Dicoelitid belemnites from the Caucasian margin of the Tethys: new data from the Upper Bajocian-Lower Bathonian of Karachay-Cherkessia, southwest Russia

Abstract

are still under investigation, with many scientific surprises for both the Boreal and Tethyan domains (e.g. Dzyuba et al. 2015, 2016, 2019; Weis et al. 2015b, 2017; Challinor & Hudson 2017; Dzyuba & de Lagausie 2018; Ippolitov 2018a, b, c; Ippolitov & Desai 2019). Among the early representatives of the suborder Belemnopseina Jeletzky, 1965, belemnites possessing long ventral and short dorsal alveolar grooves on the rostrum, i.e. members of the Tethyan family Dicoelitidae Sachs & Nalnjaeva, 1967, are the least studied group, especially in the MediterraneanCaucasian Tethys (western Tethys). This family includes only two genera, elongate and hastate Dicoelites Boehm, 1906 and more robust, cylindriconical to conical Cono­ dicoelites Stevens, 1965a. Apart from ?Dicoelites sp. A described from the Lower Bajocian of Morocco (Weis et al. 2017, p. 221, fig. 7a, b) and “Belemnites” jacquoti Terquem & Jourdy (1869, p. 41, pl. 1, figs 6–9) from the Upper Bajocian of northeastern France, which is presumably a dicoelitid (Weis et al. 2017), all known western Tethyan representatives of the family Dicoelitidae belong to the genus Conodicoelites (see below). The only dicoelitid belemnite described and illustrated from the Northern Caucasus is Dicoelites exiguus Krimholz (1953, p. 54, pl. 4, fig. 5). It comes from the “Upper Bajocian or Lower Bathonian” (Krimholz 1953, p. 56) of the former southern part of Stavropol Krai (5 km to the northeast of Zelenchukskaya Village), which is now a part of the Karachay-Cherkess Republic. This belemnite was later attributed to the genus Conodicoelites by Krimholz & Repin (1989). During fieldwork (2014 to 2018), two of us (VVM and MPSh) conducted a palaeontological-stratigraphic study of the Upper Bajocian–Lower Bathonian in KarachayCherkessia. In the course of this study, cephalopod fossil material was collected containing not only ammonites, nautilids and dicoelitid belemnites but also specimens of belemnopseid (Belemnopsis Bayle, Conobelemnopsis Riegraf, Longibelemnopsis Riegraf, Hibolithes Montfort) and megateuthidid (Megateuthis Bayle, ?Paramegateuthis Gustomesov) rostra. The current state of the art in ammon ite investigations allowed us to date belemnite occur-