Taxonomy and biostratigraphy of Early Cretaceous species of the genus Monopleura Matheron (Hippuritida, Monopleuridae) of the Mediterranean region

• Published in: Cretaceous research 2020-04, Vol.108, p.104287, Article 104287
• Main Authors: Masse, Jean-Pierre, Fenerci-Masse, Mukerrem
• Format: Article
• Language: English
• Subjects: Biostratigraphy Lower Cretaceous; Monopleura; Rudiste bivalves; Taxonomy
• ISSN: 0195-6671; 1095-998X
• DOI: 10.1016/j.cretres.2019.104287

The genus Monopleura is characterized by a right valve anterior myophore on shell wall, the posterior being on a transverse thickening. Shell habit varies from low conical to sub-cylindrical and the left valve ranges from capuloid to flat. Morphometry reveals that the overall dimensions are relatively modest. The taxonomic revision of species documents the existence, in the Mediterranean regions, of fourteen Early Cretaceous species, instead of about thirty compiled from the literature. Some Hauterivian forms recorded earlier are reappraised, Barremian taxa are complemented, and two new species are described (Monopleura alesta n. sp. and Monopleura jurensis n. sp.). Early Cretaceous representatives of Gyropleura actually belong to Monopleura. Monopleura has its first occurrence in the Berriasian, its developmental phase starts with the Valanginian and a peak in diversity is recorded in the late Barremian. There is a drastic reduction in the number of species in the early Aptian and the genus is assumed to disappear with the mid-Aptian crisis. Three main successive faunas, having each an index species with a limited biostratigraphic range are recorded from the early Valanginian (index Monopleura valangiensis), the late Hauterivian (index Monopleura michaillensis) and late Barremian (index Monopleura varians). The lower Berriasian and lower Aptian are each represented by a single species, Monopleura taurica and Monopleura kiliani respectively. The absence of representatives of Monopleura in the upper Valanginian–lower Hauterivian and in the lower Barremian suggests that our picture of Early Cretaceous Mediterranean Monopleura species is rather incomplete.