Abstract:
Tsvetkovitids and nathorstitids (Ammonoidea) from the entire Boreal realm are revised on the basis of most recent data on their morphology, systematics, and evolution. The elucidated stratigraphic ranges of both taxonomic groups are used to establish the correlated ammonoid zonation in Ladinian deposits of northeastern Asia, Svalbard, Arctic Canada, Franz JosefLand and British Columbia. Ammonoid faunas from British Colum bia consist of mixed Boreal and Tethyan taxa useful for correlation of Ladinian biostratigraphy in Boreal regions with the standard Alpine scale.
