Ampharos, Absol and Mawile Mega Evolution details confirmed

The official site has confirmed the Mega Evolutions of Ampharos, Absol and Mawile and provided clearer pictures.

Mega Ampharos, Mega Absol, Mega Mawile

When Ampharos Mega-Evolves, apparently the red orbs on its body emit a strong light.
Mega Absol increases its Attack and Speed.
Mega Mawile increases its Defense and Special Defense.

Our Pokedex has been updated with the latest details. For now, the Mega Evolutions are listed as forms. Based on currently-known information, Mega Evolution works in the same way as an in-battle form change.

A few other additions we haven't yet already mentioned in news are a new attack, Nuzzle (learnt by Dedenne), and a new Ability, Cheek Pouch (possessed by Dedenne and Bunnelby).

A new trailer for Mega Evolutions has also been released: