Mosasaurus; King of the Cretaceous Seas
Dwarfing the land carnivores, Mosasaurus grew up to 80 feet long, weighing 8 tons (think tour bus).
So how do you become the biggest, the baddest, the top carnivorous predator? Well, you keep what works and toss what doesn't. Over time, to evolve to be so in tune with your environment, that you are part of it.
Mosasaurus kept the forked prey-tasting tongue to locate prey in water. This monster adapted it's reptilian ears to hear incredibly well underwater, and added sonar sensors along it's muzzle like Orcas.
Jaws that can unhinge like your snake cousins- let's keep that cool feature.
Keratin found in the skin cells show that this ambush predator was dark on top, and light on the bottom. Better to lie in wait and surprise your dinner with a quick burst of speed from below- (think crocodilians).
Speaking of crocks, what about that tail?! The lizard like tail evolved over time to endow this creature with speeds of 30mph. Let's trade in your claws for huge steering flippers to add agility.
Since Mosasaurus did not even sport T-Rex sized arms, another incredible adaptation ensured the slippery prey had no chance of escape: backward-facing teeth and a second row of independently moving top teeth meant today was a good day to showcase super powers of death dealing.
This Massive hunter was not a picky eater. Mosasaurus remains have been found with turtles, hard-shelled ammonites, birds, fish, other reptiles, massive sharks, and even other mosasaurus parts where the stomach would be. Yes, he was a cannibal-(we can't entertain sensitive morality and be King, right)?
Let's talk about focus! Every top athlete needs focus! Lady Mosasaurus never even left her hunting grounds to give birth like any other self-respecting marine reptile does. Oh, no, she gave birth to live young.
Speaking of world domination, breeding like rabbits never hurts- Mosasaurus remains have been found with twin skeletons awaiting their birthday debuts.
And that, my friend is how you rule the world (at least until a the next cataclysmic event wipes you, and all your pesky competition off the map).