The VOIDRUNNER'S CODEX is LIVE! Explore new worlds, fight oppressive empires, fend off fearsome aliens, and wield deadly psionics with this comprehensive boxed set expansion for 5E and A5E!
No land speed whatsoever, or 5 feet at the most. Get rid of the amphibious subtype. It appears that these guys had a hard time on land and a fossil bed of them died in a drought.
Sounds fair to me. I was a little unsure whether we'd be justified in getting rid of amphibious, but it works. We could give them hold breath, maybe, if we give them the slow land speed.
A paracyclotosaurus is 6 to 8 feet long, weighing around x pounds.
For massy...
15-foot cone for vortex maw?
Swallow Whole (Ex): A mastodonsaurus can try to swallow a grabbed opponent of up to two sizes smaller by making a successful grapple check. The swallowed creature takes (2d8+8?) points of bludgeoning damage and (1d6?) points of acid damage per round from the gizzard. A swallowed creature can cut its way out by using a light slashing or piercing weapon to deal (15?) points of damage to the gizzard (AC 12). Once the creature exits, muscular action closes the hole; another swallowed opponent must cut its own way out.