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Bremer, Oskar
Publications (10 of 15) Show all publications
Bremer, O., Niedzwiedzki, G., Blom, H., Dec, M. & Kozłowski, W. (2018). Vertebrate microremains from the upper Silurian Winnica Formation of the Holy Cross Mountains, Poland. Geological Magazine, 155(7), 1523-1541
Open this publication in new window or tab >>Vertebrate microremains from the upper Silurian Winnica Formation of the Holy Cross Mountains, Poland
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2018 (English)In: Geological Magazine, ISSN 0016-7568, E-ISSN 1469-5081, Vol. 155, no 7, p. 1523-1541Article in journal (Refereed) Published
Abstract [en]

Vertebrate microremains from the upper Silurian Winnica Formation in the Holy Cross Mountains, Poland are described from the Winnica and Rzepin sections. Both sites record the uppermost part of the Supianka Member, but represent different depositional environments. The Winnica samples come from a low-energy environment, while the Rzepin sample was taken from a high-energy, oolitic facies. Both sites contain thelodonts Thelodus parvidens, Thelodus trilobatus, an anaspid cf. Liivilepis and a number of acanthodian scales of 'nostolepid', poracanthodid and 'gomphonchid' types. Notable differences between the sites are the addition of the osteostracan Tahulaspis cf. ordinata, the thelodont Paralogania ludlowiensis and acanthodian scales identified as Nostolepis gracilis in the Rzepin section. Placing the vertebrate faunas within the vertebrate biozonation established for the Silurian proved difficult. The suggested late Ludlow age for the Supianka Member based on sequence stratigraphical and chemostratigraphical correlations cannot be definitely confirmed or refuted, but a late Ludfordian age seems the most plausible based on invertebrate and vertebrate faunas. The much lower abundance of poracanthodid acanthodians in the Rzepin sample supports the notion of Poracanthodes porosus Zone as a deep-water equivalent to a number of vertebrate biozones. The presence of P. ludlowiensis only in the oolitic sample confirms a long temporal range, but restricted environmental distribution for this taxon.

National Category
Other Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-281657 (URN)10.1017/S0016756817000681 (DOI)000443814900008 ()
Available from: 2016-03-29 Created: 2016-03-29 Last updated: 2018-11-06Bibliographically approved
Jarochowska, E., Viira, V., Einasto, R., Nawrot, R., Bremer, O., Männik, P. & Munnecke, A. (2017). Conodonts in Silurian hypersaline environments: specialized an dunexpectedly diverse. Geology, 45(1), 3-6
Open this publication in new window or tab >>Conodonts in Silurian hypersaline environments: specialized an dunexpectedly diverse
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2017 (English)In: Geology, ISSN 0091-7613, E-ISSN 1943-2682, Vol. 45, no 1, p. 3-6Article in journal (Refereed) Published
Abstract [en]

Hypersaline environments are commonly assumed to be barren of metazoans and therefore are avoided by paleontologists, yet a number of early Paleozoic jawless vertebrate groups specialized to live in such settings. Sampling bias against restricted settings resulted in substantial underestimation of their diversity. Rare studies venturing into such environments yielded multiple new species of conodonts, suggesting that the diversity and habitat range of these hyperdiverse predators of the early oceans are equally underestimated. We describe here autochthonous conodont fauna from evaporite-bearing horizons from the middle Silurian of Estonia that provide evidence for efficient osmoregulation in this group. Based on a global compilation of coeval conodont assemblages, we show that marginal-marine, periodically emergent environments were characterized by higher conodont diversity than open-marine shallow settings. This diversity is due to a high number of species occurring in these environments only. The high degree of specialization is also reflected by the highest within-habitat variability (β diversity) in marginal settings. Most conodont species had narrow environmental niches and, unlike in marine invertebrates, extreme environments were inhabited by the most specialized taxa. Such environments represent a large proportion of early Paleozoic tropical epicratonic basins. Our analysis allows quantification of the degree to which mid-Silurian conodont diversity is underestimated as a result of sampling bias against marginal-marine settings.

National Category
Geology
Identifiers
urn:nbn:se:uu:diva-306884 (URN)10.1130/G38492.1 (DOI)000396124000003 ()
Available from: 2016-11-04 Created: 2016-11-04 Last updated: 2017-11-29Bibliographically approved
Jerve, A., Bremer, O., Sanchez, S. & Ahlberg, P. E. (2017). Morphology and histology of acanthodian fin spines from the late Silurian Ramsåsa E locality, Skåne, Sweden. Palaeontologia Electronica, 20(3), Article ID 56A.
Open this publication in new window or tab >>Morphology and histology of acanthodian fin spines from the late Silurian Ramsåsa E locality, Skåne, Sweden
2017 (English)In: Palaeontologia Electronica, ISSN 1935-3952, E-ISSN 1094-8074, Vol. 20, no 3, article id 56AArticle in journal (Refereed) Published
Abstract [en]

Comparisons of acanthodians to extant gnathostomes are often hampered by the paucity of mineralized structures in their endoskeleton, which limits the potential preservation of phylogenetically informative traits. Fin spines, mineralized dermal structures that sit anterior to fins, are found on both stem-and crown-group gnathostomes, and represent an additional potential source of comparative data for studying acanthodian relationships with the other groups of early gnathostomes. An assemblage of isolated acanthodian fin spines from the late Silurian Ramsasa site E locality (southern Sweden) has been reconstructed in 3D using propagation phase contrast synchrotron X-ray microtomography (PPC-SR mu CT). The aim is to provide morphological and taxo-nomical affinities for the spines by combining morphology and histology with the taxo-nomical framework previously established for the site mainly based on isolated scales. The high-resolution scans also enable investigations of the composition and growth of acanthodian fin spines when compared to similar studies of extinct and extant gnathostomes. In total, seven fin spine morphotypes that have affinities to both Climatiidae Berg 1940 and Ischnacanthiformes Berg 1940 are described. The majority are interpreted as median fin spines, but three possible paired spines are also identified. The spines display differences in their compositions, but generally agree with that presented for climatiids and ischnacanthiforms in previous studies. Their inferred growth modes appear to be more similar to those of fossil and extant chondrichthyan fin spines than to those described from placoderms and stem-osteichthyans, which is congruent with the emerging view of acanthodians as stem-chondrichthyans.

Place, publisher, year, edition, pages
COQUINA PRESS, 2017
Keywords
fin spines, histology, acanthodians, 3D-reconstructions, Silurian, Baltic Basin
National Category
Evolutionary Biology
Identifiers
urn:nbn:se:uu:diva-328517 (URN)10.26879/749 (DOI)000419760900004 ()
Available from: 2017-08-24 Created: 2017-08-24 Last updated: 2018-02-19Bibliographically approved
Bremer, O. (2017). Silurian vertebrates of Gotland (Sweden) and the Baltic Basin. (Doctoral dissertation). Uppsala: Acta Universitatis Upsaliensis
Open this publication in new window or tab >>Silurian vertebrates of Gotland (Sweden) and the Baltic Basin
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

During the Silurian, the Swedish island Gotland was positioned close to the equator and covered by a shallow sea called the Baltic Basin. The sedimentary rocks (predominantly carbonates) comprising most of the island today were initially formed in this warm sea, and the relatively complete succession of rocks often contains fossil fragments and scales from early vertebrates, including heterostracans, anaspids, thelodonts, osteostracans, acanthodians, and a stem-osteichthyan. Fossils of early vertebrates become increasingly more common in younger Silurian rocks, but are mostly represented by fragmentary remains and rarer occurrences of articulated jawless vertebrates (agnathans). However, the record of articulated specimens and jawed vertebrates (gnathostomes) are more numerous in rocks of the following Devonian Period. Isolated peaks of agnathan diversity during the Silurian and disarticulated remains of gnathostomes from this period hint at a cryptic evolutionary history. A micropaleontological approach with broader sampling may provide a better understanding of early vertebrate distribution patterns and hopefully give some insights into this history. The objective of this study was to build upon previous sampling on Gotland and to use established frameworks for disarticulated remains with the aim of making comparisons with similar studies performed in the East Baltic. However, difficulties locating the collections from these previous works necessitated a different focus. Undescribed museum collections and newly sampled material enabled some taxonomical revisions and greatly improved the understanding of vertebrate distribution in the youngest part of the Gotland sequence. It also indicated that this interval may represent the early stages of the diversification of gnathostomes that become increasingly dominant toward the end of the Silurian. Furthermore, the description of samples from partly coeval sections in Poland enabled some preliminary comparisons outside of Gotland, and presented a striking example of restricted environmental occurrences for a thelodont taxon. This is encouraging for future sampling and investigations on Gotland. Together with the establishment of a facies-framework comparable to that developed in the East Baltic and correlations to other areas, this may prove fruitful for an increased understanding of early vertebrate distribution and evolution during the Silurian.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2017. p. 61
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1544
Keywords
early vertebrates, vertebrate microremains, scale taxonomy, early vertebrate distribution, environmental preferences, Silurian, Baltic Basin, Gotland, Sweden
National Category
Evolutionary Biology Other Earth and Related Environmental Sciences
Research subject
Biology with specialization in Evolutionary Organismal Biology
Identifiers
urn:nbn:se:uu:diva-328234 (URN)978-91-513-0039-9 (ISBN)
Public defence
2017-10-06, Ekmansalen, EBC, Norbyvägen 14, Uppsala, 13:00 (English)
Opponent
Supervisors
Available from: 2017-09-15 Created: 2017-08-21 Last updated: 2017-10-17
Bremer, O., Niedźwiedzki, G., Blom, H., Dec, M. & Kozłowski, W. (2017). Vertebrate microremains from the upper Silurian Winnica Formation of the Holy Cross Mountains, Poland. In: : . Paper presented at 14th International Symposium on Early and Lower Vertebrates in the Holy Cross Mountains, Poland, July 3-8 2017.
Open this publication in new window or tab >>Vertebrate microremains from the upper Silurian Winnica Formation of the Holy Cross Mountains, Poland
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2017 (English)Conference paper, Poster (with or without abstract) (Other academic)
National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-328147 (URN)
Conference
14th International Symposium on Early and Lower Vertebrates in the Holy Cross Mountains, Poland, July 3-8 2017
Available from: 2017-08-18 Created: 2017-08-18 Last updated: 2017-11-27Bibliographically approved
Jarochowska, E., Viira, V., Einasto, R., Nawrot, R., Bremer, O., Männik, P. & Munnecke, A. (2016). Conodont Diversity Across The Onshore-Offshore Gradient: Cozy In Brine. In: Geological Society of America Abstracts with Programs.: . Paper presented at GSA Annual Meeting, Denver, Colorado, USA, 25–26 September, 2016.. , 48
Open this publication in new window or tab >>Conodont Diversity Across The Onshore-Offshore Gradient: Cozy In Brine
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2016 (English)In: Geological Society of America Abstracts with Programs., 2016, Vol. 48Conference paper, Poster (with or without abstract) (Other academic)
National Category
Geosciences, Multidisciplinary
Identifiers
urn:nbn:se:uu:diva-311974 (URN)10.1130/abs/2016AM-285673 (DOI)
Conference
GSA Annual Meeting, Denver, Colorado, USA, 25–26 September, 2016.
Note

Paper No. 45-5

Available from: 2017-01-04 Created: 2017-01-04 Last updated: 2017-04-28Bibliographically approved
Bremer, O. (2016). Distribution of Silurian vertebrates on Gotland, Sweden. In: : . Paper presented at 1st International Meeting of Early-stage Researchers in Palaeontology XIV Encuentro de Jóvenes Investigadores en Paleontología, Alpuente, April 13-16, 2016.
Open this publication in new window or tab >>Distribution of Silurian vertebrates on Gotland, Sweden
2016 (English)Conference paper, Poster (with or without abstract) (Other academic)
National Category
Other Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-287367 (URN)
Conference
1st International Meeting of Early-stage Researchers in Palaeontology XIV Encuentro de Jóvenes Investigadores en Paleontología, Alpuente, April 13-16, 2016
Available from: 2016-04-24 Created: 2016-04-24 Last updated: 2016-05-06Bibliographically approved
Jarochowska, E., Bremer, O., Heidlas, D., Pröpster, S., Vandenbroucke, T. R. .. & Munnecke, A. (2016). End-Wenlock terminal Mulde carbon isotope excursion in Gotland, Sweden: Integration of stratigraphy and taphonomy for correlations across restricted facies and specialized faunas. Palaeogeography, Palaeoclimatology, Palaeoecology, 457, 304-322
Open this publication in new window or tab >>End-Wenlock terminal Mulde carbon isotope excursion in Gotland, Sweden: Integration of stratigraphy and taphonomy for correlations across restricted facies and specialized faunas
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2016 (English)In: Palaeogeography, Palaeoclimatology, Palaeoecology, ISSN 0031-0182, E-ISSN 1872-616X, Vol. 457, p. 304-322Article in journal (Refereed) Published
National Category
Earth and Related Environmental Sciences
Research subject
Earth Science with specialization in Historical Geology and Palaeontology
Identifiers
urn:nbn:se:uu:diva-299498 (URN)10.1016/j.palaeo.2016.06.031 (DOI)000380598800025 ()
Available from: 2016-07-21 Created: 2016-07-21 Last updated: 2017-08-21
Bremer, O. (2016). Geology, stratigraphy, and fossil vertebrates of Gotland, Sweden: a review. (Licentiate dissertation). Uppsala: Acta Universitatis Upsaliensis
Open this publication in new window or tab >>Geology, stratigraphy, and fossil vertebrates of Gotland, Sweden: a review
2016 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The Silurian limestones of Gotland, Sweden, and their exceptionally well-preserved fossils have attracted the interest of scientists for more than 200 years. The sedimentary rocks represent approximately 10 million years of time, and were deposited in a shallow, equatorial inland sea named the Baltic Basin. The majority of the sediments are composed of reef-associated strata, but a general transition can be seen along the strike from shallow water in the northeast to deeper shelf environments in the southwest. The understanding of the stratigraphy and the geology of Gotland has greatly improved during the last decades. This research on Gotland has also led to the discovery of a series of stable isotope excursions and extinctions among several faunal groups. These events were probably linked to cycles in atmospheric and oceanic states, and three of them have been recognized globally. The Baltic Basin was also home to a variety of early vertebrates. The first fossil vertebrates from Gotland were reported in 1861, but the most extensive study of these early fishes was performed in the late 1900s. More recently it was shown that the vertebrates were also affected by one of the extinction events. This thesis is an extensive review of previous work and will form a geological basis for future studies. In this work, all previous reports of vertebrates have been gathered, reviewed, and the old samples have been placed in an updated stratigraphical framework. The scale taxonomy of Gotland vertebrates, including the Baltic acanthodians, has been evaluated and partly revised. Additionally, the depositional environments of the sampled areas have been investigated. Studying the vertebrates of Gotland is important for understanding the distribution of vertebrates through time and in different environments during the Silurian. Initial results indicate environmental preferences among vertebrates on both group and species-level, which may prove useful for testing the vertebrate biozonation developed for the Silurian.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2016. p. 78
Keywords
Silurian, Gotland geology, Baltic Basin, extinction events, isotope excursions, atmospheric and oceanic cycles, early vertebrates, scale taxonomy, environmental preferences, vertebrate biozonation.
National Category
Other Earth and Related Environmental Sciences
Research subject
Earth Science with specialization in Historical Geology and Palaeontology
Identifiers
urn:nbn:se:uu:diva-281659 (URN)
Presentation
2016-04-27, EBC/9:2008, Norbyvägen 22, Uppsala, 10:15 (English)
Opponent
Supervisors
Available from: 2016-12-15 Created: 2016-03-29 Last updated: 2016-12-15Bibliographically approved
Jarochowska, E., Bremer, O., Heidlas, D., Pröpster, S., Vandenbroucke, T. & Munnecke, A. (2016). Multielement skeletal taphonomy in conodonts: are robust species more common or selectively preserved in shallow-water facies?. In: : . Paper presented at 87th Annual Conference of the Paläontologische Gesellschaft e. V, Dresden, 12.-14.9., 2016.
Open this publication in new window or tab >>Multielement skeletal taphonomy in conodonts: are robust species more common or selectively preserved in shallow-water facies?
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2016 (English)Conference paper, Poster (with or without abstract) (Other academic)
National Category
Geosciences, Multidisciplinary
Identifiers
urn:nbn:se:uu:diva-311973 (URN)
Conference
87th Annual Conference of the Paläontologische Gesellschaft e. V, Dresden, 12.-14.9., 2016
Available from: 2017-01-04 Created: 2017-01-04 Last updated: 2017-04-28Bibliographically approved
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