Development of Triassic and Jurassic siliceous sponges (Porifera) of the Northern and Southern Tethys with special consideration of the Triassic-Jurassic boundary.

Why are silicious sponges, the most primitive of the metazoan organisms, such a demanded subject of research recently? The purely scientific side lies in the aspect of how and with which strategies this animal group managed the breakthrough to the metazoan. On the contrary the practical, pharmaceutical-medical approach pursues the analysis and reproduction of those immune substances developed by the sponges. In this project the development of the silicious sponges was examined in the earth`s middle ages (Triassic and Jurassic) a period of over 90 million years. Thereby it has become evident that some large groups have newly developed the construction plans of long since extinct ancestors. The silicious sponges have revealed themselves as being very adaptable even after sudden changes in their environment. The fast transformation of the sea following abrupt tectonic activity (forces from the interior of the earth) has above all by means of the formation of a strong relief on the sea floor almost challenged the silicious sponges to conquer the new colonies. The offer of recesses on the rough surface of the relief were responsible for this. The silicious sponges of the earth middle ages appear in almost all the marine sedimentation in comparison with the research results till now. They are however missing in extremely shallow water sediments. The exception are those forms specialised on shallow water conditions which resist the tides. Such forms were identified from the Upper Trias of the Northern Calcareous Alps. Highly diverse and very rich sponge faunas have developed in marine areas with strong subsidence often even become rockforming. Contrary to opinions up to now the accumulations of silicious sponges are not restricted to the Upper Jurassic but are also represented in the Middle and Upper Triassic as well as in the Lower and Middle Jurassic, partly rockforming. The critical period, as accepted by many scientists, at the turn of Triassic/Jurassic has left no signs of becoming extinct in the silicious sponges. The so-called modern sponges (meaning those which have only developed in the recent geological past) have their roots in the Middle Triassic and belong to a group of silicious sponges which is 235 million years old.