A large two headed lizard or perhaps a small two headed hydra?
Dualizard (CR 2)
N Large Dragon
Init +1; Senses Dragon senses, scent; Perception +7
AC 14, touch 10; flat-footed 13 (+1 Dex, +4 natural, -1 size)
hp 31  (3d12+12); Fast Healing 4 [2 heads]
Fort +7, Ref +6, Will +3
Immune Paralysis, Sleep; Resist Ice 5, Fire 5
Speed 20 ft., Swim 20 ft.
Melee 2 Bites +5 (1d8+4)
Space 10 ft.; Reach 10 ft.
Special Attacks Pounce, 2 Breath Weapons (15-ft. cone, DC 15, 1d4 fire or ice)
Str 16, Dex 12, Con 18, Int 2, Wis 10, Cha 8
Base Atk +3; CMB +7; CMD 18
Feats Combat Reflexes, Lightning Reflexes
Skills Perception +7, Swim +8; Racial Modifier +2 Perception
SQ Hydra Traits, Fast Healing
Fast Healing (Ex)
A dualizard’s fast healing ability is double to its current number of heads. A dualizard loses all fast healing when it is reduced to a single head.
Hydra Traits (Ex)
Any critical hit has a 75% chance to sever a head also you cannot sever the last head but a dualizard loses its fast healing if they only have one head remaining. A dualizard can’t attack with a severed head, but takes no other penalties. A dualizard also loses one of its breath weapons per head lost.
When a dualizard makes a charge, it can make a full attack.