I did a bit of research on Platypi, so I hope this came out well enough. Not 3.5
Dire Platypus
Large Animal
Hit Dice: 4d8+12 (32 HP)
Initiative: +1
Speed: 20 ft, 50 Swim, burrow 20
AC: 13 (+1 Dex, +3 Natural, -1 Size)
Attacks: +6 Kick, +1 Bite
Damage: 1d8+4 Kick + Poison (for males only), 1d6+4 Bite
Face/Reach: 5 ft by 10 ft/5ft
Special Attacks: Nil
Special Qualities: Poison Quills (males only), Blindsight, cold immunity, waterproof
Saves: Fort:+7, Ref:+2, Will:+ 2
Abilities: Str:18, Dex:12, Con:17, Int: 2, Wis: 12, Cha:12
Skills: Hide +3, Swim +18
Feats: Nil
Climate/Terrain: Streams, rivers, marshes
Organization: Solitary, Pair, Family 1d4
Challenge Rating: 3
Treasure: Nil
Alignment: Usually Neutral
Advancement: Huge: 5d8-7d8
Combat
Blind Sight (Ex): While underwater Platypi can ascertain all foes within 40 feet as a sighted creature would. Beyond that range, they treat all targets as totally concealed. This ability is due to electrosensors in the Platypi?s bill.
Cold Immunity (Ex): Dire Platypi are immune to natural cold due to fat deposits that keep them insulated.
Poison (Ex): Fortitude save DC: 16. Initial Damage 1d4+1 Con, Secondary damage 1 Con
Waterproof (Ex): Due to the oil on it?s fur the Platypus never stays wet out of water for long.