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Late Frasnian Atrypida (Brachiopoda) from the Holy Cross Mountains, Poland, include 15 taxa and were widely distributed in foreslope habitats of the declining Dyminy Reef complex. The Palmatolepis semichatovae transgression, followed by the transgressive/hypoxic Lower Kellwasser (KW) Event during the Palmatolepis rhenana Zone did not have catastrophic effects for atrypid faunas, but were rather associated with the appearance of a new species group comprising Iowatrypa, Waiotrypa, Costatrypa, Spinatrypina, Desquamatia and Radiatrypa. Stepdown demise of the biota started during the inter-KW regression, and culminated as a result of increasing stress during the Upper Kellwasser Event in the late Palmatolepis linguiformis Zone, mainly due to catastrophic sea level changes and anoxia, possibly linked to oceanic thermal changes (cooling) and nutrification pulses. The extinction pattern was diachronous and facies-controlled in this area, and the last atrypid survivors reached the Frasnian-Famennian (F-F) boundary. Increasing expansion from the adjacent deeper-water environment of the more resistant assemblages, with productids, cyrtospiriferids, athyridids and schizophoriids, occurred in the final crisis interval. This brachiopod fauna profusion characterized the earliest Famennian survival and early recovery phases of the mass extinction in this part of the Laurussian shelf, as well as the continuity of the deeper-water rhynchonellid-inarticulate biofacies across the F-F boundary. Spinatrypina (Exatrypa) relicta sp. n. is proposed as new.
The radiolarian species Astroentactinia paronae, A. stellata, Trilonche echinata, T. grandis, T. nigra, Haplentactinia inaudita, and H. rhinophyuosa are common in late Frasnian to early Famennian rhythmic, calcareous−marly sequence of the southern Holy Cross Mts., Poland. They are known also from coeval abundant siliceous biota assemblages from the carbonate shelf of East European Platform including more than 150 taxa of radiolarians. However, in ecological terms, the moderately diverse Polish microfaunas (34 species of 12 genera) are more similar to these from Kolyma and Alaska, also marked by abundance of sphaerical entactiniids and near−absence of bilateral−symmetric Ceratoikiscidae and Palaeoscenididae. A succession of two distinctive siliceous sponges associations is established in the incipiently submerged Holy Cross carbonate platform: from an ephemeral, diverse, mostly rigid−skeletal lithistid−hexactinosan foreslope assemblage (initial phase of the late Frasnian Kellwasser Crisis), to long−lasting, basinal loose−skeletal hexactinellid−demosponge faunas (appearing abundantly just prior the Frasnian–Famennian boundary in the late Palmatolepis linguiformis Zone). Such regional blooms of marine siliceous biotas, parallel to temporary retreat of calcareous biota, are demonstrated worldwide for the Kellwasser Crisis. These suggest probable causal links with cooling pulses and at least regional, volcanically induced eutrophication.
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