Bulletin Volume 65 – 2017 : Dansk Geologisk Forening

© 2017 by Bulletin of the Geological Society of Denmark, Vol. 65, pp. 1–23. ISSN 2245-7070. (www.2dgf.dk/publikationer/bulletin).
https://doi.org/10.37570/bgsd-2017-65-01

Abstract: The vertebrate fauna in the Danian deposits of Denmark and southern Sweden is reviewed. Remains of sharks and bony fishes are widely distributed but not common in the Danian limestones, with the exception of the K/Pg-boundary clay, the Fiskeler Member, at the UNESCO World Heritage Site Stevns Klint, which can include substantial quantities of shark teeth and fragments of bony fishes.

Articulated remains of bony fishes are known from the Fiskeler Member at Stevns Klint and the København Limestone Formation in the Limhamn quarry. Sharks are only found as isolated teeth and rare isolated vertebrae. The gavialoid crocodylian Thoracosaurus is represented by a complete skull and associated postcranial material and an additional jaw fragment from the Limhamn quarry.

Remains of a crocodylian skull, a cervical vertebra, a limb bone and isolated teeth have been found in the Faxe quarry, and a single possibly alligatorid tooth is known from the basal conglomerate of the Lellinge Greensand Formationfrom now closed exposures below Copenhagen.

Fragmentary turtle material has been found in theFaxe and Limhamn quarries and in the København Limestone in Copenhagen, and bird remains are exclusively known from the Limhamn quarry. Despite the fragmentary nature of many of the finds, the total picture of the vertebrate fauna of southern Scandinavia is quite diverse comprising four classes, 23 orders, 41 families and 54 identifiable genera of which most can be identified to species level.

Keywords: Lower Paleocene, Vertebrate fauna, Osteichthyes, Chondrichthyes, Reptilia, Stevns, Faxe, Limhamn, Fiskeler.

Addresses:

Jan S. Adolfssen, Ministry of Mineral Resources, Department of Geology, Imaneq 1, DK-3900 Nuuk, Greenland.

Jesper Milàn, Geomuseum Faxe/Østsjællands Museum, Østervej 2, DK-4640 Faxe, Denmark, and Natural History Museum of Denmark, Øster Voldgade 5–7, DK-1350 Copenhagen K, Denmark.

Matt Friedman, Museum of Paleontology, Department of Earth and Environmental Science, University of Michigan, 1109 Geddes Ave, Ann Arbor, MI 48109-1079, USA.

Corresponding author: Jesper Milàn

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Holocene development of the Arresø area, north-east Sjælland, Denmark.

Bennike, O., Pantmann, P. & Aarsleff, E. 2017. Holocene development of the Arresø area, north-east Sjælland, Denmark.
© 2017 by Bulletin of the Geological Society of Denmark, Vol. 65, pp. 25–35.
ISSN 2245-7070. (www.2dgf.dk/publikationer/bulletin)
https://doi.org/10.37570/bgsd-2017-65-02

Abstract:

The Arresø area in north-east Sjælland, Denmark, was deglaciated about 18,000 to 16,000 years ago. In the Holocene it was probably a land area until it was transgressed by the sea c. 8500 years BP. During a first marine phase the area housed a species-rich marine fauna that included the oyster Ostrea edulis, the salinity and water temperatures were higher than at present, and there was a wide connection to the Kattegat sea. At about 6500 years BP there was a short-lived lake or brackish-water phase, but marine conditions were soon re-established with a fauna less diverse than before, and both salinity and water temperatures decreased. The present lake Arresø became isolated from the sea about 2500 years BP. The transition from brackish water to fresh water was rapid; the lake developed from shallow alkaline waters to deeper more acidic waters and finally to eutrophic waters.

Keywords: Holocene, Arresø, Arrefjord, Denmark, Littorina Sea, relative sea-level changes, Ostrea.

Addresses:

Ole Bennike, Geological Survey of Denmark and Greenland, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark.
Pernille Pantmann and Esben Aarsleff, Museum Nordsjælland, Frederiksgade 11, DK-3400 Hillerød, Denmark.

Corresponding author: Ole Bennike

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A new Cenozoic record of spinilomatine aporrhaids (Stromboidea, Caenogastropoda) in the early Paleocene of Faxe, Denmark

Schnetler, K.I., & Milàn, J., 2017. A new Cenozoic record of spinilomatine aporrhaids (Stromboidea, Caenogastropoda) in the early Paleocene of Faxe, Denmark.
© 2017 by Bulletin of the Geological Society of Denmark, Vol. 65, pp. 37-45.
ISSN 2245-7070. (www.2dgf/publikationer/bulletin).
https://doi.org/10.37570/bgsd-2017-65-03

Abstract:

A new find is identified as a representative of the subfamily Spinilomatinae, viz. Spiniloma? faxensis sp. nov. The specimen was found as an impression in coral limestone of the early Paleocene (middle Danian) Faxe Formation in the Faxe quarry in Denmark. The genus Spiniloma was until now known exclusively from the Mesozoic of Europe. The new find extends the stratigraphic range of the genus into the early Paleocene. Furthermore, the gastropod fauna of the Faxe Formation is dominated by gastropods with a preference for hard substrates, while soft- substrate genera like Spiniloma are extremely rare.

Keywords: Gastropoda, Aporrhaidae, Spinilomatinae, Danian, early Paleocene, Faxe Quarry.

Addresses:

Kai Ingemann Schnetler, Fuglebakken 14, Stevnstrup, DK-8870 Langå, Denmark.
Jesper Milàn, Geomuseum Faxe, Østsjællands Museum, Østervej 2, DK-4640 Faxe, Denmark, and Natural History Museum of Denmark, Øster Voldgade 5–7, DK-1350 Copenhagen K, Denmark.

Corresponding author: Jesper Milàn

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Sexual dimorphism within the stem-group arthropod Isoxys volucris from the Sirius Passet Lagerstätte, North Greenland

Nielsen, M.L., Rasmussen, J.A. & Harper, D.A.T. 2017. Sexual dimorphism within the stem-group arthropod Isoxys volucris from the Sirius Passet Lagerstätte, North Greenland.

© 2017 by Bulletin of the Geological Society of Denmark, Vol. 65, pp. 47–58.
ISSN 2245-7070. (www.2dgf.dk/publikationer/bulletin).
https://doi.org/10.37570/bgsd-2017-65-04

Abstract:

Morphometric analyses carried out on 126 specimens of the early Cambrian (Cambrian Series 2, Stage 3) stem-group arthropod Isoxys volucris from North Greenland reveal a bimodal distribution, where Morphogroup A is characterised by a significantly wider doublure than Morphogroup B. The dimorphism is interpreted as intraspecific variation related to gender (sexual dimorphism), where the relative numbers of individuals within the two morphogroups are equal (ratio 1:1). The discovery of established sexual dimorphism in Isoxys may have implications for the taxonomic discrimination of other stemgroup arthropods within the morphologically diverse and disparate animals of the early Cambrian.

Keywords: Sirius Passet Lagerstätte, Isoxys, stem-group arthropods, sexual dimorphism, early Cambrian.

Addresses:

Morten Lunde Nielsen, Natural History Museum of Denmark, University of Copenhagen, Øster Voldgade 5–7, DK-1350 Copenhagen K, Denmark.

Jan Audun Rasmussen, Fossil and Mo-clay Museum, Museum Mors, Skarrehagevej 8, DK-7900 Nykøbing Mors, Denmark.

David A.T. Harper, Department of Earth Sciences, Palaeoecosystems Group, Durham University, Stockton Road, Durham DH1 3LE, United Kingdom; also Department of Geology, Lund University, Sölvegatan 12, S-223 62 Lund, Sweden.

Corresponding author: Jan Audun Rasmussen

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After the disaster: Bony fish remains (mostly otoliths) from the K/Pg boundary section at Stevns Klint, Denmark, reveal consistency with teleost faunas from later Danian and Selandian strata.

Schwarzhans, W. & Milàn, J. 2017. After the disaster: Bony fish remains (mostly otoliths) from the K/Pg boundary section at Stevns Klint, Denmark, reveal consistency with teleost faunas from later Danian and Selandian strata.

© 2017 by Bulletin of the Geological Society of Denmark, Vol. 65, pp. 59–74.
ISSN 2245-7070. (www.2dgf.dk/publikationer/bulletin).
https://doi.org/10.37570/bgsd-2017-65-05

Abstract

This is the first study of bony fish remains across the K/Pg boundary section at Stevns Klint, Denmark. The studied specimens comprise one partly preserved articulated skeleton, a few isolated bones, and casts from several otolith imprints and voids. As otoliths are aragonitic, the remains are all dissolved. The imprints of the otoliths originate from the uppermost Maastrichtian Højerup Member or ‘Grey Chalk’, and the bone fragments and the partial skeleton were obtained from the Fiskeler Member directly above the K/Pg boundary. Further otolith imprints originated from the basal Danian Cerithium Limestone Member, which directly overlies the Fiskeler Member. Six otolith-based taxa were identified from the uppermost Maastrichtian and three from the basal Danian. One of the species found in the uppermost Maastrichtian persisted into Danian times (Polymixia? harderi), a second represents a common genus in both Maastrichtian and Danian but cannot be identified to the species level (Centroberyx sp.), and a third taxon is an unidentifiable dynematichthyid, which, however, certainly does not belong to any of the known Danian dinematichthyid species. The species recognised in the basal Danian all persisted well into later Danian times or even the Selandian, showing a remarkable consistency of the early Paleocene bony fish fauna. We find no indication of phased extinction in the aftermath of the K/Pg boundary event in the data recovered from the Danian.

Keywords: Maastrichtian, Danian, Fiskeler Member, Cerithium Limestone Member, Teleostei, otolith..

Addresses:

Werner Schwarzhans , Ahrensburger Weg 103, D-22359 Hamburg, Germany; also Natural History Museum of Denmark, Universitetsparken 15, DK-2100 Copenhagen Ø, Denmark.

Jesper Milàn, Geomuseum Faxe, Østsjællands Museum, Østervej 2, DK-4640 Faxe, Denmark; also Natural History Museum of Denmark, Øster Voldgade 5–7, DK-1350 Copenhagen K, Denmark.

Corresponding author: Jesper Milàn

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The ongoing search for the oldest rock on the Danish island of Bornholm: new U-Pb zircon ages for a quartzrich xenolith and country rock from the Svaneke Granite

Waight, T.E., Serre, S.H., Næsby, S.H. & Thomsen, T.B. 2017. The ongoing search for the oldest rock on the Danish island of Bornholm: new U-Pb zircon ages for a quartz-rich xenolith and country rock from the Svaneke Granite.

© 2017 by Bulletin of the Geological Society of Denmark, Vol. 65, pp. 75–86.
ISSN 2245-7070. (www.2dgf.dk/publikationer/bulletin).
https://doi.org/10.37570/bgsd-2017-65-06

Abstract

Previous geochronological studies on the Danish island of Bornholm have not identified any rocks older than c. 1.46 Ga. New LA-ICP-MS U-Pb zircon ages are presented for a xenolith within, and the country rock gneiss adjacent to, the Svaneke Granite on Bornholm. The xenolith is fine-grained and quartz-rich and was likely derived from either a quartz-rich sedimentary protolith or a hydrothermally
altered felsic volcanic rock. The relatively fine-grained felsic nature of the country rock gneiss and the presence of large zoned feldspars that may represent phenocrysts suggest its protolith may have been a felsic volcanic or shallow intrusive rock. A skarn-like inclusion from a nearby locality likely represents an originally carbonate sediment and is consistent with supracrustal rocks being present at least locally. Zircon data from the xenolith define an upper intercept age of 1483 ± 12 Ma (2σ, MSWD = 2.5) with a poorly defined lower intercept age of 474 ± 250 Ma, and a weighted average 207Pb/206Pb age of 1477.9 ± 4.6 Ma; both these ages are older than the host Svaneke Granite (weighted average 207Pb/206Pb age of 1465.0 ± 4.8 Ma). Zircons from the gneiss define an upper intercept age of 1477.7 ± 6.8 Ma when anchored at 0 Ma, and a weighted average 207Pb/206Pb age of 1475.4 ± 6.6 Ma which overlaps statistically with the Svaneke Granite age. These ages are currently the oldest ages determined for in situ rocks on Bornholm. Evidence for substantially older basement lithologies (e.g. 1.8 Ga as observed in southern Sweden) remains absent. The zircons display clear oscillatory zoning, have Th/U typical of magmatic zircons and in some cases preserve inherited cores, all of which suggest that the ages are robust and do not represent resetting due to incorporation within or intrusion by the Svaneke Granite. Inherited zircons are not common; they have ages (c. 1.6–1.8 Ga) that are similar to those observed in other felsic basement lithologies on Bornholm. These new
results suggest that prior to intrusion of the Svaneke Granite, the upper crust on Bornholm was dominated, at least locally, by lithologies similar in composition to the currently exposed felsic basement. The protoliths to the two samples investigated here must have been buried to mid-crustal depths over a relatively short time period (c. 10 Ma) prior to intrusion of the Svaneke Granite. This
suggests a dynamic tectonic environment and is consistent with evidence for broadly simultaneous magmatism and deformation in basement rocks at 1.46 Ga in southern Scandinavia and burial and metamorphism of sediments in southern Skåne.

Keywords: Zircon, geochronology, xenolith, granite, gneiss, provenance, Bornholm, Danopolonian Orogeny.

Addresses:

Tod E. Waight, Department of Geosciences and Natural Resource Management, University of
Copenhagen, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark.
Simon H. Serre, Department of Geosciences and Natural Resource Management, University of Copenhagen, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark; also Geological Survey of Denmark and Greenland, Øster Voldgade
10, DK-1350 Copenhagen K, Denmark.
Sebastian H. Næsby, Department of Geosciences and Natural Resource Management, University of Copenhagen, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark.
Tonny B. Thomsen, Geological Survey of Denmark and Greenland, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark.

Corresponding author: Tod E. Waight

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LA-ICP-MS U-Pb data from zircons in samples BH6, BH29 and BH3a:
Supplementary data file – xls-file (150,00 b)

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Stratigraphy of the marine Lower Triassic succession at Kap Stosch, Hold with Hope, North-East Greenland

Surlyk, F., Bjerager. M., Piasecki. S. & Stemmerik, L. 2017. Stratigraphy of the marine Lower Triassic succession at Kap Stosch, Hold with Hope, North-East Greenland.

© 2017 by Bulletin of the Geological Society of Denmark, Vol. 65, pp. 87–123.
ISSN 2245-7070. (www.2dgf.dk/publikationer/bulletin).
https://doi.org/10.37570/bgsd-2017-65-07

Abstract

The classical marine uppermost Permian – Lower Triassic succession exposed on the north-east coast of Hold with Hope in East Greenland, south-east of Kap Stosch, is placed in the Wordie Creek Group. A new lithostratigraphic subdivision of the group is proposed here. The group comprises the revised Kap Stosch Formation overlain by the new Godthåb Golf Formation. The Kap Stosch Formation is dominated by alternating fine- and coarse-grained, cliff-forming units that constitute the basis for the erection of eight new members. They are (from below): 1. The Nebalopok Member, uppermost Permian, Hypophiceras triviale ammonoid zone, and lowermost Triassic, lower Griesbachian, Hypophiceras triviale – H. martini ammonoid zones, composed of basinal and base-of-slope siltstones and turbiditic sandstones. 2. The conglomeratic Immaqa Member (H. martini ammonoid zone), consisting of a thick clinoform-bedded unit commonly overlain by horizontally bedded deposits, representing the foreset and topset, respectively, of a Gilbert-type delta. 3. The fine-grained Fiskeplateau Member (H. martini ammonoid zone), composed of siltstones and fine-grained sandstones, representing basinal and delta front deposits. 4. The conglomerate-dominated Knolden Member (H. martini ammonoid zone), comprising a clinoform-bedded unit overlain by horizontally-bedded deposits, representing foreset and topset, respectively, of a Gilbert-type delta. 5. The fine-grained Pyramiden Member, (lower–upper Griesbachian Metophiceras subdemissum, Ophiceras commune and Wordieoceras decipiens ammonoid zones), composed of variegated siltstones and sandstones deposited in proximal basin and slope environments. 6. The Naasut Member (top Griesbachian, probably Wordieoceras decipiens ammonoid zone), dominated by thick structureless coarse-grained sandstones commonly showing clinoform bedding, deposited in slope, base-of-slope and proximal basin environments. 7. The Falkeryg Member (lowermost Dienerian, Bukkenites rosenkrantzi ammonoid zone), comprising thick, commonly pebbly sandstones deposited in shelf, slope and base-of-slope environments. 8. The Vestplateau Member (lower Dienerian, Bukkenites rosenkrantzi ammonoid zone) composed of siltstones and fine-grained sandstones deposited in basinal environments. The overlying Godthåb Golf Formation (Dienerian, Anodontophora breviformis – A. fassaensis bivalve zones) is dominated by shallow marine sandstones with several coarser grained levels.
The rich ammonoid faunas of the Wordie Creek Group allow a biostratigraphic zonation which can be correlated with schemes from other parts of the Arctic region. This zonation is complemented with information on palyno, conodont, fish and isotope stratigraphy.

Keywords: Lower Triassic stratigraphy, Hold with Hope, East Greenland, Wordie Creek Group, Kap Stosch Formation, Godthåb Golf Formation.

Addresses:

Finn Surlyk, Department of Geosciences and Natural Resource Management, University of Copenhagen, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark.
Morten Bjerager, Geological Survey of Denmark and Greenland, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark.
Stefan Piasecki, Natural History Museum of Denmark, University of Copenhagen, Øster Voldgade 5–7, DK-1350 Copenhagen K, Denmark.
Lars Stemmerik , Natural History Museum of Denmark, University of Copenhagen, Øster Voldgade 5–7, DK-1350 Copenhagen K, Denmark.

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Recent earthquakes in Denmark are felt over as large areas as earthquakes of similar magnitudes in the Fennoscandian Shield and East European Platform

Voss, P.H., Gregersen. S., Dahl-Jensen, T. & Larsen, T.B. 2017. Recent earthquakes in Denmark are felt over as large areas as earthquakes of similar magnitudes in the Fennoscandian Shield and East European Platform.

© 2017 by Bulletin of the Geological Society of Denmark, Vol. 65, pp. 125–134.
ISSN 2245-7070. (www.2dgf.dk/publikationer/bulletin).
https://doi.org/10.37570/bgsd-2017-65-08

Abstract

For magnitude estimation of historical, pre-instrumental earthquakes it is useful to estimate felt areas for several intensities. From several macroseismic surveys it has been observed that an old shield such as the Fennoscandian Shield has especially large felt areas compared to California where the magnitude formula was developed. However, the newest Danish observations of felt areas and associated digitally determined magnitudes presented in this study show that the subsurface of Denmark has a response to shaking which is similar to that of the Fennoscandian Shield. This study covers the period 1996–2012 and includes an analysis of the macroseismic surveys of all felt earthquakes. Eight of these earthquakes provided new information on intensity areas in Denmark.
An aim for the future is to use the felt areas of old earthquakes in Denmark for improved estimations of their magnitudes.

Keywords: Earthquakes in Denmark, macroseismic intensity, seismicity.

Addresses:

Peter H. Voss, Geological Survey of Denmark and Greenland, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark.
Søren Gregersen, Geological Survey of Denmark and Greenland, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark.
Trine Dahl-Jensen, Geological Survey of Denmark and Greenland, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark.
Tine B. Larsen, Geological Survey of Denmark and Greenland, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark.

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Graptolite biostratigraphy of the lower Silurian of the Sommerodde-1 core, Bornholm, Denmark

Loydell, D.K., Walasek, N., Schovsbo, N.H. & Nielsen, A.T. 2017. Graptolite biostratigraphy of the lower Silurian of the Sommerodde-1 core, Bornholm, Denmark.

© 2017 by Bulletin of the Geological Society of Denmark, Vol. 65, pp. 135–160.
ISSN 2245-7070. (www.2dgf.dk/publikationer/bulletin).
https://doi.org/10.37570/bgsd-2017-65-09

Abstract

The Sommerodde-1 core provides a continuous record through the subsurface of southern Bornholm from the Wenlock Series (Silurian) through to the Lower Cambrian. The Silurian graptolite biostratigraphy of the core is described. For the Rhuddanian and Aeronian (lower and middle Llandovery), the succession and thickness of biozones are very similar to those in the Øleå rivulet nearby. For the upper Llandovery, the lower Telychian Spirograptus guerichi and Sp. turriculatus biozones are significantly thicker in the core than in Øleå, whilst the uppermost Telychian (represented by more than 30 m of strata in nearby sections) is largely absent in the core. This is likely to be a reflection of synsedimentary faulting influencing deposition. It has previously been suggested that much of the Sheinwoodian is missing on Bornholm; this is not the case. The Sheinwoodian is represented by an apparently continuous sequence, at least 31 m thick, in the Sommerodde-1 core.

Keywords: Silurian, graptolite, Llandovery, Wenlock, biostratigraphy, Denmark.

Addresses:

David K. Loydell and Natalia Walasek, School of Earth and Environmental Sciences, University of Portsmouth, Burnaby Road, Portsmouth PO1 3QL, UK.
Niels H. Schovsbo, Geological Survey of Denmark and Greenland (GEUS), Øster Voldgade 10, DK-1350 Copenhagen K, Denmark.
Arne T. Nielsen, Department of Geosciences and Natural Resource Management, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark.

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A new myriacanthid holocephalian from the Early Jurassic of Denmark.

Duffin, C.J. & Milàn, J. 2017. A new myriacanthid holocephalian from the Early Jurassic of Denmark.

© 2017 by Bulletin of the Geological Society of Denmark, Vol. 65, pp. 161–170.
ISSN 2245-7070. (www.2dgf/publikationer/bulletin).
https://doi.org/10.37570/bgsd-2017-65-10

Abstract

A new myriacanthid holocephalian is described from the Hasle Formation (probably the Uptonia jamesoni subzone to the Acanthopleuroceras valdani subzone, Early Pliensbachian, Early Jurassic) of Bornholm, Denmark, on the basis of isolated upper posterior (palatine) and lower posterior (mandibular) tooth plates. Oblidens bornholmensis gen. et sp. nov. differs from all other myriacanthids for which the same dental elements are known, in the distribution of the hypermineralised tissue covering the occlusal surfaces of the tooth plates, and the arrangement of the ridges transecting the tooth plate surface and so varying their surface relief. Oblidens is the first myriacanthid holocephalian to be recorded both from the Pliensbachian and from Denmark. The presence of a further, undetermined myriacanthid tooth plate is noted from the same locality.

Keywords: Bornholm, tooth plate, Holocephali, Myriacanthidae, Pliensbachian, Early Jurassic, new genus.

Addresses:

Christopher J. Duffin, Earth Sciences Department, The Natural History Museum, Cromwell Road, London SW7 5BD, UK; also 146, Church Hill Road, Cheam, Sutton, Surrey SM3 8NF, UK.
Jesper Milàn, Geomuseum Faxe/Østsjællands Museum, Østervej 2, DK-4640 Faxe, Denmark; also Natural History Museum of Denmark, Øster Voldgade 5-7, DK-1350 Copenhagen K, Denmark.

Corresponding author: Christopher J. Duffin

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Two abnormal pygidia of the trilobite Toxochasmops from the Upper Ordovician of the Oslo Region, Norway

Nielsen, M.L. & Nielsen, A.T. 2017. Two abnormal pygidia of the trilobite Toxochasmops from the Upper Ordovician of the Oslo Region, Norway.

ISSN 2245-7070. (www.2dgf/publikationer/bulletin).
https://doi.org/10.37570/bgsd-2017-65-11

Abstract

Two pygidia of the trilobite Toxochasmops from the Upper Ordovician (Katian) of the Oslo Region, Norway, display different types of abnormalities. A juvenile pygidium, treated in open nomenclature as Toxochasmops sp. A, has a partially developed axial ring restricted to the right side of the axis which is interpreted as a teratology. The other pygidium, treated in open nomenclature as Toxochasmops sp. B, shows a local fusion of two pleural ribs with a poorly developed furrow crossing the fused area; this may either represent a teratology or regeneration after an injury. In the latter case, it could represent a rare example of metaplasia in trilobites with replacement of a pleural furrow by an interpleural furrow during regeneration. The posterior position of the partially developed
axial rings, without corresponding pleural ribs, indicates that the posterior part of the axis possibly represents non-functional somites, and abnormalities in this part probably did not significantly affect the vital organs of the trilobite.

Keywords: Abnormalities, teratology, injury, metaplasia, Toxochasmops, trilobites, Katian, Ordovician, Oslo Region, Norway.

Addresses:

Morten Lunde Nielsen, School of Earth Sciences, University of Bristol, Wills Memorial Building, Queens Road, Bristol BS8 1RJ, United Kingdom.

Arne Thorshøj Nielsen, Department of Geosciences and Natural Resource Management, University of Copenhagen, Øster Voldgade 10, DK-1350, København K, Denmark.

Corresponding author: Morten Lunde Nielsen

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