I've come across many Dinos that I believe would fit in this game wonderfully. What are they?
Basilosaurus: Looking at the sea creatures we have, we're lacking the behemoths we see in modern day oceans. Whales. What special properties could a Basilosaurus have? Wild ones could be neutral temperament, not attacking unless provoked. Spawning only in the Snow biome's waters, Basilosaurus could be easily found near Icebergs, tamed Basilosaurus, while sluggish swimmers, would be excellent to keep you from freezing in the depths of the ocean due to it's thick blubber that provides insulation for both it and it's rider.
Anomalocaris: Insects, Arthropods, fear-inducing creatures of the island. Why not have one in the ocean as well? Wild Anomalocaris use their appendages on their heads to grab prey and prevent them from escaping certain death. Anomalocaris evolved to stay near shallow waters and wait for land creatures such as Dodos or Compys to come in for a drink so they can grab and drag them down into the waters. They generally do not attack anything bigger than them. Tamed Anomalocaris are great for transporting smaller sea creatures around, such as Megapiranhas. They also use their appendages to slow other creatures down by latching onto them, which is perfect for taming opportunities, as the creature will not be able to attack Anomalocaris.
Helicoprion: Another shark, right? Well this one is different. With it's spiral jaw that is filled with rows of serrated teeth, this beast is a force to be reckoned with. Wild Helicoprions are extremely territorial (They will only attack if their prey is killed or provoked) and can attack at range with their whip-like bottom jaw. Their attacks are not only ranged, but can cause oxygen loss. Taming a Helicoprion is rather difficult as they do not fall for the knock out and feed tactic that most creatures do fall for. Like the Troodon, they will become loyal towards a survivor when given the opportunity to hunt. Tamed Helicoprions are perfect war mounts. Their ranged whip attack (While doesn't have a lot of range) can possibly hit foes on land, and if trained correctly, they can throw some loose teeth using their bottom jaw. These teeth are actually very similar to Flint and can be used as a substitute in recipes.
Macrauchenia: Macruachenia are weird creatures. They are one of the few mammals on the island that travel in herds, yet with the attack power they have with the numbers, they prefer to run rather than fight. They will even leave behind a herd member if it means the rest can get to safety. They are not the most suitable travel mounts when tamed, as they keep their disloyal behavior. If in danger it will buck it's rider off and flee to safety. Most tribes keep them, however, because of their use in farming. Their feces are unique compared to other creatures on the island as they boost the growth of crops and can make them yield extra fruits per harvest.
Giant Camel: Giant Camels live in the hottest areas on the island. They are wonderful mounts for travelling in hot areas as they store water in their humps, which will keep the rider cool and hydrated. They are also wonderful for carrying loads over long distances, as they don't tire easily and can carry a lot of weight.
Quagga: Quaggas are herd animals, and a very desired tame for all survivors. They are very fast mounts with high stamina and movement speed. They can jump somewhat high and far, and with more Quagga following them, their speed is increased, making them one of the fastest mounts on the island, rivaling that of Gallimimus.
Just some thoughts on what I think could be added. :]
Dino Ideas
Re: Dino Ideas
All good ideas, but I think the one that sticks out the most is the giant camel. Ark is in need of a desert biome, and spawning camels in it would be awesome ways to traverse the deserts in search of other creatures or whatever things ark has in its deserts.