Silurian and Devonian Nepiomorph Bivalves from Bolivia

Abstract

Rare nepiomorph bivalves from the Silurian and the Devonian beds of the Central Andes Basin of Western Gondwanaland are herein presented. They were collected in four scattered outcrops in the Eastern Andes Cordillera and southern Interandean Bolivia. A total of 58 specimens of medium preservation were studied. Almost all of them are Ludlowian to Pridolian in age: Praecardium sp. A, Cardiola fluctuans Barrande, Dualina secunda Barrande, and one species is of Eifelian age: Praecardium sudamericanum (Kozlowski). This is both, the first report of the genus PraecardiumBarrande of Ludlowian to Pridolian age in this part of Gondwanaland and the first occurrence of the species Cardiola fluctuans Barrande in Bolivia. Through findings in the centre of the Silurian—Devonian Central Andes Basin (Pongo and Chaquimayu localities), this paper confirms the cosmopolitism of Dualina secunda Barrande. This research contributes to the as yet inaccurately known Silurian and Devonian paleogeography of the Central Andes Basin and to update old systematic descriptions of nepiomorph bivalves from late 19th and early 20th centuries.