Read e-book online Fossils and Strata, A New Silurian (Llandovery, Telychian) PDF

By Freek Rhebergen, Joseph Botting

ISBN-10: 1118906624

ISBN-13: 9781118906620

A newly found, different sponge fauna of early Silurian age, is defined from Gotland, Sweden. this can be the 1st Silurian sponge assemblage recognized from Baltica, and the single assorted Llandoverian assemblage identified world wide. The fauna contains 20 genera and 29 species, of which 3 genera and 6 species are new. Eighteen species are new to Baltica. The fauna indicates powerful similarities to later Silurian assemblages in Arctic Canada, yet one endemic species contains ca. 50% of the fauna. The fauna exhibits that lithistid sponges recovered good from the overdue Ordovician extinction in a few components, and have become greatly unfold within the early Silurian. by contrast, non-lithistid sponges like, equivalent to hexactinellids, seem to have developed speedily in the course of the past due Ordovician - early Silurian period, and a few smooth teams most likely originated in inshore habitats.

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Extra resources for Fossils and Strata, A New Silurian (Llandovery, Telychian) Sponge Assemblage from Gotland, Sweden

Sample text

D, Nanocyclopia sp. Loeblich & Wicander, 1976. 01 mm (photo: Dr. Zwier Smeenk, the Netherlands). Fig. 5. Direction of ice movements in northern Gotland during the Weichselian glaciation (after Svantesson 1976, fig. 43). The limited area at the western coast, with ice direction perpendicular to the coast, coincides with the area of concentration of Telychian sponges. Fig. 6. Terminology of sponge spicules. A, amphiarborescent or I-shaped dendroclone. B, triclonid or Y-shaped dendroclone. C, polyclonid dendroclone.

About 40 specimens could be identified as A. gislei, an obconical to cylindrical, annulate sponge. Annulations and depressions vary in distinctness, but usually the relation between them is rather consistent. Annulations are smooth, with near-regular separation of around 15 mm between successive crests. Depressions are approximately 2 mm deep, but annulations are less distinct due to surface abrasion. Available specimens vary from small, slender, complete obconical specimens with a maximum diameter of 9 mm (Pl.

Citing de Freitas (1989, p. 3 mm thick dermal surface’. This observation may be important in relation to the felted surfaces seen in numerous sponge bodies of nearly all taxa described in the present study. Archaeoscyphia aulocopiformis de Freitas, 1989 Plate 4, figures 5–9 1989 Archaeoscyphia aulocopiformis n. sp. de Freitas, pp. 1875–1876, figs 6N, 7E. Material. – NRM Sp10082, NRM Sp10143, NRM Sp10144 and NRM Sp10164; all collected from Blåhäll/Tofta. Other material. – NRM Sp10211, NRM Sp10212, NRM Sp10213, NRM Sp10260 and NRM Sp10261; all from Blåhäll/Tofta.

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Fossils and Strata, A New Silurian (Llandovery, Telychian) Sponge Assemblage from Gotland, Sweden by Freek Rhebergen, Joseph Botting

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