magic the gathering can a creature with summoning sickness use it's untap ability

[Aurelius]

can a creature with summoning sickness use its untap ability?

[Arix]

Nope.

302.6. A creature’s activated ability with the tap symbol or the untap symbol in its activation cost can’t be activated unless the creature has been under its controller’s control continuously since his or her most recent turn began. A creature can’t attack unless it has been under its controller’s control continuously since his or her most recent turn began. This rule is informally called the “summoning sickness” rule. Ignore this rule for creatures with haste (see rule 702.10).