular organization and platelet ornamentation in the new taxon offer insight into functional differentiation of plates in the scleritome. Palaeoscolecid distribution through the early Palaeozoic is reviewed, showing that the worms were widespread in the Cambrian and Ordovician, but became more restricted during the Silurian. Ordovician palaeoscolecidans are diverse in scleritome architecture, and strikingly different from Cambrian taxa, indicating that this group diversified as part of the Great Ordovician Biodiversification Event.

Conulariella sp. and possibly one other conulariid species occur in close association with Sphenothallus sp. in the lower part of the early Floian Tonggao Formation near the town of Sandu, Guizhou Province, China. This is the only known occurrence of Conulariella in Early Ordovician rocks outside of Bohemia (Perunican terrane), and also the first report of Sphenothallus from the Ordovician of China. The apertural margin of Conulariella appears to have been mostly straight, and apertural lappets probably were not present in this genus. Some Tonggao conulariids may have attached to orbiculoid brachiopods in life. Based on the most recent palaeogeographical reconstructions of Gondwana and associated terranes, Conulariella could have had a dispersal path along the Gondwanan margin.

Exceptionally well-preserved specimens of the reticulosan sponge Cyathophycus loydelli from the Sandbian (Late Ordovician) Llanfawr Mudstones Formation of Llandrindod, Waes, UK, have been examined using scanning electron microscopy (SEM). The specimens include exquisitely detailed pyritized spicules, and granular pyritization of surrounding soft tissues. Spicules frequently show axial canals of diameter similar to those of modern siliceous sponges, with hexagonal symmetry typical of modern demosponges rather than hexactinellids. In one case, the axial filament is also preserved. The largest spicules (ray diameter >20 μm) show a complex structure, with a laminar external region similar to that of the extant hexactinellid Monorhaphis. Some spicules preserve sub-micron detail of the spicule surface, resembling the reticulate collagenous sheath of Monorhaphis. The hexagonal symmetry of the canal confirms that at least some Reticulosa are not crown-group hexactinellids, but stem-group Hexactinellida or Demospongea, or stem-group Silicea. This suggests that a square canal is a sufficient diagnostic feature of total-group Hexactinellida, but that hexagonal canals were more widely distributed among Early Silicea and were probably not restricted to demosponges. Alternatively, comparison with the structure of modern verongiid fibres suggests that these may be homologous with the outer layers of Cyathophycus spicules, and Cyathophycus may instead be a stem-group demosponge. The preserved detail of the surface layer shows that pyritization can preserve certain material with extraordinarily fine resolution.

The problematic Early Palaeozoic fossil Inocaulis has been regarded as an alga, a graptolite and a hydroid by different authors. A new specimen from the Ordovician (late Darriwilian) of Guizhou Province (China) shows fusellar banding, confirming that it is a benthic graptolite.

Several species of palaeoscolecidan worm have been found in the Tonggao Formation (earliest Floian) of Guizhou Province, China. Two new palaeoscolecidan taxa are described (Sanduscolex regularis n. gen. n. sp. and Ashetscolex nuppus n. gen. n. sp.); another palaeoscolecidan (Wronascolex sp.) is left in open nomenclature. This is the youngest known occurrence of Wronascolex. A possible large free-living nematode is described and illustrated, representing the earliest known nematode in the fossil record, and a rare example from a marine setting.

The Builth Inlier of central Wales exposes a highly fossiliferous Middle to Late Ordovician (Darriwilian to basal Sandbian) siliciclastic succession in a volcanic, back-arc basin setting. Articulated echinoderm faunas are preserved in a range of paleoenvironments, together with widespread, dissociated ossicles. These have enabled a reconstruction of the distributions of echinoderm groups across a range of noncarbonate facies. The oldest echinoderm assemblages are from sandstone and siltstone deposits, and have yielded only the crinoid Iocrinus pauli and rare asteroids. The most diverse echinoderm assemblages are from a nearshore siliciclastic facies at Llandegley Rocks and equivalent sites. These are dominated by crinoids, together with rare asteroids, caryocystitid rhombiferans, echinozoans, and possible mitrate stylophorans. Deeper-water environments were dominated by the mitrate stylophoran Anatifopsis, associated with variable numbers of holothurians, cornutes, solutans, and rare cystoids (rhombiferans and undetermined blastozoans). The ecological distribution of echinoderms in the area can be summarized as follows: (1) high-diversity faunas in the shallowest environments, composed primarily of large crinoids, with asterozoans and other groups; (2) low-diversity faunas in intermediate water depths, with crinoids (one species) and asterozoans; (3) moderately diverse faunas in deep-water communities with generally small taxa, dominated by stylophorans. These results agree with previous interpretations of environmental preferences among the different groups of echinoderms, but also indicate a separation of dominantly Cambrian-type classes in offshore sediments and Ordovician-type taxa in shallow water. Based on assessments of functional morphology and previously published data, the environmental distributions of these taxa are likely to have been controlled by a complex of factors including sediment type, flow regime, nutrient availability, and temperature. Shallow-water siliciclastic settings may have been crucial environments for echinoderm diversification during the Great Ordovician Biodiversification Event.

The Protomonaxonida consist of a heterogeneous group of early fossil sponges traditionally assigned to the demosponges. However, an affinity to the hexactinellid-like Reticulosa has also been suggested, and their relationships are potentially critical to understanding the origins of the extant sponge classes. In this paper, the relationships of the protomonaxonid sponges to each other and to other sponge groups have been reassessed, using previously described specimens as well as new material from the Burgess Shale of Canada and the Hetang Biota of South China. The sponges fall into two coherent groups, one consisting of taxa with long, mostly sub-longitudinal spicules, and the other with complex arrays composed of tracts of minute (millimetre-scale) monaxons, which grade into aspiculate taxa such as the Vauxiidae. Previous ideas relating the Protomonaxonida to extant demosponge lineages are supported in the case of the second group, whereas the first group confirms the view of derivation from a hexactinellid-like ancestor. Whether the two groups were directly related or evolved monaxonid spiculation in parallel is currently uncertain.

The comment by Smith et al. rejects a previous interpretation of Middle Ordovician fossils as holothurians. This rejection is based on the use of inappropriate techniques to study the fossils, and insufficient consideration of their taphonomy. The fossils can be shown not to be sponges (the suggested alternative interpretation), and despite the taphonomic limitations, do show echinoderm characters such as the pentagonal oral ring and ambulacral structures.

A new sponge fauna has been discovered in silty mudstone of the early Migneintian (late Tremadocian, Ordovician) of North Wales. The assemblage is dominated by reticulosan hexactinellids, including several species bearing parietal gaps; this feature is common among Cambrian hexactinellids, but is rare in Ordovician faunas. Of particular significance is Valospongia bufo sp. nov., representing the first record of the genus outside the Middle Cambrian of Utah, USA. A single specimen assigned to Hintzespongia? is also described, and also represents the first occurrence outside the Laurentian Burgess Shale-type faunas. This fauna indicates that deeper-water hexactinellids from the Burgess Shale-type faunas survived in places into at least the Early Ordovician, in addition to the Cambrian-type protomonaxonid assemblage seen in the Fezouata Biota.

Palaeoscolecidan worms are rare, Early Palaeozoic fossils with uncertain affinities within the Ecdysozoa. They are locally abundant in the Cambrian and scattered in the Early Ordovician, but very sparse thereafter. Forty-four specimens have been collected from the Middle Ordovician of the Builth-Llandrindod Inlier of Mid Wales and include well-preserved material assigned to seven new genera, with four additional species in open nomenclature. An additional specimen from the Arenig Pontyfenni Formation of South Wales is also described in open nomenclature. The total demonstrates much greater palaeoscolecid diversity than hitherto suspected for this time. The specimens are preserved as cuticle fragments in shales and siltstones, often of submillimetre size but in many cases with excellent preservation. The level of detail preserved in some is equal to that found in Cambrian phosphatized faunas. The new approach to collecting, and the recognition that this material can yield taxonomically useful information, opens new avenues for palaeoscolecidan research in siliciclastic environments. The new taxa are the following: Radnorscolex bwlchi gen. et sp. nov., Aggerscolex murchisoni gen. et sp. nov., Bullascolex inserere gen. et sp. nov., Wernia eximia gen. et sp. nov., Ulexiscolex ormrodi gen. et sp. nov., Pluoscolex linearis gen. et sp. nov. and Loriciscolex cuspidus gen. et sp. nov. The high diversity, and the taxonomic separation from known groups described primarily from Cambrian carbonates, implies that palaeoscolecidans either diversified significantly during the Ordovician or were taxonomically segregated between carbonate and siliciclastic settings. Palaeobiological findings also include confirmation that some palaeoscolecid basal cuticles were solid and others reticulate, plates (and platelets) could form by lateral accretion, plates were in part primarily phosphatic and in part organic and that in at least some groups, platelet secretion occurred external to plate secretion.

Six specimens of a strongly curved, cylindrical hexactinellid sponge have been recovered from the Tommotian-Atdabanian Hetang Biota of South China, and are described as Decumbispongia yuani gen. et sp. nov. The robust, thick-walled sponge shows no evidence of an osculum or basal structures, and the body form is inconsistent with an upright, filterfeeding life position. Interpretations as a detritivore feeding by amoeboid extensions, or as a facultative chemosynthetic symbiosis of sponge and bacteria are considered. The latter interpretation is preferred due to the highly constrained body shape, and the body form is interpreted from this perspective. The species indicates that Cambrian sponges occupied at least some autecological niches that appear to have been vacant since that time.

The relationships of the extant sponge classes, and the nature of the last common ancestor of all sponges, are currently unclear. Early sponges preserved in the fossil record differ greatly from extant taxa, and therefore information from the fossil record is critical for testing hypotheses of sponge phylogenetic relationships that are based on modern taxa. New specimens of the enigmatic sponge Lenica sp., from the Early Cambrian Hetang Biota of South China, exhibit an unusual spicule structure. Each spicule consists of a siliceous core with an axial canal, an organic outer layer and a middle layer interpreted to have been originally calcium carbonate. This finding confirms previous work suggesting the existence of biminerallic spicules in early sponges. Combined with data from other early sponges, the new findings imply that the two fundamental spicule structures of modern sponges were derived from a compound, biminerallic precursor. Spicules are therefore homologous structures in Calcarea and Silicea, and if sponges are paraphyletic with respect to Eumetazoa, then spicules may also have been a primitive feature of Metazoa.

Rochdale Museum Service holds a large collection of fossils from the important Carboniferous site of Sparth Bottoms (Lancashire, UK; Middle Coal Measures). Several of these are type specimens donated by Harold Howard in 1939. These objects were stored in the museum basement for several decades, and were thought to have been lost. The types are the holotype of the scorpion Eobuthus holti Pocock, 1911 and the holotype of the crustacean Anthrapalaemon grossarti var. holti Woodward, 1911a. These species were not named after Howard, because the describers thought that Fred Holt was the rightful collector. The holotype of the myriapod Euphoberia woodwardi Baldwin, 1911 (put into synonymy with Palaeosoma robustum Baldwin, 1911) is known to have originally been in the collection, but was not located in a recent survey.

Unlike Cambrian Lagerstätten, Ordovician exceptionally preserved faunas generally differ substantially from each other in taxonomic composition, suggesting a much greater diversity of palaeocommunities during this interval. It is unclear, however, how much of the Ordovician ecological diversity is due to the atypical facies or communities being represented by most of the known exceptional biotas. This paper describes a new Lagerstätte, preserved through high sedimentation rates and early pyritization, from the Middle Ordovician (Darriwilian, Hustedograptus? teretiusculus Biozone) of Wales. A preliminary analysis of the ecology of the fauna, which includes a new methodology for translating preserved abundance of different groups into estimated life abundance, has revealed that an ostensibly trilobite-dominated fauna was dominated instead by brachiopods, reticulosan and protomonaxonid sponges, and palaeoscolecidans, with carpoids and holothurians being nearly as abundant as trilobites. Under normal preservational conditions, this community would appear as a typical Ordovician mudstone fauna, implying that it represents a relatively normal open marine community. The biota does not closely resemble any of the previously described exceptional Ordovician faunas, suggesting that there is a large amount of hidden diversity in communities of this age. Among the exceptional taxa is the earliest known articulated holothurian, Oesolcucumaria eostre gen. et sp. nov., which is a small globular form with partly skeletonised ambulacrae.

A specimen of Glyptograptus from the Silurian of Dob’s Linn is described that possessed a bifurcating virgula, with a biserial stipe along each virgula. The colony lived for some considerable time with this morphology, showing that at least some graptoloids could survive and grow with major modifications to the rhabdosome. The specimen is left under open nomenclature, but if further material is discovered it may be appropriate to name a new species. Growth abnormalities in graptolites are not common, but many examples of repaired damage, rhabdosome malformations, and abnormal growth of thecae, virgellae and virgulae are known. Growth abnormalities can provide important evidence about graptolite ecology, biology and evolution, and so should be described and illustrated whenever possible.

Few Konservat-Lagerstätten are known from the Ordovician, and most preserve atypical marginal marine communities. Thus, we have little idea of how animals with a low preservation potential evolved during the Great Ordovician Biodiversification Event. Here we report the newly discovered Llanfawr Mudstones Lagerstätte from the basal Sandbian (Late Ordovician) of central Wales, UK. This biota, which has been studied through X-ray radiography and microtomography, is dominated by sponges. It also includes cnidarians (the oldest known solitary hydroid), arthropods, priapulids, various worm-like forms, entoproct-like organisms, and a variety of enigmatic fossils. The fauna includes taxa that are rarely preserved even in exceptional fossil biotas, and offers the potential for a new perspective on Ordovician ecosystems. The dominantly filter-feeding assemblage resembles modern abyssal sponge-dominated communities, although it was formed in much shallower water. The unusual Llanfawr Mudstones fauna shows that Ordovician ecological development was considerably more advanced in offshore environments than the mineralized fossil record implies.

A new species of starfish, Siluraster caemorensis sp. nov., is described from a loose block of probably the Bryn Siltstone Formation or Teirw Siltstone Formation (Caradocian) from near Glyn Ceiriog, on the north side of the Berwyn Range, North Wales. The species is similar to Siluraster perfectus from Bohemia and indicates that there may have been closer faunal links between the areas than are generally suggested. It is separated from known Welsh species of similar age by relatively subtle structural details that are not invariably preserved. This suggests that there is a higher diversity of asterozoan species in the Late Ordovician of Wales than has previously been recognized.

A new hexactinellid sponge, Heminectere rushtoni sp. nov., has been found in an old collection in Keswick Museum and Art Gallery, UK. The species belongs to a long-ranging genus, but is one of very few Dapingian (Middle Ordovician) hexactinellids described to date, and presents additional information on the range of morphological features present in the group. Heminectere is included within the Protospongiidae, the definition of which is here restricted to vasiform or spheroidal, thin-walled hexactinellids with a regular to subregular, quadruled architecture. The specimen, collected in 1884, also shows that there is potential for further discoveries of important sponge material in the Middle Ordovician of northwest England, and highlights the lack of Dapingian sponges as being most likely a result of collection deficiency rather than genuine rarity.

The renowned soft-bodied faunas of the Cambrian period, which include the Burgess Shale, disappear from the fossil record in the late Middle Cambrian, after which the Palaeozoic fauna dominates. The disappearance of faunas of Burgess Shale type curtails the stratigraphic record of a number of iconic Cambrian taxa. One possible explanation for this loss is a major extinction, but more probably it reflects the absence of preservation of similar softbodied faunas in later periods. Here we report the discovery of numerous diverse soft-bodied assemblages in the Lower and Upper Fezouata Formations (Lower Ordovician) of Morocco, which include a range of remarkable stem-group morphologies normally considered characteristic of the Cambrian. It is clear that biotas of Burgess Shale type persisted after the Cambrian and are preserved where suitable facies occur. The Fezouata biota provides a link between the Burgess Shale communities and the early stages of the Great Ordovician Biodiversification Event.

Dennis Curry was both a businessman and a geologist. He was Chairman of Currys for many years, a job that still allowed him to spend significant time on scientific research and fossil collecting. His achievements as a scientist were impressive, with more than 120 publications and various awards from the scientific community. His collection, containing in excess of 90 000 molluscs, 700 micropalaeontological slides and other material, was donated to the Natural History Museum, London. The collection contains material from all over the world, but mostly from southern England and France. His family have made funds available to ensure proper curation of the collection. The material has been sorted, reboxed and organized, and is available to researchers.

Hypotheses about the causes of biodiversification during the Ordovician have been focused in three main areas: tectonic activity and nutrient supply, palaeogeography, and ecological escalation. There is as yet no consensus on mechanisms, and it is unclear whether it is better to study the patterns at local or regional scales. By applying ecological knowledge to the available palaeontological information, it can be shown that neither tectonic nor palaeogeographic effects could account for the permanence of the diversity rise, in the absence of elements of ecological escalation. However, it may be possible to identify trigger mechanisms resulting in enhanced speciation or reduced extinction. Areas of local diversity increase should be distinguished from speciation centres. An ongoing study of the Middle Ordovician Builth-Llandrindod Inlier of central Wales, conducted over 10 years, has identified elements of all three of the above categories of causal mechanisms affecting local diversity. This implies that the patterns of causal relationship and diversification are complex even at very local scales, and at this stage we should not anticipate a clear correlation of global diversity with any single factor. More data are needed from small-scale but intensive studies before we can generalize about the causal mechanisms of the Ordovician Radiation.

Sipunculans are sedentary marine worms, believed to represent either an early coelomate grade or a later offshoot of the annelids, but are unmineralized and extremely rare in the fossil record. Here we describe an example from the Granton Shrimp Bed, a Lower Carboniferous Konservat-Lagerstätte. This is the third known occurrence of Palaeozoic sipunculans, although they may have been previously overlooked. The recognition of fossil sipunculans is discussed, based partly on cuticle deformation due to the underlying muscle arrangement.

Please contact me if you would like a pdf of this paper.

Three monograptid and five retiolitid graptoloids, and one species of sponge, are described from late Wenlock sections (Cyr. lundgreni and Co. ludensis biozones) at Spring Creek and Wallace Creek, near Orange, New South Wales, Australia. The sponge Janussenia orangense gen. et sp. nov. is the first monaxonid demosponge to be described from the Australian Silurian. An object containing broken Testograptus testis, and interpreted as the faecal pellet of a predator or scavenger on graptoloids, is described.

The extinction event at the end of the lundgreni graptoloid biozone (Homerian, Wenlock, Silurian) was one of the most severe to affect graptoloids during the Silurian. There are many hypotheses of what caused the extinction, but little work has been done relating the extinction to graptoloid ecology. In this study, the event has been investigated in the field and using existing literature. Fieldwork was conducted in the UK and in Australia, with the aims of studying environmental changes at the time of the lundgreni event. Results from fieldwork do not support the hypothesis that the lundgreni event was caused by anoxia. Taxonomic descriptions of three monograptids and five retiolitids from Australia are also given.

Data gathered from the literature has been used to compile a global database of species occurrences before and after the event. A comprehensive review of the occurrence of Homerian graptoloids is also given. The global literature survey of pre- and post-extinction faunas revealed a much greater diversity immediately after the extinction than had previously been suspected. It appears that many species survived the extinction event in very small areas, and, if a species survived the extinction initially, it had a high chance of surviving thereafter.

Both the field-based and the literature-based studies have been used to test hypotheses of the ecological causes of the lundgreni extinction. The hypotheses considered include that extinction is random, that there is a correlation between geographical distribution and extinction probability, and that the life history strategy of a species (whether the species is K- or r-selected) affects extinction probability. At the family and sub-family level extinction is random. Numbers were too small to test at genus level. Extinction likelihood does not appear to be linked with geographical distribution for monograptids. However, for retiolitids, those species with restricted ranges were more likely to become extinct than those with wide ranges. The limited evidence available suggests that life history strategy is important in whether a species survived the extinction or not, with K-selected species being less likely to survive than r-selected ones.