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Fezouata formation
The Upper and Lower Fezouata formations of Morocco are Burgess shale-type deposits dating to the Lower Ordovician, filling an important preservational window between the common Cambrian lagerstätten and the Late Ordovician Soom shale. In the fossilized fauna were numerous organisms previously thought to have died out after the mid-Cambrian.〔((BBC News) Victoria Gill, "Fossil find resolves ancient extinction mystery" ): accessed 13 May 2010〕
== Biota ==
Over 1500 non-mineralized specimens, representing 50 distinct taxa that have a composition similar to earlier Burgess Shale type biotas, have been recovered from the formations in addition to a less abundant shelly fauna.〔 The make-up of the community varies significantly through the stratigraphic sequence, with both abundances and faunal composition changing as time progresses.〔 Small (1–3 mm wide) burrows are present in the sediment, but major burrowing is absent; this may suggest a paucity of oxygen in the water or sediment.〔 Particularly notable is the presence of bryozoa and graptolites,〔 forms that are absent in the Cambrian period. Diverse echinoderms indicate a normal range of salinity, and the overall shelly assemblage is not significantly different from the normal shelly fauna expected in open Ordovician waters.〔 The non-mineralized cohort contains a range of forms familiar from the Burgess Shale: Demosponges, lobopods, barnacles, annelids, anomalocaridids, possible halkieriids, marrellomorphs, paleoscolecid worms, naraoiids, skaniids as well as the expected ''problematica''. Other Ordovician oddballs are also present, including mitrates, machaeridia, cheloniellids and horseshoe crabs in abundance.〔
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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