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New occurrence of the Ordovician eocrinoid cardiocystites: Palaeogeographical and palaeoecological implications

100%

Nardin E.

Acta Palaeontologica Polonica

2007

tom 52

nr 1

Flattened eocrinoids are very rare in the fossil record, notably because of their fragility. Recent investigations in the Anti−Atlas (Morocco) have provided one of the oldest known specimens of Cardiocystites from the Upper Ordovician (early–middle Sandbian). This discovery increases the number of eocrinoid genera known in Morocco. This new material is the fifth published specimen of the genus Cardiocystites. It is well preserved, thus allowing morphological details, such as the location of the anal pyramid and the plane of thecal flattening, to be observed. Palaeoecological reconstruction can be deduced or confirmed from these new details. The respiration of Cardiocystites now seems due to the combination of both epidermal gaseous exchange and cloacal pumping. Stem length and synostosial articulation indicate that the stem might have been used as a mooring line allowing the theca to float in the currents. The flattening of the Cardiocystites theca seems to be an adaptation to high energy hydrodynamic conditions and cold waters. Occurrences of Cardiocystites bohemicusin Morocco, in the early–middle Sandbian, and in Bohemia, in the early Katian, indicate that the genus probably originated in the west Gondwanan margin. Migration could explain the occurrence of Cardiocystites in this area and also in Avalonia in the late Sandbian. The global sea−level rise and the presence of cool water circulation from west Gondwana to Avalonia and Laurentia in the early Sandbian favour such a hypothesis.

A new pleurocystitid blastozoan from the Middle Devonian of the Eifel (Germany) and its phylogenetic importance

63%

Nardin E., Bohaty J.

Acta Palaeontologica Polonica

2013

tom 58

nr 3

Rich echinoderm fauna from the Middle Devonian of the Eifel (Rhenish Massif, Germany) has yielded specimens of the rare recumbent pleurocystitid rhombiferans. Regulaecystis testudineus sp. nov. extends the stratigraphic range of the pleurocystitids to the Eifelian (Middle Devonian). Specimens show a strongly inflated and ornamented theca, which is unusual for the European pleurocystitids. Phylogenetic analysis of all described pleurocystitid genera suggests a close relationship of Regulaecystis with the other Devonian genera. Results indicate that the degree of inflation and of ornamentation of the theca can be interpreted as convergences within the pleurocystitids due to environmental conditions (such as surface consistency, hydrodynamism). R. testudineus sp. nov. was living as a strict epibenthic vagile organism; lying on muddy soft to firm substrates in quiet to agitated shallow warm water environments.

Ograniczanie wyników

2 Acta Palaeontologica Polonica

2 Nardin E.

1 Bohaty J.

1 2013

1 2007

Wyniki wyszukiwania

New occurrence of the Ordovician eocrinoid cardiocystites: Palaeogeographical and palaeoecological implications

A new pleurocystitid blastozoan from the Middle Devonian of the Eifel (Germany) and its phylogenetic importance