They are skittish but not anywhere near faster than humans. They have low torpor and health, so tranq darts are recommended. Tamed like any carnivore, kibble is Archeopteryx. Can be found anywhere in and around the swamps.
Fantastic utility Dino. You take oxygen from it passively while riding. The oxygen lasts a long time too; this combined with its speed means you can explore anywhere under water. That and it's a chitin machine ;)
The Diplocaulus is a swamp amphibian with one major use once tamed; becoming a living oxygen bag. When swimming to the depths of the ocean, some disgusting survivors will suck on the bladders of a tamed diplocaulus' head as an effective oxygen source.