Imagine that you travel back in time 600 million years and are looking at marine organisms. What types of skeletons would you observe in these creatures?

Hydrostatic skeletons and exoskeletons

Explanation:

A hydrostatic skeleton is found in many soft-bodied animals with a coelom and muscles surrounding the coelom, which is the body cavitiy. An exoskeleton is an external skeleton protecting the body. It acts as armor or a shell.