Graptolites (Graptolithina) from the Dapingian Arienigraptus hastatus Biozone of Newfoundland

Abstract A graptolite sample from the Cow Head Group of western Newfoundland provided a much more complete insight into the faunal diversity of the Arienigraptus hastatus Biozone of the mid-Dapingian (Middle Ordovician). The number of species found in the investigated interval increases from five, as previously reported, to at least 22 species from new chemically isolated material. The presence of similar faunal elements in the Tøyen Shale Formation of Norway indicates a wider distribution of some of these newly recognized taxa and helps to correlate the Arienigraptus hastatus Biozone with a level in the Isograptus mobergi & Maeandrograptus schmalenseei Biozone of Scandinavia. Sigmagraptus sombrero sp. nov. and Sigmagraptus introversus sp. nov. are described as new species. Six sigmagraptine species are described in open nomenclature due to the fragmentary preservation. The fauna indicates a previously unknown diversity of the family Sigmagraptidae in the Dapingian.