The percentage of endemic coral and rudist genera is plotted for each stage of the Cretaceous in the Tethyan realm. From Neocomian to Aptian times only a Mediterranean faunal province is clearly defined by endemic genera. From Albian times a Caribbean province appears and, in general, increases in endemic coral and rudist genera up to the Maestrichtian. The separation and evolution of this province is related to geographic isolation of the Caribbean from the Mediterranean by spreading of the Atlantic Ocean.