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Credneria and Platanus (Platanaceae) from the Late Cretaceous (Santonian) of Quedlinburg, Germany
Stockholm University, Faculty of Science, Department of Botany.
2008 (English)In: Review of Palaeobotany and Palynology, ISSN 0034-6667, E-ISSN 1879-0615, Vol. 152, no 04-mar, 211-236 p.Article in journal (Refereed) Published
Abstract [en]

Foliage and reproductive structures of Platanaceae from the Upper Cretaceous (Santonian) of Quedlinburg, Central Germany, were comparatively studied and their systematic affinities established. One type of foliage preserved in sandstone and rarely in clayish siltstone belongs to the extinct genus Credneria. The leaves are typically obovate with a pinnate-actinodromous venation and distinct suprabasal veins. In addition, a substantial number of leaves preserved in siltstone and rarely in sandstone are identical to modern Platanus based on leaf architecture and epidermal features. As in modern Platanus leaf margin and size were found to be of no systematic significance in both fossil leaf types. Further, staminate flower heads preserved as cleavage compressions in siltstone were found in association with Platanus leaves; they contain pollen that is identical to modern Platanus in size and type of tectum. In addition. a few three-dimensionally preserved staminate flower heads with ca. 50 flowers on a receptaculum are described. Each flower appears to have a two-whorled perianth and six or seven stamens. The organs of the outer perianth whorl show a distinct epidermal cell pattern different from the inner ones. All perianth organs have the same length as the stamens. Stamens are bithecate and contain pollen identical to that found in compression fossils. Pistillate heads preserved in siltstone consist of numerous achenes with persistent styles, which show close similarity to modern Platanus. It remains unclear, whether additional inflorescence heads of uncertain sex found in sandstone that are slightly larger than those preserved in siltstone belong to the leaves of Credneria. Association evidence links vegetative and reproductive structures preserved in siltstone and indicates the presence of the modern genus Platanus in the Santonian.

Place, publisher, year, edition, pages
2008. Vol. 152, no 04-mar, 211-236 p.
Keyword [en]
Late Cretaceous, Quedlinburg, Platanaceae, Credneria, Platanus, leaf fossils, reproductive structures, pollen, comparative morphology
National Category
Natural Sciences
URN: urn:nbn:se:su:diva-57699DOI: 10.1016/j.revpalbo.2008.05.004ISI: 000261704400008OAI: diva2:417429
authorCount :3Available from: 2011-05-17 Created: 2011-05-16 Last updated: 2011-09-29Bibliographically approved
In thesis
1. Comparative morphological studies of fossil and living plane trees (Platanaceae) and oaks (Quercus): taxonomy, ecology, evolution
Open this publication in new window or tab >>Comparative morphological studies of fossil and living plane trees (Platanaceae) and oaks (Quercus): taxonomy, ecology, evolution
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Morphological characters are essential for flowering plant identification, but also provide information about diversity patterns and ecological adaptation. In woody plant species, characters of the leaf are among the most useful and can be examined on fossils as well. In this thesis, I studied leaf architecture, epidermal anatomy and reproductive structures of some fossil Platanaceae (plane trees) and an extant group of Quercus (oak) both qualitatively and quantitatively. The aim of this study was to understand past and present patterns of distribution in these taxa, their morphological variability and possible species delimitations. Platanaceae constitute today a relict taxon with a disjunct distribution, but were a taxonomically and morphologically diverse group in the geological past. The presence of the modern genus Platanus in the Late Cretaceous of Central Germany could be demonstrated through the combined analysis of leaves, flowers, fruits and pollen. The extinct genus Credneria is only represented by leaf fossils, but a unique combination of characters proved its affinity with the Platanaceae. Although several species had been described previously, a statistical analysis showed that the observed leaf polymorphism is due to environmental constraints, pointing towards a single species, Credneria denticulata. Quercus subsection Galliferae is a small group of white oaks with a disjunct distribution in the Mediterranean region, which show a high morphological variability within and low differentiation between the species. Samples from the entire distribution range were subjected to a morphological and quantitative analysis. The results demonstrated that the established species, except for Q. canariensis, are linked by clinal variation, which in turn corresponds to geographical gradients. An evaluation of epidermal characters revealed them to be of restricted use for taxon delimitation in the group. Instead, leaf and epidermal morphology provide extensive information about the ecology and biogeographic history of oaks.

Place, publisher, year, edition, pages
Stockholm: Department of Botany, Stockholm University, 2011. 53 p.
Platanaceae, Platanus, Credneria, Quercus, Galliferae, leaf architecture, epidermal anatomy, comparative morphology, character variation, variability, sample size, diversity patterns, species concepts, ecology, biogeography, evolution, plant fossils
National Category
Research subject
Plant Ecology
urn:nbn:se:su:diva-62707 (URN)978-91-7447-369-8 (ISBN)
Public defence
2011-10-28, Föreläsningssalen, Botanicum, Lilla Frescativägen 5, Stockholm, 13:00 (English)
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 3. Manuscript. Paper 4. Manuscript. Available from: 2011-10-06 Created: 2011-09-27 Last updated: 2011-10-07Bibliographically approved

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Tschan, Georg F.
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