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MONOGRAPHIC DESCRIPTION OF THE MIDDLE CALLOVIAN GENUS PROTOLONGAEVICERAS

V. G. Knyazev 1, S. V. Meledina 2, A. S. Alifirov 2

1 Diamond and Precious Metal Geology Institute, Siberian Branch, Russian Academy of Sciences, Yakutsk, Russia; 2 А. А. Тrofimuk Institute of Petroleum Geology and Geophysics SB RAS, Novosibirsk, Russia

A new Middle Callovian ammonite genus of Protolongaeviceras is described, which is placed in one of the phyletic branches of the Cadoceratinae (Cardioceratidae) between the Lower Callovian genus of Cadoceras and Upper Callovian Longaeviceras by morphological features of the shell in ontogenesis. The genus is established in Siberia (Bolshoi Begichev Island), as well as in European Russia (the Sysola River), Orenburg Region (the Sukhaya Peschanka River), from where it was previously described as part of the Cadoceras genus. A type species of the new genus is S. (Streptocadoceras) arcticoides Kiselev et Meledina, identified with one of the two previously recognized species morphs and transformed into Protolongaeviceras. A second morph is regarded as one of the species of the Rondiceras genus.

Keywords: Ammonites, Cardioceratidae, Callovian, north of Siberia.

DOI 10.20403/2078-0575-2019-2-16-23