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Three-dimensional paleohistology of the scale and median fin spine of Lophosteus superbus (Pander 1856)
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(English)Manuscript (preprint) (Other academic)
National Category
Natural Sciences
Research subject
Earth Science with specialization in Historical Geology and Palaeontology
URN: urn:nbn:se:uu:diva-282529OAI: oai:DiVA.org:uu-282529DiVA: diva2:921942
Available from: 2016-04-21 Created: 2016-04-05 Last updated: 2016-06-15
In thesis
1. Development and three-dimensional histology of vertebrate dermal fin spines
Open this publication in new window or tab >>Development and three-dimensional histology of vertebrate dermal fin spines
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Jawed vertebrates (gnathostomes) consist of two clades with living representatives, the chondricthyans (cartilaginous fish including sharks, rays, and chimaeras) and the osteichthyans (bony fish and tetrapods), and two fossil groups, the "placoderms" and "acanthodians". These extinct forms were thought to be monophyletic, but are now considered to be paraphyletic partly due to the discovery of early chondrichthyans and osteichthyans with characters that had been previously used to define them. Among these are fin spines, large dermal structures that, when present, sit anterior to both median and/or paired fins in many extant and fossil jawed vertebrates. Making comparisons among early gnathostomes is difficult since the early chondrichthyans and "acanthodians", which have less mineralized skeleton, do not have large dermal bones on their skulls. As a result, fossil fin spines are potential sources for phylogenetic characters that could help in the study of the gnathostome evolutionary history. This thesis examines the development and internal structure of fin spines in jawed vertebrates using two-dimensional (2D) thin sections and three-dimensional (3D) synchrotron datasets. The development of the dorsal fin spine of the holocephalan, Callorhinchus milii, was described from embryos and compared to that of the neoselachian, Squalus acanthias, whose spine has been the model for studying fossil shark spines. It was found that the development of the C. milii fin presents differences from S. acanthias that suggest it might be a better candidate for studying "acanthodian" fin spines. The 3D histology of fossil fin spines was studied in Romundina stellina, a "placoderm"; Lophosteus superbus, a probable stem-osteichthyan; and sever­­al "acanthodians". The 3D vascularization reconstructed from synchrotron radiation microtomographic data reveal that "acanthodian" and Lophosteus spines grew similarly to what is observed in chondrichthyans, which differs slightly from the growth of the Romundina spine. Chondrichthyans and "acanthodians" also share similarities in their internal organization. Overall, Lophosteus and Romundina spines are more similar in terms of morphology and histology compared to chondrichthyans and "acanthodians". These results support the current hypothesis of gnathostome phylogeny, which places "acanthodians" on the chondrichthyan stem. They also emphasize the need for further study of vertebrate fin spines using 3D approaches.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2016. 53 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1382
fin spine, paleontology, early vertebrate, histology, development
National Category
Natural Sciences Geosciences, Multidisciplinary
Research subject
Biology with specialization in Evolutionary Organismal Biology
urn:nbn:se:uu:diva-286863 (URN)978-91-554-9596-1 (ISBN)
Public defence
2016-06-13, Lindahlsalen, Evolutionary Biology Center, Norbyvägen 18A, Uppsala, 09:00 (English)
Available from: 2016-05-23 Created: 2016-04-21 Last updated: 2016-06-15

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