The debated question of asymmetrical rhynchonellids (Brachiopoda, Rhynchonellida): examples from the Late Cretaceous of Western Europe
Abstract
Many Cretaceous asymmetrical rhynchonellid brachiopods (Brachiopoda, Rhynchonellida)have long been considered asRhynchonella difformis(ValenciennesinLamarck, 1819). After a revision,Owen (1962)included the Cenomanian specimens from Europe inCyclothyrisM’Coy, 1844. Later,Manceñidoet al.(2002)confirmed this decision and critically mentioned the name of another asymmetricalrhynchonellid genus from Spain,OwenirhynchiaCalzadainCalzada and Pocovi, 1980. Specimens with anasymmetrical anterior margin (non particularly ecophenotypical), from the Late Coniacian and the Santonianof Les Corbières (Aude, France) and Basse-Provence (SE France) are here compared to specimens of theoriginal Cenomanian speciesC. difformis. They are also compared to new material from the NorthernCastilian Platform (Coniacian-Santonian, N Spain) and toRhynchonella globataArnaud, 1877(Campanian,Les Charentes, Dordogne, SW France) andRh. vesicularisCoquand, 1860(Campanian, Charente, SWFrance). These observations document the great morphological diversity among all these species and lead usto erect a new species:Cyclothyris grimarginanov. sp. from the type material of Arnaud, and two new genera:Contortithyrisnov. gen. includingContortithyris thermaenov. sp.,Beaussetithyrisnov. gen. includingBeaussetithyris asymmetricanov. sp. All of these brachiopods fundamentally present an asymmetrical statewhich origin is discussed.
Origin | Publication funded by an institution |
---|
Loading...