Hit Dice: 32d8+300 (444 hp)
Speed: 20 ft.
AC: 11 (-8 size, -1 Dex, +10 natural), touch 1, flat-footed 11
Attacks: Tail slap +31 melee
Damage: Tail slap 4d10+22
Face/Reach: 120 ft. /25 ft.
Special Attacks: Trample 10d10+22
Special Qualities: Darkvision 60 Ft., Low-Light Vision, Scent
Saves: Fort +27, Ref +17, Will +12
Abilities: Str 40, Dex 9, Con 29, Int 1, Wis 14, Cha 14
Skills: Listen +22, Spot +21
Feats Alertness, Awesome Blow, Diehard, Endurance, Improved Bull Rush, Power Attack, Run, Toughness x4
Climate/Terrain: Warm forests, plains, hills, and marsh
Organization: Solitary, pair, or pod (5-20)
Challenge Rating: 12
Alignment: Always neutral
Advancement: 33-64 HD (Colossal)
Level Adjustment: -
Seismosaurus is the largest known of the dinosaurs. It feeds on plants, often defoliating several square miles of terrain within the course of a few weeks.
Seismosaurus is an immense four-legged dinosaur with a small head, a bulky body, and a long neck and tail. Its nostrils are located high up on its head.
Seismosaurus is simply too big to have natural enemies—it dwarfs even the likes of allosaurus and tyrannosaurus (see the Monster Manual). Seismosaurus is more likely to inadvertently step on an opponent than to intentionally use its tail slap attack.
Trample (Ex): As a standard action during its turn each round, seismosaurus can trample opponents at least one size category smaller than itself. This attack deals 10d10+22 points of bludgeoning damage. A trampled opponent can attempt either an attack of opportunity at a -4 penalty or a Reflex save (DC 41) for half damage.