| 1. |
- 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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| 2. |
- 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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| 3. |
- 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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| 4. |
- 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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| 5. |
- 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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