Question

an ichthyosaurus which fights a plesiosaurus and wins. they continue exploring and see a 12 - foot tall prehistoric human watching a herd of mastodons. dan they saw a lot of different animals down there in that cavern. realistically, which animal do you think would most likely be living underground?

Explanation:

Bats are known to roost in caves and other underground - like environments. Mastodons were large land mammals that lived on the surface, Plesiosaurs were marine reptiles, and Ichthyosaurs were also marine reptiles.

Answer:

Bats