Hmm...the Wikipedia article seems to indicate it is quite a bit smaller than the 3 HD dire weasel.
Otter: Str 3, Dex 15, Con 12, Int 2, Wis 12, Cha 5
Weasel: Str 3, Dex 15, Con 10, Int 2, Wis 12, Cha 5
Dire Weasel: Str 14, Dex 19, Con 10, Int 2, Wis 12, Cha 11
Based on all that, I'd recommend 2 HD, Str 12, Dex 17, Con 12, Int 2, Wis 12, Cha 11.
I was thinking the stats Xidoraven posted were for a dire version of
Potamotherium.
The stats look alright, except I'd give them Cha 7 or so for the non-dire version. A giant weasel is 10 feet long and these are 5 feet, which suggests Small size for a regular
Potamotherium. We can always do a dire version as well.
EDIT: Checking on the living species of giant otter,
Pteronura brasiliensis, it's a bit bigger than
Potamotherium and is just on the border of the 3E Small/Medium divide, being 5-6 feet long and 45-100 pounds. I'm acting on the presumption that the "River Beast" could have been a Small-sized 40-50 pounds animal, but it could easily be Medium-sized and a bit heavier. :END EDIT
EDITED EDIT: Further on that, I found a webpage with the
Proceedings of the San Diego Society of Natural History which contains the following: "The body weight of
Potamotherium (based on regression of dental dimensions in living carnivorans) has been estimated as 7.3 kg (Legendre and Roth 1988)", and a number of other sources that quote weights in the 5-15 kg or somewhere under 30, so it looks like it should be Small.
Well, there was one page that said they were 8 foot long and weighed 450 pounds, must have been talking about a dire
Potamotherium! :END EDITED EDIT
Not so sure about the 2 Hit Dice. 1 HD might be enough, but I'll leave it at 2 for the time being.
Oh, and I agree with Rappy that they need a respectable bite damage. How about a Small-sized regular version with a 1d6 bite, and a Medium-sized dire version with a 2d6 bite?
Something like:
Potamotherium
Small Animal
Hit Dice: 2d8+2 (11 hp)
Initiative: +3
Speed: 20 ft. (4 squares), swim 30 ft.
Armor Class: 15 (+1 size, +3 Dex, +1 natural), touch 14, flat-footed 12
Base Attack/Grapple: +2/-1
Attack: Bite +6 melee (1d6+1) [includes bonus Weapon Finesse feat]
Full Attack: Bite +6 melee (1d6+1)
Space/Reach: 5 ft./5 ft.
Special Attacks: ?
Special Qualities: Hold breath, low-light vision
Saves: Fort +4, Ref +6, Will +1
Abilities: Str 12, Dex 17, Con 12, Int 2, Wis 12, Cha 7
Oh, and the typo "Potatotherium" is just begging to be converted into some kind of plant monster, a Tuber Beast which takes extra damage from oil and hot fat, presumably.
