Monday 15 December 2014

A new species of Sponge from the Late Ordovician of Sweden, Germany and the Netherlands.

Reworked Late Ordovician Sponges have been collected from Miocene to Pleistocene across a wide area of northern Europe for over two centuries. These are associated with the course of the Baltic River System, which drained much of northern Europe for much of this time period. There are four main assemblages of such fossils recognised. The German-Dutch Sponge Assemblages are collected from the border area between Germany and the Netherlands, and were deposited on the Baltic River Delta in the Early Pleistocene. The material here is found in brown silicified limestones and chert (these are common materials in fossil assemblages rich in Sponges, as the silica spicules of the Sponge dissolve, then precipitate out with chemical changes in the buried sediments, replacing other materials), and is referred to as the Brown Sponge Assemblage. The deposits around Lausitz, to the southeast of Berlin, were deposited in the Middle Miocene, and comprise largely bluish-grey or black silicified material, known as the Lavendel Blaue Hornsteine. The Island of Sylt in northwestern Germany produces reworked material laid down in the Pliocene; this is dominated by material from the Lavendel Blaue Hornsteine, with a small amount of Brown Sponge Assemblage material. The Brown Sponge Assemblage is also found on the Swedish island of Gotland, in the Baltic, where a wide variety of Sponges have been recognised.

In a paper published in the journal Scripta Geologica in March 2014, Freek Rhebergen of Emmen in the Netherlands describes a new species of Anthaspidellid Demosponge from reworked Ordovician material from Gotland, the Dutch-German border region and the Island of Sylt.

The new species is named Brevaspidella dispersa, where ‘Brevaspidella’ means ‘little-short-shield’, in reference to the shape of the Sponge, short and cylindrical with a shield-like top, and ‘dispersa’ means ‘disperse’ a reference to the scattered osculi (exhalent openings) on its surface (Sponges are filter feeders that pump water in through tiny canal-openings all over their surface, and out through one or more larger openings known as ‘osculi’). The species is described from specimens from the Museum of Gotland, the Swedish Museum of Natural History, the Archiv für Geschiebekunde in the Geologisch-Paläontologisches Institut und Museum of the University of Hamburg and several private collections.

 Specimen of Brevaspidella dispersa from unknown locality on Gotland, Sweden. Flat to slightly concave upper surface with cluster of osculi and some converging lateral canals. Rhebergen (2014).

Brevaspidella dispersa is a small Sponge, typically less than 5 cm across, with the height and diameter about the same. The upper surface is slightly concave with scattered osculi, the base flat or slightly concave with a thickened dermal layer with concentric wrinkles.

Brevaspidella dispersa. (A, B) Specimen from beach near Västlanda, Gotland, Sweden. (A) View on upperside with dispersed osculi and radial surface canals. (B) Lateral view with concentrically wrinkled dermallayer in the lower part. (D, E) Specimen from unknown locality on Gotland, Sweden. (D) The top shows morethan 50 osculi, scattered over the flat surface. (E) Side view. Dermal layer poorly developed and restrictedto the base. Rhebergen (2014).

See also…

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