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Scales and Dermal Skeletal Histology of an Early Bony Fish Psarolepis romeri and Their Bearing on the Evolution of Rhombic Scales and Hard Tissues
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
2013 (English)In: PLoS ONE, ISSN 1932-6203, Vol. 8, no 4, e61485- p.Article in journal (Refereed) Published
Abstract [en]

Recent discoveries of early bony fishes from the Silurian and earliest Devonian of South China (e. g. Psarolepis, Achoania, Meemannia, Styloichthys and Guiyu) have been crucial in understanding the origin and early diversification of the osteichthyans (bony fishes and tetrapods). All these early fishes, except Guiyu, have their dermal skeletal surface punctured by relatively large pore openings. However, among these early fishes little is known about scale morphology and dermal skeletal histology. Here we report new data about the scales and dermal skeletal histology of Psarolepis romeri, a taxon with important implications for studying the phylogeny of early gnathostomes and early osteichthyans. Seven subtypes of rhombic scales with similar histological composition and surface sculpture are referred to Psarolepis romeri. They are generally thick and show a faint antero-dorsal process and a broad peg-and-socket structure. In contrast to previously reported rhombic scales of osteichthyans, these scales bear a neck between crown and base as in acanthodian scales. Histologically, the crown is composed of several generations of odontodes and an irregular canal system connecting cylindrical pore cavities. Younger odontodes are deposited on older ones both superpositionally and areally. The bony tissues forming the keel of the scale are shown to be lamellar bone with plywood-like structure, whereas the other parts of the base are composed of pseudo-lamellar bone with parallel collagen fibers. The unique tissue combination in the keel (i.e., extrinsic Sharpey's fibers orthogonal to the intrinsic orthogonal sets of collagen fibers) has rarely been reported in the keel of other rhombic scales. The new data provide insights into the early evolution of rhombic (ganoid and cosmoid) scales in osteichthyans, and add to our knowledge of hard tissues of early vertebrates.

Place, publisher, year, edition, pages
2013. Vol. 8, no 4, e61485- p.
National Category
Natural Sciences
URN: urn:nbn:se:uu:diva-200692DOI: 10.1371/journal.pone.0061485ISI: 000317909600117OAI: oai:DiVA.org:uu-200692DiVA: diva2:624726
Available from: 2013-06-03 Created: 2013-06-03 Last updated: 2015-01-12Bibliographically approved
In thesis
1. Three-dimensional Virtual Histology of Early Vertebrate Scales Revealed by Synchrotron X-ray Phase-contrast Microtomography
Open this publication in new window or tab >>Three-dimensional Virtual Histology of Early Vertebrate Scales Revealed by Synchrotron X-ray Phase-contrast Microtomography
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Vertebrate hard tissues first appeared in the dermal skeletons of early jawless vertebrates (ostracoderms) and were further modified in the earliest jawed vertebrates. Fortunately, histological information is usually preserved in these early vertebrate fossils and has thus been studied for more than a century, done so by examining thin sections, which provide general information about the specific features of vertebrate hard tissues in their earliest forms. Recent progress in synchrotron X-ray microtomography technology has caused a revolution in imaging methods used to study the dermal skeletons of early vertebrates. Virtual thin sections obtained in this manner can be used to reconstruct the internal structures of dermal skeletons in three-dimensions (3D), such as vasculature, buried odontodes (tooth-like unites) and osteocytes. Several body scales of early vertebrates have been examined using this imaging method and in situ 3D models of internal structures are created. Andreolepis (an early osteichthyan) scale shows linear growth pattern of odontodes in early developmental stage, which is not observable in traditional thin sections. The scale of another early osteichthyan Psarolepis was studied in the same way. Comparison between Andreolepis and Psarolepis shows that cosmine, a tissue complex in dermal skeleton of early sarcopterygians, originated by a developmental change of odontode shape. Two scales of osteostracans, a group of extinct jawless vertebrates, were studied in 3D and more details have been revealed in comparison to previous results based solely on 2D thin sections. 3D data enables us to compare the vasculature and canal system in different taxa in great detail, which forms the basis of formulating primary homology hypothesis and phylogenetic characters.

The new data resulting from this study suggests that vertebrate fossils have preserved much more histological information than we currently appreciate, and provide a new data source of microanatomical structures inside the fossils that can contribute new characters for phylogenetic analysis of early jawed vertebrates.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2015. 49 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1213
3D virtual paleohistology, scales, ontogeny, jawed vertebrates, phylogeny
National Category
Evolutionary Biology
Research subject
Biology; Earth Science with specialization in Historical Geology and Palaeontology
urn:nbn:se:uu:diva-238056 (URN)978-91-554-9128-4 (ISBN)
Public defence
2015-02-02, Lindahlsalen, Norbyvägen 18A, Uppsala, 14:00 (English)
EU, European Research Council, 233111
Available from: 2015-01-09 Created: 2014-12-09 Last updated: 2015-02-03Bibliographically approved

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