Tanystropheus
Huge Animal
Hit Dice: 6d8+24 (51 hp)
Initiative: +2
Speed: 20ft (4 squares), swim 40ft
Armor Class: 14 (-2 size, +2 Dex, +4 natural), touch 10, flat-footed 12
Base Attack/Grapple: +4/+16
Attack: Bite +8 melee (1d8+6)
Full Attack: Bite +8 melee (1d8+6)
Space/Reach: 15ft/10ft (15ft with bite)
Special Attacks: Improved grab
Special Qualities: Low-light vision, scent
Saves: Fort +9, Ref +7, Will +2
Abilities: Str 19, Dex 14, Con 18, Int 1, Wis 11, Cha 6
Skills: Hide +8, Listen +5, Spot +5
Feats: Alertness, Skill Focus (Hide), Weapon Focus (bite)
Environment: Warm aquatic and marsh
Organization: Solitary
Challenge Rating: 5
Treasure: None
Alignment: Always neutral
Advancement: 7-12 HD (Huge), 13-18 HD (Gargantuan)
Level Adjustment: -
This bizarre creature looks like a snake with webbed feet on stubby legs. Its neck is almost half of its body length.
The tanystropheus is a strange semi-aquatic reptilian predator from the age of the dinosaurs.
A tanystropheus is about thirty feet long, and much of this is neck. They are ambush predators, waiting in caves and underwater to grab passing prey. They feed mostly on fish, but they do grab larger prey, such as humanoids, on occasion.
Combat
A tanystropheus usually attacks from hiding, striking with its needle-sharp teeth and grabbing hold of its prey. It will then retreat, dragging its prey with it.
Improved Grab (Ex): In order to use this ability, a tanystropheus must hit an opponent with a bite attack. It can then make a grapple check as a free action without provoking an attack of opportunity. If it gets a hold, it deals bite damage each round it maintains the grapple.
Skills: A tanystropheus gains a +8 racial bonus to all Hide checks.
A tanystropheus has a +8 racial bonus on any Swim check to perform a special action or avoid a hazard. It can always choose to take 10 on a Swim check, even if distracted or endangered. It can use the run action while swimming, provided it swims in a straight line.
They should probably be only Large, but should still have 15 foot reach. Dunno about Improved Grab...