New Data on the Systematic Composition of Early Triassic Ammonoids from the Shimanskyites shimanskyi Zone of the Kamenushka River Basin, South Primorye, and Their Phylogenetic and Stratigraphic Significance

The systematic composition of ammonoids and conodonts from the Shimanskyites shimanskyi Zone of the lower (Smithian) Substage of the Olenekian Stage in South Primorye is revised and supplemented. This is based on the material from the Lower Triassic sections of the Kamenushka River basin, specifically from the Kamenushka-2 and Perevalny sections. Based on the correlation of these sections, it is proposed that the Scythogondolella milleri conodont Zone in this region corresponds to two ammonoid zones (Anasibirites nevolini and Shimanskyites shimanskyi) of the Smithian Substage in South Primorye. The new species of the genera Owenites (O. golozubovi sp. nov.) and Preflorianites (P. lelikovi sp. nov.) are described herein. The clarification and emendation of the diagnosis of the genus Submeekoceras, and its comparison with other genera of the family Arctoceratidae, permit a reconsideration of the generic affiliation of the majority of species currently assigned to the genus Arctoceras. The obtained results make it possible to reconstruct the phylogeny of some genera in the families Lanceolitidae and Ussuritidae (order Prolecanitida Miller et Furnish, 1954), as well as Proptychitidae and Arctoceratidae (order Ceratitida Hyatt, 1884). The presence of diverse and abundant ostracod assemblages in the Shimanskyites shimanskyi Zone, and a relatively diverse ammonoid community in the bottom waters of the late Smithian marine basin of South Primorye, suggest that anoxia was absent, although it is assumed to have been present in marine basins in other regions of the world at that time.