| 1. |
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| 2. |
- Bowman, Chelsie N., et al.
(författare)
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Linking the progressive expansion of reducing conditions to a stepwise mass extinction event in the late Silurian oceans
- 2019
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Ingår i: Geology. - 0091-7613. ; 47:10, s. 968-972
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Tidskriftsartikel (refereegranskat)abstract
- The late Ludlow Lau Event was a severe biotic crisis in the Silurian, characterized by resurgent microbial facies and faunal turnover rates otherwise only documented during the "big five" mass extinctions. This asynchronous late Silurian marine extinction event preceded an associated positive carbon isotope excursion (CIE), the Lau CIE, although a mechanism for this temporal offset remains poorly constrained. Here, we report thallium isotope data from locally reducing late Ludlow strata within the Baltic Basin to document the earliest onset of global marine deoxygenation. The initial expansion of anoxia coincided with the onset of the extinction and therefore preceded the Lau CIE. Additionally, sulfur isotope data record a large positive excursion parallel to the Lau CIE, interpreted to indicate an increase in pyrite burial associated with the widely documented CIE. This suggests a possible global expansion of euxinia (anoxic and sulfidic water column) following deoxygenation. These data are the most direct proxy evidence of paleoredox conditions linking the known extinction to the Lau CIE through the progressive expansion of anoxia, and most likely euxinia, across portions of the late Silurian oceans.
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| 3. |
- Eriksson, Mats E., et al.
(författare)
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Darriwilian (Middle Ordovician) worms of southern Sweden
- 2016
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Ingår i: GFF. - : Informa UK Limited. - 1103-5897 .- 2000-0863. ; 138:4, s. 502-509
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Tidskriftsartikel (refereegranskat)abstract
- The record of scolecodonts (polychaete jaws) from the Ordovician of Sweden is very poor. In this paper, we document a Darriwilian (Middle Ordovician) assemblage recovered from palynological samples from the “orthoceratite limestone” (Lanna and Holen limestones) of Mount Kinnekulle, Västergötland, southern Sweden. The collection of diminutive specimens forms an assemblage taxonomically composed mainly of simple placognath (mochtyellids, xanioprionids) and ctenognath (tetraprionids) taxa, whereas labidognaths (polychaetaspids) and taxa with other evolutionary grade-type apparatuses are very rare or absent. In addition, putative priapulid (penis worm) teeth were identified, possibly representing the first fossil representatives recorded in Sweden. The highest scolecodont abundance coincides with the lower to middle part of the “Täljsten” interval (lower Kunda Baltoscandian Stage). These strata are interpreted as having been formed during a marked regressional phase, suggesting that the palaeobathymetry and/or bottom substrate was optimal for polychaete colonization at that time. This new assemblage from Kinnekulle adds to the global scolecodont record in which data on Middle Ordovician and older specimens are still rudimentary but of importance for understanding early polychaete phylogeny.
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| 4. |
- Eriksson, Mats, et al.
(författare)
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Kingnites diamondi gen. et sp nov., an exceptionally large Silurian paulinitid (Annelida; Polychaeta) from shallow marine settings of Baltoscandia
- 2012
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Ingår i: GFF. - : Informa UK Limited. - 2000-0863 .- 1103-5897. ; 134:3, s. 217-224
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Tidskriftsartikel (refereegranskat)abstract
- The polychaete annelid Kingnites diamondi, a new paulinitid genus and species, is described from the Silurian of Baltoscandia. Its large maxillae differ morphologically from those of all other known paulinitids, particularly in being very elongate and having conspicuous myocoele openings and posterior portions of the first maxillae (MI). Albeit rare, this polychaete taxon is highly characteristic and appears to be confined to the Wenlock-Ludlow transitional interval on Gotland, Sweden, and ranges into the upper Ludlow on Saaremaa, Estonia. All samples yielding this species derive from strata formed in proximal carbonate platform environments. The temporal and geographical distribution indicates that it first appeared in Gotland and subsequently spread north-eastwards to the present-day Saaremaa. Kingnites diamondi adds to the list of known members of the Paulinitidae and reinforces the importance of this family, in terms of abundance and diversity, in Silurian polychaete faunas of Baltica. This is the biggest paulinitid recorded from the Silurian with an inferred body length of approximately half a metre and its diagnostic jaws may serve as a proxy for shallow water, backreef (marginal marine to lagoonal) environments.
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| 5. |
- Eriksson, Mats, et al.
(författare)
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Ordovician and Silurian polychaete diversity and biogeography
- 2013
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Ingår i: Early Palaezoic Biogeography and Palaeogeography. - 0435-4052. ; :38, s. 265-272
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Konferensbidrag (refereegranskat)abstract
- Eunicidan polychaetes formed a significant part of Early Palaeozoic marine invertebrate communities, as shown by the abundance and diversity of scolecodonts (polychaete jaws) in the fossil record. In this study we summarize the early radiation and biodiversity trends and discuss the palaeobiogeography of these fossils. The oldest (latest Cambrian-Early Ordovician) representatives had primitive, usually symmetrical, placognath/ctenognath type jaw apparatuses. The first more advanced taxa, possessing labidognath-type jaw apparatuses or placognath apparatuses with compound maxillae, are first recorded in the Middle Ordovician. The most significant increase in generic diversity occurred in the Darriwilian, when many common taxa appeared and diversified. The Ordovician and Silurian scolecodont occurrences allow some palaeobiogeographical units and distribution patterns to be explored and outlined. The most robust data presently at hand derive from successions in Baltica and Laurentia. That information, together with new records from other palaeocontinents, reveals a wide distribution for the most frequent and species-rich genera and families, similar to the biogeographical patterns of extant polychaetes. Like many other benthic and pelagic fossil groups, scolecodont-bearing polychaetes show an increased cosmopolitan character in the Silurian as compared with the Ordovician. Species-level endemism appears to be relatively common, inferring a potential for scolecodonts as biogeographical tools in the future.
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| 6. |
- Eriksson, Mats, et al.
(författare)
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Vagrant benthos (Annelida; Polychaeta) associated with Upper Ordovician carbonate mud-mounds of subsurface Gotland, Sweden.
- 2009
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Ingår i: Geological Magazine. - 0016-7568. ; 146:3, s. 451-462
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Tidskriftsartikel (refereegranskat)abstract
- Micropalaeontological investigations of Upper Ordovician carbonate mud-mounds and enclosing strata of subsurface Gotland, Sweden, demonstrate that jaw-bearing polychaetes formed the most diverse faunal element associated with these build-ups. Although not present within the mound cores (intra-mound facies), scolecodonts, or polychaete jaws, occur abundantly immediately below and particularly above the mounds; the supra-mound facies also has the most diverse fossil assemblages. By contrast to the scolecodont distribution, the most diverse conodont faunas were recorded in the intra-mound facies. This reinforces the fact that scolecodont and conodont abundance and diversity numbers are commonly inverse to one another, suggesting that these metazoans occupied different niches and responded differently to taphonomical processes. The polychaete assemblage has no less than 27 species belonging to 12 genera, of which Oenonites, Mochtyella and Pistoprion are the most abundant. The assemblage has a characteristic Baltic signature and is similar in taxonomic composition to coeval ones from other areas of the Baltoscandian palaeobasin, such as that of present-day Estonia. A principal component analysis clusters the Gotland assemblage most closely to those recorded from shallow to transitional shelf environments of Estonia, indicatino that the mud-mounds were formed in such environments.
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| 7. |
- Hints, Olle, et al.
(författare)
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Biodiversity patterns of Ordovician marine microphytoplankton from Baltica : Comparison with other fossil groups and sea-level changes
- 2010
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Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier BV. - 0031-0182 .- 1872-616X. ; 294:04-mar, s. 161-173
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Tidskriftsartikel (refereegranskat)abstract
- Based on the extensive literature on Ordovician acritarchs, biodiversity curves of marine microphytoplankton of the palaeocontinent Baltica have been compiled. The dataset is derived from more than 100 publications and includes over 600 species whose ranges can be used in diversity analysis. Stratigraphically well-constrained data from the Rapla and Mannamaa boreholes, northern Estonia, are analysed separately in order to provide additional information on the Middle to Late Ordovician microphytoplankton evolution on shallow shelf settings. The total species diversity and normalised diversity curves based on range-through data show a slight decrease from the Tremadocian to Floian, which may partly be attributed to limited data available. A continuous increase in diversity from the base of the Dapingian to late Darriwilian - early Katian can be observed, with highest total diversity approaching 250 species in the Keila Regional Stage. The highest appearance rates are recorded in the Dapingian and Darriwilian. Diversity progressively diminished after the early Katian with a more pronounced decrease in the upper Ordovician Porkuni Regional Stage, corresponding to the Hirnantian. A significant faunal turnover took place in the uppermost Ordovician Pirgu and Porkuni stages, with high extinction rates as well as the appearance of many acritarch taxa that are typical of the Silurian floras. The phytoplankton diversity curves match rather well with those of several other fossil groups in Baltica, notably brachiopods and ostracods. Comparison with other palynomorphs reveals both similarities and differences. The chitinozoans show the highest diversities in the upper Darriwilian, but their later decline predates that of acritarchs. A rapid diversification of scolecodonts (jawed polychaetes) can also be observed in the upper Darriwilian. However, unlike acritarchs or chitinozoans, their diversity continues to increase until the uppermost Katian. The acritarch diversity changes are analysed and discussed in the context of palaeogeographic (northwards drifting of Baltica) and palaeoclimatologic changes (rising sea levels up to the middle part of the Upper Ordovician). The increasing diversity of the phytoplankton not only roughly correlates with the Baltic and global sea-level changes, but also with the diversification of marine invertebrate groups.
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| 8. |
- Hints, Olle, et al.
(författare)
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Diversification and biogeography of scolecodont-bearing polychaetes in the Ordovician
- 2007
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Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier BV. - 1872-616X .- 0031-0182. ; 245:1-2, s. 95-114
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Tidskriftsartikel (refereegranskat)abstract
- Scolecodonts are common microfossils in Palaeozoic rocks, bearing witness to the extensive radiation of jawed polychacte worms during the Ordovician Period. Information on Ordovician scolecodonts is increasing, though it is still patchy and strongly skewed towards Baltica and Laurentia. Comparison of the faunas of these two palaeocontinents indicates that approximately 50% of the genera, but only a few species, had intercontinental distribution. Meagre data from other terranes also show that several genera were cosmopolitan. In total, more than 50 Ordovician genera are known. The first records are from the Furongian (latest Cambrian), but scolecodont diversity and abundance remained very low until the Darriwilian. The earliest jawed polychaetes had primitive, usually symmetrical, placognath/ctenognath type jaw apparatuses. Xanioprionids, tetraprionids? and/or conjungaspids seem to have played an important role in the early evolution and diversification of scolecodont-beating polychactes. The first more advanced taxa, such as the polychaetaspids with labidognath type jaw apparatuses and mochtyellids with placognath type apparatuses and compound maxillae, are first recorded in the earliest Mid Ordovician. The most significant increase in global generic diversity, but also regional species-level diversity, occurred in the late Mid Ordovician, when many common taxa appeared. Accordingly, the origination rate is highest in that interval. Since many Ordovician polychaete genera are relatively long-ranging, extending into the Silurian, the extinction rate is low throughout the Period, increasing only slightly in the latest Late Ordovician. The normalised diversity curve is characterised by an increasing trend in the Mid Ordovician, followed by a plateau in the Late Ordovician. (c) 2006 Elsevier B.V. All rights reserved.
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| 9. |
- Hints, Olle, et al.
(författare)
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Early Middle Ordovician scolecodonts from north-western Argentina and the emergence of labidognath polychaete jaw apparatuses
- 2017
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Ingår i: Palaeontology. - : Wiley. - 0031-0239. ; 60:4, s. 583-593
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Tidskriftsartikel (refereegranskat)abstract
- Scolecodonts provide fossil evidence of the evolution and diversification of jaw-bearing polychaetes from the latest Cambrian onwards. However, their record before the Darriwilian (Middle Ordovician) is scarce worldwide, which limits our understanding of key evolutionary events. One such event is the emergence of taxa possessing the asymmetrical labidognath-type jaw apparatus architecture, which became common in the Middle Ordovician and is often dominant throughout the Palaeozoic. Here, we document a small collection of Dapingian scolecodonts from the Capillas section, Sierras Subandinas, north-western Argentina. The isolated elements recovered allowed us to reconstruct the distinctive jaw apparatus, and to introduce a new taxon, Andiprion paxtonae gen. et sp. nov. The maxillary apparatus of Andiprion is intermediate between the symmetrognath type of the Early Ordovician Kadriorgaspis and the labidognath type that is present in polychaetaspids and related taxa. The apparatus architecture of Andiprion corresponds best to the labidognath type, but the morphology of the individual jaws suggests that it may be the most primitive representative of this lineage currently known. We propose that Andiprion-like forms were ancestral to polychaetaspids, polychaeturids and ramphoprionids. The Capillas collection provides supporting evidence for the evolutionary homology of the 'basal plate' and the left first maxilla. Thus the labidognath-type asymmetry, with an unpaired left maxilla III, developed as a result of gradual reduction in size of the first right jaw ('basal plate') in front of the carriers, instead of loss or fusion of anterior maxillae.
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| 10. |
- Hints, Olle, et al.
(författare)
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Ordovician polychaeturid polychaetes: Taxonomy, distribution and palaeoecology
- 2010
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Ingår i: Acta Palaeontologica Polonica. - : Polska Akademia Nauk Instytut Paleobiologii (Institute of Paleobiology, Polish Academy of Sciences). - 0567-7920. ; 55:2, s. 309-320
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Tidskriftsartikel (refereegranskat)abstract
- The fossil polyclinic family Polychaeturidae is considered as monogeneric and comprises four species of the genus Pteropelta. Pteropelta, originally established on isolated scolecodonts (the carriers), is revised and the apparatus-based Polychaetura is shown to be a junior synonym of Pteropelta. In addition to Pteropelta gladiata and Pteropelta kielanae. Pteropelta huberti sp. nov., and Pteropelta sp. A are herein described from the Upper Ordovician of Estonia and Sweden. Polychaeturids include some of the most common and characteristic scolecodont-bearing polychaetes in the Ordovician of Baltoscandia. They first appeared in the early Darriwilian (Mid Ordovician), flourished in the Late Ordovician and disappeared in the early Silurian. The distribution patterns of individual polychaeturid species infer regional biostratigraphical potential. Polychaeturids were geographically widespread during the Ordovician and have been recorded from at least three palaeocontinents.
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| 11. |
- Popov, Leonid E, et al.
(författare)
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Glendonite occurrences in the Tremadocian of Baltica : first Early Palaeozoic evidence of massive ikaite precipitation at temperate latitude
- 2019
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- The Tremadocian (Early Ordovician) is currently considered a time span of greenhouse conditions with tropical water surface temperature estimates, interpolated from oxygen isotopes, approaching 40 °C. In the mid-latitude Baltoscandian Basin, conodonts displaying low δ18O values, which suggest high temperatures (>40 °C) in the water column, are in contrast with the discovery of contemporaneous glendonite clusters, a pseudomorph of ikaite (CaCO3·6H2O) traditionally considered as indicator of near-freezing bottom-water conditions. The massive precipitation of this temperature sensitive mineral is associated with transgressive conditions and high organic productivity. As a result, the lower Tremadocian sediments of Baltoscandia apparently contain both "greenhouse" pelagic signals and near-freezing substrate indicators. This paradox points to other primary controlling mechanisms for ikaite precipitation in kerogenous substrates, such as carbonate alkalinity, pH and Mg/Ca ratios, as recently constrained by laboratory experiments. Preservation of "hot" conodonts embedded in kerogenous shales rich in δ18O-depleted glendonites suggests both the onset of sharp thermal stratification patterns in a semi-closed basin and the assumed influence of isotopically depleted freshwater yielded by fluvial systems.
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| 12. |
- Tonarova, Petra, et al.
(författare)
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A jawed polychaete fauna from the late Ludlow Kozlowskii event interval in the Prague Basin (Czech Republic)
- 2012
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Ingår i: Bulletin of Geosciences. - : Czech Geological Survey. - 1214-1119 .- 1802-8225. ; 87:4, s. 713-732
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Tidskriftsartikel (refereegranskat)abstract
- This paper deals with a diverse fauna of polychaetes possessing jaws (= scolecodonts) from the late Silurian Kopanina Formation of the Prague Basin (Czech Republic). The most common genera are Kettnerites, Oenonites and Pistoprion; the entire collection contains at least 16 genera. This is in stark contrast to the four genera recorded from this region by previous authors. The fauna described shows great similarities with coeval ones reported from the Baltic area (Gotland and Estonia), Siberia, Arctic Canada and the British Isles. These new data thus extend the palaeobiogeographical and palaeolatitudinal distribution of several taxa, particularly at the genus but also the species level. The sampled interval embraces the Kozlowskii event and its effects on the polychaetes are briefly discussed. Although the collections are relatively small, particularly from post-event strata, a faunal reorganisation is apparent. The studied collection enabled the stratigraphical ranges of some taxa, including tretoprionids and possibly polychaeturids, to be extended into the late Ludlow. One new species, "Mochtyella" pragensis, is described.
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| 13. |
- Tonarova, Petra, et al.
(författare)
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Impact of the Silurian Ireviken Event on polychaete faunas: new insights from the Viki drill core, western Estonia
- 2014
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Ingår i: GFF. - : Informa UK Limited. - 2000-0863 .- 1103-5897. ; 136:1, s. 270-274
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Tidskriftsartikel (refereegranskat)abstract
- The impact of the Llandovery-Wenlock Ireviken Event (IE) on the jawed polychaete faunas is explored in this study, based on new data on scolecodonts from the Viki drill core of western Estonia. A distinct faunal reorganisation is observed, with the most abrupt changes recorded between datum points 4 and 6 of the IE, which coincides with the major turnover interval of other fossil groups. Based on what is now known, polychaetaspids and mochtyellids suffered most severely during the event, whereas the members of other families seem to have been less affected.
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