Distribution in tropical America of Turritellas of the phylum of Turritella ocoyana

Abstract

Large, strongly keeled ocoyana-like Turritellas have an extensive distribution in tropical America. So far they have been found in Mexico, Colombia, and Venezuela, all on the Caribbean side, and in Peru, Ecuador, Darien, Chiriqui Province, Panama, and Lower California, on the Pacific side. In the Caribbean region these Turritellas are found in two middle Miocene zones, the lower corresponding to the Cercado formation of the Dominican Republic, and the upper corresponding to the Gurabo formation of the Dominican Republic and the Gatun formation of the Panama Canal Zone. On the Pacific side they apparently are confined to the upper zone. Though six names have already been proposed for these tropical Turritellas, they clearly fall in the ocoyana phylum and they may eventually be considered as representing a subspecies of ocoyana. This phylum appears in California as an invader. According to available evidence it reached the Pacific from the Atlantic by way of the Central American seaways. Perhaps it developed from a lower Miocene stock represented by Turritella subgrundifera of the Chipola formation of Florida.

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