Bajocian-Early Bathonian (Jurassic) brachiopods from the Subbetic domain (Betic Cordillera, SE Spain): Taxonomy and palaeobiogeographic implications

摘要

Brachiopod fauna is recorded in the Parkinsoni-Zigzag zones from the Subbetic area (Betic Cordillera) for the first time. This fauna also represents the only record from the epioceanic areas of the Iberian platform system in this timespan. The assemblage recognized includes five different taxa: Septocrurella companyi nov. sp., formally described in this paper, Septocrurella? aff. defluxa, Karadagithyris eduardi, Karadagithyris cf. eduardi, and Linguithyris nepos, mostly showing a bra- chidium-supported internal architecture. Palaeobiogeographical analyses reveal clear affinities with the epioceanic areas of the most intra-Tethyan platforms from the Mediterranean province, very different from the unique epicontinental record in this timespan from the northern Iberian margin. The distribution pattern of the brachidium-supported taxa is inferred due to their persistent concurrence in the Middle Jurassic epioceanic environments, unlike the epicontinental ones. It has been hypothesized that it is likely that this singular brachidial structure can be interpreted as an additional adaptive factor related to epioceanic habitats, probably coinciding with the well-known gradual deepening of the Mediterranean palaeobioprovince.