Does a creature enchanted by Animate Dead retain its original abilities?

When Animate Dead returns a creature card from a graveyard to the battlefield, that creature enters as itself — with all its printed keywords, activated abilities, triggered abilities, and static abilities intact. Animate Dead modifies the creature only by giving it -1/-0 and attaching itself as an Aura that imposes the 'exile when Animate Dead leaves' clause. No original abilities are overwritten or removed.

Under CR 400.7, an object that moves zones becomes a new object, but its copiable characteristics (its rules text, abilities, power, toughness, etc.) come from its printed card. Animate Dead does not use any wording like 'it loses all abilities,' so the creature's own ability text is fully active.

Animate Dead does add one restriction: the creature can't block. This comes from Animate Dead's own text modifying the enchanted creature. Beyond that limitation and the -1/-0 penalty, the creature functions normally in every way.

Concrete example: You cast Animate Dead targeting a Grave Titan in your graveyard. Grave Titan enters the battlefield under your control with its deathtouch, its 'enters the battlefield' trigger (creating two 2/2 Zombie tokens), and its 'attacks' trigger — all functioning normally. It is simply a 5/-0 (effectively 5/5 with -1/-0 = 5/5 net) creature that cannot block while Animate Dead is attached.

Relevant rules: CR 400.7 (objects changing zones), CR 303.4 (Auras attaching to permanents), and CR 112.1 (abilities are part of an object's characteristics). Since Animate Dead grants no 'loses all abilities' effect, every original ability of the reanimated creature remains fully functional.