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| Titel |
Possibilities of 3-D modelling and quantitative morphometric analysis of decimeter-sized Echinoids using photogrammetric approach |
| VerfasserIn |
Bálint Polonkai, Ágnes Görög, Andrea Raveloson, Emese Bodor, Balázs Székely |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250138477
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| Publikation (Nr.) |
 EGU/EGU2017-1510.pdf |
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| Zusammenfassung |
| Echinoids (sea urchins) are useful fossils in palaeoenvironmental reconstruction for e.g.
palaeobiogeography, palaeoclimatology or sedimentatological researches. In the Hungarian
Badenian stage (Langhian, Middle Miocene) the species Parascutella gibbercula (DE
SERRES 1829) is a common taxon and indicate shallow marine environment. The specimens
of this extinct species show high morphological variability within relatively small
geographical areas, even within one given strata. These differences can have a relevant
palaeontological and/or palaeoenvironmental information. It is necessary for the
interpretation of the value of the morphological parameters to quantify them in
properties.
Among the possible quantification methods 3D photogrammetric reconstruction is found
to be suitable; recent years have seen its increasing palaeontological application both on
invertebrates and vertebrates. In order to generate proper 3D models of the specimens with
the required details a great number of digital images have to be shot. In case of proper data
acquisition and precise model generation it is possible to outperform the traditional 2D
morphometric studies of the echinoids that are often inaccurate when the spatial
characters as well as ambulacral system and the conical shaped apex (top of the test) are
measured.
An average P . gibbercula specimen is about 10 cm diameter. Therefore, desktop image
acquisition is possible if appropriate lighting conditions are provided. For better results we
have designed an elaborate target background pattern that enhances the chances to find
homologous points in the imagery. Agisoft Photoscan software has been used for the model
generation. The generated models typically show high-resolution details and reproduce
original colours. However, various problems may occur: improper focusing and/or poor
lighting conditions may cause hardly patchable aboral and oral side, and/or shallow surface
undulations cannot be modelled appropriately.
Another issue is the proper georefering the specimen: the definition of the specimen-related
inherent coordinate systems should be transformed to a common one in order to get
comparable results. The resulting point clouds are exported to other rendering systems for
further processing.
In these systems the operation of the palaeontologically relevant morphometric characters is
possible, like generation of profiles, measurement of various parameters, volume calculations,
and surface analysis. These results can be interpreted in palaeontological context.
Potentially taxonomical, palaeopathological (e.g. parasite-affected), palaeoenvironmental
conclusions can be drawn. Furthermore detection of intraspecific variability is of great
importance.
Bálint Polonkai was supported by the Hantken Foundation. Balázs Székely contributed as
an Alexander Humboldt Research Fellow. |
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