The first record of nautiloids (Cenoceras intermedius) from the early Pliensbachian of Rgotina, (Getic nappe, eastern Serbia)

ABSTRACT

Cenoceras intermedius (J. Sowerby) is one of the most widespread species among the Early Jurassic nautiloid fauna and its geological range still controversial up to the present day. The specimen of Cenoceras intermedius from the sandy bioclastic limestones of Rgotina (Getic nappe of eastern Serbia), is a large half conch representing the phragmocone. Viewing our findings in light of previous results suggests the main morphological changes occurred during the ontogenetic evolution. The coiling starts with a round-square whorl section, to become almost quadrangular (penultimate whorl) and trapezoidal-triangular for the last one. Moreover, the siphuncle foramen moves within the septum towards the venter border from a slight upper position against the centre in the inner whorls. It exhibits a typical suture line for the genus Cenoceras with two saddles and three lobes. This finding certainly extends the geological range of the species to after the Sinemurian contrary to several earlier works that confined it only to this stage. This assertion is based on the accurate assignment of the nautiloid-bearing bed of Rgotina to the early Pliensbachian by the index species Uptonia jamesoni. The Serbian specimen supports the species’ palaeobiogeographic widespread range within the north-western margin of the Neo-Tethys Ocean framework.

KEYWORDS:

• Cephalopoda
• Cenoceras intermedius
• ontogenetic changes
• geological range
• northwestern Neo-Tethys
• Pliensbachian

Acknowledgments

We are grateful to Gareth Dyke (Editor-in-Chief) and reviewers Michael R. Sandy (University of Dayton), Howard R. Feldman (American Museum of Natural History, New York) and László Bujtor (University of Pécs) for their critical remarks and suggestions as well as correcting our English which significantly improved the quality of this paper. Great thanks are due to Tatjana Perišić (Belgrade) for the donation of the specimen. Thanks are also due to the Biodiversity Heritage Library, Internet Archive, Google Books, Harvard University Library, Bayerische StaatsBibliothek Digital, Gallica.bnf.fr (Bibliothèque nationale de France), Niedersachsische Staats- und Universitatsbibliothek Gottingen, IRIS ‒ LILLIAD, Université Lille for free access to the very old and useful nautiloid works. This research was carried out during the preparation of project No. 176015 sponsored by the Ministry of Education, Science and Technological Development of the Republic of Serbia (grant to BVR and MT). The common work was facilitated by a CEEPUS mobility grant at the University of Belgrade performed by the first author.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The research was supported by the Ministry of Education, Science and Technological Development of the Republic of Serbia, Project No. 176015 (grant to BVR and MT).