Advanced Mezzanine Card [AMC], used on the AdvancedTCA [ATCA] carrier cards.
The AMC standard is not based on the Common Mezzanine Card [CMC] and is not compatible with Compact PCI or the VME board standards.
The AMC board [AMC Module] dimensions are 74mm x 183.5mm for single width modules and are 149mm x 183.5mm for double width modules.
A carrier card can handle up to four single width modules or two double width modules.
Double stacked [one over the other] are allowed, provided the carrier card has a cut-away beneath the AMC boards.
Two types of connectors are defined for the carrier card, one which supports a single stacked card and one which supports dual stacked modules.
I/O for the AMC board may be through the front panel face plate for the board-to-board connectors.
AMC boards use Guide rails on the carrier card {motherboard} to allow for installation.
The AdvancedTCA [ATCA] carrier cards are also defined in the standard.
The electrical interfaces may include; PCI Express, Advanced Switching, Serial RapidIO, and Gigabit Ethernet.
Of course the pinout is defined in the specification, but not yet listed here.
The JTAG interface is also included as part of the I/O interface. AMC Board Manufacturers

A MicroTCA chassis may hold up to 11 AMC boards.
The MicroTCA interface uses the AMC board with out a carrier card [the backplane is the carrier].
The AMC board plugs directly into the MicroTCA back plane, which implies that in this case it is not a mezzanine card.