Ankylosaurus (CR 7)

Huge Animal
Alignment: Always neutral
Initiative: -2 (Dex); Senses: darkvision 60 ft., low-light vision, scent, Listen +7, and Spot +7

AC: 22 (-2 size, -2 Dex, +16 natural); touch 6, flat-footed 22
Hit Dice: 9d8+78 (118 hp)
Fort +16, Ref +4, Will +2
Speed: 20 ft.
Space: 15 ft./10 ft.
Base Attack +6; Grapple +23
Attack: Tail slap +13 melee
Full Attack: Tail slap +13 melee
Damage: Tail slap 2d6+13
Special Attacks/Actions: Trample 2d12+13
Abilities: Str 29, Dex 7, Con 26, Int 1, Wis 9, Cha 8
Special Qualities:
Feats: Alertness; Great Fortitude; Toughness (x2)
Skills: Listen +7 and Spot +7
Advancement: 10-18 HD (Huge); 19-27 HD (Gargantuan)
Climate/Terrain: Warm forest, hills, plains, and marsh
Organization: Solitary, pair, or herd (20-40)
Treasure/Possessions: None

Source: Monster Manual II

Trample (Ex): As a standard action during its turn each round, ankylosaurus can trample opponents at least one size category smaller than itself. This attack deals 2d12+13 points of bludgeoning damage. A trampled opponent can attempt either an attack of opportunity at a -4 penalty or a Reflex save (DC 23) for half damage.

Scent (Ex): A dinosaur can detect approaching enemies, sniff out hidden foes, and track by sense of smell.

Ankylosaurus rarely attacks unless it or its herd is threatened. Though it is slow to action, once this dinosaur views another creature as an enemy, it fights until either it or its attacker is dead. In battle, it stands put, swinging its tail at any creature that comes within reach. If it takes 80 or more points of damage or finds itself cornered, it attempts to flee, trampling any creatures in its path.