Megalosaurus amazing for caving during the night
Arthropleura will not be attacked passively by many creatures (use in caves, slither right by!)
Titanosaur amazing for leveling you and your dinos up!
Onyc they have no use in pvp as well, they are put in the game to make getting delicious cave loot a little bit more challenging
Diplodocus amazing for carrying things and easy to tame!
Brontosaurus stellar for gathering berries
Procoptodon very fast traveler and great weight(knock back is useful as well!)
Stegosaurus also good for gathering berries early on when you have minimal resources, it is also a good tame to protect you early game from raptors!
Anyways, i hope this answered your questions!