Stunning Roar (Ex): Every 1d4 rounds, a sirrush can loose a sonic attack of such volume that it stuns all creatures in a 60-foot spread for 1d4 rounds if they fail a Fortitude saving throw (DC 47, or DC 51 for a three-headed sirrush). The DC is

Pounce (Ex): If a sirrush charges or leaps upon a foe during its first round of combat, it can make a full attack even if it has already taken a move action.

Headloss Resistance (Ex): A sirrush's thick bony plate protects its neck like a shield and provides resistance from effects that could normally behead it, such as a vorpal weapon. When a sirrush or three-headed sir-rush would otherwise lose its head, it instead makes a Fortitude saving throw (DC 10 + 1/2 HD of attacker + attacker's Str modifier). On a failed save, the sirrush's head leaves its shoulders normally, but on a successful save, the sirrush is unaffected by the beheading. A sirrush dies when beheaded; a three-headed sirrush goes on fighting until all its heads are lost (the only penalty it incurs is one or two fewer bite attacks when it makes a full attack).