Morphology and histology of acanthodian fin spines from the late Silurian Ramsåsa E locality, Skåne, Sweden
File(s)
Published version
Author(s)
Jerve, A
Bremer, O
Sanchez, S
Ahlberg, PE
Type
Journal Article
Abstract
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 Ramsåsa site E locality (southern Sweden) has been reconstructed in 3D using propagation phase contrast synchrotron X-ray microtomography (PPC-SRµCT). The aim is to provide morphological and taxonomical affinities for the spines by combining morphology and histology with the taxonomical 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.
Date Issued
2017-11-07
Date Acceptance
2017-11-07
Citation
Palaeontologia Electronica, 2017
ISSN
1935-3952
Publisher
Coquina Press
Journal / Book Title
Palaeontologia Electronica
Copyright Statement
Copyright: November 2017 Palaeontology Association.
This is an open access article distributed under the terms of Attribution-NonCommercial-ShareAlike 4.0 International (CC BY-NC-SA
4.0), which permits users to copy and redistribute the material in any medium or format, provided it is not used for commercial
purposes and the original author and source are credited, with indications if any changes are made.
creativecommons.org/licenses/by-nc-sa/4.0/
This is an open access article distributed under the terms of Attribution-NonCommercial-ShareAlike 4.0 International (CC BY-NC-SA
4.0), which permits users to copy and redistribute the material in any medium or format, provided it is not used for commercial
purposes and the original author and source are credited, with indications if any changes are made.
creativecommons.org/licenses/by-nc-sa/4.0/
Subjects
0403 Geology
0602 Ecology
0603 Evolutionary Biology
Paleontology
Publication Status
Published online
Article Number
20.3.56A