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摘要
A newly collected trilobite fauna from the lowermost part of the Alum Shale Formation at Olea, Bornholm, Denmark, demonstrates the presence of a thin but richly fossiliferous Middle Cambrian Acidusus atavus Zone (Paradoxides paradoxissimus Superzone). The lower part of the zone (the Tomagnostus fissus-Ptychagnostus atavus Zone of older Scandinavian literature) is represented by a discontinuous limestone bed, up to 20cm thick, whereas the upper part (Hypagnostus parvifrons Zone of older literature) is represented by shale, less than 80cm thick, containing lenses of bituminous limestone. A total of 39 agnostid and 21 polymerid species are recorded from the A. atavus Zone (including 12 taxa treated under open nomenclature). One additional polymerid species collected from an ice-rafted boulder derived from the Bornholm area is also treated. The fauna is described and illustrated, with designation and reillustration of relevant lectotypes. The abundance of polymerid trilobites in comparison with nearby Scania, southern Sweden, where 25 agnostid and nine polymerid species have been reported from equivalent strata, is indicative of a less dysoxic environment in the Bornholm area, which was probably uplifted. The trilobite fauna resembles the coeval assemblages described from England, Wales, eastern Newfoundland and eastern Siberia, sharing several species not reported previously from Baltica, including Anopolenus sp., Agraulos longicephalus, Bailiella ornata, Clarella impar, Solenopleura? applanata, Acadagnostus aff. bulkurensis and Phalagnostus ovalis. A few faunal elements originally described from Bohemia and Australia are also present, viz. Hydrocephalus aff. carens, Phalagnostus nudus, Skryjagnostus pompeckji, Hypagnostus aff. clipeus, Euagnostus aff. interstrictus and Euagnostus? aff. glandifer.
- 出版日期2014-1-2
- 单位中国地质博物馆
