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Silurian vertebrates of Gotland (Sweden) and the Baltic Basin
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
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 [en]
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: urn:nbn:se:uu:diva-328234ISBN: 978-91-513-0039-9 (print)OAI: oai:DiVA.org:uu-328234DiVA, id: diva2:1134493
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
List of papers
1. An updated stratigraphic and environmental framework for the distribution of Silurian vertebrates on Gotland
Open this publication in new window or tab >>An updated stratigraphic and environmental framework for the distribution of Silurian vertebrates on Gotland
2015 (English)In: Estonian journal of earth sciences, ISSN 1736-4728, E-ISSN 1736-7557, Vol. 64, no 1, p. 13-18Article in journal (Refereed) Published
Keywords
vertebrate distribution, stratigraphy, facies, Silurian events, Gotland, Sweden
National Category
Developmental Biology Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-251824 (URN)10.3176/earth.2015.03 (DOI)000351327700004 ()
Available from: 2015-04-27 Created: 2015-04-24 Last updated: 2017-08-21
2. End-Wenlock terminal Mulde carbon isotope excursion in Gotland, Sweden: Integration of stratigraphy and taphonomy for correlations across restricted facies and specialized faunas
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
3. Vertebrate remains and conodont biostratigraphy in the Ludlow Burgsvik Formation of Gotland, Sweden
Open this publication in new window or tab >>Vertebrate remains and conodont biostratigraphy in the Ludlow Burgsvik Formation of Gotland, Sweden
(English)Manuscript (preprint) (Other academic)
National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-328226 (URN)
Available from: 2017-08-20 Created: 2017-08-20 Last updated: 2017-08-25
4. Vertebrate dermal remains and conodont distribution in the upper Silurian Hamra and Sundre formations of Gotland, Sweden
Open this publication in new window or tab >>Vertebrate dermal remains and conodont distribution in the upper Silurian Hamra and Sundre formations of Gotland, Sweden
(English)Manuscript (preprint) (Other academic)
National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-328227 (URN)
Available from: 2017-08-20 Created: 2017-08-20 Last updated: 2017-08-21
5. Vertebrate microremains from the upper Silurian Winnica Formation of the Holy Cross Mountains, Poland
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

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