Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Web of Science (2) Citing Articles via Google Scholar Google Scholar Articles by Dommergues, J.-L. Articles by Meister, C. Search for Related Content GeoRef GeoRef Citation

Exploration of the Oxynoticeratidae ornamentalmorphospace using the discrete cosine transform (DCT) to analyze rib patterns

¹ Jean-Louis Dommergues and Cyril H. Dommergues. Biogéosciences (UMR CNRS 5561), Centre des Sciences de la Terre, Université de Bourgogne, boulevard Gabriel 6, F-21000 Dijon, France. Jean-Louis.Dommergues{at}u-bourgogne.fr
² Christian Meister. Muséum d'histoire naturelle de Genève, Département de Géologie et de Paléontologie, route de Malagnou 1, CH-1211 Geneva, Switzerland. christian.meister{at}mhn.ville-ge.ch

The discrete cosine transform (DCT) is a Fourier-related transform widely used in signal processing and well suited to analyzing open outlines such as ammonite ribs. The method is applied here to depict and decipher the ribbing morphospace of a large group of Lower Jurassic ammonites composed of the Oxynoticeratidae and their close ancestors. Because they are clearly associated with buoyancy and/or swimming ability, the usually clearly involute, comparatively smooth and compressed shells of these ammonites may well be misleading taxonomic markers. In this context, quantitative analysis of the ribbing pattern using the DCT may significantly improve our perception of the ornamental patterns expressed within the group. A set of 251 specimens illustrating the worldwide fauna and selected from more than 80 publications is analyzed. Big differences are found in the evolutionary patterns of the two main lineages of Oxynoticeratidae currently accepted in the literature. A previously unsuspected Mediterranean group comprising principally the genus Parasteroceras is identified from its distinctive ornamentation. The northwest European and Mediterranean genera Eparietites, Oxynoticeras, and Parasteroceras do not feature among the American (East Pacific) faunas. This finding calls into question some generally accepted correlations between European and American stratigraphic frameworks. The study shows that the DCT is a valuable tool for discriminating between species within the huge and often puzzling range of ornamental variation of the main genera (e.g., Gleviceras and Radstockiceras).