| Graptolite nature of the Ordovician microfossil Xenotheka Piotr Mierzejewski |
| Acta Palaeontologica Polonica 2000, 45, 1, 71-84 |
| [Text] Abstract - Light microscopic, SEM and TEM investigations show that the periderm of the problematic Ordovician microfossil Xenotheka klinostoma Eisenack, 1937 is built of five layers: inner lining, endocortex, fusellum, ectocortex and outer lining. The outer lining is made of previously unknown material named here verrucose fabric. The outer lining was presumably an adaptation which aided survival through periods of unfavourable conditions. The general morphology of the test as well as of the fusellar structure of the wall indicate that Xenotheka is an aberrant camaroid graptolite. This finding thus extend the upper stratigraphic limit of the Order Camaroidea from the Early Arenig to Llandeilo. |
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| Graptolite Net | Graptolites and Graptoliters | Evolution of Graptolites | Cephalodiscida | Rhabdopleurida |
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| ______________________________________________________________________________ Compiled by Countess Maja Anna Korwin-Kossakowska 2002-2004 |
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| Xenotheka klinostoma Eisenack, 1937. TEM micrograph - Transverse section through the autothecal periderm. Abreviations: e, ectocortex; en, endocortex; i, inner lining; l, electron dense line; o, outer lining; v, verruca; ve, verruca vesicle; vf, interfibrillar vesicle. |
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| Xenotheka klinostoma is a distinctive sessile organic microfossil known from the Lower Ordovician beds of the Isle of Öland (Sweden) and from Ordovician glacial boulders. The species also occurs in the Ordovician of Estonia. J. Jansonius (1964) considered it to be a chitinozoan incertae sedis. Some authors interpreted Xenotheka as a member of Foraminifera. |