| Summary: | mportant occurrences of Late Ordovician trilobites of the Taimyr Peninsula, Arctic Russia have been known for nearly 70 years through the work of Balashova (1959/1960) but have been neither well-understood nor revised. A study and revision of 56 Sandbian-Katian species from the Peninsula, including new and previous described material, gives a clear picture of their diversity and distributionfor the first time. The new material is well-preserved and constrained stratigraphically, while the original Balashova specimens are more incomplete and from isolated finds made during mapping in the 1950’s. A new monorakine subgenus and seven new species are recognized in press. Previously thought to be an endemic, Taimyraspisis shown to be an ityophorid close to Effnaspis, Yumenaspis, Ityophorus, and Frognaspis from Laurentia, Baltica and China. The monotypic Goldillaenoides is shown to be close to Failleana. The remopleuridid Pararemopleuridesis recognized for the first time in Taimyr, a genus with other possible occurrences including China, North-eastern Russia and Australia. The genus may be closely related to Robergiella Whittington. Two new species of Robergia prompted a re-investigation of the type species which revealed the presence of a narrow anterior border. This finding suggests that the concepts of Robergia and Pugilator Nikolaisen must be revised. A new species of Dionide is exceptional in having about 30 axial rings on the pygidium. It is found in dark sediments suggestive of a depletion of oxygen at the sea floor, and the high number of segments with accompanied limb pairs and gills may reflect an adaption to such an environment. Eight species of monorakines are described, but while Ceratevenkaspis dominates Monorakos is apparently absent from the Taimyr Peninsula. Seven species of isoteline asaphids are recognized, but with the exception of Homotelus only very fragmentary material is available. Our study clearly distinguishes between two biofacies in the Upper Ordovician. The first is a widespread ...
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