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Anke Brückner:

Taxonomy and paleoecology of lyssacinosan Hexactinellida from the Upper Cretaceous (Coniacian) of Bornholm, Denmark, in comparison with other Postpaleozoic representatives

2006. 103 pages, 25 figures, 1 table, 19 plates, 30x21cm, 520 g
Language: English

(Abhandlungen der Senckenbergischen Naturforschenden Gesellschaft, Band 564)

ISBN 978-3-510-61382-3, paperback, price: 19.80 €

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Contents

Synopsis
Contents
Synopsis
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Sponges occur in three large groups. The Hexactinellida, the Demospongiae and the Calcarea. The Hexactinellida are divided into the Hexactinosa, the Lychniscosa and the Lyssacinosa. The first two have a rigid skeleton, whereas the latter are sponges with loose spicules sitting in their soft parts. They are widely spread over the oceans today. It is difficult to study Lyssacinosa, due to their preferred deep sea habitat, and therefore little is known about their way of living.

To sutdy fossil Lyssacinosa is even more challenging. Not only are these sponges rare, but the microscleres (the spicules, which are used as tools for identification) are almost always lost in the fossil record. So other tools must be used to describe them. One way is to use the megascleres, spicules which hold the sponge body in shape. This method is used within this work to describe a lyssacinosan sponge fauna from the Upper Cretaceous of Bornholm, Denmark. Three new genera and eighteen new species are described. They are compared with other, Paleozoic Lyssacinosa and with living ones with regard to diversity, geographic and bathymetric distribution, and features such as shape, anchoring modi and wall thicknesses, to discuss adaptation to sedimentation rates, different substrates and water energy.

The sedimentology and the faunal composition of the Arnager Limestone (ca. 88 Ma), aside from the sponges, is discussed. Together with the sponge fauna a three-dimensional picture can be drawn to show the conditions and the nature of the habitat the Lyssacinosa lived in.

Contents
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Porifera 2

Problems 2
Recent Porifera 3
Phylum Porifera Grant, 1836 3
Problems of the phylogeny and monophyly/paraphyly of the
Porifera 3
Introduction to siliceous sponges 8
Distribution of recent siliceous sponges 10
Controlling factors of the occurrence of siliceous
sponges 11
Fossil Porifera 12
Sponge history since the Precambrian 12
Fossilisation potential of Mesozoic siliceous sponges 15
Occurrence of Hexactinellida verified by isolated micro-
and megascleres from the Mesozoic 15
Occurrence of bodily preserved hexactinellid sponges during
the Late Cretaceous in NW Europe 16
Paleoclimate and sponge occurrences in Northern Europe
during the Creatceous 16

Geology and paleontology of Bornholm, Denmark 18
Geological setting 18
Arnager Limestone Formation 19
Faunal and facial composition of the Arnager Limestone 20
The sponge fauna of the Arnager Limestone 22

Material and methods 23

Systematics 24
Further classification and characteristics of the sponge
fauna 40
Comparison of fossil and recent lyssacinosan sponge faunas 45
Diversity, geography and environmental influences of the
Arnager and recent Lyssacinosa 45
Comparison of Triassic, Cretaceous and Tertiary
lyssacinosan faunas 46
Comparison of appearance, skeletal structure and habitat
of Cretatceous, Tertiary and recent Regadrella-species 48

Conclusions 50
Zusammenfassung 51
Acknowledgement 52

References 53
Table of characteristics 64
Plates 66