>>2347752>I wonder what kind of colossal fossils researchers could find of giant prehistoric aquatic animals at the bottom of the ocean.
Tectonic plates grow from mid-ocean ridges as magma upwells and cools into rock. Subduction zones along the continental shelf swallow the oceanic crust and it is absorbed back into the mantle. Most of the oceanic seabed is younger than 150 million years old and we'll never know anything about the ocean depths before the Cretaceous beyond that which we can glean from areas where the coast seabed rose to form part of a continental landmass (ie: Burgess Shale).
I find it likely that there were larger marine animals than Mosasaur (or just larger Mosasaurs). The Mosasaur specimens we have were all taken from areas that would have been coastal waters- I don't think this necessarily means they were coastal animals, but like Killer Whales were clearly very prolific and it would make sense that they'd be so well represented in the fossil record. There is fucking gigantic amount of prehistoric seabed that isn't accounted for.
With that said, I think there are further ecological precedents to believe that larger sea-dwelling animals may have existed. First of all, there is nothing filling the ecological niche of feeding on Plankton in the way that modern baleen whales do. Thinking Mosasaurs were the biggest marine animals of the Cretaceous would sort of be like thinking Killer Whales are the biggest marine animals today.
Secondly, it doesn't follow that the largest marine animals would be smaller than the largest terrestrial animals. From a physics standpoint, marine animals can grow large much more easily because much of their weight is carried by their buoyancy rather than having to rely upon their bone structure to move around. Plankton as a base food source allows marine life to grow larger than terrestrial animals simply because plankton feeders can graze vast quantities of protein- there is no terrestrial analogue.