New Find of Inoceramus-Like Bivalves of the Genus Atomodesma in the Southern Verkhoyansk Region, and Invasions of Extra-Boreal Mollusks into Northeastern Asia during the Permian

Inoceramus-like bivalves of the bipolar species Atomodesma variabile Wanner were first found and precisely associated with the Upper Permian (Wuchiapingian) section in the Southern Verkhoyansk Region. The appearance of this exotic taxon in Boreal basins is associated with the short-term invasion of several Tethyan taxa into high-Boreal basins due to transgression. It is concluded that the similarity of the Permian marine biota from the Boreal and Notal (Gondwanan) paleobiogeographic superrealms is largely due to periodic invasions of notal elements into Boreal basins. The species A. variabile is described and illustrated.