Late Jurassic (Kimmeridgian) bivalves from northwestern Algeria (Daïa and Nador mountains): Systematics and palaeobiogeography

Abstract

The bivalve fauna of the Upper Jurassic (Kimmeridgian) successions belonging to the Daïa and Nador mountains (NW Algeria) is taxonomically described and figured. For the first time, sixteen bivalve taxa were identified, partly in open nomenclature because of their poor state of preservation. Most taxa are represented by internal casts. The fauna was collected from two different formations of the same age: the Dolomies de Tlemcen Formation in the Daïa Mountains and the Faïdja Formation in the Nador Mountains. The lithologic characteristics of these formations, together with their fossil content and taphonomic features, confirm that these localities are characterized by marine conditions. The north-western Algerian bivalve assemblage holds the largest portion of cosmopolitan species.