The Kinzers Formation (Pennsylvania, USA): the most diverse assemblage of Cambrian Stage 4 radiodonts

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AbstractRadiodonta, apex Cambrian predators such asAnomalocarishave been known from the Kinzers Formation (Cambrian Series 2, Stage 4 – Pennsylvania, USA) for nearly 100 years. Work over the last ten years, mainly on radiodont material from the Chengjiang (Cambrian Series 2, Stage 3 – Yunnan, China) and Burgess Shale (Miaolingian, Wuliuan – British Columbia, Canada), has greatly improved our knowledge of the diversity and disparity of radiodonts and their frontal appendages, including the description of new species, genera and families. Previous work identified two species of radiodonts from the Kinzers Formation:Anomalocaris pennsylvanicaResser, 1929 andAnomalocaris? cf.pennsylvanicabased on isolated frontal appendage material (Briggs, 1979). A restudy of Kinzers Formation material shows that only some of the specimens can be confirmed asAnomalocaris pennsylvanica, and a number of specimens previously attributed toAnomalocarisin fact belong to other more recently discovered radiodont generaAmplectobeluaandTamisiocaris. This reinterpretation makes the Kinzers Formation the most diverse Cambrian Stage 4 Burgess Shale Type Lagerstätten in terms of number of radiodont species. This assemblage includes the youngest knownTamisiocarisand the first from outside Greenland, the onlyAmplectobeluafrom Stage 4 and the oldest from Laurentia, two specimens tentatively assigned to the recently described Chengjiang genusLaminacaris, and the endemicAnomalocaris pennsylvanica. The identification of these new radiodont taxa increases the total known diversity of the Kinzers Formation to more than ten species, and so it should now be considered a Tier 2 Lagerstätte.