Paper No. 76-36
Presentation Time: 9:00 AM-5:30 PM
NEW CRETACEOUS ECHINOID FINDS IN SOUTH AMERICA STRENGTHEN PALEOBIOGEOGRAPHIC CONNECTIONS WITH NORTH AMERICA, NORTH AFRICA, AND EUROPE
The fossil record of Cretaceous echinoids in South America is well represented in Brazil and Peru with ten to thirty species in each geologic stage. The record is smaller in Argentina, Colombia, and Venezuela, with ten or fewer species in each Cretaceous stage. Even smaller numbers of species (three or fewer) have been collected in Bolivia, Chile, and Ecuador through the entire Cretaceous. This paucity of data makes echinoid paleobiogeographic patterns difficult to interpret. Here we expand the South American record through new fieldwork and previously unpublished museum collections. New field collections from the El Way Formation of the Caleto Caloso Basin in northern Chile near the city of Antofagasta add at least four new species to the Lower Cretaceous record of Chile. The high abundance of some material from the El Way Formation allows for ontogenetic study of some species. Undescribed material from Area de Pelambres and the Lo Valdés Formation reposited at Univerdad de Concepción furthers the Cretaceous record, making ten total echinoid species known from Chile. Previously undescribed material at the US National Museum of Natural History collected in the 1920s adds six species to the record of the central Andean valleys of Peru and Ecuador. Material collected in 2013 in collaboration with the Colombian Geologic Survey near Zapatoca, Santander may also include two new species for Colombia. The new records in each country do not represent new species in most cases, rather these species are often found in other regions of South America, and frequently in North America and North Africa. Occasionally, species have affinities with Europe. General diversity and affinity patterns across South America match, as expected, with changes in sea level, subsequent opening of epicontinental basins, and separation of Gondwana. Further exploration of basins in central Chile may establish connections with Argentinian basins in the Lower Cretaceous. New searches for material in Bolivia and Northern Argentina could elucidate echinoid diversity patterns in the Upper Cretaceous due to the overland connection from the Pacific to the southern Atlantic that was present at that time.