Fig 4
Hydraspongia polycephala gen. et sp. nov. Paratype (NRM Sp1864). Erratic from Sanda, Gotland (Sweden). Unpublished pictures by Liljevall drawn near the end of the nineteenth century; a. Successive growth stages in the lower part are indicated by conspicuous rims of dermal layer; b. Ramification of a lateral oscular head which was not subsequently overgrown. The upper part illustrates lateral view of oscular heads which developed at a latter growth stage.
Source publication
Compound orchocladine sponges are unusual in the Early Palaeozoic. In Europe, silicified material of Late Ordovician age has hitherto been referred to as Aulocopium aurantium Oswald, 1847 and the invalid Aulocopium compositum Conwentz, 1905. An examination of new material has resulted in the recognition of a new genus, Hydraspongia, with two new sp...
Similar publications
Observations of new material from the Silurian of Got land, including first studies with a scanning electron microscope, and a revision of the Iilerature indicate that Halysis HOEG, 1932, is a morphologically highly variable, palisade-like Cyano-phyceae and probably not a Codiaceae as suggested by several authors. The genus F/abellia SBUYSKY, 1973,...
Citations
... Rhebergen & van Kempen (2002) summarized a discussion between Lindstr€ om, Schmidt (1891) and Stolley (Stolley 1900(Stolley , 1929 on the age and lithostratigraphical origin of the sponges. Lindstr€ om probably intended to describe at least part of the sponge assemblage, because he had drawings made by Lilljeval, but did not complete the work (Rhebergen 2007). Schl€ uter (1884) reported on a remarkable sponge specimen, Astylospongia gothlandica, which has been figured by Rauff (1894) as an aberrant form of the Ordovician species Caryspongia diadema. ...
... Hydraspongia Rhebergen, 2007 includes compound sponges that usually form bulbous oscular heads and show conspicuously distinct growth stages. Postperissocoelia n. gen. ...
... Canals that achieved their maximum length induced the formation of a new cluster of excurrent canals, in order to drain the newly formed parts. This continuous growth apparently caused the development of new oscular heads, while the formation of stacked skeletal trabs series continued uninterrupted (Rhebergen 2007). ...
A diverse assemblage of silicified sponges, including orchocladines, rhizomorines, stromatoporoids, hexactinellids and non-lithistid demosponges, has been collected from scree accumulations in a restricted area along the western coast of the Island of Gotland, Sweden. The assemblage comprises 29 species in 20 genera, 18 species of which have not previously been recorded from Baltica, together with several taxa in open nomenclature. This chapter discusses this sponge assemblage in detail. It first gives a brief introduction on the geological settings, and the material, repository, methods and terminology used for the study of the assemblage. The chapter discusses the sponge assemblage under various families, classes and orders such as Hexactinellida, Orchocladina, Stromatoporoidea, Rhizomorina and Streptosolenida.
... During the 20 th Century, sponge research in Estonia and Russia decreased to a small number of papers in which sponge taxa were listed, such as those by Asatkin (1931Asatkin ( , 1949 and Rõõmusoks (1970), but has undergone a revival in Germany and the Netherlands since about 1980. An extensive and diverse sponge fauna has been revealed by a series of works on material from fluvial deposits in the Netherlands and adjacent parts of westernmost Germany (Van Kempen, 1978, 1990Von Hacht, 1985, 1994Reitner & Kohring, 1990;Von Hacht & Rhebergen, 1996, 1997Rhebergen, 1997Rhebergen, , 2007Rhebergen et al., 2001). ...
A new species of complex hexactinellid sponge, Haljalaspongia inaudita, is described from fluvially transported blocks found in northwestern Germany, near the Dutch border, but which probably originated from the eastern Baltic region. The heavily folded wall is composed of multiple spicule layers, including dermal and gastral layers of acanthohexactines, and a central layer of sub-parallel monaxons. The monaxial layer is lined on one side by a reticulate array of smooth monaxons. The sponge is difficult to assign to any known fossil or recent group, but shares some features with the dictyospongioid family Docodermatidae.
There are few sponges known from the end-Ordovician to early-Silurian strata all over the world, and no records of sponge fossils have been found yet in China during this interval. Here we report a unique sponge assemblage spanning the interval of the end-Ordovician mass extinction from the Kaochiapien Formation (Upper Ordovician-Lower Silurian) in South China. This assemblage contains a variety of well-preserved siliceous sponges, including both Burgess Shale-type and modern type taxa. It is clear that this assemblage developed in deep water, low energy ecosystem with less competitors and more vacant niches. Its explosion may be related to the euxinic and anoxic condition as well as the noticeable transgression during the end-Ordovician mass extinction. The excellent preservation of this assemblage is probably due to the rapid burial by mud turbidites. This unusual sponge assemblage provides a link between the Burgess Shale-type deep water sponges and the modern forms. It gives an excellent insight into the deep sea palaeoecology and the macroevolution of Phanerozoic sponges, and opens a new window to investigate the marine ecosystem before and after the end-Ordovician mass extinction. It also offers potential to search for exceptional fossil biota across the Ordovician-Silurian boundary interval in China.
