The evolution of asymmetry in Upper Cretaceous Cyclothyris (Brachiopoda, Rhynchonellida)

ABSTRACT

The study of Upper Cretaceous Cyclothyris from Spain and the revision of asymmetrical rhynchonellides from numerous European collections have led to improve some systematical, biostratigraphical and palaeobiogeographical questions, allowing to update taxonomically this group. The species studied here are the following: Cyclothyris difformis (Valenciennes in Lamarck, 1819); Cyclothyris nekvasilovae sp. nov.; Cyclothyris? contorta? (d’Orbigny, 1847); Cyclothyris zahalkai Nekvasilová, 1973; Cyclothyris segurai Berrocal-Casero, 2020; Cyclothyris cardiatelia Berrocal-Casero, 2020; Cyclothyris claudicans (Coquand, 1879); Cyclothyris globata (Arnaud, 1877); and Cyclothyris? vesicularis (Coquand, 1860). Starting from the preliminary interpretation about the functional meaning of the asymmetry in C. cardiatelia, a hypothesis about the origin of the obligate asymmetry in Upper Cretaceous Cyclothyris has been proposed here, which implies a phylogenetic relationship between C. segurai, C. cardiatelia, C. globata and, possibly, C.? vesicularis.

KEYWORDS:

• Cyclothyris
• Upper Cretaceous
• systematics
• palaeobiogeography
• obligate asymmetry

Acknowledgements

We are very grateful to Manuel Segura from the Universidad de Alcalá (UAH, Madrid, Spain) and Paloma Sevilla from the Universidad Complutense de Madrid (UCM, Madrid, Spain) for their help during fieldwork and also to Javier Gil from the UAH for facilitating some specimens from Castrojimeno section. We also thank the editors of this journal and the reviewers Ane Elise Schroeder (Copenhagen, Denmark), and an anonymous referee for their useful comments. Mélani Berrocal-Casero is indebted to all the curators and researchers from many countries who helped with access to Cretaceous brachiopods: Zoe Hughes (NHM, London, the United Kingdom), Silvain Charbonnier and Danielle Gaspard (MNHN, Paris, France), Stéphane Jouvre (UPMC, Paris, France), Bálint Szappanos and Lazzló Makádi (MBFS, Budapest, Hungary), Petr Budil (CGS, Prague, the Czech Republic), Vladan and Barbara Radulović (RGF, Belgrade, Serbia), Enric Vicent and José María Pons (UAB: Barcelona, Spain), José Francisco Baeza Carratalá (UA, Alicante, Spain) and Latinka Hristova (NPMS, Sofia, Bulgaria). The stays of M B-C in Paris and Budapest were supported by a Synthesys project and a UCM grant, respectively. This research project is supported by a Predoctoral Research Training Grant CT45/15-CT46/15 from the UCM and is a contribution to the Research Project CGL2015-66604 from the Spanish MINECO (Economy and Competitiveness Ministry) and to the Research Groups Procesos Bióticos Mesozoicos (PBM) of the UCM and PaleoIbérica and IberCreta of the UAH.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary Material

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Additional information

Funding

This work was supported by the Universidad Complutense de Madrid [UCM CT45/15-CT46/15 and EB40/18 and by SYNTHESYS Project 2017 (FR-TAF-6747)].