New Species of Sirenitidae (Ammonoidea) from the Upper Carnian (Upper Triassic) of Eastern Yakutia

The study of the Upper Carnian material from Northern Kharaulakh and the upper reaches of the Adycha River basin allowed the species composition of the genera Yakutosirenites Tozer, 1994 and Orientosirenites Konstantinov, 2018 to be clarified. Based on the study of the shell shape, sculpture and sutural outline, the new species Yakutosirenites (Yakutosirenites) selivanovae sp. nov. and Orientosirenites insolitus sp. nov. are established and described. Based on the new data, the taxonomic composition of the late Carnian ammonoids of Eastern Yakutia is emended.