I thought I saw once on the history channel that at one time when the AF "retired" the A-10 the MArines said they wanted them. I also thought that they said they were flown by Marines to support Marines on the ground and that the Marine pilots had originally been ground troops because they knew first hand how important the air support was to their brothers on the ground. Maybe I am having a bout of CRS and have that confused with something else.
The ones the Marines have is the AV 8 Harrier, everything in the Marine arsenal is capable of Carrier landings. As far as I know the A - 10 has never been qualified for them.
Blackwolfe is correct about the Marine Pilots being Infantrymen FIRST, THEN going through flight training.
Back in the "Old Corps", the Forward air controllers were TAD pilots, they could visualize what the pilots were seeing which made them better at directing air strikes.