Lower-Middle Devonian Fenestellidae (Bryozoa) of NW Spain: implications for fenestrate palaeobiogeography

摘要

The Emsian-Eifelian succession of NW Spain contains an abundant and diverse bryozoan fauna, fenestrates being the most outstanding group. The Fenestellidae of the Moniello Formation (upper Emsian-lower Eifelian, Asturias, NW Spain) comprise 13 species, four of which are new: Rectifenestella covae n. sp., Cavernella asturica n. sp., Hemitrypa adversa n. sp., and Hemitrypa terentei n. sp. The other species composing the assemblage studied are: Fenestella aff. parallela Hall, 1881, F. vera Ulrich, 1890, Rectifenestella pioneri (Krasnopeeva, 1935), Spinofenestella aff. antiqua (Goldfuss, 1826), S. estrellita (McKinney and Kriz, 1986), S. strigilla (McKinney and Kriz, 1986), Laxifenestella capillosa (Poc. ta, 1894), Hemitrypa aff. tubulosa (Nekhoroshev, 1948), and Ptylopora aff. nodosa Hall, 1883. Taking into account species reported in previous studies, the assemblage of Fenestellidae of the Emsian-Eifelian of NW Spain is composed of nine genera and 21 species. This fauna shows affinities with that of the Lower Devonian of Bohemia and also to those of the Middle Devonian of North America, Russia, and Asia. C. asturica n. sp. is the earliest and westernmost reported species of the genus, which was previously known to occur in the Carboniferous and Permian rocks from Hungary to Tibet. H. adversa n. sp. is the only known species of Hemitrypa with autozooecial apertures placed on the inner surface of the cone; some of the specimens of H. adversa n. sp. collected in the Moniello Formation developed unusually flat colonies.