I don't know but I wouldn't be surprised if the ATmega16U2, 16U4, 32U2 or 32U4 were close enough to the ATmega168 or 328 to be easily adapted to the Arduino IDE. I think they only come in surface-mount packages. 
I don't know but I wouldn't be surprised if the ATmega16U2, 16U4, 32U2 or 32U4 were close enough to the ATmega168 or 328 to be easily adapted to the Arduino IDE. I think they only come in surface-mount packages.