The ancient fossils are a record of when shallow seas covered much of the united states. while the fossils are of organisms that are the precursors of many modern day organisms, changes in ocean geography and other factors eventually caused those older species to become

-- It is considered to be the link between the lobe-finned fishes and early ... Climate andgeography ... Sea levels were high with much of western North America under water. ... By the mid-Devonian, the fossil record shows evidence that there ... Plants, which had begun colonizing the landduring the Silurian ...

When you are making a guess you are forming a hypothesis