Diplocaulus

Originally Posted by Shade of the En World forums. 

On this Thread

This three-foot-long amphibian has a pancack-shaped body and a large, boomerang-shaped head. Its legs are short, and its tail is long and flat. A diplocaulus is a prehistoric amphibian with an odd-shaped head. This oversized head makes it difficult to swallow by the many larger predators in its environment. A diplocaulus spends most of its time on the bottom of rivers and streams, waiting for small fish and insects on which to prey. A diplocaulus is about 3 feet long.

Diplocaulus is known for the long protrusions on the sides of its skull, which cause the skull to be shaped similar to a boomerang. Judging from its weak limbs and relatively short tail, it is presumed to have swum with an up-and-down movement of its body, not unlike cetaceans today. The wide head could have helped the creature glide through the water. Also, it is thought to have had defensive purposes as any predator (even the large-headed Eryops) would have a hard time trying to swallow a creature with such a wide head.

Diplocaulus
Small animal (Aquatic)
Hit Dice	1d8+1 (5 hp)
Initiative	+2
Speed	5 ft. (1 square), Swim 40 ft.
Armor Class	14 (+2 size, +2 Dexterity), touch 14, flat-footed 12
Base Attack/Grapple	+0/-9
Attack	Bite +4 melee (1d4-1)
Full Attack	Bite +4 melee (1d4-1)
Space/Reach	2-1/2 ft./0 ft.
Special Attacks	–
Special Qualities	Amphibious, hard to swallow, hydrofoil, Low-Light Vision
Saves	Fort +3, Ref +2, Will +0
Abilities	Strength 9, Dexterity 14, Constitution 13, Intelligence 1, Wisdom 11, Charisma 5
Skills	Hide +12, Listen +3, Move Silently +7, Spot +3, Swim +8
Feats	Alertness, Weapon Finesse (B)
Environment	Warm aquatic
Organization	Solitary
Challenge Rating	1/2
Treasure	None
Alignment	Always neutral
Advancement	2 HD (Tiny), 3-4 HD (Small)
Level Adjustment	–

COMBAT

A diplocaulus generally attempts to escape if threatened by a larger creature.

Hard to Swallow (Ex): A diplocaulus counts as one size category larger for the purposes of being swallowed whole.

Hydrofoil (Ex): A diplocaulus gains a +4 bonus on any Swim check made to Swim against a current.

Skills: A diplocaulus has a +4 racial bonus on all Hide and Move Silently checks. A diplocaulus has a +8 racial bonus on any Swim checks to perform some special action or avoid a hazard. It can always take 10 on Swim checks even if distracted or endangered. It can use the run action while swimming, provided it swims in a straight line.

Originally appeared in Dragon Magazine #112 (1986) as “Labrynthodont”.