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- Blom, Henning, et al.
(författare)
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Silurian and earliest Devonian Birkeniid anaspids from the northern Hemisphere
- 2001
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Ingår i: Transactions of the Royal Society of Edinburgh. Earth sciences. - 0263-5933 .- 1473-7116. ; 92:3, s. 263-323
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- The sculpture of scales and plates of articulated anaspids from the order Birkeniida is described and used to clarify the position of scale taxa previously left in open nomenclature. The dermal skeleton of a well-preserved squamation of Birkenia elegans Traquair, 1898 from the Silurian of Scotland shows a characteristic finely tuberculated sculpture over the whole body. Rhyncholepis parvula Kiær, 1911, Pterygolepis nitida (Kiær, 1911) and Pharyngolepis oblonga Kiær, 1911, from the Silurian of Norway show three other sculpture types. Northern Hemisphere disarticulated scales and plates are described here, supporting a new anaspid taxonomy that includes both articulated and disarticulated material. The diversity, distribution, evolutionary trends and biostratigraphy of anaspids are described in the context of this new taxonomy, which includes six families (two are new) subdivided into 16 genera (10 are new) and 22 species (15 are new). New taxa among Birkeniidae Traquair, 1898 are Birkenia robusta sp. nov. and Hoburgilepis papillata gen. et sp. nov.. Rhyncholepididae Kiær, 1924 includes Rhyncholepis butriangula sp. nov., Silmalepis erinacea gen. et sp. nov., Vesikulepis funiforma gen. et sp. nov., Maurylepis lacrimans gen. et sp. nov., and the previously described Schidiosteus mustelensis Pander, 1856 and Rytidolepis quenstedtii Pander, 1856. Tahulalepididae fam. nov. is represented by Tahulalepis elongituberculata gen. et sp. nov. and the revised T. kingi (Woodward, 1947). Septentrioniidae fam. nov. contains Septentrionia lancifera gen. et sp. nov., S. mucronata gen. et sp. nov., S. dissimilis gen. et sp. nov., S. seducta gen. et sp. nov., Liivilepis curvata gen. et sp. nov., Spokoinolepis alternans gen. et sp. nov. and Manbrookia asperella gen. et sp. nov. The family level position of Ruhnulepis longicostata gen. et sp. nov. is uncertain. Pterygolepididae Obruchev, 1964 and Pharyngolepididae Kiær, 1924 remain monogeneric.
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- Dahlqvist, Peter, et al.
(författare)
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The lowermost Silurian of Jamtland, central Sweden: conodont biostratigraphy, correlation and biofacies
- 2005
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Ingår i: Transactions of the Royal Society of Edinburgh. Earth Sciences. - 0263-5933. ; 96:1, s. 1-19
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Forskningsöversikt (refereegranskat)abstract
- The Late Ordovician-Early Silurian succession in Jamtland includes the marine Kogsta Siltstone, which is unconformably overlain by the shallow-water Ede Quartzite that grades into the open-marine Berge Limestone. A Hirnantia shelly fauna dates the uppermost Kogsta Siltstone as Hirnantian, and shelly fossils indicate an Aeronian age for the Berge Limestone. Biostratigraphically highly diagnostic conodonts of the early-middle Aeronian Pranognathus tenuis Zone provide the first firm date of the Upper Ede Quartzite and the lowermost Berge Limestone. The Lower Ede Quartzite has not yielded fossils, but sedimentological data suggest it to be of Hirnantian age and reflect the glacio-eustatic low-stand. The contact between the Lower and Upper Ede Quartzite, here taken to be the Ordovician-Silurian boundary, appears to be an unconformity associated with a stratigraphic gap that at least includes the Rhuddanian Stage. The biostratigraphically important conodonts Pranognathus tenuis, Kockelella? manitoulinensis, and Pranognathus siluricus are recorded from Sweden for the first time, and these and other conodonts are used for correlations with coeval units in Europe and North America. In a regional review of Aeronian conodont faunas, three intergrading, apparently depth-related, conodont biofacies are recognised, the Jamtland conodonts representing the one characteristic of the shallowest water.
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- Jeppsson, Lennart, et al.
(författare)
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The Silurian Mulde Event and a scenario for secundo-secundo events
- 2003
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Ingår i: Transactions of the Royal Society of Edinburgh. Earth Sciences. - 0263-5933. ; 93, s. 135-154
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Forskningsöversikt (refereegranskat)abstract
- Graphic correlation using graptolites and conodonts provides a high-resolution timescale for correlating from coastal to deep oceanic sections and, thereby, also a detailed record of the sequence of changes during the Mulde Secundo-Secundo Event. That interval includes sedimentary facies otherwise unknown in older Wenlock to early Ludlow strata on Gotland. The identified sequence of changes includes a detailed record of, in order: two extinctions (Datum points 1 and 1-5); widespread deposition of carbon-rich sediments extensive enough to cause a delta(13)C increase of c. 4.8parts per thousand, the onset, maximum and end of a sea-level fall and rise of at least 16m during 30 kyr; a third extinction (Datum 2); a disaster fauna; and a slow faunal recovery. Thus, a secondary result of the event was a weakened greenhouse effect triggering a glaciation: the Gannarve Glaciation (new term). The order of changes proves that regression did not cause the extinctions. Faunal and sea-level changes, as well as the sedimentary succession, fit well with predictions based on an oceanic model. Extinctions were primarily caused by a severe drop in primary planktonic productivity, causing starvation among planktonic larvae in non-coastal settings. The Grotlingbo Bentonite (new term), the thickest in the Wenlock of Gotland, was deposited across the basin shortly after Datum 2. Temporal resolution is high enough to permit some comparison with Quaternary glaciations.
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- Lindgren, Johan, et al.
(författare)
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Tylosaurus ivoensis: a giant mosasaur from the early Campanian of Sweden
- 2002
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Ingår i: Transactions of the Royal Society of Edinburgh. Earth Sciences. - 0263-5933. ; 93, s. 73-93
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Forskningsöversikt (refereegranskat)abstract
- The nominal species Mosasaurus ivoensis from the latest early Campanian of the Kristianstad Basin in southern Sweden, is redescribed and assigned to the tylosaurine genus Tylosaurus on the basis of its dental and vertebral morphology. A partial skeleton (KUVP 1024) from the late Coniacian to earliest Campanian Smoky Hill Chalk Member of the Niobrara Formation in western Kansas, USA, was previously referred to 'M'. ivoensis. Nevertheless, its marginal teeth are markedly different, both in size and morphology, from those of topotypic T. ivoensis. Examination of type specimens and topotypic material of the nominal tylosaurines Hainosaurus pembinensis from the late early Campanian of Manitoba, Canada, H. gaudryi from the late Santonian or early Campanian of northwestern France, and H. lonzeensis from the Coniacian or Santonian of Belgium, indicates that all three may be Tylosaurus. The utility of isolated tooth-crowns in mosasaur taxonomy has been hampered by the often poor quality of the published illustrations of these fossils in combination with poor stratigraphic control. All Swedish remains of T. ivoensis, including 172 marginal teeth, 6 pterygoid teeth, several jawbone fragments and 12 vertebrae, were collected from a narrow stratigraphic interval corresponding to the highest biozone in the German eight-fold division of the early Campanian, providing the first good insight into the intraspecific dental variation in a tylosaurine mosasaur.
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- Mellgren, Johanna, et al.
(författare)
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A model of reconstruction for the oral apparatus of the Ordovician conodont genus Protopanderodus Lindström, 1971
- 2006
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Ingår i: Transactions of the Royal Society of Edinburgh. Earth Sciences. - 0263-5933. ; 97, s. 97-112
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Tidskriftsartikel (refereegranskat)abstract
- Elements of the Ordovician conodont genus Protopanderodus have been investigated in order to provide a model of reconstruction for its oral apparatus. In total, 4202 elements from the five named species representing this genus in the Swedish Middle Ordovician are included in this study; P. rectus, P. parvibasis, P. graeai, P. robustus, and P. calceatus. The well-preserved specimens were studied in detail for identification of distinct element types and calculations were made to determine element ratios and minimum number of elements in a single apparatus. Three element groups, M, S and P, were recognized for all five species and their relative ratio is indicative of apparatuses consisting of at least 21 elements. The number of element types and their distribution, however, varies between the species. The four bicostate species, P. rectus, P. parvibasis, P. graeai, and P. robustus, have similar morphological characters and are believed to belong to the same evolutionary lineage. They possessed apparatuses consisting of M, Sa, Sb1, Sb2, Sc, Pa, and Pb elements. By contrast, the multicostate species P. calceatus is morphologically different and had an apparatus consisting of M1, M2, Sa, Sb, Sc, ”Sd”, Pa, Pb1, and Pb2 elements. These differences indicate that P. calceatus is not so closely related to the other species, possibly representing a separate evolutionary lineage, and may warrant an exclusive generic assignment.
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