| 1. |
- Atkins, Christian J., et al.
(författare)
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Yochelcionella (Mollusca, Helcionelloida) from the lower Cambrian of North America
- 2008
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Ingår i: Bulletin of Geosciences. - : Czech Geological Survey. - 1214-1119 .- 1802-8225. ; 83:1, s. 23-38
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Tidskriftsartikel (refereegranskat)abstract
- Five named species of the helcionelloid mollusc genus Yochelcionella Runnegar & Pojeta, 1974 are recognized from the lower Cambrian (Cambrian Series 2) of North America: Yochelcionella erecta (Walcott, 1891), Y. americana Runnegar & Pojeta, 1980, Y. chinensis Pei, 1985, Y. greenlandica Atkins & Peel, 2004 and Y. gracilis Atkins & Peel, 2004, linking lower Cambrian outcrops along the present north-eastern seaboard. Yochelcionella erecta, an Avalonian species, is described for the first time, other species are derived from Laurentia. A revised concept of the Chinese species, Y. chinensis, is based mainly on a large sample from the Forteau Formation of western Newfoundland and the species may have stratigraphic utility between Cambrian palaeocontinents.
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| 2. |
- Dahlqvist, Peter, et al.
(författare)
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Late Ordovician shelly faunas from Jamtland: palaeocommunity development along the margin of the Swedish Caledonides
- 2010
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Ingår i: Bulletin of Geosciences. - : Czech Geological Survey. - 1214-1119 .- 1802-8225. ; 85:3, s. 505-512
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Tidskriftsartikel (refereegranskat)abstract
- Late Ordovician shelly faunas occur at several localities in the Ostersund area of Jamtland (Sweden) and developed against a background of intense and rapid global climate change. In the eastern part, approximately in the middle parts of the Krykas Quartzite, and in the western part in the uppermost Kogsta Siltstone changes in faunas and sedimentary patterns provide regional evidence of these global events. In both areas the faunas occur in shale and siltstone facies and are used to effect correlations between the eastern and western parts of the region, which show major differences in facies development. These sub-basins, situated on the margins of a developing mountain belt, reacted differently to global signals providing further evidence of the heterogeneous responses to climate change at the end of the Ordovician Period.
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| 3. |
- Ebbestad, Jan Ove R., 1967-, et al.
(författare)
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Late Ordovician rostroconchs (Mollusca) from fluvial erratics in northwestern Europe
- 2017
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Ingår i: Bulletin of Geosciences. - : Czech Geological Survey. - 1214-1119 .- 1802-8225. ; 92:4, s. 405-438
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes 3 species of ribeirioid and 2 species of conocardiid rostroconchs from fluvially transported erratics in the Dutch-German border area. The material probably stems from Ordovician deposits of the North Estonian Confacies Belt. The ribeirioid specimens from the flaljala group of erratics (Sandhian 2) are represented by Tolmachovia subliratu sp. nov., Beukeria plicata gen. nov. sp. nov. and Ischyrinia viator sp. nov. The single specimen of Tohnachovia is hitherto the youngest occurrence of this genus and the first in Baltica. The presence of subordinate radial ornamentation is added to the emended diagnosis of the genus. The new genus Beukeria is an ischyriniid rostroconch with an elongated conch, two thick pegmas and a plicate shell posterior to vertical axis. Ischyrinia viator is similar to the coeval. I. notTegica Soot-Ryon, 1960 but this has a ventrolateral sinus that is subparallel to the dorsal axis. Conocardild specimens from the Pirgu Ojlemyr chert (Katian 4) are represented by Bitrigonocardia lindstroemi (Isberg) and Pojetaconcha costulata sp. nov. The identification of Bitrigonocardia lindstroemi is circumstantial as the type specimens are missing, but as understood here new details of morphology and ornamentation are given. Pojetaconcha is for the first time recognized outside Laurentia and Australia. Pojetaconcha costulata sp. nov. is distinguished by 14 or 15 broad and flat-topped radial ribs on the body and snout and compares closely with the Chazyan P. alabamensis (Pojeta & Runnegar, 1976), USA. Ischyriniids occur mainly in Baltica with Ischyrinia migrating into Laurentia. A general exchange of Bitrigonocardia and Pojetaconcha is seen between Laurentia and Baltica.
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| 4. |
- Geyer, Gerd, et al.
(författare)
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A remarkable Amgan (Middle Cambrian, Stage 5) fauna from the Sauk Tanga, Madygen region, Kyrgyzstan
- 2014
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Ingår i: Bulletin of Geosciences. - : Czech Geological Survey. - 1214-1119 .- 1802-8225. ; 89:2, s. 375-400
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Tidskriftsartikel (refereegranskat)abstract
- Early Middle Cambrian bituminous coquinoid limestones from a tectonically isolated outcrop in southwestern Kyrgyzstan yield a remarkably diverse fauna, with stem-group cnidarians, trilobites, rhynchonelliformean brachiopods, and other shelly fossils. The fossil site is in the northern foothills of the Turkestan Range and thus forms part of the westernmost extension of the South Tien Shan. The fauna includes two fairly well known trilobite species, Glabrella ventrosa Lermontova, 1940 and Dorypyge richthofeniformis Lermontova, 1940, that provide confident support for an Amgan age of the rocks. New described taxa include the stem-group cnidarian Cambroctoconus kyrgyzstanicus Peel sp. nov., the trilobite Olenoides sagittatus Geyer sp. nov., and the helcionelloid Manasoconus bifrons Peel gen. et sp. nov. Additional fossils within the samples include the trilobites Olenoides sp. A, Kootenia sp., and Pseudoeteraspis? sp.; the rhynchonelliform brachiopods Narynella cf. ferganensis (Andreeva, 1962), Narynella? sp., Austrohedra? sp. nov., and two species of uncertain generic affinity; the tommotiid Tesella sp.; the hyolithelminth Hyolithellus sp.; and the palaeoscolecid Hadimopanella oezgueli Gedik, 1977. Of particular interest is Cambroctoconus kyrgyzstanicus with an octagonal corallum and a sparsely septate calyx.
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| 5. |
- Geyer, Gerd, et al.
(författare)
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The Henson Gletscher Formation, North Greenland, and its bearing on the global Cambrian Series 2-Series 3 boundary
- 2011
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Ingår i: Bulletin of Geosciences. - : Czech Geological Survey. - 1214-1119 .- 1802-8225. ; 86:3, s. 465-534
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Tidskriftsartikel (refereegranskat)abstract
- The Henson Gletscher Formation of North Greenland yields moderately diverse trilobite faunas which bracket the Cambrian Series 2-Series 3 boundary interval. A number of the trilobite taxa permit correlation into other parts of Laurentia and to other Cambrian continents, thus enhancing correlation within this stratigraphical interval of the traditional Lower-Middle Cambrian boundary. In particular, the occurrence of Ovatoryctocara granulata and O. yaxiensis substantially improves the intercontinental recognition of the O. granulata level, a prime GSSP candidate. In contrast, the level with Oryctocephalus indicus cannot be located in a number of Cambrian continents with sufficient precision, making this level unsuitable for the definition of a GSSP for the base of the Cambrian Series 3 and Stage 5. Further support for the correlation potential of the base of the range of Ovatoryctocara granulata comes from recent carbon isotope studies that indicate a striking negative excursion in sections of South China (ROECE event) that probably coincides with similar excursions in Laurentia. Four new trilobite species are described: Zacanthopsis blakeri sp. nov., Protoryctocephalus arcticus sp. nov., Eoptychoparia pearylandica sp. nov. and Onchocephalus? freucheni sp. nov.
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| 6. |
- Hansen, Jesper, et al.
(författare)
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Diversity fluctuations and biogeography of Ordovician brachiopod faunas in northeastern Spitsbergen
- 2010
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Ingår i: Bulletin of Geosciences. - : Czech Geological Survey. - 1214-1119 .- 1802-8225. ; 85:3, s. 497-504
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Tidskriftsartikel (refereegranskat)abstract
- Investigations of Lower and Middle Ordovician brachiopods in northeastern Spitsbergen have revealed strong ties to faunas in North America and Greenland at the generic level, although the fauna appears mostly endemic at the species level. During the early Palaeozoic, the archipelago of Svalbard, including Spitsbergen, was located at equatorial latitudes along the northeastern margin of Laurentia. The northeastern part of Spitsbergen experienced significant sea level changes, changing from very shallow water in the Tremadocian to deep water in the Floian and slowly back to shallow- water carbonate environments in the Middle Ordovician. The Tremadocian and early Floian brachiopod fauna was of low diversity with a high proportion of cosmopolitan warm-water related rhynchonelliform genera. In the late Floian there was an abrupt diversification event, taking place against the background of the increasing isolation of Laurentia, leading to a diverse, mostly endemic fauna. This diverse fauna remained into the Middle Ordovician. A similar diversification event has been recorded in North America, but here it occurs later, in the Dapingian. The diachroneity of brachiopod diversification within different parts of a continent has previously been shown for South China, suggesting that it may be a common phenomenon. In contrast to the mostly endemic Middle Ordovician rhynchonelliform genera, the linguliform brachiopods included many genera with a wide distribution. This difference is attributed to their different dispersal strategies.
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| 7. |
- Jensen, Soren, et al.
(författare)
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Scratch circles from the Ediacaran and Cambrian of Arctic Norway and southern Africa, with a review of scratch circle occurrences
- 2018
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Ingår i: Bulletin of Geosciences. - : CZECH GEOLOGICAL SURVEY. - 1214-1119 .- 1802-8225. ; 93:3, s. 287-304
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Forskningsöversikt (refereegranskat)abstract
- Scratch circles - bedding plane parallel sedimentary structures formed by the passive rotation of a tethered organism into the surrounding sediment - are relatively rare in the geological record. Here new occurrences of scratch circles are described from the Ediacaran-Cambrian Stahpogieddi Formation, Digermulen Peninsula, Arctic Norway, and from the Ediacaran Nudaus and Urusis formations, Nama Group, of southern Africa. A literature survey confirms a previously noted concentration of scratch circles reported from shallow marine upper Ediacaran-lower Cambrian and paralic Carboniferous rocks. Scratch circle identification and nomenclature are discussed. The stratigraphical range of the trace fossils Treptichnus pedum and Gyrolithes isp. in the Stahpogieddi Formation are extended downward. Combined with earlier reports of Harlaniella podolica this adds new precision to the placement of the Ediacaran-Cambrian boundary on the Digermulen Peninsula.
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| 8. |
- Lerosey-Aubril, Rudy, et al.
(författare)
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Arthropod appendages from the Weeks Formation Konservat-Lagerstatte: new occurences of anomalocaridids in the Cambrian of Utah, USA
- 2014
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Ingår i: Bulletin of Geosciences. - : Czech Geological Survey. - 1214-1119 .- 1802-8225. ; 89:2, s. 269-282
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Tidskriftsartikel (refereegranskat)abstract
- The Guzhangian Weeks Formation (house Range, Utah, USA) contains a virtually unstudied but diverse assemblage of "soft-bodied" organisms. This fauna includes several enigmatic appendages of arthropods that are described in this contribution. Six appendages (two isolated and four paired appendages) are interpreted as frontal appendages of a probably new species of Anomalocaris. They are characterized by a slender morphology, 14 podomeres, ventral spines alternating in size, up to three auxiliary spines per ventral spine, and only two dorsal spines. Another isolated appendage is also tentatively assigned to Anomalocaris, but it exhibits a more robust morphology, a stronger distal tapering, and apparently simple ventral spines, suggesting that it may represent a distinct taxon. These frontal appendages represent the youngest occurrence of anomalocaridids in Laurentia and demonstrate the persistence of older, Burgess Shale-type taxa in the Weeks Formation. An assemblage of four antenniform and six robust and heavily-armed appendages is also described. These are interpreted as the serially arranged, anterior appendages of a single individual of an undetermined arthropod species. This association of three pairs of robust, spiny appendages with two pairs of antenniform structures in a Cambrian arthropod is unique.
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| 9. |
- Lindström, Anna, et al.
(författare)
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Shell repair and shell form in Jurassic pleurotomarioid gastropods from England
- 2010
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Ingår i: Bulletin of Geosciences. - : Czech Geological Survey. - 1214-1119 .- 1802-8225. ; 85:4, s. 541-550
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Tidskriftsartikel (refereegranskat)abstract
- Specimens of the vetigastropods Pleurotomaria Defrance, 1826 and Pyrgotrochus Fischer, 1885, from the Jurassic of England were separated into three morphological groups and surveyed for traces of shell repair. Two measures of shell repair frequencies were calculated: 1) ratio of the number of specimens with at least one repaired injury to the total number of specimens; 2) ratio of the total number of injuries to the total number of specimens in the sample. The Pleurotomaria anglica (Sowerby, 1818) group containing large, high spired trochiform shells showed the lowest repair frequency with 28.8% and 75.3%, respectively. The shell repair frequency in the low spired trochiform Pleurotomaria actinomphala Deslongchamps, 1848 group was 44.4% and 81.0%, respectively. Lastly, the Pyrgotrochus group containing conoidal trochiform shells showed the highest frequency calculated by both methods, 46.2% and 92.3%. Three types of injuries were found in all morphological groups, although in different proportions. Breaks across the entire whorl constitute the majority of repaired injuries in shells of the Pleurotomaria anglica group; in the P. actinomphala group the figure is about 50% and in Pyrgotrochus only 35%. The coniodal shell form and a deep slit in the aperture margin probably proved to be a defensive strategy for Pyrgotrochus, with many fractures terminating at the margin of the slit, whereas Pleurotomaria anglica was protected by its size.
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| 10. |
- Niedzwiedzki, Grzegorz, 1980-, et al.
(författare)
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Middle Devonian invertebrate trace fossils from the marginal marine carbonates of the Zachełmie tetrapod tracksite, Holy Cross Mountains, Poland
- 2014
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Ingår i: Bulletin of Geosciences. - : Czech Geological Survey. - 1214-1119 .- 1802-8225. ; 89:3, s. 593-606
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Tidskriftsartikel (refereegranskat)abstract
- The dolomitic deposits of the Middle Devonian Wojciechowice Formation exposed at the tetrapod tracksite in the Zachełmie Quarry in the Holy Cross Mountains (Poland) are characterised by a low diversity of invertebrate trace fossilassociation. Four ichnoassemblages can be identified in the track-bearing, lower part of the succession. The most conspicuous are trace fossils produced by arthropods (probably crustaceans), which can form distinctive and large horizontal burrows. The described ichnotaxa (cf. Skolithos isp., cf. Balanoglossites isp., Alcyonidiopsis isp., Spongeliomorpha isp., Gordia isp., and Rhizocorallium isp.) are well known from typical marginal-marine and shallow-marine deposits. Nevertheless, the studied assemblages were found in sparsely distributed horizons and are dominated by a single or a few ichnotaxa with locally high trace-densities. Distribution and composition of the trace fossil assemblages probably reflects occurrence of the impoverished, stressed Cruziana ichnofacies. It was affected by changes in water depth with intermittent periods of subaerial exposure connected with salinity fluctuations. The invertebrate trace fossil assemblage, tetrapod tracks and associated sedimentological features point to deposition in a marginal-marine, mostly peritidal and lagoonal environment with minor terrestrial influences.
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