Pinegopora chilensis, a new Permian bryozoan species of the Andean bryozoan province in southwestern Gondwana

Abstract

We studied here a bryozoan accumulation in mixed carbonate-siliciclastic successions of the Cerro El Árbol Formation in the central region of Antofagasta, Northern Chile. These stratigraphic units are characterized by an invertebrate marine fossil assemblage integrated by brachiopods, bivalves, gastropods, and crinoids. In certain levels the bryozoan fauna is clearly abundant and dominant, forming coquina-like accumulations together with crinoid fragments. The bryozoan fauna is composed by a ramose, small (no more than 3 cm long), single cryptostome species. In the macroscopic samples and in the thin-sections analyzed, the specimens appear well preserved, moderately fragmented, as simple stalks or dichotomously branched colonies. A new species of Pinegopora Genus Shishova, 1965, is identified. The biotic compositions of this unit, including a monospecific an abundant bryozoan, and their sedimentological characteristics, are distinctive of a subtropical to temperate shallow marine setting. We can state that the Andean bryozoan province records a climatic latitudinal gradient from the equatorial to subtropical areas in Venezuela, Peru and Bolivia to temperate conditions in Northern Chile. The gradient can be followed to Southern Gondwana with the development of typical high latitude bryozoan associations.