[MARMAM] Fossil walrus or sea lion in Gulf of Mexico?

I have a congressional office asking whether there are any fossil records of any species of walrus and/or sea lion ever occurring in the Gulf of Mexico, or what has become the Gulf of Mexico? I haven't been able to locate any references to such, but need to check to see if anyone might have run across such a record. Gene Buck, specialist in natural resources policy Congressional Research Service Washington, DC