The whale Leviathan was perhaps one of the megalodon's greatest rivals. It was also an apex predator, one of the largest animals to ever live on Earth. The Leviathan whale lived in the Miocene Epoch and different sources believe that it may have spread into the oceans 12 to 13 million years ago or 10 to 9 million years ago. Regardless, Leviathan whales and megalodons live together, which can be a headache for our shark friends.
The giant squid can grow into a large individual, weighing around 500 kilograms and measuring up to 14 meters long. If the megalodon attacks it in deep enough water, the squid can attack it with its powerful beak and entangle it with its tentacles. This would stop the shark from moving and the megalodon would drown. Squids are intelligent, they know how to use tools when hunting and can successfully camouflage themselves if necessary.
Mosasaurs are theone of the coolest scaly reptiles on the planet. It is a huge and deadly monster that feeds on large aquatic creatures in the ocean and is a powerful opponent of the Megalodon. Can reach 17 meters in length. Its body was thinner than modern whales and easier to maneuver. Mosasaurus horti was the most evolved of the mosasaurs and probably possessed excellent eyesight. Its teeth can withstand a very powerful bite, so the poor megalodon will feel it fully on its skin.
Deinosuchus is a famous ancient crocodile that resembled a walking nightmare that terrorized prehistoric lands. This ancient reptile was an apex predator, preying on large dinosaurs, large fish and even large turtles. He is very fast and has bony plates called "bony skin" that protect him from almost everyone. An adult Deinosuchus is approximately 12 meters long (with a tail) and weighs approximately7 to 8 tons. It looks a lot like modern alligators.
The basilosaurus is a large animal, its length is comparable to that of the megalodon, ranging from 14 to 20 meters. This animal was once mistaken for a reptile, but it is actually a whale with enormous teeth and a slender body. In its diet, Basilosaurus only eats large sharks and fish. An interesting fact about this whale is that Basilosaurus is capable of biting and chewing its prey. If we're talking about diet, Basilosaurus looked a lot like its modern cousin, the killer whale.