Lower Ordovician (Chewtonian to Castlemainian) Radiolarians of Spitsbergen

Abstract

Synopsis Diverse and well‐preserved radiolarian faunas are found in a biostratigraphically precisely dated succession in the Lower Ordovician of Spitsbergen. The faunas are from the Didymograptellus bifidus and Isograptus victoriae lunatus graptolite Biozones. They document the transition from the Upper Cambrian to Lower Ordovician spicular dominated to spumellarian dominated Middle and Upper Ordovician faunas and yield important data for a more precise biostratigraphical use of Ordovician radiolarians. The faunas are dominated by early spumellarians of the Antygoporidae and Aspiculumidae, while the Protoentactiniidae and Palaeospiculumidae are rare elements surviving from the earlier Palaeozoic. Members of the Echidninidae have not been found. The precise definition of a number of important structural characters of early Palaeozoic radiolarians is discussed. The early spumellarians of the family Antygoporidae possess a distinct microsphere formed from a number of curved bars and provided on the outside with a variable number of outer spines, representing the oldest known type of microsphere. The development of the spherical skeletons of spumellarian and entactinarian radiolarians is developed in a number of different ways that are important for phylogen‐etic considerations. The following taxa are new: Svalbardospiculum gen. nov., Svalbardospiculum arenigium sp. nov., Protoentactinia bifurcata sp. nov., Sphaeroentactiniidae fam. nov.,Sphaeroentac‐tinia gen. nov., S. hexaspinosa sp. nov., S. bispinosa sp. nov., S. integrata sp. nov., Nyfrieslandia gen. nov., N. sphaeroidea sp. nov., N. complicata sp. nov., Parechidnina densa sp. nov., Antygoporidae fam. nov., Antygopora bella sp. nov., A. compacta sp. nov., A. microspina sp. nov., A. labyrinthina sp. nov., Labyrinthia gen. nov., Labyrinthia inexpectata sp. nov.