Mass Effect 3 Kakliosaur Fossil location for the scientist side quest
There are many side quests in Mass Effect 3, and most of them are really quite simple - be tasked with finding something, fetch it - often from a hidden spot during a side mission or even main story mission - and then return it to the person searching for it. One such quest is Citadel: Kakliosaur Fossil, which tasks Shepard with finding a perfectly preserved specimen of an ancient beast for the war effort.
Specifically, you'll be able to find a Salarian Scientist NPC in the Apartments area of the Citadel's Presidium Commons. He's near Apartment 90. He only appears after you've played and completed Priority: The Citadel II, the main story mission where a bunch of major events occur on your second story-driven, compulsory visit back to the Citadel in ME3.
You'll be able to hear the Salarian talking about how he could improve the Krogan's fighting force for the war effort... if he had a Kakliosaur Fossil. His logic is simple: in ancient times, the Krogan used to ride Kakliosaurs into battle. They're long since extinct, but if a fossil were to be found, they could be cloned to join the Krogan squads fighting in the war. Kakliosaur are immune to poisons and toxins, which will allow the Krogan to fight on worlds with toxic environments.
The next step for you, naturally, is to find yourself a Kakliosaur Fossil.
Where to find a Kakliosaur Fossil in Mass Effect 3
There's only one place to find a Kakliosaur Fossil in Mass Effect 3 - and that's on a specific planet out in the galaxy. First of all, in order to reach the Kakliosaur fossil location, you'll need to have completed the Priority: Geth Dreadnought mission; this mission is a gatway to unlocking the system where the fossil is found.
Head to the Phoenix System of the Argos Rho cluster. The planet you're looking for is Intai'sei. Scan the planet and you'll find the perfectly preserved skull of a Kakliosaur. This is the artifact you need for the quest; a skull alone is enough.
Return to the Citadel at your earliest convenience, either right away or in line with the suggestions in our ME3 mission order, and turn the quest in to the Salarian. In return you'll get 15,000 credits ideal for spending on weapons and upgrades, 5 Reputation points, and an update to the Krogan Clans War Asset, adding 40 Military Strength points to your War Assets.
While you never do get to see a Krogan riding a Kakliosaur into battle, you can at least imagine it's majestically happening somewhere off-camera during the final battle. That enhances the ME3 ending, right?