Wyniki wyszukiwania

1

Artykuł dostępny w postaci pełnego tekstu - kliknij by otworzyć plik

Late Frasnian Atrypida [Brachiopoda] from the South Urals, South Timan and Kuznetsk Basin [Russia]

100%

Rzhonsnitskaya M. A., Markovskii B. P., Yudina Y. A., Sokiran E. V.

Acta Palaeontologica Polonica

|

1998

|

tom 43

|

nr 2

Late Frasnian Atrypida (Brachiopoda) from the South Urals, South Timan and Kuznetsk Basin in Russia (east Laurussian and south Siberian shelf domains in Devonian time) reveal significant generic and specific diversity in the broadly defined Frasnian-Famennian (F-F) bio-crisis time. Eighteen species of atrypid brachiopods have been recorded, representing 4 subfamilies and 10 genera. The new genus Gibberosatrypa Markovskii & Rzhonsnitskaya, and the new subgenus Spinatrypa (Plicspinatrypa) Rzhonsnitskaya are proposed. Four new species Spinatrypina (Spinatrypina) sosnovkiensis Yudina, Spinatrypa (Plicspinatrypa) rossica Rzhonsnitskaya, Iowatrypa nalivkini Rzhonsnitskaya & Sokiran, and Cartnatina(?) biohermica Yudina are described. The representatives of the Variatrypinae (including especially common Desquamatia (Desquamatia) alticoliformis), Spinatrypinae (Spinatrypina) and Atypinae (Pseudoatrypa, ?Costatrypa) are widely distributed in the studied regions. The Pseudogruenewaldtiinae are represented by Iowatrypa and Pseudogruenewaldtia, of which the first is distributed worldwide, whereas the only undoubted species of the second is restricted to South Timan, and probably represents a localized latest Frasnian descendant of Iowatrypa. The decline phase of atrypid development was controlled by a variety of environmental factors tied to the global Kellwasser events, although it was not directly triggered by anoxic conditions. The investigated atrypid brachiopods, which were all confined to lower latitudes, disappeared during the F-F mass extinction, independently of their environmental and biogeographic settings.

2

The Late Frasnian rhynchonellid genus Pammegetherhynchus [Brachiopoda] in Poland, and its relevance to the Kellwasser Crisis

100%

Sartenaer P., Racki G., Szulczewski M.

Acta Palaeontologica Polonica

|

1998

|

tom 43

|

nr 2

The rhynchonellid species, Pammegetherhynchus kowalaensis sp. n., occurs in the late Frasnian (Early to Late Palmatolepis rhenana, and possibly early Palmatolepis linguiformis conodont zones) marly-bituminous succession at Kowala (various outcrops) in the Gałęzice Syncline, south of Kielce in the Holy Cross Mountains, Poland. The only other known species of this genus is the type species, Pammegetherhynchus merodae Sartenaer, 1977, from the late Frasnian (somewhere in the Early and Late Palmatolepis rhenana Zones) of the French Fagne (dark shales of 'Matagne' aspect), and, probably, of the Eifel ('Büdesheimer Goniatitenschiefer'). P. kowalaensis sp. n. occurred in level-bottom pioneer assemblages, thriving in reef downslope, mostly poorly-oxygenated habitats of the Kellwasser interval. The species finally disappeared near the Frasnian-Famennian boundary. The genus Pammegetherhynchus seems to be particularly suited to stressed deep-water shelf environments in the European part of the Laurussian shelf, widely distributed in this crisis time.

3

Late Frasnian Athyridida [Brachiopoda] from Poland and the Late Devonian biotic turnover

88%

Grunt T. A., Racki G.

Acta Palaeontologica Polonica

|

1998

|

tom 43

|

nr 2

Late Frasnian representatives of the order Athyridida from the Holy Cross Mountains, Poland, support the idea that the Laurussian basins were the places of origin and radiation of the subfamilies Athyridinae and Meristinae during the middle and early late Paleozoic. At least three new species have been identified from two localities (Łgawa Hill and Kowala) in the Gałęzice Syncline. Of these, one was probaby endemic (Merista rhenanensis sp. n.; maybe also ?Zonathyris sp. A), and two (Athyris postconcentrica sp. n. and Pachyplaxoides postgyralea gen. et sp. n.) were more widely distributed in this part of the Laurussian shelf, being known also from the East European Platform and Rheinisches Schiefergebirge, respectively. This confirms an intermediate biogeographic position of the Holy Cross Mountains area, belonging to an important centre of brachiopod origin and diversification. In contrast to other articulate brachiopods, athyridids reveal a higher rate of diversification, especially at the species (and partly also generic) level, during the global Kellwasser Crisis.

4

The Frasnian-Famennian brachiopod extinction events: A preliminary review

88%

Racki G.

Acta Palaeontologica Polonica

|

1998

|

tom 43

|

nr 2

Preliminary review of taxonomy of the brachiopod order Atrypida and its stratigraphic distribution in the late Frasnian Kellwasser Crisis of several regions of Laurussia, western Siberia and South China point to their moderate diversity and stepdown but irregular extinction pattern. The distinctive character of the late Frasnian atrypid fauna is emphasised by several relict genera, marked by recurrent and possibly aberrant characters (mainly in ornamentation types), tendency to size reduction and homeomorphy in some taxa. The transgressive/hypoxic Lower Kellwasser Event and preceding eustatic changes during the Palmatolepis rhenana Zone had only a regional destructive effect, and were linked rather to an enhanced dispersal of the last generic set of atrypids. The Variatrypinae, Spinatrypinae and Iowatrypa-group seem to belong to the latest surviving atrypids. The final demise of the remaining atrypids (and some other articulate brachiopods, e.g., gypidulids) coincided with the transgressive/hypoxic Upper Kellwasser Event, followed by catastrophic eustatic fall during the late Palmatolepis linguiformis Zone (F-F Event). This was probably exacerbated by accelerated submarine volcano-hydrothermal activity, and consequent progressive regional eutrophication, and climatic destabilization. The level-bottom rhynchonellid-inarticulate biofacies crosses the fatal F-F boundary horizon without major changes. No reliable data exist for the presence of atrypids in the Famennian survival and recovery biota, even for the smooth lissatrypid Peratos. Sustained competition from radiating and diversifying productid-cyrtospirifrid-athyrid faunas may have provide an additional biotic factor in the collapse of the Frasnian shelly benthos at the time of sfress, as well as in a post-extinction offshore repopulation from inner shelf habitats.

Ograniczanie wyników

4 Acta Palaeontologica Polonica

3 Racki G.

1 Grunt T. A.

1 Markovskii B. P.

1 Rzhonsnitskaya M. A.

1 Sartenaer P.

1 Sokiran E. V.

1 Szulczewski M.

1 Yudina Y. A.

4 1998

Late Frasnian Atrypida [Brachiopoda] from the South Urals, South Timan and Kuznetsk Basin [Russia]

The Late Frasnian rhynchonellid genus Pammegetherhynchus [Brachiopoda] in Poland, and its relevance to the Kellwasser Crisis

Late Frasnian Athyridida [Brachiopoda] from Poland and the Late Devonian biotic turnover

The Frasnian-Famennian brachiopod extinction events: A preliminary review