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An updated stratigraphic and environmental framework for the distribution of Silurian vertebrates on Gotland
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
2015 (English)In: Estonian journal of earth sciences, ISSN 1736-4728, E-ISSN 1736-7557, Vol. 64, no 1, 13-18 p.Article in journal (Refereed) Published
Place, publisher, year, edition, pages
2015. Vol. 64, no 1, 13-18 p.
Keyword [en]
vertebrate distribution, stratigraphy, facies, Silurian events, Gotland, Sweden
National Category
Developmental Biology Earth and Related Environmental Sciences
Identifiers
URN: urn:nbn:se:uu:diva-251824DOI: 10.3176/earth.2015.03ISI: 000351327700004OAI: oai:DiVA.org:uu-251824DiVA: diva2:808187
Available from: 2015-04-27 Created: 2015-04-24 Last updated: 2017-08-21
In thesis
1. Geology, stratigraphy, and fossil vertebrates of Gotland, Sweden: a review
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. 78 p.
Keyword
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
2. Silurian vertebrates of Gotland (Sweden) and the Baltic Basin
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. 61 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1544
Keyword
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

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