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A new genus of terebratulid brachiopod from the Siegenian of the Rheinisches Schiefergebirge

100%

Schemm-Gregory M., Jansen U.

Acta Palaeontologica Polonica

2007

tom 52

nr 2

A new genus Crassirensselaeria (Terebratulida, Rhenorensselaeriidae) from the Siegenian (middle Lower Devonian) of the Rheinisches Schiefergebirge (= Rhenish Slate Mountains, Germany) with the type−species Crassirensselaeria crassicosta is erected. Exceptionally well−preserved material of this taxon has recently been obtained from a temporary outcrop at an ICE (= InterCityExpress) railway construction site close to Aegidienberg near Bonn. As representatives of Crassirensselaeria have hitherto been included into the terebratulid genus Rhenorensselaeria; they are compared with the two Lower Devonian species of that genus from the Rheinisches Schiefergebirge: Rhenorensselaeria strigiceps and Rh. demerathia. Crassirensselaeria is chiefly distinguished from these by more globular shells, the presence of very strong plications, long and strong dental plates, different ventral muscle field, and thickened cardinalia. Representatives of the new genus are excellent index fossils for the Siegenian of the Rheinisches Schiefergebirge, even in deposits of restricted−marine and probably brackish environments. New material of articulated specimens in life position shows that both rhenorensselaeriid genera lived in clusters with the longitudinal axes of the shells oriented steep or perpendicular to the seafloor. The new genus is abundant in the Rheinisches Schiefergebirge (Germany) and the northern Ardennes (Belgium), it also occurs in the Hrubý Jeseník Mountains (Czech Republic). Its occurrence in Cornwall (Great Britain), however, is still questionable.

A monospecific assemblage of terebratulide brachiopods in the Upper Cretaceous seep deposits of Omagari, Hokkaido, Japan

80%

Kaim A., Bitner M. A., Jenkins R. G., Hikida Y.

Acta Palaeontologica Polonica

2010

tom 55

nr 1

The Campanian (Upper Cretaceous) seep carbonate at Omagari (Hokkaido, Japan) yields a monospecific association of the terebratulide brachiopod Eucalathis methanophila Bitner sp. nov. The association is the only occurrence of brachiopods known from the post−Early Cretaceous history of chemosynthesis−based communities. Unlike many earlier rhynchonellide−dominated hydrocarbon seep associations—which disappeared in Aptian times—this association is composed of chlidonophorid terebratulides. It is hypothesised here that large rhynchonellide brachiopods have been outcompeted from chemosynthesis−based associations by large chemosymbiotic bivalves (especially lucinids) and that this seep association containing numerous terebratulide brachiopods originated as a result of immigration from the background fauna settling in a seep that lacked numerous large bivalves but offered some hard substrates for brachiopod attachment. Some living chlidonophorids are known to settle around seep/vent localities or more generally in deep−water hard−substrate settings. We review occurrences of brachiopods in chemosynthesis−based associations and show that brachiopods immigrated repeatedly to seep/vent environments. Eucalathis methanophila Bitner sp. nov. represents the oldest and single Mesozoic record of the genus. The new species is similar in ornamentation to three living species, Indo−Pacific E. murrayi, eastern Atlantic E. tuberata, and Caribbean E. cubensis but differs in having a higher beak and wider loop. Additionally the studied species is nearly twice as large as E. tuberata.

Ograniczanie wyników

2 Acta Palaeontologica Polonica

1 Bitner M. A.

1 Hikida Y.

1 Jansen U.

1 Jenkins R. G.

1 Kaim A.

1 Schemm-Gregory M.

1 2010

1 2007

Wyniki wyszukiwania

A new genus of terebratulid brachiopod from the Siegenian of the Rheinisches Schiefergebirge

A monospecific assemblage of terebratulide brachiopods in the Upper Cretaceous seep deposits of Omagari, Hokkaido, Japan