The taphonomic analysis of the Osteichthyes and Condrichthyes of the Arenas de Huelva Formation permits to delimitate three parts into this Neogene unit: a) basal, glauconitic layer, with numerous teeths and caudal stings well preserved of the carchariniforms, lamniforms and skates that lived in a open marine environment; b) intermediate layer with several rich-shell horizons due to storms, with scarce eroded otholithes and teeths; and c) upper layer, without any remain of these groups because of the high dissolution level