Parasaurolophus (CR 7)

Huge Animal
Alignment: Always neutral
Initiative: +0; Senses: low-light vision, scent, Listen +14, and Spot +11

AC: 14 (-2 size, +6 natural), touch 8, flat-footed 14
Hit Dice: 14d8+79 (142 hp)
Fort +14, Ref +9, Will +6
Speed: 40 ft., swim 20 ft.
Space: 15 ft./15 ft.
Base Attack +10; Grapple +26
Attack: Slam +16 melee
Full Attack: Slam +16 melee
Damage: Bite 1d8+12
Special Attacks/Actions: Trample 1d8+12
Abilities: Str 26, Dex 10, Con 20, Int 2, Wis 14, Cha 10
Special Qualities:
Feats: Alertness; Run; Toughness (3)
Skills: Hide -8*, Listen +14, and Spot +11
Advancement: 15-28 HD (Huge), 29-42 HD (Gargantuan)
Climate/Terrain: Warm marsh
Organization: Solitary, pair, or herd (3-12)
Treasure/Possessions: None

Source: Dragon #318

A parasaurolophus is a relatively gentle creature that prefers to wallow in swamplands. They feed on all forms of vegetation that grow in such areas, using their duckbill-shaped jaws to scoop up mouthfuls of algae and swamp plants. Their crests are complex sounding chambers that allow them to generate shockingly loud and haunting, almost mournful cries that can carry for miles. Their skin is capable of changing through a wide variety of colors and shades. During mating season, these dinosaurs can put on a veritable symphony of sound and color as they try to attract mates.

A parasaurolophus is usually about 35 feet long.