Can you post the AD&D stats in that case? The chelonians don't seem to have anything like that.
Sure.
Here's the most recent AD&D version, from
Monstrous Compendium Annual Volume Two (1995).
Turtle, Sea, Giant
Climate/Terrain: Any sea
Frequency: Uncommon
Organization: Solitary
Activity Cycle: Any
Diet: Omnivore
Intelligence: Non- (0)
Treasure: Nil
Alignment: Neutral
No. Appearing: 1-3
Armor Class: 2/5
Movement: 1, Sw 15
Hit Dice: 15
THAC0: 5
No. of Attacks: 1
Damage/Attack: 4d4
Special Attacks: Upset craft
Special Defenses: Hide limbs
Magic Resistance: Nil
Size: G (50’ diam.)
Morale: Champion (15-16)
XP Value: 5,000
Giant turtles are simply huge varieties of the normal species encountered daily in the wild. They resemble their common counterparts in every respect except for size.
A turtle is characterized by its bony outer shell. The lower portion of the shell is known as the plastron, while the upper shell is referred to as the carapace. It is within this shell that a turtle withdraws its legs and head when threatened. Some turtles are incapable of completely shielding their limbs in this way, and plaster their legs very close to the shell for protection.
Giant turtles eat whatever is available in their environment, from living plants to all types of insects, small mammals, and fish of all kinds. They prefer fresh green plants and live worms, as turtles do not enjoy feeding on carrion or rotting vegetation. Naturally, such foods are fair game if the turtle is in danger of starvation.
Turtles have very long life spans—from 30-150 years, depending on the species. They are slow-moving and thus would rather withdraw into their shells when faced with an enemy, rather than either fight or flee. However, when harmed or persistently molested, the strong, quick bite of a giant turtle is a deadly weapon indeed.
Giant turtle meat is considered a delicacy in most cultures, and it is highly nourishing and palatable. The upper shells of giant turtles are also greatly preferred as they can be made into small huts, strong roofs, or even boats. Without exception, the tropical marine varieties of sea turtles are the finest tasting and have the most attractive shells.
Giant Sea Turtles
These basically non-aggressive marine creatures fight fiercely if annoyed or threatened. The tearing bite of giant sea turtles causes 4d4 points of damage to the unlucky victim. If one surfaces beneath a small craft, there is a possibility of upsetting the vessel. There is a 90% chance for a rowboat but only 10% for a typical drakkar. Adjust this base chance for other sea-going vessels according to the size and stability of the craft.
The head and flippers of giant sea turtles are Armor Class 5, while the shell is AC 2. If the turtle withdraws its head and flippers into its shell either for defense or while resting, all attacks are considered to be directed against the shell.
There's also a "Father Of All The Turtles" in a Dragon #190 (Feb 1993) article Monsters of the Deep by Greg Detwiler, but statwise it's pretty close to the Giant Sea Turtle:Father-of-all-the-turtles
Father-of-all-the-turtles : Named after a similar creature from Sumatran legends, this is basically a giant sea turtle 60’ long and 40’ wide. It has a mouth so wide that it splits the head in two when it opens (one report claims the inside of the mouth is brilliant red color), large eyes, and a shell whose front slopes up and backward in front, then slants down toward the rear. The scales on the front are hardly noticeable, while those to the rear of the shell are so large they have been compared to roofing shingles. Sometimes fleshy filaments are reported hanging around the mouth. There are only a few reports of this beast, the last in 1960. Oddly for a reptile, it is found in cold temperate areas. However, really large reptiles lose heat more slowly than their smaller fellows, and the Leatherback turtle does travel far to the north.
If it exists, the Father-of-all-the-turtles is probably an enlarged descendant of the Cretaceous sea turtle Archelon. Stats are those from the MC3, with the following exceptions: 16 HD; THAC0 5; DAMAGE/ATTACK 2-20; SIZE G (60’ long by 40' wide); XP VALUE 8,000.
Finally, here's another Turtle I think we should convert. I suggest calling it a Ferry Turtle rather than a Giant Freshwater Turtle:From The Sylvan Veil (1999)
Most visitors to Silvanost must cross the Thon-Thalas to enter the city. During the city’s early days, traditional ferryboats used rope lines or magic to move passengers from Fallon Island and the mainland. However, priests of the Blue Phoenix later enlarged several turtles to do the job.
As time passed, these large turtles bred, creating even more turtles to replace the older ones. When Speaker Lorac’s Nightmare twisted the forest and tainted the river, most of the turtles died. Thankfully, when Porthios and his forces cleared the forest of the Nightmares, the kirath discovered several turtles and a clutch of large eggs. Since then, this clutch has hatched, and now large turtles pull barges between the island and the mainland. Even the drain of the Silvanesti Shield hasn’t stopped these strong creatures performing their job.
Giant turtle: AC 1; MV 3; Sw 9; HD 4+4; hp 30; THAC0 17; #AT 1, Dmg 2d6 (bite); SZ L (8’ long); Int low (5); Al N.
The Int 5 and being trainable strongly suggests these aren't simply smaller freshwater versions of Giant Sea Turtles.
