Preliminary insights into Lower Devonian hyoliths from the Argentine Precordillera

ROMERO LEBRÓN, EUGENIA; RUSTÁN, JUAN JOSÉ

General Roca

Congreso; Congreso de la Asociación Paleontológica Argentina; 2016

The siliciclastic deposits of the Lower Devonian Talacasto Formation, in the Central Precordillera of the San Juan Province, constitute the best source of paleontological information of this age in Argentina. Contrasting patterns of its faunas have been discussed in relation to the recognition and origin of the Malvinokaffric Realm, a major Devonian paleobiogeographic unit involving basins from southwestern Gondwana. In addition to the high number of endemic taxa, this Realm has been supported by virtual absence of some typical Paleozoic groups such as conodonts and graptolites and striking abundance of others like conulariids and hyoliths. A preliminary revision of hyoliths from the Talacasto Formation indicates they are, indeed, very well recorded along the unit. However, they do not appear to exhibit a clear Malvinokaffric signature as previously reported from coeval associations from Bolivia. Among recognized taxa in the Talacasto Formation Orthothecida would include the Bolivian Bolitheca Marek and Isaacson, 1992, Devoniotheca Malinky, 1987, already recorded in the Devonian of North America, and Panitheca Marek, 1967, with records in the Ordovician of North America. Representatives of the Order Hyolithida would include Hyolithes malimanensis Sabattini et al., 2001 (recorded in the Carboniferous of San Juan, Argentina) and two new genera. Forthcoming contributions on these faunas will be relevant in order to provide new interpretative insights into contrasting paleobiogeographic Devonian patterns recognized in different groups in these basins (e.g. nearly cosmopolitan distribution of bivalves in the Argentine Precordillera versus remarkable endemic signatures in trilobites).