As long as the top card of your graveyard is a creature card, Volrath's Shapeshifter has the full text of that card and has the text ": Discard a card." (Volrath's Shapeshifter has that card's name, mana cost, color, types, abilities, power, and toughness.)
: Discard a card.
10/4/2004 If the top card in the graveyard has any other undefined characteristics, then those characteristics are not acquired and the shapeshifter uses the characteristic from its own card.
10/4/2004 If the top card in your graveyard is a creature card, this card uses the listed characteristics, including color and any other types. But, this card keeps the granted ability in addition to those from the card being copied.
10/4/2004 When it changes forms, any “enters the battlefield” abilities of the card it “copies” do not trigger.
10/4/2004 A copy of a Volrath’s Shapeshifter will have the shapeshifting ability.
10/4/2004 If the top card in your graveyard isn’t a creature card (meaning a card with the type Creature, which may or may not have other types such as Artifact or Enchantment), then it’s just a 0/1 blue creature. Older cards of type Summon are also Creature cards.
8/1/2008 The ability that sets its characteristics is a text-changing effect.