Revision of the Age and Species Composition of Some Early Cretaceous Belemnites of Northern East Siberia (Nordvik Peninsula)

An early Ryazanian age for the “Late Valanginian” records of the belemnites Arctoteuthis angusta Efremenko and Boreioteuthis mirifica Efremenko, as well as rostra from the Nordvik Peninsula, previously assigned to the species Lagonibelus necopinus (Gustomesov) is substantiated based on Sr-isotope stratigraphy (SIS) and data from co-occurring bivalve mollusks of the genus Buchia. The lithological features of the host sedimentary rocks and, to some extent, taphonomic observations are also considered. Based on the reidentification of the rostra of L. necopinus, a new belemnite species L. pseudonecopinus Efremenko, sp. nov. (Cylindroteuthididae) is established.