| 1. |
- Ahlberg, Per, et al.
(författare)
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Faunal turnovers and trilobite morphologies in the upper Cambrian Leptoplastus Zone at Andrarum, southern Sweden
- 2006
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Ingår i: Lethaia. - : Scandinavian University Press / Universitetsforlaget AS. - 0024-1164. ; 39:2, s. 97-110
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Tidskriftsartikel (refereegranskat)abstract
- The Furongian (upper Cambrian) Leptoplastus Zone marks a time of critical changes in the evolution of olenid trilobites. This zone, unexposed at Andrarum in Skane, southern Sweden, has been re-excavated and the sequence of faunas and sediments logged in detail. The faunal succession accords with that previously described from borehole cores by Westergard, and the subzones of L. paucisegmentatus, L. raphidophorus, L. crassicornis, L. ovatus, L. angustatus, and L. stenotus have been recognized. In the first two subzones the olenid assemblages are monospecific. At the base of the L. crassicornis Subzone more than one species is present and morphotypes with long genal spines appear for the first time. Faunal turnover is rapid, but the incoming of new species is invariably linked to an abrupt change in sedimentation, or follows an unfossiliferous interval; species either arose or migrated in after a time of environmental perturbation. Particular faunal associations are often confined to discrete sedimentary packages though some species may range through a succession of sedimentary changes. Leptoplastus crassicornis has very long genal spines, adapted for resting on the sea floor; it may have competed with the coeval, and very similar, L. angustatus. Subsequently, L. angustatus is accompanied by the stout-bodied, short-spined L. ovatus, which presumably occupied a different niche within the same environment. Leptoplastus stenotus is convergent on the much earlier L. paucisegmentatus, and likewise is found as a monospecific assemblage, presumably being adapted to a similar niche.
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| 2. |
- Ahlberg, Per, et al.
(författare)
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Phosphatised olenid trilobites and associated fauna from the Upper Cambrian of Vastergotland, Sweden
- 2005
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Ingår i: Acta Palaeontologica Polonica. - 0567-7920. ; 50:3, s. 429-440
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Tidskriftsartikel (refereegranskat)abstract
- Secondarily phosphatised olenid trilobites from organic-rich limestones (orsten) in the Furongian (Upper Cambrian) of Vastergotland, south-central Sweden, are described and illustrated. All trilobites originate from the Peltura scarabaeoides Zone and were collected on the western slope of Kinnekulle. Only the dorsal exoskeletons have become secondarily phosphatised, and the ventral appendages are not preserved. Yet the material is otherwise remarkably well preserved and reveals the morphology of the olenid trilobites in greater detail than hitherto known. Species belonging to the genera Ctenopyge, Sphaerophthalmus, Parabolina, and Peltura are identified, and several juvenile specimens are present in the material. The material is disarticulated and fragmentary, and it has only been possible to identify a few specimens to species level. In addition to chaetognaths and conodonts, the trilobites are associated with pelmatozoan columnals, a possible camaroid, and fossils of uncertain affinities. These fossils, along with a probable conulariid fragment from the Peltura minor Zone, are also described and discussed. The presence of a benthic fauna of pelmatozoans, and possible conulariids and camaroids, indicates that at least parts of the Peltura zones were deposited during dysoxic rather than anoxic periods. Moreover, the sea floor must have been firm enough to allow colonisation by sessile organisms.
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| 3. |
- Clarkson, ENK, et al.
(författare)
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Ontogeny and structure of a new, miniaturised and spiny olenid trilobite from Southern Sweden
- 2002
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Ingår i: Palaeontology. - : Wiley. - 1475-4983 .- 0031-0239. ; 45, s. 1-22
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Tidskriftsartikel (refereegranskat)abstract
- Several hundred specimens of a tiny olenid trilobite, Ctenopyge ceciliae sp. nov., have been found in stinkstone nodules in the upper Cambrian Peltura scarabaeoides Zone in southern Sweden. This exceptionally spinose form is known only from disarticulated specimens, but is quite well preserved, and all growth stages are represented. The early ontogenetic stages are exceptionally small, the protaspis being only half the size of that of the associated Peltura species. There may have been no more than three thoracic segments. Thus the whole ontogeny was compressed, and this together with the very small size of the adult indicates a true miniaturisation. Whereas the likely control of the origin of the tiny C. ceciliae was basically progenesis, the extreme spinosity had a different origin; allometric growth or possibly peramorphosis. C. ceciliae is small enough for the spines to have appreciably retarded sinking through frictional effects, and this small trilobite is interpreted as a free-swimming or floating form.
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| 4. |
- CLARKSON, ENK, et al.
(författare)
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TAXONOMY AND PALEOECOLOGY OF THE MOLLUSK PTEROTHECA FROM THE ORDOVICIAN AND SILURIAN OF SCOTLAND
- 1995
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Ingår i: LETHAIA. - : SCANDINAVIAN UNIVERSITY PRESS. - 0024-1164. ; 28:2, s. 101-114
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Tidskriftsartikel (refereegranskat)abstract
- A large sample of the bizarre bellerophontiform mollusc Pterotheca from the Upper Llandovery Wether Law Linn Formation in the Scottish Pentland Hills shows marked polymorphic asymmetry. A survival strategy that presents to a predator a mosaic of different
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| 5. |
- Terfelt, Fredrik, et al.
(författare)
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Furongian (upper Cambrian) biostratigraphy and trilobites of the Haslov-1 drill core, Scania, S. Sweden
- 2005
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Ingår i: GFF. - 2000-0863. ; 127, s. 195-203
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Tidskriftsartikel (refereegranskat)abstract
- A drilling made in 1972 at Haslov, Scania, southern Sweden, penetrated a 2572 m thick succession of Phanerozoic strata. The only cored parts of the succession derive from the Upper Ordovician and the Furongian (upper Cambrian) series. Merely the uppermost part of the Furongian was recovered, comprising eight metres of Alum Shale with limestone concretions. Nine species and subspecies of trilobites are identified and their succession is used for subdividing the core into the Peltura scarabaeoides Zone, comprising the Parabolina lobata and the Peltura paradoxa subzones, and the Acerocare Zone, comprising the Peltura transiens Subzone. The conodont Cordylodus proavus? was found in the uppermost part of the core. The faunal succession is interrupted by conspicuous unfossiliferous intervals; the most extensive one measuring 3.39 m. Approximately coeval barren intervals have been recorded from other localities in Scania. Although the ecological significance of these intervals remains to be evaluated, it can be concluded that they are a regional feature in the Furongian of Scania.
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| 6. |
- Weidner, TR, et al.
(författare)
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The middle Cambrian Ptychagnostus punctuosus and Goniagnostus nathorsti zones in Vastergotland, Sweden
- 2004
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Ingår i: Bulletin of the Geological Society of Denmark. - 0011-6297. ; 51:1, s. 39-45
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Tidskriftsartikel (refereegranskat)abstract
- New trilobite discoveries from eight localities in Vastergotland, south-central Sweden, demonstrate that the middle Cambrian Ptychagnostus punctuosus and Goniagnostus nathorsti zones are present in most Lower Palaeozoic outcrop areas of Vastergotland, though as a thin and impersistent conglomeratic limestone, up to approximately 15 cm thick. These zones have not previously been recognised in Vastergotland, except for a thin bed of limestone on Hunneberg.
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