From taxonomy to evolutionary Paleoecology, the case of Cretaceous bivalves from the San Juan Raya Formation, Puebla, Mexico

Abstract

Diversity of bivalves from San Juan Raya Formation has been recognized since the 19th century, when the first reports on the Zapotitlán-San Juan Raya area were published. However this diversity was documented until the middle of the last century, on the basis of taxonomic studies by Dr. Alencáster. Recent autoecologic analysis of species recognized by Dr. Alencáster, and some other species studied in recent years, confirms that in Early Cretaceous times there was an extense platform covered by waters of Tethys in this part of Mexico, where rudists and oysters formed banks or reef structures, there were also mytilids that perforated shells and corals, wood-perforating pholadids, semi-infaunal non-siphonated trigoniids, and species belonging to orders Veneroida and Pholadomyoida which burrowed deep below the water-sediment interface. These works have allowed to establish relationships with other faunas of the same age and to compare them with other more ancient founded in the geologic record from Mexico. Thus, bivalves from San Juan Raya Formation are a clear example of ecosystems evolution, which become more complex on time, as the number of life style increases, and with it, taxonomic diversity and use of ecospace.